A question about installing 3400 heads on my 3.4

[jimjimmyjimjim]

I have a 1993 3.4 iron head that I rebuilt to stock and have been running for a couple of years now. I have some intake work to do and I was wondering if it would make sense to install aluminum heads from a 3400? My biggest concern is the compressed ratio I would get since I have the stock flat pistons in there. I don't want to tear down the whole motor to replace the pistons in addition to all the other work I would have to do. Is there another reasonable alternative, head spacers, modifying the iron heads?

[caffeine]

I think there have been a few people who have dealt with the higher compression ratio with pump gas before

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[robertisaar]

good excuse for a cam fat enough to bleed off enough dynamic compression to allow 91/93 octane?

[Superdave]

3500 heads and a healthy cam with 3400 headgaskets.


the 3400 gaskets are .020 thicker compressed and will fit the 3.62" bore better so less carbon buildup. Makes for 11.57:1 SCR

[jimjimmyjimjim]

3500 heads and a healthy cam with 3400 headgaskets.


the 3400 gaskets are .020 thicker compressed and will fit the 3.62" bore better so less carbon buildup. Makes for 11.57:1 SCR

That would mean premium gas wouldn't it?

[Superdave]

Yes.

You could probably grind in some valve reliefs and get that a little lower but you're still in 91/93 territory. With good tuning and a good cam like Robert mentioned it would be fine though. It'll sound mean too. lol

[Blacktree]

3500 heads and a healthy cam with 3400 headgaskets.

the 3400 gaskets are .020 thicker compressed and will fit the 3.62" bore better so less carbon buildup. Makes for 11.57:1 SCR

But that will yield a 0.070" quench height, which is terrible.

IMO, the OP would be better off just biting the bullet and getting 3400 pistons & rings.

[Guest]

But that will yield a 0.070" quench height, which is terrible.

IMO, the OP would be better off just biting the bullet and getting 3400 pistons & rings.

you don't know what his quench height would be, because you don't know what his quench height is currently.

If you have e85 where you live OP, then you can get away with the higher CR no problem. Cali has 91 oct other than that, so you might have to retard the timing a bit otherwise with aluminum head swap.

[Blacktree]

you don't know what his quench height would be, because you don't know what his quench height is currently.

I think it's safe to say he's not going to have anything close to optimal quench height, using the F-Body pistons and 3400 head gaskets. It doesn't take a math wizard to figure that out.

That said, the 3400 in stock form has a better quench height than a 3.4 V6 in stock form (0.040" for the 3400 vs 0.050" for the 3.4). So switching to 3400 head gaskets and pistons will be a win-win.

Of course, this all assumes the OP intends to use regular gasoline. If he wants to use E85, then the F-body pistons with thinner head gaskets (whatever thickness is needed to get optimal quench height) would be the way to go.