3100 and 3400 exactly the same?

[mobileaudio219]

Topic should of read 3100 and 3400 heads exactly the same???

Long story short..

I bought a 96 monte carlo with a 3100. When I bought the car it had a blown head gasket dumping water into the oil...

I'm unsure how long the car was driving like this, so I'd yanked the motor..

My uncle has a 3400 out of my cousin 99 Grand am, it's believe to have a blown head gasket or cracked head... He gave me to motor to to rebuild if I choose too..

But if it has cracked head can I use one of the heads off the 3100? I know that they will physically fit, but is there a differences in valve size and/or flow????

Thanks for any help, Justin...

[Azrael]

The valves on the 3400 are bigger so you'd have to use both heads from the 3100. The 3400's lower intake manifold won't line up perfectly either. It'll still make a good seal but it will reduce flow a bit. I'd only recommend using the 3100 heads if you need to get the motor running as they will kill some of the performance.

[mobileaudio219]

Yeah, thats what I thought...

My uncle thought they were the same, but I thought I heard something about swapping the 3400 heads and intake on the 3100 for small increase in power...

I havent really messed with the 3100 much, I've had 4 fox body mustangs, including a 86 gt t-top that I brought back to life...

[IsaacHayes]

2000+ 3100 had same heads and intake as 3400. Older years were small port intakes and slightly smaller intake valves. You can mix and match if you are creative....

I put 3400 lower intake on my 94 3100, and 3500 upper intake on that, with a 3.5L DOHC throttle body from an olds intrigue.... And this is my one and only car... I did get a large increase in power despite not having roller rockers (had to grind the lower intake to clear them), larger intake valves, and the perfectly match on the heads to the intake manifold. I did not feel like swaping 3400 heads, or 2000+ 3100 heads for those things, since my motor has over 200,000 on it. Doesn't burn any oil though and runs great. The cost in gaskets then would have equaled to what a whole lower mileage 3400 would have cost me. The cost in the intakes added up quick since I had to source them.