[GMCnet] Why engine bearings can fail in the Olds 455, and 403 as we use them.

[Bob Dunahugh]

Bad maintenance to start. We all know about that one. These engines as we use them in the GMC are subjected to vary high bearing loads. This is created by a large cylinder bore that has a reciprocating mass operating a rotating shaft at a low RPM rate. Basically lugging it in comparison to the car application with 15 inch tires that it was designed for to start with. This sort of lugging ( in our case ) will run the bearing pressure up, and creates ideal conditions for the vary destructive ping that you've heard of. Thus these two conditions together put the bearing pressures off the chart. This is acerbated by bearing companies that put wider oil groves in their bearing that are wider then the stock GM units. Thus decreasing the load carrying surface of their bearings. This wider grove is great for high revving engines. The wider grooved bearings sound great. Just not for us. This is part of the reason we can use higher oil pressures. Not higher volumes of oil. The
y are NOT the same. And this is part of some of the confusion, and misunderstandings.. You've heard it said that our engines need special care in rebuilding. This is because of what we subject them too. Don't be proud that you keep you're RPM's down. Decrease you're bearing load on hills by shifting down. And run the RPM's up. There are vary few people that pull all the time, the loads I do. With any engine. Let a loan a 403. And it has 154,000 miles on it. I get by. By running it at higher RPM's. The 455 from Glen, and BJ's GMC will be here tomorrow. It will be interesting on what went wrong with the bearings. Bob Dunahugh
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[Robert Mueller]

Bob,

What about the negative effects of high piston speeds in a long stroke engine like the 455?

Regards,
Rob M.
The Pedantic Mechanic
Sydney, Australia

[Johnny Bridges]

Are the piston speeds really high enough to matter at the speeds the engine turns in the GMC?

--johnny
--
'76 23' transmode Norris upfit
Braselton, Ga.

"Sometimes I wonder what tomorrow's gonna bring when I think about my dirty life and times" --Warren Zevon

[Robert Mueller]

Depends on the engine, the final drive ratio, and the speeds you drive. I drive at the speed limit plus a bit but my upper limit is
75 pretty much. Having said that Double Trouble with a 455 and a 3.21 to 1 final drive will run all day at 75 and if I'm not careful
will drift up to 80. I can't remember what the rpm is at that speed.

Regards,
Rob M.

-----Original Message-----
From: Johnny Bridges

Are the piston speeds really high enough to matter at the speeds the engine turns in the GMC?

--johnny

[Carey Bryan]

Rob,

I love it when I can reassure the pedantic mechanic.

At 5000 RPM, the Oldsmobile 403 with a stroke of 3.385 inches gives a mean piston speed of 2821 feet per minute.
At 4200 RPM, the Oldsmobile 455 with a stroke of 4.250 inches gives a mean piston speed of 2975 feet per minute.
At 4100 RPM, the Cadillac 500 with a stroke of 4.304 inches gives a mean piston speed of 2941 feet per minute.

I am quoting below from epi-eng.com about recommended mean piston speed:

"For purposes of rules of thumb, it is generally agreed that for an engine in aircraft service, 3000 fpm is a comfortable maximum MPS and experience
has shown that engines having an MPS substantially exceeding that value have experienced reliability issues."

Aircraft service, a high reliability application. High enough for a former Hamilton Standard employee, I think.

I recall a limit of 4000 feet per minute limit for design of motorcycles, so three thousand is pretty conservative. My 1970 Honda CB350 of hallowed
memory with a stroke of 1.99 inches had a redline of 10,500 rpm, for a MPS of 3483. It never broke.

I was interested to see the MPS of the 455. Just for general principles, I would keep the RPM below 4200 if I had an Oldsmobile 455. No great trick
to do so, I think. That would be extremely conservative, I think. And, as friction in an engine varies as the square of the rpm, I do like to keep
the revs down.

Best,

Carey
--
Carey from Ennis, Texas
78 Royale, 500 Cadillac, Rance Baxter EFI.

[John R. Lebetski]

I got a rod knock after a kick down passing move on my new to me coach. I had changed oil twice to try to clean out the engine, but on tear down found
a good quart of sludge in the pan. Assuming dirt got bypassed to oil passàge or strainer restricted. I don't think it's the piston speed issues as
much as the crack throws slinging oil away at RPM and trying to keep the bearings under enough pressure and volume to maintain the oil film thickness
on the throws. That is why they say you need X PSI per 1000 RPM to overcome the incresaed bleed off at the throws as RPM increases. When these were
new I used to wind them out to the programmed shift point with no issues, but now try to keep the 455 in a midrange sweet spot not lugging or revving
to the limit. So far no problems.
--
John Lebetski
Woodstock, IL
77 Eleganza II
Source America First

[Bob Dunahugh]

The Old's 455 has been used in racing for a long time. And operated in the 6 to 8000 RPM range. Cams are designed to make an engine run in different RPM ranges. The SFPS ( surface feet per second ) isn't an issue in our application. GM makes crate racing engines that are over 550 cubic inches that have longer strokes then the 455. SFPS was a big issue back in the day of steel pistons. Bob Dunahugh

Bob

[Keith V]

