What kind of oil?
Quang Ngo
I have a datsun 260Z year 74. It has 2 round carburators (I think
that's what they are called). Each has a cap on it which I can be turned
to open/close. Oil is supposed to be in there. I notice the oil
is almost empty. What kind of oil do I put in these things? I stopped
Kragen's Auto Parts store over here where I live and asked the guys and they
had no idea.
Thanks,
--
__ _ _ ________________________________________________
/ \ | \| | / /_
/ /\ \| \ | / Computer Science Department of CSUFresno, Ca. / /
\ \/ /| \ | / Internet: qu...@yosemite.CSUFresno.EDU / /
\__ \|_|\_|go /_______________________________________________/ /
\_\uang /_______________________________________________/
Larry Harris
>I have a datsun 260Z year 74. It has 2 round carburators (I think
>that's what they are called). Each has a cap on it which I can be turned
>to open/close. Oil is supposed to be in there. I notice the oil
>is almost empty. What kind of oil do I put in these things? I stopped
>Kragen's Auto Parts store over here where I live and asked the guys and they
>had no idea.
These are oil bath air filters. My friend has these on his '71 240, but
I forget what oil he uses in them (It seemed like a heavy weight if I
remember correctly), but he found out by asking at a Nissan dealer.
--
-Larry Harris- | '86 Mustang lx 5.0 notchback
lha...@hubcap.clemson.edu | Meyer's Tow'd Dune Buggy
lha...@clemson.bitnet | OS-9, a leaner meaner UNIX
Clemson Computer Engineering | RUSH, YES, R.E.M, The Who
David Basiji
>qu...@YOSEMITE.CSUFRESNO.EDU (Quang Ngo) writes:
I don't think so. As I recall, those carbs use a variable venturi system,
increasing venturi size with increased manifold vacuum. The oil acts to
damp venturi movement during rapid changes in manifold vacuum and counteracts
the momentum of the venturi piston to keep the engine from bogging down
during fast stomps on the accelerator. I'd call a Datsun racing conversion
shop and ask them what they recommend.
Dave
Paul Harvey
during acceleration.
Straight SAE-30 is what you want.
These carbs are the sore spot for 260Z's. They eventually wear
out the throttle bushings and the air leak makes the idle
erratic and degrades performance. Parts are not available, so
the usual solution is to use the 70-72 carbs which are smog
legal in CA.
The Z-club used to have a 74-73 carb tossing contest to provide
members with something to do with these carbs.
These carbs are variable venturi by the way, and are on many
old British cars(SU). Most people are surprised to hear that someone
needs oil for their carbs, the Kragen person probably thought
you were nuts!
Paul Harvey
A thiner oil, say SAE 20, will give you less acceleration enrichment
which will increase your gas mileage and decrease acceleration,
or a thicker oil, say SAE 40, will give you more enrichment with
better acceleration and lower gas mileage.
The ideal is probably the point were you get no hesitation while
accelerating, SAE-30.
Use only straight weight oil, no 10W-30! You want the oil to thicken
at low temps and thin at high!
There are little marks on the dipstick, fill to the top mark.
If you have to replace the oil frequently, you have a leak and
this is probably an indication that the carbs are on their last leg.
Ken R. Dye
>qu...@YOSEMITE.CSUFRESNO.EDU (Quang Ngo) writes:
>
>
>>I have a datsun 260Z year 74. It has 2 round carburators (I think
>>that's what they are called). Each has a cap on it which I can be turned
>>to open/close. Oil is supposed to be in there. I notice the oil
>>is almost empty. What kind of oil do I put in these things? I stopped
>>Kragen's Auto Parts store over here where I live and asked the guys and they
>>had no idea.
>
>These are oil bath air filters. My friend has these on his '71 240, but
>I forget what oil he uses in them (It seemed like a heavy weight if I
>remember correctly), but he found out by asking at a Nissan dealer.
Nope, the carbs in question are "SU" carbs. I'm suprised
none of the UK dudes followed up on this. Trivia time: What
does SU stand for?
SU carbs use a variable sized venturi to maintain
a constant velocity of airflow through the venturi. The oil
is used as damping fluid to slow the opening of venturi
during acceleration. This increases, temporarily, the speed
of the air through the venturi and enriches the mixture
(basically taking the place of an acceleration pump on
a non-SU carb).
During the winter, a thinner oil is recommended (some
use ATF fluid). For the summer, I'd expect 20 or 30 weight
to work out OK.
The people who are really in the know are across the pond.
Any U.K. SU dudes want to let us in on the hot setup?
--Ken
--
Ken R. Dye an optimist is a guy |
Interactive Systems Corp., Chicago that has never had |
(800) LAI-UNIX x341 much experience |
d...@i88.isc.comm archy |
Mike Hejl
>
>
>>I have a datsun 260Z year 74. It has 2 round carburators (I think
>>that's what they are called). Each has a cap on it which I can be turned
>>to open/close. Oil is supposed to be in there. I notice the oil
>>is almost empty. What kind of oil do I put in these things? I stopped
>>Kragen's Auto Parts store over here where I live and asked the guys and they
>>had no idea.
