Brig993

My 964 has 125k miles I'm the second owner. The engine has never been out of the car and its an early 91' motor without the head gaskets. It was leaking oil everywhere and felt down on power. After reviewing my options its time for a rebuild! What should I be doing? What are the latest and greatest parts for a OEM/OEM+ rebuild in 2021? I'm not going to increase displacement so not interested in 3.8. any comments are appreciated.

Rocket Rob

Before rebuilding, I would isolate the source of the oil leaks. Back in 1996, my car would leave drips on the floor. My local dealer recommended a full engine re-seal for $12K plus parts. I laughed saying, do you know how many quarts of Mobil 1 I can buy for that? I went to a different mechanic who found that my oil pressure sender was faulty. He replaced it and 90% of my oil drip went away. These engines have multiple places to leak and most can be easily fixed without a rebuild. Save your money and investigate. Rebuilds are for worn out valve guides and other internal faults.

I got 237K miles on my engine before it needed to be rebuilt.

IMHO

Brig993

I’ve tracked them all down in the time I’ve owned the car. The engine was burning over a quart per 1000 miles. It needs a top end. We have leaks from the cylinders, heads, power steering pump, cam covers, valve covers, case through bolts, in addition to the RMS. The oil pressure sender is also leaking. The car was neglected when I bought it - I’ve driven it for two years and it’s time to address everything.

I intend to keep the car for a long time and while I always value trying to save money by doing only what’s necessary - I want to go beyond that and have the car be completely reliable and bulletproof for years to come. By posting here I’m seeking to see what I should be looking to get done for a “split case” rebuild, what parts I should absolutely upgrade for a 3.6 rebuild and to make sure the shop doing the work and I are on the same page, I know what to ask for/expect and can keep them honest.

peterpullin

one of the most happening fault of 1991 cars is breaking head studs. they often have dilavars mounted this year.
other exhaust guides. no oem exhaust valves. mine broke after 350 miles.
would source others or reuse yours if in spec.

look for damaged teeth in your oilpump.

all other things you can find in threads about engine rebuild.

Brig993

Thank you!

Rocket Rob

When I rebuilt mine, I talked to Steve Weiner at Rennsport (https://rennsportsystems.com/). His advice was very good and he was able to supply all of the parts needed. You can also talk to EBS Racing (https://www.ebsracing.com/). They all also very good.

Earlydays

As an aside...the factory stipulated that burning a quart of oil per 1000 miles is not unusual.

Brig993

it is more than that more like quart per 750-800

titleistaddict87

First question, are you doing yourself or sending out? Just did this, tons of work but now leaks no oil and runs like new.

Brig993

I am sending out. I cannot make the time commitment nor do I have a lift to do this job properly. I have a shop I’m working with and I want to know the questions to ask and what to expect/what the consensus is on what parts should be used/work should be done.

I have been through this with two 993s several years ago with other shops and I didn't ask the right questions back then.

Brig993

Thank you! I will reached out and try to schedule a consultation with rennsport systems.

Goughary

Typically a shop will send the heads off to be done by the head experts...which is what we did with mine. So another nod for Steve Weiner. Steve was very helpful making proper decisions relative to the way the car was going to be used.

In my case- the heads were done for a non-head gasket car- as my engine designer decided to fix what Porsche did wrong- and we kept the no head gasket design, but just made it work correctly. For the heads, we sent them to Steve and he did his head magic, and then used 993 intake and exhaust valves, Steve's valve guides, titanium retainers and aesco springs. We wanted to lighten up the valve train a bit, but were not looking for real performance gain.

Anyway....I'm now over 70k on that top end build and the heads still don't leak. Porsche machining these things for the head gaskets, after the fact, was just a quick easy fix- and not the right way to do it on the early cars. The tops of the later cylinders are designed for a head gasket and they are more appropriate there...

titleistaddict87

Good idea. I wanted the experience to do it once and I enjoyed it but will send it out next time as well. As you know with the 993s you did, it's hard to say ahead of time what the car will need. With the mileage I would expect you're going to want to do most everything including at a minimum, inspecting the crank, rebuilding or replacing the oil pump, and up from there. With re: to which parts to use for each step, there are many many choices and if it was me sending a motor out, I would pick my mechanic based on my trust in him being able to present me with a few choices for the major decisions along with pros / cons and then using his experience to decide on the other bits and bobs. If your intention is to keep the motor stock, then your decisions will be fewer and easier.

EDIT: I also wanted to clarify that the 1 quart "burned" you quoted above is the total of leaks + burned oil, meaning your engine is actually consuming much less than 1 qt / 1000 miles.

-nick

Unless the nose bearing is leaking badly or there is debris in the oil, I can’t see any reason to split the case at 125k.

Sounds like a thorough top end would get it back in shape. Opt for a 993SS cam grind (Dogherty/Webcam/etc) for a small power bump and stock ecu friendly. If the valves need replaced, go with the thinner-stem 993 valves for a tad more flow. Good tip above on the head studs, 993tt studs are the current de facto. Through-bolt o-rings can be replaced one at a time without case splitting too.

Otherwise, check and replace worn out bits as needed.

Edit- forgot to mention to have the rockers resurfaced and re-bushed along with the cam grind. Those bits are easy to forget.

titleistaddict87

Ooops. I got confused by the second post stating the engine had 237k miles. Yes, agree completely with -nick on this one. My car has 130k miles, so same age as the OP. When we got into it, we were pleasantly surprised at how great things looked. Diagnostic tests we did included leakdown / compression, identifying source of leaks, inspecting cam lobes, scoping all the cylinders, inspecting the valves, and testing for guide wear. We also checked and set timing. Based on our findings, we didn't feel the need to go further and I suspect you may be in the same boat. Since the rebuild, zero leaks and car runs great.