Cool, 4200 RPM redline for my 455 then.
Thanks!
--
Keith Vasilakes
Mounds View. MN
75 ex Royale GMC
69 Vette
29 Dodge

[Carey Bryan]

According to a GMC Western States seminar, and extrapolating:


A 3.07:1 (stock ratio) produces a cruise speed of 83.5 mph at 3,000 rpm (Second Gear 56 mph)
A 3.21:1 ratio produces a cruise speed of 80 mph at 3,000 rpm. (Second gear 54 mph)
A 3.42:1 ratio produces a cruise speed of 75 mph at 3,000 rpm. (Second gear 51 mph)
A 3.55:1 ratio produces a cruise speed of 72 mph at 3,000 rpm. (Second gear 49 mph)
A 3.70:1 ratio produces a cruise speed of 69 mph at 3,000 rpm. (Second gear 47 mph)

Given a (very) arbitrary redline of 5000 for the 403, maximum speed for second gear assuming an accurate speedometer, good luck with that, is:

3.07 93 mph
3.21 90 mph
3.42 85 mph
3.55 82 mph
3.70 78 mph
Kanomata 105 mph

For the 455 with an arbitrary 4200 rpm redline for second gear, neglecting torque converter slip, watch tire size, speedometer accuracy:

3.07 78 mph
3.21 76 mph
3.42 71 mph
3.55 69 mph
3.70 66 mph

For the 500 Cadillac at 4100 rpm:

3.07 76 mph
3.21 74 mph
3.42 69 mph
3.55 67 mph
3.70 64 mph

Bob Dunahugh may well be right, and that the piston feet per minute concerns might be outmoded, though I am sure the talk of it didn't cease after
aluminum pistons came into being starting in automotive production about 1915 give or take (so I read, I wasn't there). Remember also that in aircraft
engines those pistons are mighty heavy, too. So looking at the above, in any case the limiting case is pretty high even in second gear, and in drive,
it's ridiculously high. Note there is torque converter slip to take into account though at high rpm, it will be at its smallest.

I enjoy these ruminations, it keeps me from doing real work on the motorhome.

Carey

--
Carey from Ennis, Texas
78 Royale, 500 Cadillac, Rance Baxter EFI.

[Robert Mueller]

Carey, Thanks for the numbers! I raised the subject from a long term engine reliability viewpoint. I would assume that higher piston speeds would
equate to faster bore / piston / ring wear.
--
Regards,
Rob M. (USAussie)

The Pedantic Mechanic
Sydney, Australia

'75 Avion - AUS - The Blue Streak TZE365V100428
'75 Avion - USA - Double Trouble TZE365V100426

[Bob Dunahugh]

John, and Teresa brought me the complete drive train out of the GMC they got from Glen, and BJ about 7:30 tonight.Removed the final drive. Then the trans. Next the intake, heads, and oil pan. Pulled 3 mains, and 2 rod bearings. All Bearings were well into the copper base. Oil pump drive was fine. Engine was vary clean inside. The piston's showed no signs of pre ignition. The problem seems to have come from the high volume oil pump that failed. More bearing inspection time tomorrow. As beer time arrived one hour latter at 8:30. Bob Dunahugh

[Robert Mueller]

Bob,

Responses below each one of your paragraphs below.

Regards,
Rob M.
The Pedantic Mechanic

-----Original Message-----
From: Bob Dunahugh

John, and Teresa brought me the complete drive train out of the GMC they got from Glen, and BJ about 7:30 tonight.Removed the final
drive. Then the trans. Next the intake, heads, and oil pan. Pulled 3 mains, and 2 rod bearings. All Bearings were well into the
copper base. Oil pump drive was fine. Engine was vary clean inside. The piston's showed no signs of pre ignition. The problem seems
to have come from the high volume oil pump that failed. More bearing inspection time tomorrow. As beer time arrived one hour latter
at 8:30. Bob Dunahugh

WHAT FAILED IN THE HIGH VOLUME OIL PUMP?

The Old's 455 has been used in racing for a long time. And operated in the 6 to 8000 RPM range. Cams are designed to make an engine

run in different RPM ranges. The SFPS (surface feet per second) isn't an issue in our application. GM makes crate racing engines

that are over 550 cubic inches that have longer strokes then the 455. SFPS was a big issue back in the day of steel pistons. Bob
Dunahugh

AS I NOTED IN AN EARLIER MESSAGE THE REASON I BROUGHT UP PISTON SPEEDS IS HOW IT RELATES TO LONG TERM ENGINE RELIABILITY AND ENGINE
WEAR.

SEEMS TO ME THAT THE FASTER THE PISTONS MOVE UP AND DOWN THE BORE THE FASTER THE PISTONS, BORE, AND RINGS WILL WEAR.

YES OR NO? IF THE ANSWER IS NO I'D LIKE TO KNOW WHY NOT TO CLEAR UP MY MISCONCEPTION.