>
>These are oil bath air filters.
Bzzzt - you loose. These are "dashpots" (British phraseology, right?) for
the SU-type carbs. They damp the piston/jet movement to keep the engine from
running too rich/lean. Use ATF and don't overfill them: it only takes a couple
cc.
Of course, since you don't know if it is a carb, I don't know if my answer is
correct :-)
Besides, stock 240/260s never used "oil bath" filters.
--
+=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=+
| Mike Hejl NEC America, Inc. Switching Systems Division Irving, Texas |
| he...@ssd.dl.nec.com I don't even speak for myself, much less NEC... |
+=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=+
Mike Hejl
>These carbs are variable venturi by the way, and are on many
>old British cars(SU).
The 240/260 carbs are clones of the SU and Stromberg carbs (more closely
resemble SUs) made by Asian (I think).
As you stated, throttle shaft wear is a *big* problem. However, I have had
*very* good luck with replacing (or installing) bushings for the throttle
shaft on SUs. At one time, reamers, bushings, and oversized throttle shafts
were available from Victoria Brittish, Moss, Roadster Factory, etc. The
reamers were used to enlarge the hole in the body (which originally did *not*
have bushings; hence the wear) to accept the bronze bushings. If the bore
wasn't too bad, you could use a .002" oversized shaft.
Does anyone make bushings/shafts to fit the Z carbs?
Lawrence Buja
> Nope, the carbs in question are "SU" carbs. I'm suprised
>none of the UK dudes followed up on this. Trivia time: What
>does SU stand for?
>
>Any U.K. SU dudes want to let us in on the hot setup?
This was posted on the british-cars group:
-------------------------------------------------------------------------
>From: gar...@theory.TC.CORNELL.EDU (Roger Garnett)
>Date: Thu, 1 Aug 1991 14:26:45 EDT
>Subject: Re: lever shock oil (again?)
Here's a chart of some acceptable, available fluids for your British car:
{NOTE: as always, check the specs for your car!}
Brake and Clutch
DOT4 (DOT4 should be flushed and replaced at 2-3 yr intervals)
-Castrol LMA -Low Moisture Absorbant, easy on seals
-Girling
DOT5 (Silicone) Doesn't absorb water, or remove paint.
Can be a bit harder to get the air out, and may
be more prone to boiling in heavy braking usage.
Fantastic for long term storage -Good for 5+++ years.
(Do not mix DOT4 and DOT5. Do not use DOT3 -it WILL rot your seals.)
Hydralyic Lever Arm shocks -This must be an hydraulic oil designed for
this application, with anti-frothing additives.
-OEM Girling or Lockheed Shock oil, if you can find it.
-Motor Cycle Fork oil.
-Castrol Fork Oil. Available in 20 & 30 wt. (30 works good)
-90 Wt Gear oil or STP. For really stiff shocks (competition use.)
Carburetor Piston Dampers
-Solex Carb Damper oil, availble from some mail-order places.
-For light damping:
-Marvel Mystery Oil (very good for this application)
-Automatic Trans Fluid
-3 in 1 oil
-For heavier damping:
-20 or 30 wt Engine Oil
-20-50 wt Engine Oil
Manual Gearbox (Check your specs! Some cars specify Hypoid gear oil, some
engine oil, and others, others!)
90 or 85-140 Hypoid Gear oil -For required high shear strength usage.
75-90 GL5 MTL (Redline synthetic)
30 wt, non-detergent, or engine oil (MGB Spec)
Automatic Trans Fluid -This can be good for short term usage, to
clean things out & free sticky syncros. May be prone to
more leakage. Speced for some newer gearboxes.
Rear Differential -usually a high shear strength "Hypoid Gear Oil"
90 wt, or 85-80.
Some older cars require STRAIGHT 140wt.
Steering Gear- Usually a 90wt Hypoid Gear Oil is good.
(this is not for power steering, which use a variety of fluids)
Wheel Bearings -use a high quality, high tempature bearing grease. ie:
-Castrol wheel bearing grease.
Grease fittings- (the stuff you use your grease gun for)
-Lithium Grease
Trunion Fittings (TR's and others)
-90 wt Oil. (Not Grease) - an application method:
Rather than fill the cartridge with oil, invert the top of the gun
with the lever, fill the depression with oil and pump away.
Cooling System
50-50 mix of water and Anti-Freeze is best for *most* applications.
This offers the best Anti-Corrision, Anti-Freeze, and Cooling
capibilities.
If you have an Aluminium head or block, you may need an
anti-freeeze speced for use with Al.
-Water with a corrosion preventing additive.
Battery
Top up cells with distilled water. Do not use tap water.
Operator
Usually a good stiff Ale will do the job. Preferences vary.
