Have you guys(gals) heard or read about taking the circlip off and placing a(thin) fibre washer under the plunger,then replacing the circlip?

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The oil that works best for someone else, on some other car, might not work for you. Finding the best oil is much like finding the perfect needle.

My theory, from what i've found with my limited experience with SU's is that the smaller the carby (for eg a single 1.25") the thicker the oil you can get away with. There is more force pushing the piston up in a smaller carby, hence you can get away with a thicker oil.

I've also found that thicker the oil, the smoother the engine will be at low revs.

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I think i will go with the ATF Oil, because thats what most people say they use.

Thanks a lot for your help

Yer thats a good bet.

Don't be scared to try different oils though.

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Can anybody give me any suggestions as to what type of oils can be used in the ol' su...

I have tried ATF, proper dashpot oil, a type of sewing machine oil, so am thinking maybe a thicker oil, like an engine oil of some description. Just unsure as what to use, as my knowledge of su's isn't great...

The set up consists of '92's sc12 kit on a 1098 with a hif38 carb, if that helps!
The oils i've tried so far haven't made much of a difference in losing the dead spots when accelerating from low revs... Maybe a change of spring as well, but thought i'd try the simple things first.

<edit> have also tried no oil, to no advantage!

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Carl
Previous Owner & Driver of 1 Morris "It's not a Cooper!!" 850

Try engine oil next.

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If you need a thicker oil, try a 30 W monograde, such as a 4 stroke mower oil. Don't try engine oil, multigrade is NOT wanted here!

You may get 'dead' spots in acceleration from an incorrect needle, or from the spring being wrong. The oil is to damp sudden piston movements, the spring is to change the amount the piston is liftwing throught the rev range. (the needle and spring have to be matched to your engine to make sure it is operning enough to give the right fuel at the right revs.

Get an Oxygen sensor in your exhaust, and a gauge in the car and you can have a go at approximating it.

Check out:

http://wbo2.com/3b1/default.htm

For the best you can get, $600 that will probably save you a lot of time and money in the long run!!

Cheers

Matt

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68 Deluxe.... it's shiny..... I like shiny!!

A old timer who tuned SU,s talked about this little modifction.The end result is to elimate the deadspot under hard acceleration.
The fibre washer has to be exactly the same width as the little plunger.
Maybe worth try?

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I'm probably just a little dense, but what exactly do you mean by this?

Is it just packing the bottom part of the plunger to restrict the valving more, and thereby provide more damping?

If so is this not the same effect as using a thicker oil?

Don't forget the dead spot on acceleration may not be caused by too thin an oil, could be the wrong needle profile in that range, incorrect mixture adjustment, or the spring too weak.

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68 Deluxe.... it's shiny..... I like shiny!!

try baby oil or some form of mineral oil -

tried a new one today - penetrating oil - worked well

Revs all the way out and back with no hesitation

Thanks for the tips all...

I've just tried some engine oil as a temporary little trial. It seemed way too heavy even just sitting there pushing it up by hand, so i diluted it a little bit with some lighter oil
It did seem to make some improvement on my little test drive, but it is all a little bit of guesswork without a meter. Just going on feel ATM.

As far as spending $600 on a proper meter (did look into this previously), i think that $$ could be spent on the dyno with somebody who knows what they're doing We'll see.

I did get told when i picked the car up, the spring maybe too heavy, so i will look into that as well.
Will give that monograde a go, and possibly the baby oil?!? BIAM, is that thicker than standard ATF?

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Carl
Previous Owner & Driver of 1 Morris "It's not a Cooper!!" 850