Bad maintenance to start. We all know about that one. These engines as we use them in the GMC are subjected to vary high bearing
loads. This is created by a large cylinder bore that has a reciprocating mass operating a rotating shaft at a low RPM rate.
Basically lugging it in comparison to the car application with 15 inch tires that it was designed for to start with. This sort of
lugging ( in our case ) will run the bearing pressure up, and creates ideal conditions for the vary destructive ping that you've
heard of. Thus these two conditions together put the bearing pressures off the chart. This is acerbated by bearing companies that
put wider oil groves in their bearing that are wider then the stock GM units. Thus decreasing the load carrying surface of their
bearings. This wider grove is great for high revving engines. The wider grooved bearings sound great. Just not for us. This is part

of the reason we can use higher oil pressures. Not higher volumes of oil. They are NOT the same. And this is part of some of the

[Bob Dunahugh]

Rob. Good questions. The bearings that I took out, all had about the same amount of damage. ( middle ones ) And were dry between the bearings and crankshaft. The crank has some grooves starting. Roller chain that drives the cam looks good. The camshaft ramps appear OK from what I see now. Lifter bottoms also look fine. Cam, and lifters need to be checked with a microscope for imperfections. . 4 lifter plungers in the lifters were collapsed due to lack of oil. The crank is locked up at this point. The front main bearing, and front rod bearings should be the locked up ones. The oil level on the dip stick was at full. I'm thinking that the relief valve spring in the HV pump failed. The HV pump relief valve spring has to move farther then a stock spring due the the extra oil that it's dumping back into the bottom of the oil pan. Thus has more load on it. And movement then stock.As to your thought on higher piston speeds would cause more ring, piston, and bore wear. Reasonable
thought. The piston assemblies travel up, and down the bore the same number of times per mile at 20 MPH or at 70 MPH. The thing is that at acceleration at 20 MPH you are running a lower manifold vacuum. Thus you are running a much higher combustion chamber pressures due to the increase of fuel in the charge that is drawn into the combustion chamber. The compression ring is designed to use the combustion chamber pressures to increase the ring pressures that the ring applies to the cylinder wall. Thus the ring pressure on the cylinder is greater. With a low manifold vacuum. Your manifold vacuum gauge is a good indicator of the load on your pistons. Back to SFPS. GM used steel pistons into the 50's. The cast aluminum pistons that went into the 403, and 455. SFPS is of no concern. If you really want to reduce the load on your engine, and trans. Increase mileage. Lower your engine, and trans temps. Put in a 3:70 final drive from Jim K. Bob Dunahugh 78 Royale Member GMCMI

[John R. Lebetski]

Need to find who's aftermarket pump and if offshore parts. I'm not a fan of high volume pumps due to drive stress loads trying to compress a liquid
beyond designed flow (bleed off) designs. Adding 15w50 to the equation compounds it. Remember the "Keep your GM car all GM" air cleaner sticker
might apply here. I think a good Olds boat motor and MH motor are very different animals and race parts don't always apply. Do you know oil brand,
type and weight they were using as I always ask this after failures (though not the cause per se looking for trends). Thanks.

--
John Lebetski
Woodstock, IL
77 Eleganza II
Source America First

[Robert Mueller]

Bob,

Responses in CAPS for clarity interspersed in your email below, I'm not shouting.

Regards,
Rob M.

-----Original Message-----
From: Bob Dunahugh

Rob. Good questions. The bearings that I took out, all had about the same amount of damage. (middle ones)
And were dry between the bearings and crankshaft. The crank has some grooves starting.

I ASSUME THAT (middle ones) WERE 2, 3, & 4 PLEASE CONFIRM

Roller chain that drives the cam looks good.

TIGHT?

The camshaft ramps appear OK from what I see now. Lifter bottoms also look fine. Cam, and lifters need to be checked with a
microscope for imperfections.

4 lifter plungers in the lifters were collapsed due to lack of oil.

IS IT POSSIBLE THAT THE OIL IN THE LIFTER WAS PUSHED OUT BECAUSE OF SPRING PRESSURE ON THE ROCKER ARMS?

The crank is locked up at this point. The front main bearing, and front rod bearings should be the locked up ones.

WHY DO YOU SAY IT IS THE FRONT BEARINGS?

The oil level on the dip stick was at full.

I'm thinking that the relief valve spring in the HV pump failed. The HV pump relief valve spring has to move farther then a stock
spring due the the extra oil that it's dumping back into the bottom of the oil pan. Thus has more load on it. And movement then
stock.

I WOULD SUGGEST A SIDE BY SIDE COMPARISON OF THE DIFFERENCES BETWEEN AN OEM PUMP AND A MELLING HIGH VOLUME PUMP.

As to your thought on higher piston speeds would cause more ring, piston, and bore wear. Reasonable thought.

THANKS!

The piston assemblies travel up, and down the bore the same number of times per mile at 20 MPH or at 70 MPH.

I'M SORRY BUT I DON'T UNDERSTAND THIS; WOULD NOT AN ENGINE BE RUNNING AT A HIGHER RPM AT 70 MPH THAN AT 20 MPH AND THEREFORE PISTON
SPEEDS BE HIGHER?

The thing is that at acceleration at 20 MPH you are running a lower manifold vacuum. Thus you are running a much higher combustion
chamber pressures due to the increase of fuel in the charge that is drawn into the combustion chamber. The compression ring is
designed to use the combustion chamber pressures to increase the ring pressures that the ring applies to the cylinder wall. Thus
the ring pressure on the cylinder is greater. With a low manifold vacuum.