________
/___ _ \ Roger Garnett (gar...@BATCOMPUTER.TC.CORNELL.EDU)
/| || \ \ Agricultural Economics | South Lansing Centre For
| |___|| _ | 3 Warren Hall | Wayward Sports Cars
| | \ | | | Cornell University | (Lansing, NY)
\| \ |__/ / Ithaca, N.Y. 14853 | Safety Fast!
\________/
Lawrence Buja
>Any U.K. SU dudes want to let us in on the hot setup?
This was posted on the british-cars group:
-----------------------------------------------------------------------
>From: gar...@theory.TN.CORNELL.EDU (Roger Garnett)
>Date: Tue, 9 Apr 1991 13:01:59 EDT
>Subject: SU Tuning, updated
Next:
On Apr 8, 3:23pm, Daniel J. Dasaro wrote:
} Can I get this car in tune with no more than a Unisyn?
You bet! You don't even need a Uni-Syn, just a piece of vacumn line and
your ear will do the trick. Which means, that it's about time for a
posting of how to twiddle SU's. Hmm- it's been a year since I updated this,
and I've been promising to add Type HIF info. So, here it is, the new,
SU-it-yourself proceedure.
***************************************************************************
Tuning Your S.U. Carbs
-Roger Garnett Rev. 4/9/91
Well, it's not really that hard to set up SU's, just different. Of course
it always gets more interesting when you have more than one...
There is a very good Haynes SU carb manual available, reccommended reading.
The basic syncing process also applies to Zenith-Stromberg's, but the adjustment
mechanisms are different. Here is a laymans guide to adjusting SU's (long):
step 1- Tune up the rest of the engine- REALLY! clean or replace, and set
the points, set the timing, plugs, valve lash, and remove the air filters.
(have new ones ready) All of these things can affect the setting of the
carbs, which should be done LAST, (if at all). The carbs rarely need to be
adjusted, once set. Also replace/install the gas filter. Of course, it helps
if the carbs are in good mechanical condition as well. But you can consider
a rebuild once you have gotten things working first!
step 2- clean the carbs! use gum-out or similar stuff, clean all external
linkages, shafts, and stuff.
step 3- Remove the float bowl covers, clean the float bowls, remove old
sediment, and check/adjust the float setting. (turn the cover upside down,
and get a *1/8" in drill bit, set the drill bit accross the cover, the float
tab should just touch the bit.) Make sure the needle is moving and seating
properly. This is just like *most* floats. Replace the cover.
* This is for HS4 SU's- (1/8-3/16") if you are dealing with 1",
H's, HS2's HS6's, HIF's, etc.- check the spec for your carb.
Note: You can check for matching float settings, after setting the
mixture, by removing the pistons, and peering down at the jets.
The fuel level should be about the same on both carbs, a little
below the top surface of the jet. (After car has been run only)
step 3b- Go get a pint of ale, or something close, and set it nearby.
step 4- Remove the piston covers. CAREFULLY remove the piston, DO NOT
BEND THE NEEDLE. Set the piston down on a clean wadded rag to prevent
rolling. Clean the inside of the carb. Check operation of the throttle.
Check the throttle shaft slop- this is the most common place for wear
on an SU, and is often where air/vacumn leaks occur. The bushings and
shafts can be replaced, but it requires some machining. A small amount
of leakage can be tolerated, the car just won't idle as evenly.
Clean the piston. Stare in awe at the odd carborator design, simple and
effective, (constant velocity). Dump the old oil out of the damper if
you haven't already spilled it. clean. Reassemble, check piston movement,
raise it, then let go, it should fall freely. If not, check assembly
again, make sure the piston isn't binding against the carb body, it should
ride only on the damper shaft. Do not strech the spring. When all is operating
properly, fill the damper with Marvel Mystery Oil for light damping, or use
motor oil for heavier damping. (I use MMO) If you get "flutter" on,
acceleration, you might try the heavier oil.
step 5- Start the car and warm it up, then turn off/disconnect/otherwise
disable the choke mechenism. (Loosen the nuts on the clamps so that the
choke stuff isn't doing anything) This will get set later.
(Later Zenith-Strombergs have a thermostatic choke, not a cable.)
step 6- Check coarse throttle adjustments- make sure the throttle cable
pulls on both carbs equally, and returns completly when released. This
is adjusted by loosing the set screws on the throttle shaft and matching
the two sides. You can also adjust the cable length at this time, using
the cable set screw/retainer at the end of the cable. You can check the
float adjustments now by removing the piston & cover, and looking at the
fuel level in the needle seats. Both carbs should be about even, a little
below the top surface of the jet. If not, readjust one or both floats to
match the level.
step 7- Syncronize the throttles- if you have a uni-syn, here's your
chance to use it, (or other air flow guage), if not use a tube and listen
to the airflow. The Uni-Syn is much easier to use, and can result in
better balance. Alternatly adjust the idle screw on each carb, attempt
to set the idle as low as possible (~800-1000 RPM). Adjust until the
airflow is *close* to the same at each carb. The engine may now be running
rough, just keep the idle speed high enough to keep running. Give the
throttle a quick snap to make sure everything is settled, then check
sync again. Periodicly snap the throttle to make sure everything is seated.
