Head Gasket Surface Preparation
Thread Starter
Instructor
Joined: Jan 2007
Posts: 232
Likes: 41
From: Simpsonville SC
Head Gasket Surface Preparation
I need a little direction from the folks here with experience replacing head gaskets. I have my heads off and removed the gaskets. The gasket came off relatively clean except for a little crud around the water passages and an outline of where the bead on the gasket contacted the deck. Some of the spots where the old gasket bead appear to be stained. You can see the outline of the old gasket. Is this just a stain of is it actually gasket material? What’s the best way to prepare the deck for a new gasket? Can I carefully use a gasket scraper for the crud, then a scotch brite pad or sanding block w/600 grit for the finishing touch? How clean does it need to be?
Racer
Joined: Apr 2004
Posts: 401
Likes: 0
From: IL
Razor blade is less damaging than a gasket scraper. You may have to shave debris in layers but better than accidentally gouging of the surfaces. DO NOT use scotch brite pads as they can leave the fine grit everywhere, no matter how well you cover the area. That "grit" could eventually do damage. We always used a fine wire brush in a 90 deg grinder to clean the surfaces without damage to the surface finish. Which is very important in sealing performance. Even with this process the "staining" you mentioned is still visible but at least you know it's clean.
Don't forget to chase the cylinder bolt hole threads before reinstalling. Teflon sealer on the threads during reassembly will give good insurance against leakage later.
Hope this helps,
Later.
Don't forget to chase the cylinder bolt hole threads before reinstalling. Teflon sealer on the threads during reassembly will give good insurance against leakage later.
Hope this helps,
Later.
Team Owner
Joined: Aug 2006
Posts: 24,125
Likes: 15
From: Columbia Missouri
I always use a fresh razor blade in a holder to scrape the surface completely clean. Be very careful around the water passages because the razor blade can get caught and chip out and those pieces can fall in and then where the chips came out you can leave scratches. I always stuff some moist paper towels down in the cylinders and in the water passages to catch as much of the debris as I can and when you're done vacuum most of it before pulling the paper towels.You'll have a little bit of trouble around the head alignment pins so go slow and be careful and remember, lots of extra light from drop lights will really help you here. Not the best time to be squinting in the dark.
Melting Slicks
Joined: Mar 2008
Posts: 2,989
Likes: 198
From: Meriden CT
I just use the gasket scraper for the deck. I think it's impossible to gouge the cast iron with a scraper, and it's easier on my hands. I just wipe the surfaces with a clean shop towel and re-assemble. With aluminum heads I'm a little more careful with the scraper, but I still never gouged one. I don't use any abrasives on the mating surfaces. You don't want to sand any surface irregularities into them.
Thread Starter
Instructor
Joined: Jan 2007
Posts: 232
Likes: 41
From: Simpsonville SC
Can't seem to find a thread chase locally. Can I just use a tap or take an old head bolt and cut a small groove in it? I thought I read somewhere that using a tap as a chase was not a good idea because it removes some of the thread material.
Last edited by bytor; Nov 25, 2008 at 08:40 PM.
Le Mans Master
Joined: Jun 2004
Posts: 6,231
Likes: 65
From: Seattle WA
St. Jude Donor '14
This is the sweet thread restore kit 
http://www.sears.com/shc/s/p_10153_12605_00942275000P
I really wouldn't use a tap - people do, but as you note it's a cutting tool not a cleaning tool. Just use a bolt and clean 'em out best you can.
I generally wipe down the head and block deck with some brake cleaner before I make the change...and it's a good time to be SURE you didn't drop anything in the bore.
http://www.sears.com/shc/s/p_10153_12605_00942275000P
I really wouldn't use a tap - people do, but as you note it's a cutting tool not a cleaning tool. Just use a bolt and clean 'em out best you can.
I generally wipe down the head and block deck with some brake cleaner before I make the change...and it's a good time to be SURE you didn't drop anything in the bore.
