TheFlyfish

I have two 4.5 16V engines in the workshop, the plan is to make a boat engine out of one of them.

When I look into the exhaust ports on the heads, it seems like there is a thin steel sleeve pressed into each port. On one head, this is quite corroded, so maybe I should replace them.

Has anyone ever replaced these sleeves ?

Dave928S

Are you referring to the valve guides, which you can see when you look into both exhaust and intake ports? There are no other sleeves.

Once you have a few more posts you should be able to add a photo, which would be helpful.

Here's a pic of a standard exhaust port, which shows the valve stem and guide, and the small air bleed hole drilled into each port, which is fed by the air pump. This from a 4.7 litre head, but I'm not aware that 4.5 litre heads have major differences, such as sleeves.

TheFlyfish

No, not the valve guides. If you look along the circumference of the hole it looks like there are two lines, mostly visible to the right, in your picture.

I would sustect that this is a steel sleve, pressed into the hole.

When I removed one exhaust header yesterday and put a finger into the hole, there was clearly rust on the surface, just inside the hole. I didn't have a magneto, to test if there is some steel there.

The engine has been standing for several years, so enough time for a little rust to build up.

Dave928S

The port is definitely all alloy with no steel sleeve. The line you see is the edge of a slight radius/chamfer, and another line is a gasket mark. The rust you're seeing is probably from the 'boat anchor' 16V cast iron manifolds.

hacker-pschorr

I have a set of EuroS heads with a pressed in steel sleeve in the exhaust ports.

The 944 Turbo heads also have a pressed in sleeve like this.

James Bailey

Correct some of the later Euro heads did have steel sleeves...no idea when or why they were used. Never seen them as a separate part.

docmirror

I've seen the pressed in sleeve on engines before as well. I'm sure it's not a replaceable part that could be ordered, so you would be doing this home-brewed with a lathe if you go that route. I also would consider that the steel of the sleeve is likely a rather esoteric blend of metallurgy. Maybe Inconel, or possibly Maraging steel. Hard to say, but I don't think you would have much fun if you just put in some cold-rolled piping.

If the corrosion isn't too deep, I'd just keep what you have.

V2Rocket

944T has a CERAMIC exhaust port liner that the alum head is cast around.
It slightly changes the shape of the port but not enough to matter - it was to keep the outgoing gas hot to help light off the catalytic converter faster due to the length of piping from head to cat on a 944T.

No steel in there except for the valve itself.

mark kibort

ive seen those too in my euro heads for my old 5 liter part euro build... always wondered why they were in there.

And Dave's pic, i believe is a euro head .. they had the small air ports in the exhaust ports for the air pump, where with the US heads, had the small port in the intake port for cold start. i forgot where the air pump routes air on the US versions.

hacker-pschorr

I know about the ceramic ports, but I also had a 944 head with steel sleeves in the exhaust ports, couldn't remember where it came from or if there was a year change.

I say "had" since I have no clue where it went. It might have been cut up for testing.

GlenL

My '80 Euro S has these. Not pressed in...at least not anymore. Sort of rattle around.

Had to check the PET and I couldn't find them as 928 or 944 parts. With their use you'd expect them to rot and be available for purchase. Must be in the internal-only parts system as a component of the head.

Strosek Ultra

My 1985 928S 4.7L 16v LH-Jetronic non-cat car had the pressed in exhaust port steel sleeves. I removed the sleeves when I did the porting job. I wonder why they were there, must be for heat insulation. Anyhow the ported exhaust ports are flowing very well. The steel sleeves cannot be found in the Porsche spare part catalog (PET).
Åke

FBIII

Just take a high speed grinder to clean up the finish. I have done that in the past to Euro heads I have had. I never had rust but would concentrate on the transition from the aluminum port to the insert and clean up the finish of the insert.

Dave928S

Well I'll be doggoned ... never seen them. Definitely not on mine (euro), and haven't seen them on others. You learn something new every day.

I'm intrigued as to the purpose, and why on some and not others.

Maybe Roger, or perhaps Greg might have a clue.

James Bailey

My guess is that since aluminum melts at around 1,220 degrees F and exhaust temperatures run around 1,200-1,600 (the higher temps if run very lean) Porsche was seeing some erosion of the aluminum on European cars being driven at high speeds for extended periods of time and the Turbo 944s obviously build up more heat due to the restriction of driving the turbo....hence the ceramic liners to transfer heat out of the 944 turbo heads, they also got special exhaust valves, sodium filled as I recall.