Large differences in where you can adjust the two carbs may indicate
air/vacumn leaks, or other problems, such as a bad valve)
Magic Time- Relax, and shake your voodoo rattle...
step 8- Adjust the mixture- this is done with the spring-loaded hex fitting
under the carb, where the fuel supply tube enters from the float. Turning the
fitting raises and lowers the needle seat. Pick a carb, and turn the fitting 3
flats (1/2 turn), first in one direction, then back 3, then 3 in the other
direction. Note where the engine runs better, idle speed should increase.
Turn to the best setting. Repeat this proceedure until you get the best
operation you can, (higest idle speed), keeping track of flats turned will
help you remember where you were. If you get lost, turn all of the way in,
then back out 12 flats and start again. Periodicaly snap the throttle and
push up on the fitting to make sure everything is seated.
Note: Type HIF carbs (With integrated float bowl) no longer have
the hex nut to adjust the mixture. Instead, there is a screw to twiddle,
on front of the front carb, and behind the rear. The screw is connected
to the needle seat through a temperature compensated gizmo, which is
said to make the carbs more stable. Adjustment can be done in much the
same way, by counting turns/flats of your screwdriver. There is less
adjustment range than with the the basic models.
When you think you're close, stop, uncramp your fingers, breath deep,
and do the same to the other carb. Then retune the first carb, and then the
second again. This serves to match the mixture of the 2 carbs, and prepare
you for the beer sitting over there in the sun. (why do you think the British
drink warm beer?)
step 9- repeat step 7, setting the idle speed as low as possible, and
re-syncing the idles. Now go back and readjust the mixtures. After a couple
of iterations, the engine should be running smoothly (controlled by mixture)
and at a low idle. Repeat as necessary. Set the final idle to 800-1000 RPM,
depending on the condition of the rest of the engine.
step 10- DRIVE! Take a quick spin up the lane, you need the reward of driving
a properly tuned car.
step 11- Adjusting the choke- I won't get into the temperature compensation
in the type HIF, or the Thermostatic choke in the later strombergs.
Check the manual for more info.
The choke is supposed to do two things; the first half of travel moves a
cam on each carb which opens the throttle, for warm up. The second half
pulls down on the needle seat to enrichen the mixture, for starting.
Start with the choke in the off position (knob in). Adjust the
so that the cam only starts moving the throttle after you start pulling
out on the cable (adjust with shafts and adjusting screws). Try to get both
carbs adjusted the same, so that both screws begin to hit the cam at the
same time. This is not real critical, but you can use your Uni-Syn to
match air-flow on both sides, with the choke partly engaged.
After the cable is about halfway out, it should start engaging the
lever which pulls down on the needle seats. Adjust the linkages so both
carbs are acted on equally. You can do this by adjusting for even running
of the engine. Of course, for a warm engine, the richness of this mixture
will cause some roughness. Make sure the needle seats return freely
when you release the choke.
step 12- Drink that warm beer (only one, no DWI now...) it will taste great
at this point!, go wash up, and go for a ride.
The first time through carb adjustments can be confusing, once you've done
it, all of the stuff in the manuals makes sense. Go back and read them again-
As always, I reccommend Bentleys, which is a repro of the original factory
manuals, and then Haynes, and throw out the Chiltons. (orginal factory manuals
are to be read in a clean enviroment, repros are for smearing grease all over,
except, if that's all you got, use it!) Haynes has an excellent manual just
for SU carbs, it covers operation, theory, rebuild of all models, and has
needle charts for hundreds of car/engine/carb setups. They also have a
manual for Zenith-Strombergs, which, while similar, are a whole 'nother beast.
******************************************************************************
Anybody who publishes this is required under penality of leaky throttle
shafts to give credits, and send or bring a copy to me at the below address!
Roger Garnett
________
/___ _ \ | South Lansing Centre For
/| || \ \ | Wayward Sports Cars
| |___|| _ | | 39 Ridge Rd. Lansing, NY, 14882
| | \ | | | | Rte. 34B, near the intersection of Rte. 34.
\| \ |__/ / |
\________/ | SAFETY FAST!
Frank Mallory
LH> >that's what they are called). Each has a cap on it which I can be
LH> turned
LH> >to open/close. Oil is supposed to be in there. I notice the oil
LH> >is almost empty. What kind of oil do I put in these things? I
LH> stopped
LH> >Kragen's Auto Parts store over here where I live and asked the guys
LH> and they
LH> >had no idea.
LH>
LH> These are oil bath air filters. My friend has these on his '71 240,
LH> but
LH> I forget what oil he uses in them (It seemed like a heavy weight if I
LH> remember correctly), but he found out by asking at a Nissan dealer.
NO - NO - NO! Evidently he has the Jap equivalent of the SU carbs; what he
is referring to is the fittings on top of the dashpots. Engine oil is correct
for the SUs, and presumably is correct for the Jap equivalent as well.
