3100 top end port + polish vs. 3400 top end swap

[Compufreek]

Which is more to my advantage for the price involved? I have a '95 GP SE with a head gasket on it's way out (noticed a little foaming in the oil) so I figure it is time for a top end rebuild. While I have it apart why not do the performance mods I want. I was thinking about a top end swap to a 3400 or 3100 port and polish and maybe a cam regrind or maybe one off J-body performace. Either way it comes down to money but what do you guys thinks is a better performance route when I can?

[RebelGT]

The 3400 top end will outflow ANY ported 3100 top end (with the exception of the new style 3100). And you can usually find the parts relatively cheap. You can even buy the parts brand new from GM for about the same price as buying a set of P&P'd 3100 pieces.

[Compufreek]

Do you know of any company's that sell a well priced but quality top end rebuild set? If that is the case with the top then hell why not! As far as the cam goes while it's out may as well do it. What is the price of the regrind and how long does it take?

[robby1870]

If your just changing head gaskets, then you wont be taking out the cam. You would have to pull the motor to make taking the cam out easier. I heard of a way to do by dropping the cradle and taking it out through the passenger wheel well, but that is too much work, IMO.

[Compufreek]

Good point, I thought it was on top of the block. Excuse me for that I am more focused on the top end right now. I am just hoping that the bottom end holds up for a while longer. I figured this would happen, hearing all the horror stories about the head gaskets on these motors so I have done alot of research on it.

[RebelGT]

Head gaskets aren't the problem with these engines... its the intake manifold gaskets that leak. Head gasket issues are few and far between to well maintained engines.

[Compufreek]

Oh well that makes sence that it's not that bad a leak and I am not burning any coolant! That is accually a bit of a releif. Do you know the GM part numbers for the new 3400 plenums and will they bolt to my 3100 heads?

[v6h.o.]

the 3400 intakes will bolt to your 3100 heads... but. the intakes have a bit taller intake port to match the taller intake port of the 3400 heads...

you might run into gasket matching problems with this.
the 3100 intake gaskets are different from teh 3400 intake gaskets. as on the heads the locating notch/tab that pushes into the 3100 head for the gasket is on one side of the 3100 #3 and #5 ports and on the 3400 its on the oposite side of the same ports.

ive used 3400 intake gaskets on my 3100 heads(ported to match) i just put a dab of silicone to hold the gasket in place because the locating tab doesnt work.

3400 top end and the 00+ 3100 parts are better at flowing than the older -99 parts. however teh 3400 heads do have the larger 1.76 intake valves. (1.72 stock)

as to who sells a kit? no one. just go to a local wrecker and find the parts. or check ebay, pieces get sold for fairly cheap most times.

GM does have decent prices on the intake manifolds if you get them through gm parts direct.

[Anonymous]

'stock' hp from top-end swaps?

Obviously putting on stock (non ported/polished) 3400 top end onto a 3.1 or 3100 woun't be the same as a 3400 block due to slightly less cubic inches; BUT how much power is expected out of a 3100, 3.1, 2.8(?) compared to swapping it with a whole 3400 engine?

Also I've never heard of this done, but is a 3400 top end swap possible or been done to a 2.8L?


GM websites:
New GM minivans with 3400: 185hp@5200rpms
New GM cars (GA, Alero): 170-175hp@4800rpms

one last thing.. if you wanted to supercharge a 3.1 with 3400 top end would a 3400 supercharger work?

[Manitcor]

Yes, a SC for the 3400 will work on a 3100 and vice versa, only one I know of thoug is the RSM kit, unless you plan on doing something custom

[Carlo1prix]

I have a 01 3100 will porting just the upper intake help anything, i have to do an intake this weekend pissing antifreeze