Can I use the LG8 pistons out of a 2000 model year GM car FWD 3.1L, IF I CAN then that would give me 9.6 to 1 compression, what would that give me in HP with porting and polishing and 3.4L cam and High flow cat.

sorry!!!!!!! the reason that engine has such high compression is mainly due to the cylinder head design..............not the pistons.......and as we all should know, those cylinder heads CAN NOT be used on our cars

I heard they had problems w/ those pistons being noisy anyway. If your going to tear it down to do pistons, go w/ some brand name ones. Just my $.02

1991tealRSt-topGuy
hmmm I think your thinking of how the aluminum heads help with running higher compression so that the fuel doesn't pre-ignite on lower octan because here is what ROSS pistons says about compression.

The compression height is the distance from the center of the pin hole to the deck of the piston. ROSS custom pistons are available in any practical compression height to compensate for stroker or destroker cranks, long rods, or blocks which have been milled excessively, etc.

So I think Compression only has to do with piston height not the head design. As long as these LG8 pistons don't go past the deck of the block my heads should be fine.

Ken Kaniff

Why would they be noisy, I drove a 2000 buick Centrey as a rental car once, it was quiet. If it where noisy it must have been something else on the engine because the piston would have to vibrate to make noise.

KED85 do you have an opinion???

You asked.
I also tend to say out of a response IF I'M NOT SURE.
BUT
When ever you rebuild an engine, you bore out, larger, the cylinder hole.
Thus, you cannot use a stock sized piston from any example you are trying.
It sounds like you are trying to ue a domed piston to raise compression.
Talk to engine exerts of several manufactures for your true correct situation answer.
Again, you'll find it'll cost money and then you have to decided.

I still can only say, go get a good used 3.4 block and swap it in. IF ya wanna build something, still start with the largest block you can play with, which is also a 3.4.
I know engine rebuilds go for the $2K range (parts/machining/labor to build).
I paid over $1,000 for parts to rebuild my "1970 LT-1" Chevy V-8.
That's why I spent $850 for my engine swap. It was done and easy swap mission.
800-831-0884 Northern Auto Parts may offer ya a solution to your specific raising compression domed piston question.
PS If ya get those LG8 Pistons, you are not thinking of using used pistons, are you? They would have to be new & usually .030 oversized.

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Chat Soon,
KED85
Karl
1985 Firebird 2.8 to 3.4 swap project for Smog Happy LA, CA

The 3.1's had specially designed pistons so they wouldn't smack the valves of the FWD "Generation II" heads. Those heads have a splayed valve arrangement; if they're run with flat-top pistons (like of our 2.8/3.1 Generation engines), the flat-tops will smack the Gen II's valves.

So, moving to a Gen II motor's pistons (w/valve reliefs), while keeping the Gen I heads, might reduce your compression.

You could also have your heads (and/or deck) milled a bit; keep in mind the more you mill, you'll also have to get the intake manifold milled to keep the sealing surfaces parallel. Say for example, stock form, the intake meets the heads at the "top" of a "V". After milling the heads, you'd make the intake meet the heads at the "center" of the "V"- and the intake won't seat, it'll be too wide (expecting the top of the "V"). Heh, that probably didn't make sense, eh?


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-Tom P (Hot rodded 1986 Firebird 2.8l)

Thanks TomP and Ked85,

NO I wasn't going to use used pistons, I was just wondering what was out there.

KED85, like I said before, I'm not after a RACE engine, just want to KEEP my BLOCK because of the VIN number and just get a little more HP.

I'll have my engine professonally rebuilt with some higher compression and over bored pistons put in, and have my heads ported and polished and call it GOOD.

How much HP would it be if I have a 3.1L with 9.5 to 1 compression, 3.4L cam, high flow cat, and 3.4L injectors and ported/polished?? Would that give me 200HP at the fly wheel???? Thats all I want.

I'M REAL SURE, you'll be knocking at that 200 HP door, tho.
Will it be dyno'd?
Phone up Northern see if they offer a rebuild kit to the parts you're after.
See if Northern offers .060 pistons for your ride.
Tom's point on milling is correct. IF ya cut one area, you must also cut into another, to keep all intake head surfaces tight and no leaks (oil/vacuum).
Keep asking local racers for suggestions for machinists, too!

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Chat Soon,
KED85
Karl
1985 Firebird 2.8 to 3.4 swap project for Smog Happy LA, CA