Gilmore27

83 Project 944 NA
I have an engine that I may need to rebuild. However, I found that the piston/cylinder clearance is out of tolerance (.080 mm).

Cyl 1 = .0838 mm
Cyl 2 = .0965 mm
Cyl 3 = .1143 mm
Cyl 4 = .1193 mm

I'm interested in your thoughts and opinions on this.

Resleeving or boring over may be cost prohibitive.

I don't want to scrap the car, but I don't want to spend a lot of time and money on a engine with a bad block either.

here's a video in case you get really bored:

V2Rocket

cheap and "improper" solution but what's stopping you from reinstalling the original pistons and rings to their respective cylinders?

they're worn out, but they're worn out together

951and944S

Are you saying the measured spec you posted is cylinder diameter id minus piston od...?

There are three tolerance groups for the blocks, 0, 1 and 2.

Do you have the factory engine manual...?

If you part it, I need a left front fender....

T

jderimig

Can you get under the wear limit with new or different tolerance group pistons? Probably not the way to go but just asking.

Gilmore27

Thats what I was thinking.

I know they're out of tolerance, but don't know how bad that is. The manual states .08 mm as a wear limit, but is that a manufacturer being conservative? Is there a "real world" limit that people go by.

Also, wouldn't a new set of rings improve the situation?

Gilmore27

yes, Cyl ID - Piston OD, would that be correct?
I have tolerance group 0. But I thought all the tolerance groups have the same clearance, just at different size piston/bores.

I dont have a hard copy of it. I have a PDF.

Gilmore27

You would think so. I'd like to hear from someone who had done this.

jderimig

This process sounds interesting and not that expensive as far as refinishing bores go...

http://www.kuhnperformance.com/model...nder-treatment

tempest411

I've seen and purchased myself. 020 over Wossner pistons for ~$650.00/set, so not bad at all.

V2Rocket

pricing for the overbore work varies widely and wildly depending on where one is...
best price i've found is about $300 for the proper overbore/AN30 hone-conditioning treatment by a shop i have 100% confidence in here in CA.

so for pistons and machining you're looking at ~$1k, best case...

MAGK944

Did the factory hone the blocks first then choose from the tolerance groups the correct pistons? It seems likely but backwards to me, every block I've had honed was toleranced to the pistons I supplied.

Gilmore27

Thanks for everyone's input.
I going to use another engine that has a few scratches but is within spec.

tempest411

Mr. Gilmore, you have a pm.