Jon Betts

Just taken the head off 87 944 NA to replace bent exhaust valve, There are 2 head gaskets? How can you tell if the head has been resurfaced? there is some pitting around a couple of the water channels can this be repaired if so how?

Thanks Jon

ERAU-944

2 head gaskets??? doesnt sound normal to me... the pitting can be repaired by using stuff called "marine tex" found at auto parts stores... i did this after having the head resurfaced. you put it on where it should be, let it set, then flatten it with acetone soaked rag... making sure that you put the surface back where its supposed to be... grinding the head will take some pitting away. other alternatives is to have the head pits aluminum welded before grinding, filling in the spots then the grinding makes it flat. the machine shop can measure the head to see how much more can be ground off it... it can be measured there, they will tell you if it has been previously ground.

good luck!
-Mike

david fracolli

Take the head to a machine shop and have them measure it. Porsche also makes 2 differtent head gaskets. One is 1.1mm thick that is for stock heads and one is 1.4mm thick for surfaced heads. I would be very surprised if the head has had that much material removed.
I had .025" inch removed from my head and still have plenty of piston to valve clearance with the 1.1mm gasket.
Dave fracolli
85.5 944

Jon Betts

I have access to a machine shop and have many years experience not sure if I would want to machine it myself but would like to make measurements anyone know where I can get the specifivations to compare it to? Anyone used JB weld to fill the water pitting?

Thanks Jon

tt9714

In a previous post:

</font><blockquote><font size="1" face="Verdana,Tahoma,Arial,Helvetica,Geneva">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Arial,Helvetica,Geneva">
Take the head to a machine shop and have them measure it. Porsche also makes 2 differtent head gaskets. One is 1.1mm thick that is for stock heads and one is 1.4mm thick for surfaced heads.</font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Arial,Helvetica,Geneva">According to my calculations, the difference between the "thick" (1.4 mm ) and "thin" (1.1 mm) headgaskets is about 0.012". That is exactly the amount of material that the machine shop expects to remove to resurface my head. Therefore, I plan to order the "thick" headgasket for my job.

Have other people used this part as well? It seems like maintaining the correct compression ratio (not to mention the valve& piston clearance issues) would be particularly important for turbo engines.

*Michael.*

</font><blockquote><font size="1" face="Verdana,Tahoma,Arial,Helvetica,Geneva">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Arial,Helvetica,Geneva">Originally posted by david fracolli:
<strong>I had .025" inch removed from my head and still have plenty of piston to valve clearance with the 1.1mm gasket.
</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Arial,Helvetica,Geneva">Do you know what your compression is at now? Have you had your car dyno'd after your mods?

944Play

</font><blockquote><font size="1" face="Verdana,Tahoma,Arial,Helvetica,Geneva">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Arial,Helvetica,Geneva">Originally posted by Jon Betts:
How can you tell if the head has been resurfaced? there is some pitting around a couple of the water channels can this be repaired if so how?
</font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Arial,Helvetica,Geneva">The tangs on the end(s?) of the head, according to the Parts and Tech book, should measure 23.8 to 23.6mm to the face of the head after resurfacing. Presumably, 23.8mm would indicate an unresurfaced head.

The machine shop (actually a cylinder head specialist) that worked on my 944's head had to weld up some corroded areas. This, plus cleaning, resurfacing, new valve guides, valve lapping, and seal installation (seals were provided in my head gasket set) ran me US$370, IIRC.

I did not bother to source a thicker head gasket, and this is an M44/09 (10.2:1) engine. YMMV!
<img border="0" alt="[ouch]" title="" src="graemlins/c.gif" />

Danno

"Have other people used this part as well? It seems like maintaining the correct compression ratio (not to mention the valve& piston clearance issues) would be particularly important for turbo engines."

I have actually milled off 1.5mm (0.060") a Turbo head and still had enough clearance. This is to raise compression to about 8.5:1. However, this gives zero leeway on belt-tension and alignment. Not to mention worn lifters and springs. A lot of the other guys like PowerHaus and Milledge tend to mill off 1.0mm (0.040") for 8.3:1 compression.

I wouldn't suggest this unless you're sure that you have new valve-springs and lifters. Or else you'll end up with something that looks like this :

<img src="http://members.rennlist.com/951_racerx/Pistons-951interference.jpg" alt=" - " />

BTW - anyone have a good way to take photos of what you see through a bore-scope?

*Michael.*

</font><blockquote><font size="1" face="Verdana,Tahoma,Arial,Helvetica,Geneva">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Arial,Helvetica,Geneva">Originally posted by 944Play:

valve lapping,[/QB]</font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Arial,Helvetica,Geneva">What is this???

944Play

Valve lapping, as in a "valve job," where they grind the valves against their seats using lapping paste....

david fracolli

Mike,I have 88 pistons along with the milled head. When I reassembled the engine last summer I measured everything and came up with a compression ratio of right around 10.7 to 1 if my memory serves me correctly.
I have not had a chance to dyno it as I have been mostly unemployed for the last 11 months and just do not have the money. I have though run some 50-70 times and am pretty happy with the numbers. According to data that I can find the euro, 163 hp, 944 does 50-70 in 6.4 seconds. The US 944s at 208 HP does it in 5.5 sec. My cars avg over 5 runs is 5.91 sec.
I have asked numerous times for people to try this test in fourth gear to see how my numbers compare but so far I have had no takers on this list.