bp944

iTrader: (4)

What does it take to fit a 4.250 stroke in a ls1 block? Is it even possible and reliable? I'm wondering about putting some good hard road racing miles on it. Its a callies magnum II crank.

00pooterSS

iTrader: (40)

Generally speaking I would keep a smaller stroke on a road race car, its going to be wound up tight all the time and the motor would be a lot happier with a shorter stroke and less side load on the pistons and cylinders.

What about using that money to just buy a bigger LS block, say like a LS2,7,X etc if you can, that way you get some cubes from bore instead of stroke. I would think a stock LS7 would hold up really well if your wanting a good road race motor. I mention the LS7 because you could probably about buy one of those by the time you fully build and LS1 and put in a Callies 4.250 crank. Although I dont really know the going rate on a LS7

bp944

iTrader: (4)

I've located a really cheap Callies magnum II. Other than that my option would be a bottom of the line callies, eagle, or just a stock crank. A callies magnum II aught to be alright for high end rpm if I had forged internals and a lightweight racing valvetrain. Or is that still too much side load?

Taspeed

iTrader: (1)

to use a 4.25 inch stroke you have to have one of 2 things...an aftermarket block with a taller deck height or you have to get deck spacer extensions that fit under the head.

nysbadmk8

4.25in crank needs a tall deck, Or a ERL type of deck extension.

00pooterSS

iTrader: (40)

damn forgot about that, saw those deck extensions/spacers on a 500 cube Z06.

rednari

You do not necessarily need to deck the block. Shorter rods, or better yet, pistons with shorter shirts and higher wrist pin placement should work.

But, to maintain high RPM the motor should be over square (larger bore than stroke), and it would be impossible to achieve that being limited by the 3.9" LS1 bore coupled with a 4.25 crank. You would have a problem getting an LS2 block larger than 4.25 for an over square road racing motor. The crank is probably too big for anything less than an LS7 or LSX block.

For drag racing, well thats another matter.

racer7088

We do 4.250 strokers a lot but use sleeved blocks with longer sleeves. The big stroke causes power to occur earlier in the rpm range and can make more total power as well but it is a tight fit and you have to know what you are doing. The ones we have run are all doing fine so far after several years.

TT427

iTrader: (1)

I know this is an old thread, but what about using cut journals 1.88-2.00 and .827-.787 wrist pins for strictly NA. Would that help the stack any vs cost?

racer7088

Yes absolutely. With a CCW we use 2.000 and sometimes an .866 pin

TT427

iTrader: (1)

So what is the comp height under sizing journals and pins?

jjtoma

Journal size will not change comp height. Pins ?? - just subtract the difference between the two sizes, then divide by 2.

racer7088

basically around 1.000

LS6

Eric

Have you done a project on LQ4/LQ9 using 4.25" stroke with out sleeving?

MRT

racer7088

Yes but drag race only due to short piston.

LS6

You mean not a regular postion high like 1.344".

I found a stroker kit with 4.25" is the same price as 4.000" and I thought if it is the same price why not get the maximum if the block permits.

If this will require special none shelf postion compression hight then is it best to go with 4.125" stroker.

Thanks

SSCamaro99_3

iTrader: (1)

I may have a conservative point of view, but I wouldn't run more the 4 inch on a car I was going to drive alot. The tradoff is small, given the potential for issues.

PREDATOR-Z

I agree for a stock 6.0 block.

dtroike

iTrader: (4)

I think with the standard deck non sleeved bock you may want to run a shorter rod with some custom pistons. I've never put one together but you will probably need to do some block clearancing for the rods as well.

racer7088

send me a link as the kit is probably a train wreck.