lapping block in car w/ steel block? HG install - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

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.

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.

11-01-2008, 10:28 AM	#1
jt1583 Zilvia Member Join Date: Jul 2005 Location: Georgia Age: 33 Posts: 262 Trader Rating: (3) Feedback Score: 3 reviews	lapping block in car w/ steel block? HG install 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?

11-01-2008, 10:42 AM	#3
Sileighty_85 Post Whore! Join Date: Dec 2006 Location: Misawa, Japan Posts: 6,815 Trader Rating: (8) Feedback Score: 8 reviews	What Brand H/G Blew? And what brand are you putting on? __________________ 後輪駆動車１番 1989 Built SR GT2871R -363whp 1998 S14 W/RB25- 250ish (For Now) 1986 SR86 - 200ish 1990 R32 GTR - 320hp Don't Buy Engines from JDM-Online http://zilvia.net/f/businesses/207457-jdm-online.html Don't Buy XS-Power or SSAC Shit

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11-01-2008, 10:40 AM	#2
racepar1 Post Whore! Join Date: Jul 2007 Location: Simi Valley, CA Age: 38 Posts: 9,006 Trader Rating: (106) Rides Gallery: racepar1 Feedback Score: 106 reviews	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.

11-01-2008, 02:34 PM	#4
jt1583 Zilvia Member Join Date: Jul 2005 Location: Georgia Age: 33 Posts: 262 Trader Rating: (3) Feedback Score: 3 reviews	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

11-01-2008, 03:54 PM	#5
jt1583 Zilvia Member Join Date: Jul 2005 Location: Georgia Age: 33 Posts: 262 Trader Rating: (3) Feedback Score: 3 reviews	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. 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?

11-04-2008, 03:55 PM	#6
redline racer510 Zilvia FREAK! Join Date: Dec 2007 Location: EARFF(earth for you idiots) Posts: 1,072 Trader Rating: (1) Feedback Score: 1 reviews	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.