* Origin: Silver Bullet - Silver Spring, Md. - 301-622-2247 (1:109/417)
Frank Mallory
KR> none of the UK dudes followed up on this. Trivia time: What
KR> does SU stand for?
Skinner Union (I think -- it's been awhile!)
Codesmiths
> In article <1992Jan31.1...@hubcap.clemson.edu> lha...@hubcap.clemson.edu (
Larry Harris) writ
> es:
> >qu...@YOSEMITE.CSUFRESNO.EDU (Quang Ngo) writes:
> >
> >
> >>I have a datsun 260Z year 74. It has 2 round carburators (I think
> >>that's what they are called). Each has a cap on it which I can be turned
> >>to open/close. Oil is supposed to be in there. I notice the oil
> >>is almost empty. What kind of oil do I put in these things? I stopped
> >>Kragen's Auto Parts store over here where I live and asked the guys and they
> >>had no idea.
> Nope, the carbs in question are "SU" carbs.
Close but not quite. On a Japanese car, chances are that they are
Hitachi carbs. These are a sliding piston design almost identical to
the SU. Fill the dampers with light machine oil (3-In-1 or similar).
It only needs a teaspoon of oil, and you should be able to feel the
oil damping effect if you gently move the piston rod up & down. Do
*not* fill them right up.
Be careful when unscrewing & removing the plastic caps. They're quite
brittle plastic & the threads are easily stripped.
For oil bath air filters (pre 1970 usually), wash them out with
petrol & soak them with engine oil.
For K&N oiled paper filters, only use K&N filter oil.
When the hell did people start using oil in Triumph trunnions ?
That might work in Arizona or Nevada, but in the soggy climate
of the UK, it's asking for trouble with seized pivot bolts.
Andy Dingley din...@cix.compulink.co.uk +44 91 230 1695
Ken R. Dye
>In-Reply-To: d...@i88.isc.com (Ken R. Dye )
>
>> In article <1992Jan31.1...@hubcap.clemson.edu> lha...@hubcap.clemson.edu (
>Larry Harris) writ
>> es:
>> >qu...@YOSEMITE.CSUFRESNO.EDU (Quang Ngo) writes:
>> >
>> >
>> >>I have a datsun 260Z year 74. It has 2 round carburators (I think
>> >>that's what they are called). Each has a cap on it which I can be turned
>> >>to open/close. Oil is supposed to be in there. I notice the oil
>> >>is almost empty. What kind of oil do I put in these things? I stopped
>> >>Kragen's Auto Parts store over here where I live and asked the guys and they
>> >>had no idea.
>
>> Nope, the carbs in question are "SU" carbs.
>
>Close but not quite. On a Japanese car, chances are that they are
>Hitachi carbs. These are a sliding piston design almost identical to
>the SU. Fill the dampers with light machine oil (3-In-1 or similar).
>It only needs a teaspoon of oil, and you should be able to feel the
>oil damping effect if you gently move the piston rod up & down. Do
>*not* fill them right up.
OK, one person mailed me with the correct answer,
"Skinner's Union". The carbs that came with 240-260 Z cars
and SSS 510's are made by Hitachi, of course. I suppose I
should have said "SU-type", but was under the impression that
the term SU had grown to incorporate all carbs of that type
(kinda like Kleenex being the generic name for facial tissue).
I suppose calling the downdraft "predator" variable-venturi
carb an SU would be pushing it.
Did Stromberg and Hitachi have to pay royalties to SU?
Bob Spidell
>Nope, the carbs in question are "SU" carbs. I'm suprised
>none of the UK dudes followed up on this. Trivia time: What
>does SU stand for?
Skinner Union.
Peter Sheriff
Sorry I missed the original posting.
The S.U. plant is in my home town (Birmingham, England). It really
was an old tannery before the advent of the automobile. The outside of
the factory still has the look of those built prior to and during the
industrial revolution. At least it did when I last saw it which was over
twenty years ago now.
If I remeber correctly, Matthew Boulton had his leather O-rings and
assorted gaskets made at the Skinners Union plant for his steam driven
mine pumps.
The person who stated that 3-in-1 oil was good for SU carb damping
pistons was basically correct. You can, however experiment with oils
of lighter or heavier weight to give slightly different responses. It
is a hit and miss thing and the results are probably subjective. I
experimented with oils and different needles on my old Mini Cooper
for five years until I left the UK. I probably would still be experimenting
now if I still had that car:-)
Pete
Bob Spidell
>
>lha...@hubcap.clemson.edu (Larry Harris) writes:
>
>>qu...@YOSEMITE.CSUFRESNO.EDU (Quang Ngo) writes:
>
>
>>>that's what they are called). Each has a cap on it which I can be turned
>>>to open/close. Oil is supposed to be in there. I notice the oil
>>>is almost empty. What kind of oil do I put in these things? I stopped
>>>Kragen's Auto Parts store over here where I live and asked the guys and they
>>>had no idea.
