3400 / 3500 hybirds

[95Grand-Am]

Do 3400's with 3500 heads really make more power than if they had 3400 heads? If the compression calculater is correct you would lose @ .5 of a compression ratio. That seems like alot, can they flow that much more to make up for it?

[SappySE107]

Its not about flow, its about velocity.

[95Grand-Am]

Please give me more information. Arn't the ports larger so wouldn't that hurt velocity? or is the shape of the ports that much better that you get velocity and volume with the 3500 heads. At what RPM would you see the benifits of 3500 heads on a 3400 with a stock cam? Would you need a larger cam to benifit from 3500 heads?

[SappySE107]

The 3500 heads have smaller ports and a smaller min area compared to the 3400. The top of the intake manifold runner is part of the taper. All RPM and no cam needed to benefit but a cam goes a long way.

[95Grand-Am]

Thank you for the info. Even with the compression loss, you would make more power across the entire RPM range?

[iceyt911]

i have an oppourtunity to get 3500 heads. what can they do for my 3100?

[SappySE107]

Nothing unless you bore it .060 over. The combustion chamber is too large for a 2.8/3.1/3100 otherwise.

Compare the combustion chambers besides numbers and you will see that efficiency is way up for the 3500 heads.

[iceyt911]

ok i just checked on what it would cost for me to bore it, and it may be worth it. so if i bore it and use the 3500 heads, i will get about the same effects as the 3400, correct? and what about the lower intake? i know the upper intake has less factory flow but what about the lower and will my '98 exhaust mani (chevy malibu) fit the 3500 heads?

[SappySE107]

3500 lower only fits 3500 heads. Only the upper intake is compatible between the 3400 and 3500. They raised the ports on the 3500 heads, which was another reason they are better than the 3400 heads.

[iceyt911]

ok i just checked on what it would cost for me to bore it, and it may be worth it. so if i bore it and use the 3500 heads, i will get about the same effects as the 3400, correct? and what about the lower intake? i know the upper intake has less factory flow but what about the lower and will my '98 exhaust mani (chevy malibu) fit the 3500 heads?

[95Grand-Am]

Iceyt911, Instead of boring the 3100 out that far, why don't you just find a 3400? SAPPYSE107 How much power will the 3500 heads give me over the 3400 heads, with stock cam, with a 3400 upper, 56mm throttle body, and open exhaust on a 3400 engine?

[SappySE107]

15-20hp, 5-10 more with a 65mm TB and porting the 3400 upper.

For the cost of new pistons and boring a 3100, you can find a 3400 with lower miles. If you are going to go the overbore route, i suggest running higher compression for the power and gas mileage. I would run the 3500 manifolds if you can find them. 98 exhaust isn't that great.

[95Grand-Am]

Are those gains without porting the heads and lower intake, and with the lower compreasion ratio? That is really impressive.

[SappySE107]

Correct, the stock parts.

[zofo61]

Sappy......have you ever come up with a duration cam for my 3400 /3500 with the RSM kit........PLEASE....not looking for lift unless the new rockers would hel instead......duration duration duration...........PLEASE

Thanks