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frenchyd
frenchyd SuperDork
8/29/18 6:07 a.m.

In reply to frenchyd :

If you understand the concept of trying to suck from a straw. Maybe those who use thinner than required oil will understand the analogy of shock absorber fluid.  

We know that thinner fluid allows softer/ faster acting  shocks and thicker fluid makes the shock stiffer slower reacting shocks, right?  

So by going thinner on the fluid in an SU/Stromberg we would make the carb leaner on acceleration and by going thicker we’d make the carb richer. 

Dont think of the fluid as a lubricant. Think of that as a little shock absorber. ( which if you’ve ever taken a shock absorber apart it sort of does). 

It doesn’t keep the carburetor lubricated, it just slows the rate of the piston so the mixture is richer on acceleration. 

200mph
200mph New Reader
8/29/18 4:13 p.m.

I've used dashpot oil from Moss (expensive), ATF (cheap), and settled on motorcycle fork (shock) oil.  Shock oil has an anti-foaming agent that may be beneficial here.

Its like when we used to use STP mixed with motor oil as engine assembly lube.

I asked a smart engine builder if STP was really beneficial...  elbow deep in the stuff he mused for 10 seconds, then blurted...

"WE USE IT (long pause)... IN CASE IT WORKS".

frenchyd
frenchyd SuperDork
8/29/18 5:47 p.m.

In reply to 200mph :  Since they all have different   Properties they each will affect  each the reaction of the carbs in different ways.  True few can feel the difference in the seat of their pants so does it matter?  

Not to most people that’s true. Some people can’t feel the difference but understand there really is a difference.  

I wonder how expensive the proper oil really is,  I mean my bottle is getting pretty low but then I bought it in the 1980’s  and used it both on my MGTD and my Jaguar race car called the Black Jack. So even if the bottle was $10 divided over 30+ years  it’s chump change.  

If you’re a professional shop first you get a discount and you’ll sell it at retail so the more expensive it is the greater your profit.  Second you can ask,  tell the customer that the proper oil costs (?) but we can use (whatever) and that's Only.... 

 

cdowd
cdowd Dork
9/5/18 3:06 p.m.

I use ATF.  on 2 MGAs, a Jaguar XK120, and an Austin Healy 3000.  I always have it.  I think the most important thing is to make sure they are always topped off.

frenchyd
frenchyd SuperDork
9/6/18 4:15 a.m.
cdowd said:

I use ATF.  on 2 MGAs, a Jaguar XK120, and an Austin Healy 3000.  I always have it.  I think the most important thing is to make sure they are always topped off.

Which ATF there are differences you know.  

A lot of people use a lot of different fluids.  I suppose if you don’t care if you’ve got every last bit of power and just want easy one fluid works as well as another. Plus it’s true you can tune to compensate for the different reaction to different fluids.  But do you?   

 

cdowd
cdowd Dork
9/6/18 8:42 a.m.

Well one of the MGAs and the Austin Healey have been sold.  The othe MGA runs, but is not fully assembled.  The Jag has been tuned to the best of my abilities.  It has a 220hp Mk9 motor so missing a couple hp does not really play into the equation.

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