This is a question i have always had ....when you go to .029" impala head gaskets, do you have to get different lengthed pushrods to compensate for the slightly smaller head gasket? Or is it such a small difference that stock length pushrods would work fine?
I understand that the impy head gasket is an easy way to up the DCR, and with a 160* thermo, an aluminum headed LT-1 should be fine with it, right?

thanks
trav

 

no you do not need a longer pushrod to compensate for the smaller head gasket

 

As Mike stated, stock pushrod length is fine if Impy head gasket is the only change to valvetrain geometry.

 

how about with a 20 thousands mill?

 

If you only put on the Impala gasket the pushrods will work fine. If you mill the heads then go to a shorter pushrod. I had my AFR's redone and the machine shop milled them .003 to true them. I asked if I needed to go to shorter pushrods and was told unless you mill .010 or more the stock pushrods will work fine. This is what I was told. Other people may have a different opinion on this and please weigh in. Good luck!
HVY SS

 

I would assemble the valve train and check the contact patern to see for yourself. My guess is you would be right on the edge of needing new pushrods.

 

I milled my heads much more than that and I went with the Felpro HG's, I used a pushrod checker and mine are fine.

 

Usually on a Hydraulic valvetrain a small change in deck height will be compensated for by the lifter. but if you combined all that with say taller valves and milling a different size would definately be needed. I have also seen good contact paterns on a stock setup with .100 shorter pushtubes and an impy gasket.

 

Impy heads are cast iron right? Well this means that the gasket is desigened to be betwen 2 similar metals with similar exapinon rates. But F-body LT1s have alummiun heads which exapand at a different rate so F-body head gaskets can't be alowed to "stick" to the block or the heads because they will be pulled apart by the other metal exapanding differently Impy's LT1s dont do this. I would think.

 

The impy gasket is an embossed steel shim, which expands and contracts differently than iron does.
I ran impy gaskets on my 93 for years with no problems.
The Felpro is a coated composit material as well as the stocker.