cylinder head flow

[jwb51]

For my Fiero I wish to put in either a 3.4 dohc, 3.5 dohc or 3.6 dohc engine, which heads flow the best and where is flow figures for any of these heads located. Also which engines have forged rods and cranks or powered metal rods. Any plus or minus about any of the engines or any other information you can give. Thanks.

[pocket-rocket]

3.4 DOHC are growing more scarce (along with the parts).

3.5 DOHC is the "Shortstar", or a Northstar with 2 cylinders chopped off. Those are plagued with head gasket failures and ripping threads out of the aluminum block from what I've been told by a friend that works at a shop.

3.6 DOHC I do believe has the powdered metal rods, not sure about forged crank though. You can (if you get lucky enough) get a flavor of it with 312 hp thanks to variable valve timing and direct fuel injection. The downside to it is you need the PCM for sure, wiring and the fuel system as it is not a standard EFI fuel system. The standard version comes in with 235-275 hp depending on the donor vehicle. You would need the PCM and wiring for this one as well, but the fuel injection system is a standard GM returnless EFI I believe. It is not direct injected.

[neophile_17]

My research shows the 3.6L has a different bell housing. Something to look into before tackling this swap.

~sam

[jwb51]

Not the 3.5 shortstar but the high value engine the used from 2004 till present that was the 3.5 I was thinking of. Is this a better engine than the 3.4 LQ1.

[jwb51]

Thanks sam but was going to put trans and engine together in, the 4 speed now is the performance version and has too much gear for expressway driving even with the overdrive in 4th.

[neophile_17]

The LX9 (usually referred to as a 3500) was the "high value" 3.5L engine. It is OHV not OHC engine. It's probably the easiest to build and work on in a Fiero but lots of people have had great results with LQ1s in Fieros.

~sam