s4magman

This weekend I replaced the oil line that goes from the engine to the oil filter. To do this the heat exchangers had to come off. Not a difficult job as long as you have a 13mm flex head socket and an extra long 8mm hex bit with a square top. Once the exchanger is off, the oil line swap is very easy.

Now, what I found in the exhaust ports have me seriously worried and I hope someone can tell me what I am in for. Each of the six cylinder heads have significant chunks of ceramic lining missing. I drive my 964 almost exclusively on the track at DE events and the RPM stays pretty much north of 5000 all the time so the car lives a pretty tough life. My plans have been to do a full rebuild next winter but with the discovery of the cracked lining I'm worried I'll need to rebuild immediately. Can I DE the motor as is? Or is my season over before it even started?

Pics below...

crg53

I am guessing you are in the same boat as 90% of the rest of us. Mine has the same problem and it drives just fine.

s4magman

Thanks for the encouragement. Mine drives really nice too! She flies on the track and hasn't given me a lick of trouble thus far with 146k miles on it. The top end was rebuild at 100k but the remainder of the 46k has been exclusively on the track. I'm quite impressed with the durability of these things.

crg53

If mine was a turbo, I would worry a lot :-)), those chunks would certainly chew up the turbine, but with the Na engine, I don't see a problem.

Steve Weiner-Rennsport Systems

The ceramic port liners serve to insulate & protect the heads from excessive heat, especially when the OEM exhaust is in place.

This is becoming more common as these engines accumulate miles and see more incidences of head cracking when the ceramic pieces are missing and more so in engines used for track & racing. I would make certain that your WOT AFR's are not too lean as that exacerbates the process.

I would be on the lookout for some nice heads (no cracks or missing port liner pieces) before you undertake the rebuild as that's in your future..

s4magman

Thanks Steve and crg,

Sounds like I will be able to continue to drive the car for the season and hope the heads hold up. I will also need to find a good set of cyl. head and those don't seem easy to find. Any leads would be appreciated.

hawk911

I had 1 cylinder that was missing some of the lining. My local shade(y) tree mechanic told me I had to rebuild because of that. the common feeling on here was there was no reason to rebuild on a single head with that issue, esp for occasional driving under street conditions.

FeralComprehension

This issue is commonly reported; I've not read anything (and I try to read everything) where someone has said "Something Bad happened because I lost the port lining!"

Cosmos99

My car has 67k on it and has some small pieces of the lining missing too. I wouldn't worry about it and enjoy driving her.

crg53

Out of curiosity, if you were to install other cylinder heads, would the 993 heads be a good alternative. I understand they have slightly larger ports & valves, but they do not have the problems with the ceramic liners.

s4magman

^ I'd like to know the answer to that question as well.

Steve Weiner-Rennsport Systems

993 heads can be made to work, but just remember, they are basically the same things, albeit newer. One good aspect is that 993 engines generally tend to run cooler EGT's due to having twin cats and that affects the life & condition of the port liners.