Jet size enlargement on 94 carb

[Don]

Do you need to enlarge the jets when plugging the power valve and if so what size do you go to. I know this is not normal but can't keep PV from leaking through,causing bad idling and Louping when slowing down.

[Bruce Lancaster]

Running without is fundamentally wrong...once you richen the jets enough to allow the thing to run at full throttle, you will be too rich in the majority of your driving. This is not trivial as a rich mixture washes down the cylinders with unburned gas and causes very rapid wear.
The engine has substantially different mixture requirements at high and low throttle openings, different enough that a compromise won't work.
If the ring on the bottom of your bowl casting is not damaged, get in touch with one of the several excellent rebuilders on here and order what they consider a good valve. I assume you are fighting one from a later Holley 4 barrel that does not have a flat where it needs to seal on a 94.

[Don]

Thanks,this is what I wanted to know

[Bruce Lancaster]

Diaphragm resistance to modern fuel varies greatly, and the most commonly available valves at least are 4-barrel ones that need to be machined...so buying from one of our excellent rebuilders makes a lot of sense. This is a perfectly good contraption (in my experience the tales of valves rupturing at ever sneeze of the engine are ridiculous) that has been severely vexed by ethanol and by inappropriate supply of the different 4 barrel version. I think these guys on here have beaten the problems to death, but buying in the open market carries a lot of risk still. There are plenty of big early V8 suppliers that do not care, IMHO...

[Ol' Ron]

The use of an Air/fuel meter can improve performance as well ans economy. With the cost of re-building and fuel. They're worth the expense.

[Ross F-1]

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Have ANY of the vendors changed the PV diaphragm material to one designed for E-10/gasohol? I suspect there is a lot of old stock out there with stuff that won't take it, but how can you tell??