SU Oil Consumption

[rcb280z]

Right on the "NO" o-ring. Don't know why I agreed to that earlier. However, I disagree with you on ATF being to thin. It worked great for me when straight 20 wt. didn't. Maybe the climate difference in Nevada? Not sure, but only ATF worked. Could maybe have had something to do with the fact that the su's I had were on a '77 280 motor.

Edited August 10, 2012 by rcb280z

[Stanley]

Next time I'm wearing my glasses.

[Captain Obvious]

I wasn't expecting that the jiggly bits wore out. While that is possible, I consider it very unlikely.

I consider it much more likely that there's a goober in there affecting operation. Or the stalks are bent or misaligned. Or a previous owner took the check valves apart and got them back together incorrectly.

Or hopefully... There really isn't any problem at all and the OP is simply overfilling the tubes all the way to the top and expecting them to stay that way.

So, back to you Jetaway... What is it that makes you think you need to add oil? When you say:

I can't go much more than 350 -- 400 miles without having to refill the reservoir.

Are you filling the reservoir to the very top and then putting in the stalks, or are you filling the reservoir a little and then using the stalks as dipsticks until the level hits the fill-to line on the stalks? It takes a surprisingly small amount of oil to do this.

The reason I ask is because if you are filling them to the very top before you put the stalks in, then you are overfilling the dampers. Won't hurt anything as the excess will simply be pulled into the cylinders and burned, but if that's the reason you think you have to keep refilling them, then what you've got here is a non-problem.

[Jetaway]

I wasn't expecting that the jiggly bits wore out. While that is possible, I consider it very unlikely.

I consider it much more likely that there's a goober in there affecting operation. Or the stalks are bent or misaligned. Or a previous owner took the check valves apart and got them back together incorrectly.

Or hopefully... There really isn't any problem at all and the OP is simply overfilling the tubes all the way to the top and expecting them to stay that way.

So, back to you Jetaway... What is it that makes you think you need to add oil? When you say:

Are you filling the reservoir to the very top and then putting in the stalks, or are you filling the reservoir a little and then using the stalks as dipsticks until the level hits the fill-to line on the stalks? It takes a surprisingly small amount of oil to do this.

The reason I ask is because if you are filling them to the very top before you put the stalks in, then you are overfilling the dampers. Won't hurt anything as the excess will simply be pulled into the cylinders and burned, but if that's the reason you think you have to keep refilling them, then what you've got here is a non-problem.

Thanks for all the replies!

Captain Obvious, I will be following your previous diagnostic post. I'm curious about the jiggly bits and if I see an o-ring, well, I'll call an audible.

Yes, I am aware of the dip-stick markings on the stalks and am very sure that my oil consumption is real and not due to overfilling. Roughly 10 drops covers bottom to top of the markings. Checking the oil level has become my 2nd quick diagnosis for slightly rough running, after giving the high volt wires a push.

Just a note, The "3 in 1" oil that I am using is their Motor Oil, not the stuff found in every household in the country. It has a blue slash rather than black slash and is marked as SAE 20 Weight Oil.

Chris

[Jetaway]

Damn! I started this thread a week ago? Must be the heat, the stifling, oppressive heat that softened my brain.

My apologies for neglecting a thread I started.

Chris

[Captain Obvious]

Bummer. I was hoping that this was a non-problem and you were simply overfilling the tubes. It's been a while, but I remember someone else had a problem with dropping level in the dampers, but I don't remember if they ever reached resolution. I'll take a look for that thread when I get a chance.

Take a look at the jiggly bits. There are two washers on the top and bottom and the jiggly cylinder between them. The washers are different between top and bottom, and if memory serves, the cylinder may be as well. It's unlikely that someone took them apart and mixed up the parts, but if your oil isn't seeping out the bottom and isn't evaporating into the air, then it has to be coming back out the top of the tube somehow.

Here's some far fetched ideas... Maybe you have a crack in your suction piston near the bottom that is allowing oil to seep out? Maybe the piston was machined incorrectly and what is supposed to be a blind hole isn't and there's some passageway through to the top of the needle?

And yeah, if you find any O-rings in there, definitely take some pics and call an audible!

[Captain Obvious]

Sorry... Meant to say there are two washers on the top and a C-clip on the bottom and the jiggly cylinder between them. Dropped some words by accident.

I also wanted to explain the purpose behind the lift and drop test. You should be able to lift the suction piston all the way to the top until it won't go any further and then let it drop full speed to the bottom without any fluid loss. If the check valve is working properly and the oil is of suitable viscosity and level, then it should rush through the check valve fast enough that it won't pool on top of the valve enough to lift the oil to the point where it can escape out the top of the tube.

If, for whatever reason (for example... too thick of an oil viscosity or something wrong with the check valves), the oil does not flow through the check valve freely enough when the piston is dropping, then you run the risk of lifting oil up and out of the tubes.

Does that make sense?

[bpilati]

Okay then, so disregarding the facts as laid our herein, when you find that O-ring take a picture of it and post it here....... Just saying there ain't no O-ring!!

Like Arne said consumption of this oil should be "monster minimal" 'cause any that goes away will have to be sucked up over the top of the tube and with the tight fit between the tube and the barrel it runs uo and down in, 5 years could work too.

O-rings would interfere with the movement of the piston as I see it, unless someone can show me something different.

[Jetaway]

OK, this is what occurred.

With the stalks out, the piston lifts easily and falls quickly.

With the stalks in (i.e., normal operating position) their is progressive resistance lifting, (quicker produces more resistance) while the fall is only slightly damped from the previous condition.

Both carbs felt the same.

