schwank

Machine shop says pistons at TDC have .014 inch rise above the deck of the block. He's concerned that they will hit with a stock headgasket and I am trying to find the thickness of the stock OEM NA headgasket for him.

I will say this. I will NEVER again have a machine shop who has not worked extensively on 944 motors do a build for me. The place has gotten rave reviews from many and the guys are highly experienced but... I have seriously heard enough about our crappy cranks and crappy girdle etc. And hearing stuff like this makes me so sketchy.

Anyway, at TDC, should the piston domes clear the level of the block deck? And what is the stock headgasket thickness?

FRporscheman

I think it's about time he heard something about his crappy machining. Customers should never be served whine.

I don't know for the NA but for the 968 IIRC the standard gasket is 1mm thick and the one "for resurfaced heads" is 1.4mm. But last year when I bought the one "for resurfaced heads" it was 1.6mm. I don't get that. But if you can't find your info at least that gives you an idea.

M758

Eric,
Did the machine shop cut the top of the block? If you have stock pistons and the top of the block was not touched all should fit fine. If they machined the top of the block you may have an issue.

I have never machined the top of the block. I have only had heads machined flat. The pistons do come up to the top of the block, but I have never measured to see since I never had any reason to believe that dimension would change from stock.

BTW... stock gasket is 1.1 mm,

schwank

Perfect thanks. I am headed out to pick it up now. The block was not machined and the head was flat so it was not decked during this rebuild either. he was thinking the gasket was only .070 inch. I am taking the new one down there and we'll mic it so he can be sure. But 1.1mm is only .043. Should be interesting.

When I rebuild my current motor, I am gonna ship it to someone who does 944 motors all day long to avoid all this hassle.

schwank

Stock headgasket mic'd at .041. It will clear but not by enough for comfort.

Never ends with this stuff. But I have the motor back in my posession and boy is it shiny

joes

I'm interested in this post ! I think the pistons are supposed to flush up with the block, I could be wrong I will check when I get time. A friend of mine had a motor built and they decked the block (I don't know how much) and when we got the engine racing it had a detonation or pinging that we couldn't figure out. When we pulled the head one of the pistons was being eaten away. After some discussion the builder conceeded he had decked the block too much and did another engine for him. One of the problems with the N/A cars is that the area where the valves are small and the rest flush with the head so when the piston comes up it is very close to touching the head under normal conditions (head gasket thickness) I'm not as familiar with turbo cars and a thicker head gasket may be the trick but I would definitely know what is supposed to be.

M758

Did you have the rod journals machined? If not I would not see how it would be any differen from stock if deck on the block has not been machined.

schwank

The motor is built from a hodge podge of engine parts. I used the forged rods out of an 83. Pistons, crank, and block are 86 vintage. Head is unknown year purchased complete from a parts car... it was cleaned and given a valve job. The crank was polished. Looking at the notes, it actually does look like they decked the block. Also says 4 rods 'reconditioned' but it was only $70 so I can't imagine that involved machining. Something tells me the deck was shaved approximately .013, seeing as how that is the clearance of the piston dome above the deck according to the sheet. I was told .035 is probably the clearance you want between piston and head.

So .041 - .013 = not enough. Basically I could go with a cometic gasket at .051 from lindsey and get about the right spacing. .060 gasket sounds a bit much unless the head was decked as well, which it was not.

M758

My motors have been a hodge podge of parts. The only things in 944 motor that need to be matched are the girddle and balance shaft covers all are match set to the block. So you can't swap these from one block to another since the bores may not line up as needed. They are stamped with 4 digit numbers and all 4 need to match up. Beyond that pistons have a tolernce group that matches the diameter of th bore. The block top is stamped wth a number 0, 1, or 2 and that piston top should have the same number.


There is not reason to deck the block on these motors. Doing that unless you really know what you are doing is bad.

joes

A quick check of the factory manuals doesn't show any provisions for decking the block. Also no dimensions from the deck to the oil pan to see if it has been decked. ( I'm sure that's out there somewhere) there's no doupt that it's a trick for an N/A to raise compression but that would be unnecessary for a turbo engine. There is a shop in Georgia that has some experence with this that may be able to help. PM me and I'll give you their name.

FRporscheman

Why don't you need to deck the block? I'm just curious I'm not being smart or anything. I was going to build a motor this summer and I was thinking to deck the block at a 944 engine machinist.