>
>>I forget what oil he uses in them (It seemed like a heavy weight if I
>
>increasing venturi size with increased manifold vacuum. The oil acts to
>damp venturi movement during rapid changes in manifold vacuum and counteracts
>the momentum of the venturi piston to keep the engine from bogging down
>during fast stomps on the accelerator. I'd call a Datsun racing conversion
>shop and ask them what they recommend.
Dave is correct. Early 'Z-cars' used SU carburetters which are variable
venturi type, as he accurately described. Later models use SU copies
made by Hitachi. Most manuals recommend 20W-50 oil, but some British
car mechanics (many older British cars use SU carbs) swear by ATF
(automatic transmission fluid). I've tried 20w-50, straight 30W,
straight 50W and ATF and couldn't tell the difference. If the cap
on the dashpot has a small hole then fill 1/2 inch above the inner
piston guide, if there is no hole then fill to 1/2 inch below the
inner piston guide (unscrew the cap, and you'll see what appears to
be a hollow tube inside another hollow tube; the inner tube is the
piston guide).
Regards,
bs
Jonathan R. Lusky
>
>
>>I have a datsun 260Z year 74. It has 2 round carburators (I think
>>that's what they are called). Each has a cap on it which I can be turned
>>to open/close. Oil is supposed to be in there. I notice the oil
>>is almost empty. What kind of oil do I put in these things? I stopped
>>Kragen's Auto Parts store over here where I live and asked the guys and they
>>had no idea.
>
>These are oil bath air filters. My friend has these on his '71 240, but
>I forget what oil he uses in them (It seemed like a heavy weight if I
>remember correctly), but he found out by asking at a Nissan dealer.
>
throttle is opened quickly. This effectively richens the mixture. It's
the constant velocity carb equivalent of an accelerator pump. I'm not
sure what weight oil belongs in them, to some degree its a matter of tuning.
One thing to note, tho, is that just because the car is a 74 260Z doesn't
mean it has 74 model (Hitachi) carbs. Most of the 73 & 74 Z's I have seen
have early model (1972) SU Carbs.
Peter Sheriff
The heavier weight oil will not need to be topped up so often but
using too heavy a weight will affect throttle response. Best to find
an oil that gives good throttle response and just top it up more often.
3-in-1 was always the good starting point for finding the right oil.
Pete
Gary Goodlund
How often should the Hitachi(S.U.clone) carbs need this oil replenished?
My '72 240-Z has about 135K miles on it so I'm sure the wear on the throttle
shafts and carb bodies is causing increases over the normal consumption.
Also,...I was told when I bought this car three years ago (by the previous
owner) to use "Marvel Mystery Oil" or "3-in-1 Oil". It would that if 30wt
is actually the correct choice, then maybe this is why these carbs seem to
suck this stuff up so fast.
Who knows--maybe it's just one of those mysteries of life.:^)
'later,
Gary
Mike Hejl
>...another question for the masses:
> How often should the Hitachi(S.U.clone) carbs need this oil replenished?
I'n not real shure about the Hitachi SU clones but my old SUs rarely needed
"topping off". However, the Strombergs were notorious for this: they had a
small o-ring seal at the bottom of the bore that fit around the jet holder.
This o-ring was essentially non-replaceable: the jet holder was held at the
bottom of the bore with one of those one-way spring steel clips (what the
hell do you call those?). Consequently, I've never seen a Stromberg that
would maintain the dashpot oil for any length of time: the oil is sucked,
under manifold vacuum, past the o-ring in only a short time. This is also
the main reason that the diaphrams in the Strombergs go bad (SUs and the
Hitachis don't have diaphrams). The SUs, on the other hand, have a simple
blind hole for the bore with no "out" for the fluid except at the top.
>My '72 240-Z has about 135K miles on it so I'm sure the wear on the throttle
>shafts and carb bodies is causing increases over the normal consumption.
This won't cause the symptom you're observing. It will cause other problems,
however.
Ben Hodson
Paul Witting
For the record, its eazy to tell. The early carbs are very simple.
The 73/74 carbs are a nightmare. When I bought the 73 I was amazed
and decided that there was no way they stayed (Fortunately I had both
72 SU's and Triple Webers to choose from B-) I literally gave up
trying to unbolt the 73 carb set-up and and brought out a hacksaw.
The 73's seemed to have a squared off tower, as well.
Also, anybody familiar with these things, the 73 seems to be a real
dog, even w/ the Webers and Headers. I stripped the engine down,
cleaned all the oil paths. etc (Including removing some cheesecloth
stuff from the camshaft, perhaps an impromptu oil cap that got sucked
in. ) New gaskets, Valve timing reset, everything, but still she is
slow.
I figure its one of two things:
-The cam is dead, perhaps run without oil or with a clogged
oil sprayer. No lift = no power
-The head has MUCH lower compression.
I tried to check Nissan Parts about the Heads, but they listed 4 heads
for 72 alone.
