993 heads
 

guys - I have a few 993 heads and noticed (1) has cracked and missing chunks of ceramic liner in the exhaust port. Can this be fixed? How to fix it? It looks like 35% of the liner is missing? Is there a high temp epoxy to fill in and build up to repair? Open to thoughts, suggestions and possible solutions from the group. Thanks! Jim Dorociak
jdorociak@gmail.com

They crack... I've only seen 3-4 3.6 engines apart but all had cracks and missing parts of the liner. My engine is missing some of its liner.
Probably not ideal, 35% seems like a lot, but I wouldn't worry unless you have a turbo. The common method of repair I think is to replace the head with a better one.

One of Neil Harveys posts somewhere (recently) stated he has some sort of coating that he brushes on in layers.... No idea what he uses of course but it would be worth reaching out to him.

Thanks Mike - I sent him a PM and will do a search as well. Jim

This is why I went with Xtreme heads for my race engine. Yes, Xtreme heads are expensive, but, for my situation, I will save money in the long run not having to deal with damaged ceramic inserts or cracked heads.

Thanks Scott. Not making a race engine, but a solid street engine. Is there any repair that can be done to "fix" the missing pieces of ceramic? I have to assume everyone who had missing ceramic did not throw those heads away. Jim

I've heard several shops mention here and elsewhere that they have repair procedures for damaged ceramic inserts. At least one mentioned an epoxy substance.

I can't see how any epoxy based material would hold up to the heat in the exhaust port--that's why they are made of ceramic in the first place. Whatever they brushed into the exhaust port must be a ceramic based thermal barrier coating (TBC), that must be heat cured in an oven first, then finish cured by running the engine. See one of your local TBC specialists. FYI, I had TBC applied to the exhaust ports of my engine I built a year ago. So far, so good (6000 miles).

If the ports want to be bigger, then why fight them? (sarcasm, haha, not really a question)

"Be the port."

Peter, do you have any reliable data indicating a reduction in head temperature?

Nope. TBC's will reduce head temps. How much, and whether it makes a difference in the longevity of the heads is an open question.

I use cerakote thermal barrier on 356 exhaust/heads/valves piston top, super durable. Prep is key:
- ultrasonic clean
-heat up head to 300 to bring up any oil left over
-ultrasonic clean again
- blasting with aluminum oxyde
- ultrasonic clean
- dry
- spray cerakote
- cook for 1hr at 300