924Board.org

leadfoot · Posted: Mon Dec 29, 2003 2:42 pm Post subject: brinnel wear limit...urgent

need wear limit for 924 N/A, 81XJ motor
had partial blown head gasket and need to find out whether head is no good anymore, figures were even at 40 brinnel across the head surface...
there was no pitting around the spark plug threads or on the head surface,
leadfoot...

Peter_in_AU · Joined: 29 Jul 2001 Posts: 2745 Location: Sydney, Australia

OK, I'm going in!

What!!!???

Can't remember the last blown head gasket we had around here - that's 944 territory.

As for the brinnel measurement, are you talking about the Brinell hardness test and if so why?

Check the Haynes, it has the info for measuring head flatness and levelling.
_________________
1979 924 (Gone to a better place)
1974 Lotus 7 S4 "Big Valve" Twin-cam (waiting)
1982 924 (As featured on Wikipedia)

Learn to love your multimeter and may the search be with you

leadfoot · Posted: Tue Dec 30, 2003 11:06 am Post subject:

lizard thanks, firstly i need to find out if my heads ok, what would shipping time be from you to me in melbourne australia.??

I am sitting on the fence not knowing which side i should fall off...

anyone ever had there head tested for hardness..??

Paul · Posted: Tue Dec 30, 2003 11:08 am Post subject:

I once had someone break a pool cue over my head.

AppleBit · Joined: 16 Nov 2002 Posts: 1516 Location: Minneapolis, MN

Leadfoot-

Never done it myself. Never heard of the term. I know that you don't want to shave your head though- bad bad bad.

Take it to a shop- they can check it to make sure it's flat and the block is flat. Those are the two places I would check first...
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Classic British Sports Car Restoration v6 + v8 Engine Conversion Swaps

Porsche 924 Wide Body LS1 Corvette 500 Horsepower Engine

leadfoot · Posted: Sun Jan 11, 2004 2:00 pm Post subject:

the head is going to be shaved by less than 4 thousands, which is .04mm and the valve seats are going to be taken off the same figure... i can see that the slack in the timing belt can be taken up, as well as the spring rate is going to be a little higher, not sure if coil bing would become an issue, but as the cam grind i'm having done does not increase lift it shouldn't have any adverse effect.
why is shaving the head bad??
Leadfoot

AppleBit · Joined: 16 Nov 2002 Posts: 1516 Location: Minneapolis, MN

because the head in the NA 924 does not have a compression chamber. That is all in the block. The 931 head has the compression chamber in the head, so it can be done.
_________________
Classic British Sports Car Restoration v6 + v8 Engine Conversion Swaps

Porsche 924 Wide Body LS1 Corvette 500 Horsepower Engine

Zuffen · Posted: Mon Jan 12, 2004 12:41 am Post subject: machine a cylinder head

there is a pin/guide hole on the distributer end on the intake side.

bottom of hole to bottom of head, machined surface 139.55mm,

if you go under that you alter the cam to crank distance and the timing

.1 mm uneveness of mating surface
.4 mm max rework depth
peak to valley .015mm
_________________
Bob Dodd - 924turbo@cox.net
931 1982, 944 1982 euro, 924S 1988SE, 93 968 tip 06 Silver Cayenne S, 06 Black Cayenne S

I have Way too many cars, parts for the 931,944 and 951