I didn't read your follow-ups until I sat down to write this, so I was explicitly looking for spillage, but with the stalks out I did see the piston? (whatever surrounds the stalk and plunger) move up and did not notice any oil overflowing.

I'll check the washers and c-ring later this evening. Don't recall anything appearing amiss, but if they have always been amiss, how would I know?

Looks like I'll be becoming very acquainted with our old friend gasoline over the next day or two. I gave Jack a tune-up a week ago and a stress-test suggested fuel starvation. Measured the fuel flow, extrapolated it out and concluded it was running out of fuel. Measured the flow again sans fuel filter, flow increased by a factor of three. Replaced filter, repeated stress test, it was better, but still gave signs of starvation. Checked float levels: the front was 3 mm low while the rear was right on. Corrected front, haven't stress- tested yet, but I 'm guessing that it wasn't the entire problem. The pump (electric only) has given me some warning previously when it wouldn't self-prime after I had drained the tank to work on the sender unit. Ehh, geez, guess I should re-do the mixture settings with the bowl level change.

And I'm still not sure what is the cause of the oil consumption. I will continue to poke, though I think the most likely cure will be to save up my shekels and get a freshly rebuilt pair from ZTherapy.

I am reminded of an old half-joke, half-truism about SU carbs. They have the very beneficial effect of keeping you away from the temptations of wanton women because you spend all night adjusting them to get them right.

Chris

[Jetaway]

Thou has eyes and sees not:

I just posted:

===

I didn't read your follow-ups until I sat down to write this, so I was explicitly looking for spillage, but with the stalks out I did see the piston? (whatever surrounds the stalk and plunger) move up and did not notice any oil overflowing.

===

Actually, I _wasn't_ explicitly looking for spillage.

Chris

[Captain Obvious]

Stalks out piston lifts easily and falls quickly is perfect. Stalks in piston has resistance lifting and fall is only slightly damped is also perfect.

Not exactly sure I understand what you meant by not seeing spillage, but if you lift and drop the pistons without the stalks installed, you aren't testing anything. You won't cause any spillage or overflowing doing that. You need to have the stalks installed to do the lift and drop test.

c1) Pull the stalks out and make sure the reservoir is filled to the correct level

c2) After verifying that the oil is at the proper level, reinstall the stalks in their normal operating position

c3) Stick a finger in the mouth of the carb and lift the piston all the way to the top until it won't go any higher - Should be hard to lift

c4) Let the piston drop as fast as gravity and it's spring will allow - Should fall quickly

c5) Repeat c3 and c4 ten times

c6) Pull the stalks out and check to see if the oil level has changed. If the level has changed, there should also be fresh oil on the outside of the reservoir tube.

If the level has changed and there's oil everywhere, make sure that all the brass jiggly bits are clean and goober free and everything that is supposed to move does. The top washer is fixed to the shaft (as is the C-clip obviously). The lower washer and the cylinder should jiggle.

Also check the stalks? Do they appear straight? If you lay the stalks tits up on the bench, are the shafts perpendicular to the benchtop?

One last question that I should have asked a while ago... Do you know if the engine has to be running in order to consume the oil? By that, I mean, how many days does it typically take you to accumulate 350-400 miles? And if you would happen to let your car sit parked for that same length of time, would the level change, or does the engine have to be running to cause the disappearing oil?

[Jetaway]

Stalks out piston lifts easily and falls quickly is perfect. Stalks in piston has resistance lifting and fall is only slightly damped is also perfect.

Not exactly sure I understand what you meant by not seeing spillage, but if you lift and drop the pistons without the stalks installed, you aren't testing anything. You won't cause any spillage or overflowing doing that. You need to have the stalks installed to do the lift and drop test.

c1) Pull the stalks out and make sure the reservoir is filled to the correct level

c2) After verifying that the oil is at the proper level, reinstall the stalks in their normal operating position

c3) Stick a finger in the mouth of the carb and lift the piston all the way to the top until it won't go any higher - Should be hard to lift

c4) Let the piston drop as fast as gravity and it's spring will allow - Should fall quickly

c5) Repeat c3 and c4 ten times

c6) Pull the stalks out and check to see if the oil level has changed. If the level has changed, there should also be fresh oil on the outside of the reservoir tube.

Regardless of what I may have wrote, I've done the above, though step c5) maybe 5-7 rather than 10 times.

If the level has changed and there's oil everywhere, make sure that all the brass jiggly bits are clean and goober free and everything that is supposed to move does. The top washer is fixed to the shaft (as is the C-clip obviously). The lower washer and the cylinder should jiggle.

Also check the stalks? Do they appear straight? If you lay the stalks tits up on the bench, are the shafts perpendicular to the benchtop?

One last question that I should have asked a while ago... Do you know if the engine has to be running in order to consume the oil? By that, I mean, how many days does it typically take you to accumulate 350-400 miles? And if you would happen to let your car sit parked for that same length of time, would the level change, or does the engine have to be running to cause the disappearing oil?

Stalks are straight.

Definitely must be running. While waiting for sundry parts to arrive, Jack has sat patiently for at least a week a couple of times with no change in SU oil level. (Or engine oil level either;))

I've partially dissembled the carbs but have never taken them completely apart and I'm unclear on a couple of points:

I assume that the disappearing oil is being sucked into the engine and burned. How is the question. Am I correct in assuming, that barring defect or damage (which I'm ruling out as both carbs are using oil at roughly the same rate), that the oil reservoir is completely closed off except for the top where the oil level can be checked and added? If so, then the oil must somehow be climbing the walls and over the top of the reservoir from whence it runs down into the vacuum chamber, through the vacuum passage in the venturi, and finally into the incoming air/fuel charge.

Is my description accurate?

Chris