Any chance a 72 head will bolt right to a 73 engine? They are both
L24's, right?
paul
--
___________________________________________________________________________
Paul Witting | "In Jersey everythings legal, | Hawk GT
alias | as long as you don't get caught" | Datsun 240Z
The Shaggy man | DoD #999 -Traveling Wilburys | CRX Si
---------------------------------------------------------------------------
Michael Michels4597693
Fill the dash pot with the same oil that you have in the sump. In the
winter it's lighter, in the summer it's heavier.
If you overfill it, not to worry, stick your finger down the throat, lift
the piston until the oil shoots out the hole in the damper shaft head, then
let the piston drop. The piston should go clunk when it hits bottom or
you have an alignment problem.
Andrei Chichak
c/o the above address
'62 morris traveller (Mini station wagon with wood trim) Cooper S ized
Donald P Perley
>I don't think so. As I recall, those carbs use a variable venturi system,
>increasing venturi size with increased manifold vacuum. The oil acts to
>damp venturi movement during rapid changes in manifold vacuum and counteracts
>the momentum of the venturi piston to keep the engine from bogging down
>during fast stomps on the accelerator. I'd call a Datsun racing conversion
>shop and ask them what they recommend.
That's sort of right. When you stomp on the gas it keeps the piston
down momentarily. During that time, you are running with a smaller
ventury, and higher air velocity than "normal" for that flow, so the
mixture is rich. It acts in place of an accelerator pump. Running without
oil gave me a similar symptom to a broken pump on a normal carb. I could
also hear the pots clanking when starting the car.
car mechanics (many older British cars use SU carbs) swear by ATF
(automatic transmission fluid). I've tried 20w-50, straight 30W,
straight 50W and ATF and couldn't tell the difference.
I could sure tell the difference in winter if I used motor oil. I had
to thin it down with kerosene. (and went back to atf)
-don perley
Unknown
>
>That's sort of right. When you stomp on the gas it keeps the piston
>down momentarily. During that time, you are running with a smaller
>ventury, and higher air velocity than "normal" for that flow, so the
>mixture is rich. It acts in place of an accelerator pump.
>
damper for vacuum pulses. Anyway, I used to use Marvel Mystery oil in
all my English cars on the theory that it burns ashless and leaves no
gummy residue plus it lubricates your valve stems. Of course all the
SU carbs I ever met were sloppy enough to leak some oil into the induction
and required topping off the oil every month or two. Using motor oil
would last longer but provided somewhat sluggish performance.
So, here's another trivia question. How do you balance a dual SU setup
when they all have sloppy throttle shaft bushings?
--
Fan mail may be sent to:
zar...@rx-db.hf.intel.com
Peter Paraska
I looked in my '72 240Z Service Manual (from Datsun). On Page EF-26:
"Use Mobile Oil SAE 10W-30 for damper oil. Do not use SAE #30 of higher
weight oils."
I use Dexron ATF in mine. It does need to be "topped off" every few
thousand miles (maybe 5,000) and trottle response is good, considering
these carbs have no accelerator pump.
-Pete
|/////////////////////////////////////////////////////////////////////////////|
|Pete Paraska (par...@oasys.dt.navy.mil) |
|Carderock Division, Naval Surface Warfare Center |
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Peter Paraska
>By the way you can try different oils if you like.
>
>A thiner oil, say SAE 20, will give you less acceleration enrichment
>which will increase your gas mileage and decrease acceleration,
>or a thicker oil, say SAE 40, will give you more enrichment with
>better acceleration and lower gas mileage.
>
>The ideal is probably the point were you get no hesitation while
>accelerating, SAE-30.
I disagree. My Datsun manual (72 240z) says to use 10W-30 and NOT to
use SAE 30 or highr weight oils! I can agree with them because I have
found from experience that the lighter oil increases the damping effect
and slows trottle response and acceleration. Physics says that the
damping force is proportional to the viscosity.
Respectfully,
Pete Paraska
Mike Hejl
>So, here's another trivia question. How do you balance a dual SU setup
>when they all have sloppy throttle shaft bushings?
The best you can :-) Seriously though, I've found a ColorTune, combined with
the MotoMeter, helpfull here. Still, you generally have to bump the idle up
somewhat to get it to run evenly and you'll have to check the condition of
the plugs frequently to determine imballance. The best solution, of course,
is to either install oversized shafts or have brass bushings installed in the
carb bodies.
Now you'll ask how to set the mixture when the jets are worn (another common
problem with SUs) :-) :-)
Disclaimer: Hey, I *like* SUs - there ain't nothin like that "suuuuucking"
sound when you romp on the gas!
Mike Hejl
>found from experience that the lighter oil increases the damping effect
Methinks you got this bassackwards.
>and slows trottle response and acceleration.
By inducing an over-lean condition.
> Physics says that the damping force is proportional to the viscosity.
Yes, but not inversely proportional as you imply above.