I'M SORRY BUT I DON'T UNDERSTAND THIS EITHER. ARE YOU SAYING THAT AT 20 MPH THE CYLINDER IS FILLED WITH MORE FUEL THAN AT 70 MPH?

Your manifold vacuum gauge is a good indicator of the load on your pistons. Back to SFPS. GM used steel pistons into the 50's. The
cast aluminum pistons that went into the 403, and 455. SFPS is of no concern. If you really want to reduce the load on your engine,
and trans. Increase mileage. Lower your engine, and trans temps. Put in a 3:70 final drive from Jim K. Bob Dunahugh 78 Royale
Member GMCMI

[Robert Mueller]

John,

As noted in an earlier email Dick Paterson uses Melling High Volume oil pumps, I went to the Melling website to poke around a bit
and I found these two documents.

I have not read them but the very fact that these two documents exist shows that Melling holds vendors feet to the fire!

Here's a link to Melling's 2015 Melling Tool Company Supplier Manual:

http://www.melling.com/LinkClick.aspx?fileticket=pfdb_7Bpj8Q%3d&tabid=1127&portalid=0&mid=2520

Here's a link to Melling's Vendor Terms and Conditions Agreement:

http://www.melling.com/LinkClick.aspx?fileticket=xebNbzylPwY%3d&tabid=1127&portalid=0&mid=2520

Regards,
Rob M.
The Pedantic Mechanic


-----Original Message-----

From: John R. Lebetski

Need to find who's aftermarket pump and if offshore parts. I'm not a fan of high volume pumps due to drive stress loads trying to
compress a liquid beyond designed flow (bleed off) designs. Adding 15w50 to the equation compounds it. Remember the "Keep your GM
car all GM" air cleaner sticker might apply here. I think a good Olds boat motor and MH motor are very different animals and race
parts don't always apply. Do you know oil brand, type and weight they were using as I always ask this after failures (though not the
cause per se looking for trends). Thanks.
--
John

[Robert Mueller]

John,

Here's a link to Melling's Standard OEM replacement for the Olds 455 oil pump for a 1975 Toronado (P/N M-22F):

Tiny URL: http://tinyurl.com/nsl422e

Full URL:
http://omnitek.co/mellingcatalog/#ag/part/M-22F/from/make%3Doldsmobile%252COldsmobile%26model%3Dtoronado%252CToronado%26year%3D1975%
252C1975%26engine%3D8cyl%2525207.5%252520455cid%252C8Cyl%2525207.5%252520455Cid%26product-line%3D10%252C11%252C9%252Call/1

At the bottom of the page are three links to videos that explain:

1) How to correctly prime engines and oil pumps
2) Oil pump volume and pressure explanation
3) Oil pressure vs flow

I would suggest that everyone view all three of these videos as they are most educational.

Here's a link to the high flow version P/N M-22FHV:

http://omnitek.co/mellingcatalog/#ag/part/M-22FHV

As you can see it produces 20% more flow than the OEM version, however, it is at the same pressure.

Bob believes that the reason Glen & BJ's engine failed was because:

Quote:

I'm thinking that the relief valve spring in the HV pump failed. The HV pump relief valve spring has to move farther then a stock

spring due the extra oil that it's dumping back into the bottom of the oil pan. Thus has more load on it. And movement then stock.

Unquote:

Bob may be correct, however, it depends on the diameter of the piston in the relief valve and the area of the port through which the
oil dumps. That's why I noted that we needed a side by side comparison of a standard OEM Oldsmobile 455 oil pump and a Melling high
volume pump.

Regards,
Rob M.
The Pedantic Mechanic


-----Original Message-----

From: John R. Lebetski

Need to find who's aftermarket pump and if offshore parts. I'm not a fan of high volume pumps due to drive stress loads trying to
compress a liquid beyond designed flow (bleed off) designs. Adding 15w50 to the equation compounds it. Remember the "Keep your GM
car all GM" air cleaner sticker might apply here. I think a good Olds boat motor and MH motor are very different animals and race
parts don't always apply. Do you know oil brand, type and weight they were using as I always ask this after failures (though not the
cause per se looking for trends). Thanks.
--
John

[Ken Henderson]

IIRC, it was Joe Mondello who reported having seen the oil pump's relief
valve stick open as Bob suspects. The pumps he sold (and perhaps the
company still does) were very slightly modified in the area of the relief
valve to eliminate that possibility. AFAIK, that's the only reason for
their premium over the price of the standard Mellig pumps. When I
installed a HV pump, I used a Dremel tool to clean up the casting as Joe
described. Sad part is, my memory's too bad to remember what exactly I
did. Careful examination should show what's needed.

Ken H.

On Sat, Jun 13, 2015 at 10:31 PM, Robert Mueller <robmu...@iinet.net.au>
wrote:

> ​...

>
> Bob believes that the reason Glen & BJ's engine failed was because:
>
> Quote:
>
> I'm thinking that the relief valve spring in the HV pump failed. The HV
> pump relief valve spring has to move farther then a stock
> spring due the extra oil that it's dumping back into the bottom of the oil
> pan. Thus has more load on it. And movement then stock.
>

[Robert Mueller]

Ken,

Your email caused a memory synapse to fire and I remembered these photos by Bob Drewes:

http://www.gmcmhphotos.com/photos/mechanical/p50094-oil-pump-housing.html

I then decided to do a search for "Oil Pump" and here's what came up.

