13-1/2 to 1 compression ...on the street?
M.Burns
apparently has been at some statewide cruises, rod runs, etc, so I know it's
been driven. My question is, what kind of fuel must the owner be running for
the engine to survive. Heard claim that by retarding the timing somewhat,
pump gas with octane booster works(?) Race fuel? Any ideas (...from guys
familiar with similar cars or situations). Thanks
Nate Nagel
Need more info, what kind of engine? Cast iron or aluminum heads? Any
more details on the engine build will help us give you better answers.
I may not be able to directly answer your question, but I know enough to
know that you need to give more info :)
nate
--
replace "roosters" with "cox" to reply.
http://members.cox.net/njnagel
Pete C.
#2 diesel?
Mike
"M.Burns" <mhb...@cox.net> wrote in message
news:91QRj.30840$KJ1....@newsfe19.lga...
Why not ask the owner ? With a compression ratio that high I think you
wiil need race gas.
Steve W.
What engine and what type of heads? What cam & lifters?
If it has aluminum heads and the proper cam it probably would run just
fine on 93 octane with water injection and playing with the timing some.
--
Steve W.
Scott Dorsey
How old is it? If it's old enough to run without a catalytic converter,
100LL aircraft fuel should be okay on the street. May not be high enough
octane.
The "octane booster" in a bottle stuff is usually just MTBE. You can also
still get tetraethyl lead.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Stan Weiss
Cast iron or aluminum heads?
Camshaft spec.'s
Carb or EFI
What might also help is what is the cranking compression of the engine
(Do a Compression Test)
wstiefer
spamT...@yahoo.com
I know a bit about cars, but not why the ?? about Al heads is
important- is it the fact it's Al and not cast iron, or just that Al
heads are likely to be better engineered?
Dave
N8N
Aluminum heads shed heat to the cooling system better than do cast
iron. You'd think that this would be a disadvantage, but in a high-
compression engine, it helps to prevent detonation. I have heard as a
rule of thumb that aluminum heads, all other factors being equal,
allow you to safely run a half point more compression on the same
octane fuel than do cast iron.
nate
Stan Weiss
As Nate said "Aluminum heads shed heat"
"all other factors being equal, allow you to safely run a half point
more compression on the same octane fuel than do cast iron."
But since most Aluminum heads are after market or late model factor
design and most are some what better engineered / more efficient
combustion chamber design, they can run more compression.
John Kunkel
"wstiefer" <wsti...@sbcglobal.net> wrote in message
news:Nl0Sj.12289$2g1....@nlpi068.nbdc.sbc.com...
>
Alcohol
My thought, too. If the CR is actually that high I can't see it ever running
on pump gas regardless of the heads, cam, etc.
HLS
Having driven a high powered high compression car on the street for a few
years,
I will say that it is not always as much fun as one thinks it might be.
Others have already posted that it depends upon the engine, timing, etc.
In my case, the car's cooling system was marginal for that type of engine,
and
that added to the distress.
I had to run 98 octane at all times, and was running less compression than
this car.
It just wasnt a pleasure at all.
But the suggestion to ask the present owner what is involved is a good one.
Steve W.
> "wstiefer" <wsti...@sbcglobal.net> wrote in message
> news:Nl0Sj.12289$2g1....@nlpi068.nbdc.sbc.com...
> Alcohol
>
> My thought, too. If the CR is actually that high I can't see it ever running
> on pump gas regardless of the heads, cam, etc.
>
>
Why not? NASCAR runs 12.5:1 on 98 octane using iron heads. They ran 13:1
on the old 105 octane leaded fuel. I have run 13:1 on pump gas with
aluminum heads on a 427 with a set of Rhodes lifters to drop the cam
down some. No problems at all.
--
Steve W.
N8N
> John Kunkel wrote:
> > "wstiefer" <wstie...@sbcglobal.net> wrote in message
I would think the Rhodes lifters would actually hurt, not help -
they'll improve idle quality but at the cost of increased low RPM
cylinder pressures. or am I thinkin' wrong?
I will say that at anything over 10.x:1 you probably need to have
someone GOOD (not me!) tune the engine to avoid an inadvertent
detonation incident.
nate
(currently running 10.25:1 with iron heads - stock 63-64 spec
Studebaker R1 engine...)
Steve W.
No real pressure increase. You just need to play with the bleed rate
some. Mine was set up to "hide" the real power of that engine. The only
problem I ever had with it was that I kept putting my foot through the
firewall....
Tuning of a true HP engine is an art. Not something you get from books
or online.
--
Steve W.
Near Cooperstown, New York
Nate Nagel
OK, so you tuned down the rumpity idle some... but how do you tune out
that "sharp" exhaust sound that you only get with high compression or a
blower?
nate
(appreciates stealth performance)
Steve W.
