mahoney944

Hi. I'm in the process of an engine build. Currently rebuilding the head and cam tower. I was wondering how many of you replace the head freeze plugs / do they go? Also while rebuilding the cam should I just clean everything up and replace all the seals or should it be resurfaced as well? I don't think it has any damage. Not sure if it got distorted in any way from years of use. Any tips for checking the cam wear and internals would be great too. Thank you.

V2Rocket

never bothered with the head freeze plugs. not a bad idea though.
no need to cut the cam tower - just clean it up.
look at the cam...as long as there aren't any gouges or pits you should be fine. never seen a bad 944-8v cam.

they should be shiny lobes, maybe evidence of fine lines on the surface but not scratches. they usually have a little black/brown triangle on one side of the tip of the lobe where the lobe doesn't contact the lifter so the factory surface treatment hasn't worn off yet.

make sure there's no rings worn into the top of the lifters...if uniform and shiny, just clean everything and reassemble.

H.F.B.

Here is a photo of a bad camshaft. Notice the difference left vs. right.

V2Rocket

Is that deep pitting on the bearing surface that can't be polished out?

H.F.B.

This is a typical example for camshaft scuffing. You can regrind the camshaft, but you reduce the base circles. The reason? Either bad oil or bad material, I assume the first.

divil

You think that's bad? Here's what mine looked like when I resealed the cam tower:

H.F.B.

That's pitting. My posting was an example for scuffing. Displayed on a cellphone you hardly recognize the difference.

mahoney944

Thanks for the responses. Let's dive into heads for a minute though. My head has a damaged exhaust port. So I'm looking into a replacement turbo head or Na head with turbo components. How many people just use Na heads without coating the exhaust ports? Are the ports all the same or does the Na head need ported to match a stock turbo head?

Can I just swap my good turbo head internals into the Na head and get the same stock flow?

refresh951

What does the damaged exhaust port look like? Pic?

mahoney944

Theres a big chunk of ceramics missing about the size of a 50 cent piece. All the way to the aluminum

I'll try to get a pic later

PorscheFanatic202

i would want the turbo for the ceramics. I wouldn't put a n/a head into a turbo. Same thing happened to me, you should be able to find a good used turbo head. I'm not sure where you are at, but here is one for sale.

http://allentown.craigslist.org/pts/5644333984.html

V2Rocket

The ceramic in the 951 head is an emissions feature, not a performance feature...to heat the cat faster.
Not for turbo spool.

John Milledge always started with an NA head for his high-flow 951 heads.

divil

Were the emissions standards stricter for the Turbos?

mahoney944

My question is does the Na head flow exactly the same if the turbo components are installed to it? Seems like eliminating the ceramic failing point to turbo heads while retaining stock flow is pretty ideal...

Is it as simple as installing turbo head parts to a Na head? Or is porting required to fit the turbo head parts?

V2Rocket

Maybe, but it's more likely because the exhaust piping is so long and the compression is low, that the catalytic converter would take too long to heat up which adds cold-start emissions.

The port exit is the same size but the internal geometry of the port is different because of the ceramic liner.
But I doubt you'd ever notice a difference in output.