Here's a photo that Gene posted:

http://www.gmcmhphotos.com/photos/misc/p37898-patterson-oil-pump.html

Here's one from Kelvin:

http://www.gmcmhphotos.com/photos/455-r-26amp-3br-engine-work/p10860.html

Here's something on the oil pump from Arch:

http://www.gmcmhphotos.com/photos/melling-22fhv-oil-pump-pressure/p18204.html

This is most interesting as it notes the Melling pump only puts out 6 to 8 psi more.

Regards,
Rob M.
The Pedantic Mechanic


-----Original Message-----

From: Gmclist [mailto:gmclist...@temp.gmcnet.org] On Behalf Of Ken Henderson
Sent: Sunday, June 14, 2015 1:22 PM
To: gmclist
Subject: Re: [GMCnet] Why engine bearings can fail in the Olds 455, and 403 as we use them.

IIRC, it was Joe Mondello who reported having seen the oil pump's relief
valve stick open as Bob suspects. The pumps he sold (and perhaps the
company still does) were very slightly modified in the area of the relief
valve to eliminate that possibility. AFAIK, that's the only reason for
their premium over the price of the standard Mellig pumps. When I
installed a HV pump, I used a Dremel tool to clean up the casting as Joe
described. Sad part is, my memory's too bad to remember what exactly I
did. Careful examination should show what's needed.

Ken H.

[Bob Dunahugh]

Pistons, and rods are out. Now need to find out why the HV pump wasn't able to deliver oil to the crankshaft bearings. Whenever the proper amount of oil isn't provided by the oil pump. The bearings that are the farthest from the pump. Will be the first to deteriorate. And the bearings closest to the pump will survive a little longer. In this case. 1,and 2 rod bearings sized up. 3, and 4 spun. And took the bearing locking tabs off. Crankshaft, and rods for 3, and 4 are severely damaged. May not want to repair the crank, and #3, and 4 rods.Rob. As to you're questions. Above should have answered 2 of them. Roller chain was a little loose. But that's how roller chains run. Yes. The 4 lifters should have staid up. As they have check valves in them. I'm taking them apart to see what happened. As to the HV oil pump. HV pumps generally have a 23, to 50 % longer pump gears. Thus pump 23, to 50 % more oil. And take 23 to 50 % more HP to operate with the same amount of excess heat prod
uced.Not more pressure. As to the 20 to 70 MPH comment. The distance a piston travels in it's bore per mile of road traveled. Is always the same no mater the speed of the coach. Thus the SFPS will increase over a shorter period of time. As to the air/fuel charge put into the combustion chamber at 20 MPH. Generally at 20 you are increasing you're speed. And you're vacuum is low. Thus you have more air/fuel going into the chamber. At 70. You're generally just cruising with a high vacuum with a lower air/fuel charge. If you're pulling a hill at 70. The vacuum is low. So the air/fuel mixture is larger.. Hope this adds some clarity to my E-mail. Thanks for asking.Tomorrow I'l be working on the trans, and final drive.Bob Dunahugh

Rob. Good questions. The bearings that I took out, all had about the same amount of damage. ( middle ones ) And were dry between the bearings and crankshaft. The crank has some grooves starting. Roller chain that drives the cam looks good. The camshaft ramps appear OK from what I see now. Lifter bottoms also look fine. Cam, and lifters need to be checked with a microscope for imperfections. . 4 lifter plungers in the lifters were collapsed due to lack of oil. The crank is locked up at this point. The front main bearing, and front rod bearings should be the locked up ones. The oil level on the dip stick was at full. I'm thinking that the relief valve spring in the HV pump failed. The HV pump relief valve spring has to move farther then a stock spring due the the extra oil that it's dumping back into the bottom of the oil pan. Thus has more load on it. And movement then stock.As to your thought on higher piston speeds would cause more ring, piston, and bore wear. Reasonable
thought. The piston assemblies travel up, and down the bore the same number of times per mile at 20 MPH or at 70 MPH. The thing is that at acceleration at 20 MPH you are running a lower manifold vacuum. Thus you are running a much higher combustion chamber pressures due to the increase of fuel in the charge that is drawn into the combustion chamber. The compression ring is designed to use the combustion chamber pressures to increase the ring pressures that the ring applies to the cylinder wall. Thus the ring pressure on the cylinder is greater. With a low manifold vacuum. Your manifold vacuum gauge is a good indicator of the load on your pistons. Back to SFPS. GM used steel pistons into the 50's. The cast aluminum pistons that went into the 403, and 455. SFPS is of no concern. If you really want to reduce the load on your engine, and trans. Increase mileage. Lower your engine, and trans temps. Put in a 3:70 final drive from Jim K. Bob Dunahugh 78 Royale Member GMCMI

John, and Teresa brought me the complete drive train out of the GMC they got from Glen, and BJ about 7:30 tonight.Removed the final drive. Then the trans. Next the intake, heads, and oil pan. Pulled 3 mains, and 2 rod bearings. All Bearings were well into the copper base. Oil pump drive was fine. Engine was vary clean inside. The piston's showed no signs of pre ignition. The problem seems to have come from the high volume oil pump that failed. More bearing inspection time tomorrow. Teresa's a good wrench er on this project. Bob Dunahugh

