boring 3.0 to 3.2, wall thinckness.

[jthod]

May have some good info for those looking to bore their 3.0 out.

I have been working on my engine at school with the engine maching instructor in a weekly night class. Tonight came time to bore the block. I've found many posts saying that a Gen 1 3.0 block CAN be bored to a 3.2. I've seen just about as many saying just the opposite.

Well, tonight I had the opportunity to use one of these: click here.

It can measure the thinkness of metal up to 19.999" thick, and measures to .001"

I spent about 30 minutes on my '90 3.0 block finding the minimum thinkness. I checked around 20-30 points in each cylinder at various depths and radii. I found the minimum in cylinder #2, on the side closest to the front of the motor about 2/3 of the way down the cylinder.

****.196"****

Most of the block measure between .300" and .240", The thinest part in almost all cylinders being on toward the front of the block, and about 2/3 of the way down.

The instructor said most times the minimum thinkness of the walls he likes to see is .185" after machining.

Going from a 3.0 to a 3.2 bore, in standard (minimum) measurements, the block will need to be bored and finished honed at ~.1181" over.

I have yet to do all the math, but him and his 22 years of experience said it should not be a problem. I havn't done any cutting yet, but I've done enough research that I know it can and has been done many times.

Too bad I don't have one of each block to measure...

 

[AREA 91]

Good to know. I was told .200 is the wall thickness.

 

[jonheese]

From back in the old SHOShop days, the standard accepted thickness was .200", so that's pretty darn close.

Boring a 3.0L block to 3.2L (to use stock 3.2L pistons) would be a ~.122" overbore (from 3.500" to 3.622"), which leaves roughly .074" of wall left (according to your .196" wall thickness measurement).

Boring a 3.0L block to 3.3L (which is reportedly possible) would be a ~.184" overbore (from 3.500" to 3.684") which leaves roughly .012" of wall left... 12 thou... Pretty darn thin.

Regards,
Jon Heese

 

[firebat45]

From back in the old SHOShop days, the standard accepted thickness was .200", so that's pretty darn close.

Boring a 3.0L block to 3.2L (to use stock 3.2L pistons) would be a ~.122" overbore (from 3.500" to 3.622"), which leaves roughly .074" of wall left (according to your .196" wall thickness measurement).

Boring a 3.0L block to 3.3L (which is reportedly possible) would be a ~.184" overbore (from 3.500" to 3.684") which leaves roughly .012" of wall left... 12 thou... Pretty darn thin.

Regards,
Jon Heese

I don't think a Gen 1 block can be bored to 3.3... 12 thou is way too thin.

 

[jthod]

From back in the old SHOShop days, the standard accepted thickness was .200", so that's pretty darn close.

Boring a 3.0L block to 3.2L (to use stock 3.2L pistons) would be a ~.122" overbore (from 3.500" to 3.622"), which leaves roughly .074" of wall left (according to your .196" wall thickness measurement).

Boring a 3.0L block to 3.3L (which is reportedly possible) would be a ~.184" overbore (from 3.500" to 3.684") which leaves roughly .012" of wall left... 12 thou... Pretty darn thin.

Regards,
Jon Heese

but that .1181" overbore is off the circumfrence, so half of that will be taken off the walls.

 

[jonheese]

but that .1181" overbore is off the circumfrence, so half of that will be taken off the walls.

Oh crap! Geometry fail on my my part...

Okay, so recalculating:

Boring a 3.0L block to 3.2L (to use stock 3.2L pistons) would be a ~.122" overbore (from 3.500" to 3.622"), which leaves roughly .135" of wall left (according to your .196" wall thickness measurement).

Boring a 3.0L block to 3.3L (which is reportedly possible) would be a ~.184" overbore (from 3.500" to 3.684") which leaves roughly .104" of wall left.

That makes a lot more sense now... Thanks for the reality check, man.

Regards,
Jon Heese

 

[pjtoledo]

but that .1181" overbore is off the circumfrence, so half of that will be taken off the walls.

???? diameter maybe?

 

[jonheese]

???? diameter maybe?

Oh, you know what he meant...

Regards,
Jon Heese

 

[pjtoledo]

Oh, you know what he meant...

Regards,
Jon Heese

yeah, but it's been so slow around here lately that we need to stir something up.

 

[1993MTXSHO]

It's not that it cannot be done, but more that it gets to the point where it becomes very borderline, and some people have had issues with the gen 1 3.0's overheating when bored to a 3.2. With all the engines around and free second gen 3.0L's given away time to time why take the chance with a gen 1 block?

 

[jthod]

Because I already have a block. The SHO is a rare thing here in Nebraska. It's not boosted yet, and if it ever is, it will be low boost. I'm not trying to build a 500chp motor here.

 

[jthod]

yeah, but it's been so slow around here lately that we need to stir something up.

Listen here ********...




yes, diameter is what I meant...

 

[1993MTXSHO]

If you're going to boost it I would be very very careful, I'd almost be inclined to say keep it a 3.0 and just boost that if you can't find a different block. You'll have all sorts of problems with boost and thin walls. Not trying to be discouraging though, I just don't want you to do all that work just to find out it wont stop overheating

 

[jthod]

The boost thing is just a pipe dream at this point, and I'll probably end up leaving it as is. The engine build will be expensive enough...

 

[yamahaSHO]

There is a certain boosted 3.2L SHO that put down 520whp and using an original gen 1 block. It is strictly a track car and does not have any issues with heat (dual core radiator and an oil cooler).

My personal opinion is that a 3.3L (3.2x)is more of a "my ____ is bigger than yours". If you're boosting, a 3.2L isn't much different and you're likely not to feel the difference. JMO and YMMV.

FWIW, I am using my original 3L block.

 

[1993MTXSHO]

My personal opinion is that a 3.3L (3.2x)is more of a "my ____ is bigger than yours". If you're boosting, a 3.2L isn't much different and you're likely not to feel the difference. JMO and YMMV.

FWIW, I am using my original 3L block.

Agreed, even in a n/a situation like my own. I planned on using stock pistons but when I opened it up and saw the cylinder wear on my walls I had no choice but to bore to "3.3". It's a 4 cubic inch difference which means crap, **** it didn't even make it to a 200cid engine