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DASHPOT OIL QUESTIONS??.....

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NardisCNC

NardisCNC

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How can I determine if my dashpots have the correct amount of oil in them? Is there a way to check? Also what type of oil should I use if needed? Is it a special kind, or something readily available? Thanks in advance!
 
The way you fill them up is to unscrew the top, then reach inside the carb (with the filter off) and push the piston up. When it's up, you'll see a tube (top of the piston) that you add oil too. It only takes a few oz of oil. Don't worry if you overfill, any extra will overflow and run from the SU into the engine.

As far as what oil, that is up for debate. SU does make a specific oil. Others use engine oil, some use AFT. You don't want the oil to be too light weight or the pistons will raise too quickly and run lean. Basically, the idea is that the heavier the oil, the slower the piston and richer the mixture.
 
Lots of debate, but "the book" recommends the same oil you're putting into your tranny and engine, depending upon ambient temperature and usage. Since an oil change, with filter uses 3.7 quarts, use from what's left.

YMMV
 
20 wt is the all around best choice.
80 wt is WAY too thick, might as well screw the pistons down tight if you use 80 wt. Like 80 wt in the shocks, they stop working as shocks.
 
Oh bother. Just use th' "Leavins" from what ya pour in th' engine.
 
I'm a nut . . . but I use the SU dashpot oil that Moss sells. It's pretty light, like a sewing machine oil. My cars run well.

Phil
 
Howdy Folks,

This question seems to come up very often.

Its been noted in some past posts that "20/50" is just fine to use. Personally; I purchased the "Formulated" oil from Moss & never had a problem. Yes; Its "Pricey" but it lasts darn near forever!

Russ
 
I've used mineral oil for years. Buy it in the grocery store or pharmacy. It's cheap, it's pure and does a great job in multi-temperatures. But, if you are on to the Moss thing and it makes you feel better to have a bottle of their product in the car, then pay their high price and be happy! This topic is like asking a group of people, what's the best ice cream! Your going to get a multitude of (correct) answers. Or so it seems. :devilgrin:
 
PAUL161 said:
This topic is like asking a group of people, what's the best ice cream! Your going to get a multitude of (correct) answers. Or so it seems. :devilgrin:
Click to expand...

Ooo Ooo I know this - Castrol 20-50, awe never mind :blush:
 
I have even heard of ATF and PSF being used!! Light oil seems to be the consensus! Surely and certainly NOT 80W(much too thick!)and certainly NOT dry!!! :wink:
 
I've always used "Marvelous Mystery Oil"... I like the look of the can... Actually I guess it's a plastic bottle now...
cd
 
:iagree: and I like the smell too!!
grin.gif
 
If 80 weight is good enough for John Twist, it's good enough for me.

I'm gonna try it. :yesnod:
 
just been mucking about with the carbs this very evening. For a change I'm trying power steering fluid. Previousley just whatever engine oil I had lying about. I did think about 2 stroke oil but that'd probably be too light.

As an aside I could not get both carbs to match in resistence, one felt right and the other persisted in lacking even resistence. Assuming it was a faulty top I swapped them over expecting then to have the other carb become uneven, yet loo and behold they are now both the same in feel. Or at least way better then they were before.
 
The pistons and chambers were matched when new. They are not interchangeable. It wounds like had been swapped some time in the past. They should both drop at very nearly the same speed. If so then you have them right. As for the damper oil, its only purpose is to delay raising of the piston when you press down the gas pedal. This results in a richer mixture for acceleration. It takes the place of the accelerator pump on more conventional carbs. Thicker oil causes this rich mixture to last longer while thinner oil results in less richening. With no oil, the piston would rise almost instantly usually resulting in severe stumbling. The oil has no effect on idle or sustained speed running.
 
I have been using Marvel Mystery Oil since I raced a BE in the 70s. I still use it in both my 1275 engine in my current BE and also in the carbs on my '66 BJ8. It has always done a great job.
Charlie
 
I've used pretty much all of the above, but am currently using GM Synchromesh because I had some lying around.
 
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