[Bob Dunahugh]

I've never said that HV pumps are bad. Just use them in the applications that require their use. If you have a healthy engine with the bearing clearance in the .0003 inch range that GM recommends. After all. Their the one's that designed the 403, and 455. And they did a real good job. Time has proved that. The 455 that I'm working on now . Seems to have been well done. I've heard that some people put in HV pump as a preventative measure for the weir that will occur latter. If done correctly at rebuild time. Most of us won't live long enough to see that day. As your bearing should never touch the crank. And the HV pump didn't save this 455. It's simple. Enough oil wasn't getting to the crankshaft bearings. And I will figure out what happened. The evidence, and story is there. We all make changes to our GMC's to improve what ever, as we see it. It's how we enjoy these things. It's a hobby for many. I get the change in the final drive ratio's, fuel injection, air bags, and
that list goes on, and on for ever. And we have great vendors that enjoy our money too. ( GRIN ) The thing is that GM put in our engines the pump that they thought would do the job they wanted done. In the case of my GMC. That stock pump as done the job it was designed for. For 38 years. And a 154,000 miles. I just see no mistake to fix there. I'm not saying that anyone is wrong. The reasons that I seem to hear are ones that seem to come from opinions. I would just like to see some data that the designers at GM over looked something. The dialog has been great. But it usually is here. Thanks to all. And you never guessed that I love talking power plants. There's always something out there new to learn about.Bob Dunahugh

Pistons, and rods are out. Now need to find out why the HV pump wasn't able to deliver oil to the crankshaft bearings. Whenever the proper amount of oil isn't provided by the oil pump. The bearings that are the farthest from the pump. Will be the first to deteriorate. And the bearings closest to the pump will survive a little longer. In this case. 1,and 2 rod bearings sized up. 3, and 4 spun. And took the bearing locking tabs off. Crankshaft, and rods for 3, and 4 are severely damaged. May not want to repair the crank, and #3, and 4 rods.Rob. As to you're questions. Above should have answered 2 of them. Roller chain was a little loose. But that's how roller chains run. Yes. The 4 lifters should have staid up. As they have check valves in them. I'm taking them apart to see what happened. As to the HV oil pump. HV pumps generally have a 23, to 50 % longer pump gears. Thus pump 23, to 50 % more oil. And take 23 to 50 % more HP to operate with the same amount of excess heat pro

duced.Not more pressure. As to the 20 to 70 MPH comment. The distance a piston travels in it's bore per mile of road traveled. Is always the same no mater the speed of the coach. Thus the SFPS will increase over a shorter period of time. As to the air/fuel charge put into the combustion chamber at 20 MPH. Generally at 20 you are increasing you're speed. And you're vacuum is low. Thus you have more air/fuel going into the chamber. At 70. You're generally just cruising with a high vacuum with a lower air/fuel charge. If you're pulling a hill at 70. The vacuum is low. So the air/fuel mixture is larger.. Hope this adds some clarity to my E-mail. Thanks for asking.Tomorrow I'l be working on the trans, and final drive.Bob Dunahugh

[Bob Dunahugh]

I've never said that HV pumps are bad. Just use them in the applications that require their use. If you have a healthy engine with the bearing clearance in the .0003 inch range that GM recommends. After all. Their the people that designed the 403, and 455. And GM did a real good job. Time has proved that. The 455 that I'm working on now . Seems to have been rebuilt correctly. A nice touch was that it was balanced. I've heard that some people put in HV pump as a preventative measure for the weir that will occur latter. If done correctly at rebuild time. Most of us won't live long enough to see that day. As your bearing should never touch the crank. This 455 had Mobil 1 used in it. And the HV pump didn't save this 455. It's simple. Enough oil wasn't getting to the crankshaft bearings. And I will figure out what happened. The evidence, and story is there. As a side note. The pump drive in the 455 is a hex drive that is .323 of an inch across. ( 5/16 ) The oil pump drive i
n a 164 cubic inch 6 cyl Corvair. And the Chevy in line 6 is .485. .015 thousandths under 1/2 inch. Not knocking the Olds design. Just interesting to me. We all make changes to our GMC's to improve what ever, as we see it. It's how we enjoy these things. It's a hobby for many. I get the change in the final drive ratio's, fuel injection, air bags, and that list goes on, and on for ever. And we have great vendors that enjoy our money too. ( GRIN ) The thing is that GM put in our engines the pump that they thought would do the job they wanted done. In the case of my GMC. That stock pump has done the job it was designed for. For 38 years. And a 154,000 miles. I just see no mistake to fix here. Or advancement it technology to try to reinvent the wheel. I'm not saying that anyone is wrong. The reasons that I seem to hear are ones that seem to come from opinions. I would just like to see some data that the designers at GM over looked something. The dialog has been great. But it u
sually is here. Thanks to all. And you never guessed that I love talking power plants. There's always something out there new to learn about. Look forward to more comments.Bob Dunahugh

