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View Full Version : lapping block in car w/ steel block? HG install

jt1583
11-01-2008, 10:28 AM
engine : ca18det
Ok I'm reinstalling a headgasket (new one of course) since after the last one (done 3 weeks ago) I am leaking from the hg. I have had the head resurfaced and read on a website about taking a flat, steel block to lap the block. it said something like...

get a flat steel block (grinding at machine shop)
put 400 grit sandpaper around it securely
go in a back and forth motion across the block

It didn't say anything about when to stop, I'm assuming to use a straight edge and feeler gauges. I don't think its warped/out of spec so much since it's an iron block, but mainly to clean it up and remove any scratches.

What do you all think?
racepar1
11-01-2008, 10:40 AM
I've never had to re-surface a cast iron block to do a headgasket. I wouldn't do it. Did the gasket blow REALLY bad or something? Or are you just upgrading the gasket? If the headgasket blew up hardcore I would check the block with a straight edge, if it didn't I would just clean it and put it back together.
Sileighty_85
11-01-2008, 10:42 AM
What Brand H/G Blew? And what brand are you putting on?
jt1583
11-01-2008, 02:34 PM
it didn't blow its leaking oil from the back of the engine, exhaust side. Ride where the oil is fed to the head.

I think its either the gaskets fault, or a non resurfaced head.

I'm not sure, the gasket looked fine upon removal.

Torque was done correctly then redone after 1 heat cycle
jt1583
11-01-2008, 03:54 PM
I believe this is the cause of my oil leak. Background, oil was leaking between the head and block, exhaust side, very back. Slow leak, but it was there.
Here is the oil passage way.

http://www.prism.gatech.edu/~jthomas7/random/oil.JPG

I can get my fingernail caught in the scratch if I rub over it, so I do not think it's trivial. I may end up doing this ghetto lapping of the block to avoid engine removal and disassembly required to get the block machined by professionals.

Opinions?
redline racer510
11-04-2008, 03:55 PM
i thing you should get your block resurfaced and port out the oil passages if you can, deep scratcheds and stuff like that cause heat stress areas that can cause problems in the future. after hg install check oil pressure.