Has anyone done this swap yet? If so, I would really be interested in any info that could be given in regards to whether it works, doesn't work. The more info the better

Thanks for any help

The 3500 intake won't fit the 3.4 heads. So you'll need to swap over the heads also. Then you'll have crazy-high compression (somewhere around 13:1). So you'll need to swap in 3400 pistons... or use E85.

quote Originally posted by Blacktree: The 3500 intake won't fit the 3.4 heads. So you'll need to swap over the heads also. Then you'll have crazy-high compression (somewhere around 13:1). So you'll need to swap in 3400 pistons... or use E85.

The 3500 also has a larger bore diameter than the 3.4L so you can't swap pistons between them. The closest you can get to a descent compression with the iron heads on the 3500 is to adapt the pistons from the 3.6 DOHC motor which has the same bore. It's been some years since the 3500-3900 were still new, there was a lot of planning, checking and comparing going on that revealed this info. It would take a little machine work but nothing unreasonable. The 3.6L has a slightly greater stroke than the 3.31" stroke we are familiar with but the compression height between the two pistons was pretty close. You of course can put the 3.4L outfit on top of the 3500 and despite what some may think still have good mpg and performance with the lower compression ratio. I did it years ago with a 3100 short block and the Fiero top end and got 25+ MPG with the four speed manual. The 3500 has fast burn heads and given my experience with high compression, I'd bet you could put the aluminum heads on the 3.4L and run it without a problem with 93 octane. If I can do it with 11:1 compression and 15 psi of boost there is no reason this shouldn't work with a reasonable global drop in the spark advance which would be required even with the 3500s 9.8:1 comopression because the fast burn heads take much less ignition as can be seen between the their stock spark tables with a difference as much 10 deg in some places.

[This message has been edited by Joseph Upson (edited 12-19-2016).]

The 3400 pistons will fit a 3.4 V6 just fine. Why make things harder than they need to be?

quote Originally posted by Blacktree: The 3400 pistons will fit a 3.4 V6 just fine. Why make things harder than they need to be?

Yes, I'm not suggesting he attempt to fit 3500 pistons, if he is not aware of the intake incompatibility he may not be aware of the bore difference either. As I mentioned above though I bet he could run the 13:1 compression if it's that high on 93 octane without a problem. The heads are that efficient and spark knock resistant.

My "next" iron-head w/roller cam block rebuild will use the 3.7" bore with 3.6DOHC pistons shaved down to use longer rods and increase compression along with the 1.76" intake valve...

I'm running 93 octane with 9.9+ compression on iron heads with no issues right now once I finally tuned for timing. Knock sensor is still disabled (7730 conversion).

Looking for 10.5 compression... The longer rods will also help with knock...

[This message has been edited by lou_dias (edited 12-23-2016).]