lee101315

Has anyone sucessfully ported and polished the exhaust ports on a 951 head? I already did the intakes (slightly larger with a a mirror finish), and the only thing that is stopping me from doing the exhaust side is the stock ceramic coating. Anyone here run into problems with removing it?

Raceboy

You can have exaust ports ceramic coated after porting job.

I didn't port (not needed on 16v S head ) but had exaust ports coated to reduce heat transfer to fragile 16v head.

xsboost90

im pretty sure that those are cast into the ports- so when they crumble or come out your left with a large port- bigger than you may want. Most people porting heads for a turbo get an n/a head, port it and have the hotside ceramic coated afterwards.

ibkevin

Wasn't a textured finish in intake ports designed to keep fuel suspended?

DDP

Go with an N/A head. You don't HAVE to have the coating. Plenty of ppl have run without it. One less thing to chip off and murder your turbo.

gt37vgt

had the 951 head ported not sure if my mate used Diamond tooling to do it . but the flaking off is a massive fear the turbo is spinning so fast i think a single pubic hair could destroy it

lee101315

No, that is to cut costs. Polishing heads would cost the factory a lot of money.

Personally, I think the "textured" or "satin" finish= better fuel atomization argument is nothing more than an excuse not to spend an extra hour polishing the ports. It takes 15-30 minutes to hog out a port and leave that "satin finish" lazy people love... finishing the port to look almost like chrome takes a lot more work. So by pushing that therory around, they dont have to work as long.

Thanks guys. Ceramic coating the exhaust ports is a bit expensive... I am glad to hear that people were running without the ceramic coating. So I guess all that would have to be done to swap the NA head onto a 951 would be to swap the exhaust valves over right?

Speaking of NA heads, has anyone swapped a NA cam into a 951?

gt37vgt

yeh I ran the NA cam and it has much better torque off boost and at low boost and is just less laggy an excellent upgrade if it had cost double what it did

xsboost90

i thought that turbo cams were the same as some of the n/a cams- late i think...

I may have an n/a head fs in the next couple weeks.

951jamie

The turbo cam and the early NA cam are the same.

Tom M'Guinn

As I understand it, the heads are cast around the ceramic ports. There is a great picture in a book called Forced Induction Performance Tuning (probably a porsche pic), which shows the ceramic port without the casting around it. It looks to be 3 or 4mm's thick. (That book also has some great misinformation about the 951 -- including a paragraph on how the DME monitors knock by cylinder and can pull timing to only the knocking cylinder.)

IPSC

So the NA cams (certain years0 and the turbo cams are different then? What is the difference?

IPSC

Olli Snellman

951 uses the same cam as early N/A cam was. The only difference is height of exhaust side which is 11mm with 951 cam and 12mm with 1985 and newer n/a cams. Otherwise they are identical. 951 cam should have stamping 05R. Late n/a cam has 09R.

IPSC

So the lobes are 1 mm higher, the effect is what? The valve opens a bit more allowing a better expulsion of the exhaust gas? In the grand scheme of things how much does this help?

IPSC

Olli Snellman

I suppose effect is not so dramatical. Lobe duration are identical on both cams.