Tuned the collectors, Installed an H pipe and used 4 mufflers. The first
two were custom made and designed kind of like a straight through with
concentric baffles(like a silencer). Behind the baffles were channels
that allowed the exhaust to cancel out those hard notes. These fed into
a normal pair of flowmasters.
Until you really climbed on the loud pedal it sounded just a bit warmer
than stock. Surprised more than a few folks.
Dyno
Don Stauffer in Minnesota
But why retard timing on a performance car. That handicaps it
seriously, and can lead to overheating and other problems. Yet it
takes a LOT of octane to run that kind of CR. I would think alcohol
would be the fuel of choice. If it has a carb, conversion for alky is
easy. Not so easy with FI.
John Kunkel
"Steve W." <csr6...@yahoo.com> wrote in message
news:fvaki8$v7k$1...@aioe.org...
> John Kunkel wrote:
>> "wstiefer" <wsti...@sbcglobal.net> wrote in message
>> news:Nl0Sj.12289$2g1....@nlpi068.nbdc.sbc.com...
>> Alcohol
>>
>> My thought, too. If the CR is actually that high I can't see it ever
>> running on pump gas regardless of the heads, cam, etc.
>>
>>
>
> Why not? NASCAR runs 12.5:1 on 98 octane using iron heads.
Your local stations have 98 octane "pump gas"?
Iron heads? Not likely
Steve
It depends on a lot of things. How radical is the cam? If its a HUGE cam
with a ton of overlap, then the actual compression pressure might be
manageable enough to live on pump premium with a mild octane booster.
Same if it has aluminum heads with polished chambers- that will reduce
octane requirement, but as deposits build up as the engine is run the
octane requirements can creep back up.
But at 13.5:1 (assuming that it was computed correctly, most people tend
to over-estimate the true compression when they build an engine) then it
would be pretty hard to make it live on pump gas.
Retarding the timing is a band-aid, and not a good idea. It makes the
exhaust valves run cherry-red hot all the time and can cause valve seat
recession and burned valves.
Steve
Look up the thermal conductivity of iron vs aluminum. Aluminum carries
the heat away from the inner surfaces of the combustion chamber and to
the coolant MUCH faster than iron, to there are fewer hot-spots to
initiate detonation.
Steve
> As Nate said "Aluminum heads shed heat"
> "all other factors being equal, allow you to safely run a half point
> more compression on the same octane fuel than do cast iron."
>
> But since most Aluminum heads are after market or late model factor
> design and most are some what better engineered / more efficient
> combustion chamber design, they can run more compression.
There are a lot of REALLY shittly-engineered aluminum heads available,
too. They're not in any way guaranteed to be better than well-prepped
stock iron heads in terms of chamber design, but they will still have a
thermal conductivity advantage.
Stan Weiss
Steve wrote:
>
> M.Burns wrote:
> > Looking at a nice Pro Street car with 13.5 to 1 compression pistons. It
> > apparently has been at some statewide cruises, rod runs, etc, so I know it's
> > been driven. My question is, what kind of fuel must the owner be running for
> > the engine to survive. Heard claim that by retarding the timing somewhat,
> > pump gas with octane booster works(?) Race fuel? Any ideas (...from guys
> > familiar with similar cars or situations). Thanks
> >
> >
>
> It depends on a lot of things. How radical is the cam? If its a HUGE cam
> with a ton of overlap, then the actual compression pressure might be
> manageable enough to live on pump premium with a mild octane booster.
explain to me how overlap and not IVC will effect low rpm cylinder
pressure?
mr.som ting wong
color if they are tan all is good
Steve
>
> Steve wrote:
>> M.Burns wrote:
>>> Looking at a nice Pro Street car with 13.5 to 1 compression pistons. It
>>> apparently has been at some statewide cruises, rod runs, etc, so I know it's
>>> been driven. My question is, what kind of fuel must the owner be running for
>>> the engine to survive. Heard claim that by retarding the timing somewhat,
>>> pump gas with octane booster works(?) Race fuel? Any ideas (...from guys
>>> familiar with similar cars or situations). Thanks
>>>
>>>
>> It depends on a lot of things. How radical is the cam? If its a HUGE cam
>> with a ton of overlap, then the actual compression pressure might be
>> manageable enough to live on pump premium with a mild octane booster.
>
> explain to me how overlap and not IVC will effect low rpm cylinder
> pressure?
You obviously understand the issue. IVC timing is the key event that
controls low RPM cylinder pressure. But late IVC which lowers cylinder
pressure usually goes hand-in-hand with a bunch of overlap, so the slang
creeps in. Lots of overlap means that the IV has to stay open even
longer after the EV closes for optimum cylinder filling at high RPM, so
it leads to lower pressure at low RPM.