Gary Goodlund
One thing in your note caught my attention:
The "73's have much lower compression" part is directly related to
the low compression head which they (Datsun) went to to deal with
the smog requirements. The guys who run Z-cars in SCCA talk about
the "E33" or "E38" model head or some number close to that. This
was the standard model in '70 or '71. After that they just kept
lowering the compression ratio. Also, those flat-top Hitachi S.U.s
aren't worth messing with except at smog-check time (so save them on
the back shelf).
'later,
Gary
Peter Paraska
>In article <15...@oasys.dt.navy.mil> par...@oasys.dt.navy.mil (Peter Paraska)
>writes:
>>found from experience that the lighter oil increases the damping effect
> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>Methinks you got this bassackwards.
says to use 10W-30 but to never use SAE 30 (thicker). I saw a guy post
that he used SAE 30. I use ATF. When I first got my car (73 240Z w/
72 SUs) I dumped out the oil (thick stuff) and put in ATF (thinnest
stuff I had around). The throttle response got alot quicker.
Codesmiths
> In article <PERLEY.92...@trub.crd.ge.com> per...@trub.crd.ge.com (Donald P P
erley) writes:
> >
> >That's sort of right. When you stomp on the gas it keeps the piston
> >down momentarily. During that time, you are running with a smaller
> >ventury, and higher air velocity than "normal" for that flow, so the
> >mixture is rich. It acts in place of an accelerator pump.
Not really. It's better to think of an variable venturi (SU type)
carburettor as keeping the mixture correct, and the accelerator pump
(or capacity well, on an old design) as being a "kludge" to make
fixed venturi carbs give the right mixture under acceleration.
The effect of the damper is not to stop the piston rising when the
throttle is first opened (The damper valve doesn't work fast enough
anyway.), but to stop the piston over-shooting at the top, when it
reaches its new equilibrium position. If you run without the damper,
the initial mixture will be OK, but there will be a brief over-rich
surge shortly afterwards (fraction of a second).
> So, here's another trivia question. How do you balance a dual SU setup
> when they all have sloppy throttle shaft bushings?
You don't. Fix the damn things. I know US petrol is cheaper than over
here, but it's still worth the effort & money to have your
carburettors working correctly. Bushing an SU throttle spindle isn't
expensive anyway, just be grateful you don't have a 911 or similar
with triple barrel Webers, now they *do* mean problems if your
spindle is loose.
Thomas Tornblom
[text deleted]
I could sure tell the difference in winter if I used motor oil. I had
to thin it down with kerosene. (and went back to atf)
-don perley
I don't know what other manufacturers recommend, but way back when I
had Volvos they used ATF.
Thomas
--
Real life: Thomas Tornblom Email: Thomas....@nexus.comm.se
Snail mail: Communicator Nexus Phone: +46 18 171814
Box 857 Fax: +46 18 696516
S - 751 08 Uppsala, Sweden
Lon Stowell
>when they all have sloppy throttle shaft bushings?
>
Stick a pair of oversized paperclips in the tops of the
pistons. Bend the clips so that you have two pointers
_________ __________
| |
| |
U U
roughly as pictured. The pointers should rise and fall in
exact (or close enough) harmony as you screw around with the
throttles. Of course MINE never had sloppy bushings....but
I've seen a lot of TR spitfires which seemed to require them
to work properly...
Paul Harvey
You want the oil thickness to change with temp so you get
different enrichment depending on what temp it is.
10W-30 acts like 30 at high temp and 10 at low temp.
It might be hard to tell a diference between the two though?
After writing my previous post recommending SAE 30 ,
I realized that what I said applied to my
experience in CA. In colder climates I could see that SAE 30
might get too thick, maybe even freeze.
I noticed a lot of people said they used 3-in-1 oil which I
think is about SAE 10, seems kind of thin???
I've heard of using ATF fluid, maybe that would be OK. I
wouldn't be surprised if ATF is about an SAE10W-30.
Of course you could use olive oil and you might not notice
a difference, it only affects enrichment while accelerating.
I guess the Hitachi version should use soy bean oil since
they are Japanese?
If I remember correctly, the Datsun manuals say engine oil
or SAE-20 depending on what year. Of course they would have
been more concerned with emissions and confusing the customer. So
I think they started with SAE-20 and then decided it was too
confusing and switched to engine oil.
richard.e.stealey
> pistons was basically correct. You can, however experiment with oils
> of lighter or heavier weight to give slightly different responses. It
My 72 MGB has 105,000 miles on its original set of SUs (HIF type) and
I always just put motor oil in them. I think the owners manual said
that was ok. I just rebuilt them a few thousand miles ago (5 years ago !)
and they appear to be good as new.
What kind of performance differences would I see with different oil
weights?
Rick
richard.e.stealey
I have a set of Sus off of a 69 MGC and got a different set of needles in
the tune up kit (different than what are in the carb) so they won't fit.
I was wondering if they need to be replaced at all because they look normal.
Is it possible to see wear or imperfections on them?
The carbs had worn throttle shafts (is that the term?), the brass shafts
that go into the body of the carb. They had a flat, worn side on them,
letting air leak into the carbs. Got that fixed up but don't have them
back together yet due to the needle problem.
rick