Stroker crank

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I know a forged stroker crank using GM parts had been mentioned before. What happened with that? Thanks.

Tim

[Fierobsessed]

It's an offset cut 3500 crank. You can have this procedure done at any really good competant race engine machine shop. Maximum possible offset grind would get you about .250" extra stroke or really just a hair less. Without any bore work, 3.6L Even. If you do a .060" overbore, you can achieve an effective displacment of just over 3.7L (yikes!)

[Fiero Brick]

I just drooled on myself.

3.6 (almost 3.7? Isn't .060 over in the danger zone on the 3.4?) liter LQ1? Even not taking into account that the compression ratio would (I think) be increased by stroking the engine and any boring done, desktop dyno is showing a gain of almost 15 lb*ft and 10 horsepower. That would be an awesome base for building a high-horsepower NA LQ1... or a high-horse turbo LQ1 for that matter, too.

I never thought of offset grinding the 3500 crank... shows how much I have left to learn.

[prophiseer]

I never thought of offset grinding the 3500 crank... shows how much I have left to learn.

Not everyone knows everything about something, but everyone knows something about everything. We're all still learning, y'know? Hell, I think most people here know more than the engineers that're designing our motors and cars

[tijuana_no]

i only know, that i don't know nothing.

[timg]

Does anybody have the part number for the forged 3500 crank? Thanks.

Tim

[prophiseer]

I was thinkin earlier . . . going with the 3500 offset, if you bored a 3400 block about .050-.055" over, you'd still be relatively close to that 3.7 mark, but still be within block tolerance, especially on an iron block.

Or (unless someone has tried it), bore the block well past max allowance, and then sleeve the cylinders back down, the extra reinforcement would help.

Oh, and BTW, does anyone know how similar the 3900 block is compared to the 34/3500's? Are the target for a short block swap, or are tere too many differences to overcome?

[Dave96z34]

I just drooled on myself.

3.6 (almost 3.7? Isn't .060 over in the danger zone on the 3.4?) liter LQ1? Even not taking into account that the compression ratio would (I think) be increased by stroking the engine and any boring done, desktop dyno is showing a gain of almost 15 lb*ft and 10 horsepower. That would be an awesome base for building a high-horsepower NA LQ1... or a high-horse turbo LQ1 for that matter, too.

I never thought of offset grinding the 3500 crank... shows how much I have left to learn.

wouldn't that be like 12-1 comp. That with boost would kill a head gasket quick.

[Dave96z34]

It's an offset cut 3500 crank. You can have this procedure done at any really good competant race engine machine shop. Maximum possible offset grind would get you about .250" extra stroke or really just a hair less. Without any bore work, 3.6L Even. If you do a .060" overbore, you can achieve an effective displacment of just over 3.7L (yikes!)

wouldn't that be like 12-1 comp. That with boost would kill a head gasket quick.

[Fiero Brick]

wouldn't that be like 12-1 comp. That with boost would kill a head gasket quick.

I didn't run the math... I'm pretty sure I would have to do more research before I even knew how to go about checking that. but with 12-1... sounds like it would be awesome for an extreme-street NA application...

[Husky]

Pft, if you're gonna bore it that much, and stroke it that much, and boost it that much, and do all that work, and you don't go with a rather extreme headgasket, you deserve the blown ones. Cometic will make custom HGs, and as far as I know they'd definitely be up to the challenge. Firgure it this way... If you're going to be building a 12:1 engine for boost, the money it would cost to get a Cometic or somethign similar in there isn't a whole lot. Drop in the ocean kind of thing.

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I've blown Cometic's headgaskets before...

Tim

[Husky]

Undoubtedly. But I bet they hold up better than standard Fel-Pro gaskets.

[SappySE107]

Do you have the o ring with the cometic gaskets?

[Fierobsessed]

Bored and stroked with factory pistons, still only gets me from a stock 9.7 to 10.7 by my math. It increases the displacment about 60CC per cyl witch roughly equals the combustion chamber volume, so it adds 1 whole point to the compression ratio. If you're starting from 9.25, expect 10.25.