Using 3.4 iron head gaskets to raise compression?

[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)?

[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]

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)

[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]

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

[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

[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]

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

[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 .

[SappySE107]

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

[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.

[Superdave]

I guess I was getting at weather or not the pistons are different in the gen 3, or was the deck height changed? I'm gathering parts for my new engine and don't want to make a mistake. (basically pistons are the last thing left).

pistons are different, deck height should be the same.

[ForcedFirebird]

not sure why they did it.. maybe as a cheap way to raise compression.

I guess I was getting at weather or not the pistons are different in the gen 3, or was the deck height changed? I'm gathering parts for my new engine and don't want to make a mistake. (basically pistons are the last thing left).

[Superdave]

Is it because of the location of the wristpin?

not sure why they did it.. maybe as a cheap way to raise compression.

[ForcedFirebird]

only the gen3 3x00 pistons pop out, the gen2's and gen1's are fine.

Is it because of the location of the wristpin?