Pistons, and rods are out. Now need to find out why the HV pump wasn't able to deliver oil to the crankshaft bearings. Whenever the proper amount of oil isn't provided by the oil pump. The bearings that are the farthest from the pump. Will be the first to deteriorate. And the bearings closest to the pump will survive a little longer. In this case. 1,and 2 rod bearings sized up. 3, and 4 spun. And took the bearing locking tabs off. Crankshaft, and rods for 3, and 4 are severely damaged. May not want to repair the crank, and #3, and 4 rods.Rob. As to you're questions. Above should have answered 2 of them. Roller chain was a little loose. But that's how roller chains run. Yes. The 4 lifters should have staid up. As they have check valves in them. I'm taking them apart to see what happened. As to the HV oil pump. HV pumps generally have a 23, to 50 % longer pump gears. Thus pump 23, to 50 % more oil. And take 23 to 50 % more HP to operate with the same amount of excess heat pro
duced.Not more pressure. As to the 20 to 70 MPH comment. The distance a piston travels in it's bore per mile of road traveled. Is always the same no mater the speed of the coach. Thus the SFPS will increase over a shorter period of time. As to the air/fuel charge put into the combustion chamber at 20 MPH. Generally at 20 you are increasing you're speed. And you're vacuum is low. Thus you have more air/fuel going into the chamber. At 70. You're generally just cruising with a high vacuum with a lower air/fuel charge. If you're pulling a hill at 70. The vacuum is low. So the air/fuel mixture is larger.. Hope this adds some clarity to my E-mail. Thanks for asking.Tomorrow I'l be working on the trans, and final drive.Bob Dunahugh


Rob. Good questions. The bearings that I took out, all had about the same amount of damage. ( middle ones ) And were dry between the bearings and crankshaft. The crank has some grooves starting. Roller chain that drives the cam looks good. The camshaft ramps appear OK from what I see now. Lifter bottoms also look fine. Cam, and lifters need to be checked with a microscope for imperfections. . 4 lifter plungers in the lifters were collapsed due to lack of oil. The crank is locked up at this point. The front main bearing, and front rod bearings should be the locked up ones. The oil level on the dip stick was at full. I'm thinking that the relief valve spring in the HV pump failed. The HV pump relief valve spring has to move farther then a stock spring due the the extra oil that it's dumping back into the bottom of the oil pan. Thus has more load on it. And movement then stock.As to your thought on higher piston speeds would cause more ring, piston, and bore wear. Reasonable
thought. The piston assemblies travel up, and down the bore the same number of times per mile at 20 MPH or at 70 MPH. The thing is that at acceleration at 20 MPH you are running a lower manifold vacuum. Thus you are running a much higher combustion chamber pressures due to the increase of fuel in the charge that is drawn into the combustion chamber. The compression ring is designed to use the combustion chamber pressures to increase the ring pressures that the ring applies to the cylinder wall. Thus the ring pressure on the cylinder is greater. With a low manifold vacuum. Your manifold vacuum gauge is a good indicator of the load on your pistons. Back to SFPS. GM used steel pistons into the 50's. The cast aluminum pistons that went into the 403, and 455. SFPS is of no concern. If you really want to reduce the load on your engine, and trans. Increase mileage. Lower your engine, and trans temps. Put in a 3:70 final drive from Jim K. Bob Dunahugh 78 Royale Member GMCMI

[Bob Dunahugh]

Rob. Did this answer you're questions. Bob D

From: yenk...@hotmail.com
To: gmc...@temp.gmcnet.org
Subject: Re: Why engine bearings can fail in the Olds 455, and 403 as we use them.
Date: Sun, 14 Jun 2015 00:49:23 -0500




Pistons, and rods are out. Now need to find out why the HV pump wasn't able to deliver oil to the crankshaft bearings. Whenever the proper amount of oil isn't provided by the oil pump. The bearings that are the farthest from the pump. Will be the first to deteriorate. And the bearings closest to the pump will survive a little longer. In this case. 1,and 2 rod bearings sized up. 3, and 4 spun. And took the bearing locking tabs off. Crankshaft, and rods for 3, and 4 are severely damaged. May not want to repair the crank, and #3, and 4 rods.Rob. As to you're questions. Above should have answered 2 of them. Roller chain was a little loose. But that's how roller chains run. Yes. The 4 lifters should have staid up. As they have check valves in them. I'm taking them apart to see what happened. As to the HV oil pump. HV pumps generally have a 23, to 50 % longer pump gears. Thus pump 23, to 50 % more oil. And take 23 to 50 % more HP to operate with the same amount of excess heat prod
uced.Not more pressure. As to the 20 to 70 MPH comment. The distance a piston travels in it's bore per mile of road traveled. Is always the same no mater the speed of the coach. Thus the SFPS will increase over a shorter period of time. As to the air/fuel charge put into the combustion chamber at 20 MPH. Generally at 20 you are increasing you're speed. And you're vacuum is low. Thus you have more air/fuel going into the chamber. At 70. You're generally just cruising with a high vacuum with a lower air/fuel charge. If you're pulling a hill at 70. The vacuum is low. So the air/fuel mixture is larger.. Hope this adds some clarity to my E-mail. Thanks for asking.Tomorrow I'l be working on the trans, and final drive.Bob Dunahugh

[Robert Mueller]

Bob,

Yes and no, I need to think about this a bit and reformulate my statement / questions re piston speeds.

