Meatball911

I need help deciding whether to do a complete rebuild to stock specs or convert to 3.8. My car has 130k miles and a leak down test today revealed some ring/intake issues that will need to be addressed (2 cylinders - one at 20% and one at 16%). I originally was planning to fix the oil leaks / maintenance and install a Fabspeed exhaust/chip combo. However, due to this new knowledge, I am now thinking that my money may better be saved for a rebuild. Accordingly, my question is whether I am hurting the potential value of my 964 by converting to a 3.8 for the horsepower when I have no intention to track the car aside from a few DEs per year. I use the car on the weekends and plan to keep it for my kids. I have retained all the original parts thus far from any mods (new radio, air ducts, front lip, lowered). The car is a blast as is but the oil leaks prevent me from participating in DEs and the smell and drops are getting annoying. Comments?

race911

I'd work with a known engine expert to maximize what you can do with a 3.6. Of course, it sounds like a PC set is in your future, so you can weigh what you get in the extra cost of going 102mm + boring the spigots--a whopping 150cc.

kreeshp

I went through a similar decision recently on my 964 engine rebuild (100% street driven, no DE's).

Conclusion I arrived at (similar to Ken's ^^^), after talking to my mechanic and crunching the numbers: it was better value to keep the stock 3.6 displacement and put the money that would have been spent on a 3.8 upgrade towards either a closer ratio transmission re-gear or other mods (suspension or exhaust etc.)

Mondrian

You might just be ok with new rings in which case no need to put money into pistons, besides 16 & 20 on a couple is not too bad, probably get another 10-15k out of it if all else is ok ie no smoke and pulls strong.

Navaros911

You will really only be able to answer once opened up.

My cylinders were scuffed on the inside, so needed replacing. Something I didn't expect.

So if you can open up first and then get parts, I would suggest that.

porsche mania

Personally I would only bother with 3.8 if the cylinders need replacing, it's a minimal price hike over 3.6 if you go for the slip in cylinders so why not if your buying them anyway! It does also leave the options for a wide choice of cams you may wish to add at a later date as the pockets on the piston tops are much deeper. As for resale value I wouldn't think it matters, it's a Porsche part your fitting and doesn't involve any machining of the cases or any other permanent changes.

Flat6 Innovations

I've got a great set of OE 3.6 cylinders and pistons. I pulled them from an 80K mile 964 (1990) engine that I am using as a base for my 4.1

I have ultrasonically cleaned them already :-)

-nick

^ Definitely. And don't forget the extra $400 for a Wong chip to go along with the p&c. I wouldn't trust any other off-the-shelf chip.

Flat6 Innovations

Absolutely... I am installing a Wong chip into my 993 today, and my 964 is next, as soon as I get the time to finish it. You can't go wrong, with a Wong!

CRG

" converting to a 3.8 for the horsepower "....
what kind of HP increase are you expecting? More importantly what kind of money are you planning to spend? To fully maximize a 3.6 to 3.8 upgrade is gonna cost ya some coin..P/C's alone wont get you much, if anything. I considered the same modification when I rebuilt my engine but after talking to/emailing many primo builders e.g. Jerry Woods, Colin Belton, etc. I just wasnt prepared to spend the additional coin for Motec, injectors, cams, labor for tuning, engine case work, etc. to maximize the mod. and mine is a daily driver not a track car.
Best advice was from Jerry Woods- "you want a race car, then buy a race car"

Flat6 Innovations

I agree.. The larger displacement has marginal returns unless camshafts and cylinder heads are addressed. I learned long ago to never just go up on bore, the changes must be applied across the board.

Just going bigger is a good way to narrow up a power band and lose something, somewhere. In my 993 I kept the 3.6 stock all the way through, for my 964, it going straight to 4.1, and all the way. In assembly now, but I was smart enough to keep my OE engine bone stock, for later..

All the way, or not at all!

JV911

If you need new P&Cs then there is no reason not to go 3.8

perelet

Displacenet increase from 3.6 to 3.8 is marginal. To get all power out of it you'll need to redo intake, exhaust, valvertain, cams.
So that $ALOT$ more than just 3.8 set. Find good literature and read about 3.8RS developments - good reading.


After you sink all of that $$$ you'll end up with engine that will be no good for street at all. Your #3 and &6 cyls will overheat and pop up delivars every so
many miles. Can't use steel studs on that engine. Rocker arms/cam will wear off at same rate as as tires - need to replace every few gas refills.

Factory never went with 3.8 air cooled engine for street and they had years of R&D, street & race testing to backup.

Meatball911

Thank you for all the replies! After much consideration, I think a stock 3.6 rebuild makes the most sense for many reasons already stated. My budget is $15-20k but my new plan is to post pone the rebuild one winter as the car still runs and drives very well. However, it does have some maintenance and oil leaks that must be addressed this year. As such, and in conjunction, I plan to order a Fabspeed exhaust kit and chip that will also be used post-rebuild. I think the extra time will allow me to research the build more extensively in order to make it bullet proof. Thanks again for all the help and I truly appreciate the wealth of experience offered on this forum. Have a great night!

Ken D

Sure they did. Both the 964 RS 3.8 and subsequently in the 993 RS.