3500 Heads/Changing compression ratio back to stock

[Pacho]

When doing a 3500 Top End Swap (Stock 3500 heads and competition 3500 lower with competition 3400 upper), I know the compression ratio will lower because the combustion chamber of the 3500 heads is a little bigger than the 3400 heads.

Does anyone know how much the compression ratio will drop from that of the stock compression ratio?

How much would I have to shave off of the 3500 heads to bring the compression ratio back to stock? .005, .010, .015, .020 etc

I will be using Fel-Pro 3500 Head Gaskets.

Thanks.

[hotrodwolf]

You'll really need to watch your tolerance because i heard the pushrods dont clear well. Even a little drop makes all the angles and geometry wrong all the way to the lifters. Although apparently, it acts as a larger cam because you are making the lift greater unless you also shave the pushrods.

[Pacho]

ok-so are stock 3400 pushrods alright to use

has anyone here done the 3500 head swap?

[JLw7123]

ask blackjack

[WhiteV6]

You'll really need to watch your tolerance because i heard the pushrods dont clear well. Even a little drop makes all the angles and geometry wrong all the way to the lifters. Although apparently, it acts as a larger cam because you are making the lift greater unless you also shave the pushrods.


Wrong. All of it.

9.1 is what you will get and you can't shave the heads enough to turn 32.4cc into 28.6cc. If you did, it would be ruined. Stock pushrods are fine.

[BlackJack]

Confirmed, as Ben stated above. No clearance issues, and no notable drop in compression.

As for pushrods, I couldn't say, because I'm running one of Ben's cams at the same time that I did the 3500 head swap. But I trust his judgement on the matter.

[Pacho]

Thanks Ben.

Phillip said he will be dropping off the 3500 Lower to you this week, most likely tomorrow.

I'm looking forward to your completed work with the 3400 uppper/3500 lower.

[clutch1]

My friend did this on his 3100 Grand Prix with a bigger cam (dunno numbers) and he had problems, actually bent a pushrod.

Dunno any exacts though.. just be careful!

[mfuller]

You are not supposed to do 3500 heads on a 3100.
The piston bore is too small for the larger combustion chamber of the heads.

[clutch1]

Lmfao dunno if he knew that

[WhiteV6]

Sounds like he mixed up intake and exhaust pushrods. That's the only way you bend a pushrod.