Using 3.4 iron head gaskets to raise compression?

[ForcedFirebird]

According to the calculator the 3400 pistons have a deck clearance of .0065, does this mean they pop out that far? It doesn't matter anyways, I haven't got the short block yet and will measure them before the heads get bolted on, and as long I use the correct head gaskets, they should be fine right? I'm going to use 3500 heads on a 3.4.

[SappySE107]

They pop out .020" Use the 3400 or 3500 head gasket.

[ForcedFirebird]

They pop out .020" Use the 3400 or 3500 head gasket.

Perfect, with .020" out and .060" gaskets, the ideal .040" quench can be achieved, Thanx once again, Ben .

[FallenZ24]

Why do you guys say not to use the .040 gaskets on the gen3 motors?

I'm running i/h 3.1 gaskets on my 3100. They work fine and I have no valve/piston clearance problems. I did notice that the car pings under load with low grade gas. I have to run mid-grade now. I think the compression is ~10:1 with the heads shaved a little.

I also experienced no alignment problems with the lim and heads.

-Joseph

[SappySE107]

You have about .040" clearance using stock head gaskets because the piston stick out .020". With iron head gaskets you are down to .020 clearance. Rods will stretch at high RPM.

[FallenZ24]

You have about .040" clearance using stock head gaskets because the piston stick out .020". With iron head gaskets you are down to .020 clearance. Rods will stretch at high RPM.

So you're just worried about clearance between the piston and valves?

I rev to 6k daily and have no problems. I've been driving my car for a year this way with no problems. Maybe I'm just lucky

[ForcedFirebird]

It's still ideal to have .040 quench. Do you have a Gen3 3100? We are discussing Gen3 pistons .

[FallenZ24]

It's still ideal to have .040 quench. Do you have a Gen3 3100? We are discussing Gen3 pistons .

Well it wouldnt be a 3100 if it wasnt a gen 3, now would it?


Here's my thread for more pics and info. http://www.v6z24.com/jbodyforum/smal...light,uim.html

-Joseph

[ForcedFirebird]

http://60degreev6.com/view.php?pg=familytree
According to the family tree, Gen3 came in '92. Perhaps that's not the origional motor in your '90?

Looks good , can't wait to get my hybrid started (3.4/3500)

[IsaacHayes]

Heh, nope that's not the stock motor for his 90. It's a small port 3100 with 3400 LIM and 3500 UIM.

[ForcedFirebird]

Heh, nope that's not the stock motor for his 90. It's a small port 3100 with 3400 LIM and 3500 UIM.

Was the shortblock swapped? If not, wouldn't they be Gen2 pistons (regardless of the top end used)?

[rsisbetter]

this is all very interesting, since, i have a 3400, and would like to do a 3500 top end swap. in which i would like thinner head gaskets, (3.4 iron head, .040) as opposed to the stock .060. So what i have gathered from this thread, is that, a 3.4 iron head, .040 head gasket can be used on a 3400, (with 3x00 top end), but the quench height will only be .020? as opposed to .040 quench, with .060 head gaskets?

thanks
cody

[IsaacHayes]

It's a complete 3100 in there. The 3x00 swap is common for J-bodies. The thread he posted shows he then upgraded it with different head gaskets, and 3400 lower manifold and 3500 upper manifold and a 4.3l 70mm throttle body.

[Superdave]

this is all very interesting, since, i have a 3400, and would like to do a 3500 top end swap. in which i would like thinner head gaskets, (3.4 iron head, .040) as opposed to the stock .060. So what i have gathered from this thread, is that, a 3.4 iron head, .040 head gasket can be used on a 3400, (with 3x00 top end), but the quench height will only be .020? as opposed to .040 quench, with .060 head gaskets?

thanks
cody

correct, which is not ideal and most likely will cause problems...


you could just have .020" shaved off the tops of your pistons and be good to go.. smaler dish, thinner gaskets should bump the compression as well.


i have .045" compressed ROL gaskets but the 3500 pistons don't pop out as far as the 3400, iirc it's .010" so my quench is .035"

[rsisbetter]

interesting, i need a calculator. hahaha, that way i can picture it in my head easier, right now, just reading it, is hard to see, (compression raise)...

thanks
cody