Bart-Jan

Hi all,

I’ve got some spare time and would like to upgrade my 16v heads, if possible a little bit by trying to port&polish it with a dremel. I haven’t started yet, but found a sleeve in the exhaust port; is this a ceramic sleeve as used in the 944 turbo heads? So I guess there’s little to be done in the exhaust ports other than polishing it?

Are there other DIY guidelines for porting the 16v engine? Maybe the inlet ports and/or pipes? Or the exhaust manifold (I won’t go header/tubular style for the moment)?

I searched for related topics, but it was hard to find, apart from the Lindesy website.
Some guidelines/websites/pictures would be greatly appreciated.

Imo000

Leve it to a pro.

beentherebaby

The OE head is pretty efficient. P&P can actually lower the engine performance even if you managed to increase flow. If you are rebuilding the engine/top end then I'd have a pro clean it, check flatness, R&R the guides/valves as needed and do a precision valve job.

karl ruiter

Do you have a S motor? If so then that is pretty much as good at gets for 16V. If not, folks pretty much try to emulate the S heads, I think.

mark kibort

If they're euro heads, that is pretty good already. porting and polishing wont do much if I was going to guess. they need an even racier cam. grind down the base circle by .5mm as that would buy you some lift for a few more HP.

Bart-Jan

Thanks for the replies! Yes, they are S heads, so I will only clean the heads and add new valve stem seals while they're off. How about the exhaust manifold? Somewhere I read the opening to rest of the exhaust system is 51 mm, while the seal is 55? Is there some other grinding to improve gasflow? Or the same story: Porsche has all ready done a great deal on them?

Imo000

Better if you replace the exhaust manifolds with a par of '85-'86 32V ones.

mark kibort

+1

Dave928S

+1 too ... better than the boat anchors.

slate blue

This is a relevant link,

http://forums.pelicanparts.com/911-e...-dark-art.html

The exhaust is the first area to look at but the heads are easy to clean up and I have had good results on the dyno and road.

Greg

Bart-Jan

If the exhaust has so much impact, how about making a DIY set of headers by welding standard pipes and bends together. It'll be a huge amount of working including trial fitting etc. But now the heads are off, it's an easy start (sort of). Has anybody tried this before? Are there any measurements etc. available? e.g. what is the inner diameter of the single pipes (per cylinder) and of the final pipe? I know it would be best to have all pipes the same length. What would the optimal length be?

I've made a new downpipe for my BMW with great results. However, that was stainless steel which was difficult to weld. A complete set of headers would be the next step :-)

slate blue

Yes I made the system in this link.

https://rennlist.com/forums/928-foru...-3-system.html

Car is basically the same in acceleration as a GT3 RS except it loses a second to 60 but loses nothing to 200 from there.

Welding stainless is not difficult, I had no formal training except trade training when I did this system however there is stainless specific techniques and when you know this it is easy and you can achieve very very nice welds. I recommend doing a course before you start.

Greg

Bart-Jan

Wauw! That's nice work!
How did you grind the inside of the headers? After each weld grind it before adding a next pipe?
Just out of interest, why arent flexible pipe used in headers? https://www.jetex.co.uk/jetex/store/...productId=2785
I would say it's easier to have the same length without needing to make a huge puzzle...

beentherebaby

^^^^ Because those individual sections of flex tubing cause terrific turbulence and loss of flow.

GlenL

Get the '85 exhausts. I put these on my Euro S and really enjoy it. Added them with a bunch of other mods so no solid horsepower gain figure but I figure 10 or 15 horsepower. The left side fits, but is tight, and the right side needs to be extended. The sound is great.

Leave the flex pipe for temporary fixes. It will rust. "Galvanized" mean "rusts suddenly."