Regards,
Rob M.
The Pedantic Mechanic

-----Original Message-----

From: Bob Dunahugh

Rob. Did this answer you're questions. Bob D

From: yenk...@hotmail.com

Pistons, and rods are out. Now need to find out why the HV pump wasn't able to deliver oil to the crankshaft bearings. Whenever the
proper amount of oil isn't provided by the oil pump. The bearings that are the farthest from the pump. Will be the first to
deteriorate. And the bearings closest to the pump will survive a little longer. In this case. 1,and 2 rod bearings sized up. 3, and
4 spun. And took the bearing locking tabs off. Crankshaft, and rods for 3, and 4 are severely damaged. May not want to repair the
crank, and #3, and 4 rods.Rob. As to you're questions. Above should have answered 2 of them. Roller chain was a little loose. But
that's how roller chains run. Yes. The 4 lifters should have staid up. As they have check valves in them. I'm taking them apart to
see what happened. As to the HV oil pump. HV pumps generally have a 23, to 50 % longer pump gears. Thus pump 23, to 50 % more oil.

And take 23 to 50 % more HP to operate with the same amount of excess heat produced. Not more pressure. As to the 20 to 70 MPH

[Richard Michelhaugh]

There seems to be some misconceptions about engine bearings and oil pressure.

Our oil pumps are positive displacement pumps. They pump basically the same volume of oil per rev.
The pressure is generated by resistance to this flow. Bearing clearance and oil viscosity basically determine the resistance.
So given the same pump and oil viscosity, the oil pressure is proportional to the bearing clearance.
If you have larger bearing clearance, you can achieve the same oil pressure by using a higher volume pump.

Another misconception is that oil pressure determines the oil film thickness that our bearing journals are riding on.
This is not true. The film thickness is determined by viscosity, bearing width and rotational speed. Oil pressure is an indicator to whether the is
enough flow to dissipate heat and replace the oil that is leaking out of the bearing space. Notice the oil gallery holes are not on the same side as
the primary load bearing side of the bearing.

Lugging an engine increases the load on the bearings while at the same time reducing the film thickness by the slower rotational speed. This is the
recipe for high bearing wear and failure.

This is a simple description. There are many factors that play into this. Many of these factors change with engine speed and load, oil temp, etc, etc,
etc.

Trust me, Mother GM's engineers have spent a bunch of brain power and many years to determine bearing clearances, pump volumes and oil specs, etc. Go
by the GM specs unless you analyze your proposed changes taking into account these many factors and variables.

Rick M.




--
1974 26' Canyonlands
aka "The General"
Clinton, TN

[Bob Dunahugh]

Rick. Great job with you're description. I've talked to two GMC engine builders that told me that the have customer's that they've built engines for. Come back because the hot oil pressure is in the 35 to 45 PSI range on the road. But the hot idle is at 20 to 25 PSI range. And the owner thinks somethings wrong. The thing is that the oil pump at idle is running at 300 RPM's. On the road it's at 1400 RPM's. That's alot of difference with a fixed displacement gear pump.In the 60's, GM and many other companies remove most of the oil pressure gauges. And installed a light to indicate low oil pressure. Most of the lights came on when the oil pressure got to 7 PSI. The light solved two issues. 1 Most drivers didn't ever look at the gauge anyway. And if they did look at it. Didn't understand what the numbers meant. 2 With the red light on. It was a hint that maybe something was wrong. Or might be wrong. Now the companies use both a light, and a gauge. And then the gauge has just a L
for low. And a H for high. The L, and H keeps the customers off their backs. And only the manufactures know the values of L and H. A perfect example of that is the stock gauge, and sender in our GMC's. So with the light only. GM felt that at idle. Anything above 7 PSI was fine. And the engine was under their warranty. At idle there is vary little load. 10 to 15 PSI is fine. Remember the days of the oil dippers in car, and truck engines. They disappeared as compression went up.

[Kerry Pinkerton]

USAussie wrote on Sat, 13 June 2015 20:43
> As noted in an earlier email Dick Paterson uses Melling High Volume oil pumps,...


Dick also recommends the hardened steel shaft that drives the oil pump. Stock shafts can fail under the increased load of the HV pump. Have you
checked the shaft?

--
Kerry Pinkerton

North Alabama

77 Eleganza II, 403CI, Manny Brakes, 1 ton, tranny, lots of aluminum goodies.

77 Kingsley by Buskirk. Rear twins/dry bath, EFI Caddy.

Also a 76 Eleganza to be re-bodied as an Art Deco car hauler

[Robert Mueller]

Kerry,

The 455 I have in Humble was built by Dick so I would assume it has the hardened steel shaft. When I reassemble it I'll make sure it
is, thanks!

Regards,
Rob M.
The Pedantic Mechanic

-----Original Message-----

From: Kerry Pinkerton

USAussie wrote on Sat, 13 June 2015 20:43

> As noted in an earlier email Dick Paterson uses Melling High Volume oil pumps,

Dick also recommends the hardened steel shaft that drives the oil pump. Stock shafts can fail under the increased load of the HV
pump. Have you checked the shaft?

Kerry