94 6-speed

Guys I have a question, is it possible to bore a gen 2 block more than 60 thouands over. What about sleeving the block to 4.120. I have heard that this has been done but I would like to hear from some that have actual engine building experience. This engine by the way will be used on the street not a full on race motor. Thanks joe

rskrause

Not worth it. Put the $$$ in the heads/cam/valvetrain, etc.

Rich

ulakovic22

It's my understanding that the cylinder walls would be close to being too thin if it is bored over .060, esp for street duty with the constant heat cycles. Running sleeves is an options but like Rich said above, that's a lot of money that could be used elsewhere. Why not just buy an aftermarket block?

Z28SORR

Who makes an aftermarket LT1 block???

Rob94hawk

An aftermarket LT1 doesn't exist.

I remember long ago there was a guy here that did a 421ci LT1 (VIPRETR?) and there was even an article in GMHTP on it but it was just a fad and wasn't a good idea for longevity.

Injuneer

He claimed to have built two versions of the 421..... 4.030 x 4.125" stroke and 4.090 x 4.000" stroke... described the difficulties with doing a complete sonic thickness check on the cylinder walls, then recentering each individual bore within the block to provide the required wall thickness on the thrust side. Seemed like a lot of work for questionable benefits.

Anyone remember the screen name of the guy that built the sleeved 427? He posted a couple times when the issue of sleeving the LT1 block came up.

ulakovic22

When I typed that I was thinking of a SBC in general that could be used for a large bore project. Something like a Motown or Dart block. Staying with a factory block and trying to make it live on the street will be tough and costly.

MY91Y84

i agree, a 400+ inch factory block isnt going to last more then 20,000 miles before starting to go sour...

the way to go is call up dart, motown and order your self a big inch smallblock...there makin 472 motors now...its insane..

"nah man its just a 383 with a big cam"

94 6-speed

Thanks for the responses guys I was wondering if it would be able to be done. but you all are right it isn't worth it. Thanks again

Denny McLain

Now my curiosity is aroused.

Would it be possible to use a regular sbc and a set of regular sbc heads (ya know I’m thinking 15 degrees or so) and set the thing up with sensors so it would pass an emission test or is the Optispark the main obstacle??

Sweated bricks on that I'd have issues with sheetmetal intake and it was so simple it was pathetic. A bunch to do about nothing.

What’s the deal on the blocks that makes it so hard??

NJLT1SS

Hey Denny, as far as using an aftermarket block, I have heard that using a GM Bowtie block is an easier way to go. I understand that the Bowties use a cam retainer plate, like the production block, and that opens up the possibility of using the Opti. All you would need to do from there is mount up an electric waterpump, and bolt up your accessories. I believe OneFlynZ28 is/was using a set up like this, maybe he can chime into this and share some info.



Nick

Denny McLain

Thanks! If there is a will there is a way and boy I'd really like a 450 ci motor.

rskrause

A 450ci small block needs over $5,000 in heads and valvetrain parts to support it.

Rich

SABLT194

I've also been looking into an aftermarket block for more cubes. I'd like to stay with the opti cam position part of the opti and use my LTCC for the high tension side. I have no problems runing the GM PCM. As long as I don't go over 7000 the thing works great and the LTCC doesn't miss a beat. Can an electric water pump be spaced out far enough on a Bowtie to fit a cam driven opti? I would like a 421 for my Formula, It has a nice nostalgic Pontiac sound to it.

Steve

SStrokerAce

If you wanted to keep the opti a SBC would be some trouble, but if you wanted to go with a aftermarket ECU this would all be much much easier. 450cubes and SB2.2 heads with a sheetmetal intake would make it easy.

Bret