Racer
Joined: Apr 2004
Posts: 401
Likes: 0
From: IL
Well the type of tap is important as some can remove material because of the class of tap. Check the web for better explaination or your local tool and die supply for advise. The chasers are better, though the kits can be expensive for one time users. It is amazing though how many other times the kits come in handy.
Low buck way is to make some cuts to an existing bolt but making and mantaining the groove is important. I personally never used a cut bolt more than a few times in a jam and never for 34 bolt holes on a block I spent time and money on.
I've seen many heads and blocks scratched from guys in a hurry with an old scraper from the bottom of the screwdriver drawer. Just seems with a razor blade with holder/handle people are a little more carefull and slow down with such a sharpe blade.
Why are the heads off in the first place?
Low buck way is to make some cuts to an existing bolt but making and mantaining the groove is important. I personally never used a cut bolt more than a few times in a jam and never for 34 bolt holes on a block I spent time and money on.
I've seen many heads and blocks scratched from guys in a hurry with an old scraper from the bottom of the screwdriver drawer. Just seems with a razor blade with holder/handle people are a little more carefull and slow down with such a sharpe blade.
Why are the heads off in the first place?
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Melting Slicks
Joined: Mar 2008
Posts: 2,989
Likes: 198
From: Meriden CT
Well the type of tap is important as some can remove material because of the class of tap. Check the web for better explaination or your local tool and die supply for advise. The chasers are better, though the kits can be expensive for one time users. It is amazing though how many other times the kits come in handy.
Low buck way is to make some cuts to an existing bolt but making and mantaining the groove is important. I personally never used a cut bolt more than a few times in a jam and never for 34 bolt holes on a block I spent time and money on.
I've seen many heads and blocks scratched from guys in a hurry with an old scraper from the bottom of the screwdriver drawer. Just seems with a razor blade with holder/handle people are a little more carefull and slow down with such a sharpe blade.
Why are the heads off in the first place?
Low buck way is to make some cuts to an existing bolt but making and mantaining the groove is important. I personally never used a cut bolt more than a few times in a jam and never for 34 bolt holes on a block I spent time and money on.
I've seen many heads and blocks scratched from guys in a hurry with an old scraper from the bottom of the screwdriver drawer. Just seems with a razor blade with holder/handle people are a little more carefull and slow down with such a sharpe blade.
Why are the heads off in the first place?
Thread Starter
Instructor
Joined: Jan 2007
Posts: 232
Likes: 41
From: Simpsonville SC
I'm doing a Vortec head and cam swap.
Le Mans Master
Joined: Sep 2001
Posts: 7,739
Likes: 630
From: Unreconstructed, South Carolina
gasket tool
pocketknife (small & inexpensive) ... works great, is easily resharpened & affords some emergency protection. An essential that's right up there with baling wire, visegrip & wd40.
Le Mans Master
Joined: Sep 2001
Posts: 7,739
Likes: 630
From: Unreconstructed, South Carolina
gasket abrasive
3M Bristle Disc (Non-radial) ... they leave very little scat, safe & easy on decks-heads (much easier than fuzzy rolocs), also OK with aluminum. No BS, that 3" yellow one works great for me ... does Not cut bore-deck between cylinders like a fuzzy roloc can. When used behind a pocketknife, one will do 2-3 motors w/ heads. Alum heads/blocks should use a white bristle disc (fine).
An electric drill won't spin these fast enough; you need a die grinder etc.
http://solutions.3m.com/wps/portal/3...d=GSJJHB5N8Vge
when I get done scraping/cleaning off the decks of an assembled short block ... I vacuum out the bores around piston tops ... then lite spritz em with brake/carb cleaner ... and vacuum them again. Then wipe everything down with carb/brake cleaner etc.
An electric drill won't spin these fast enough; you need a die grinder etc.
http://solutions.3m.com/wps/portal/3...d=GSJJHB5N8Vge
when I get done scraping/cleaning off the decks of an assembled short block ... I vacuum out the bores around piston tops ... then lite spritz em with brake/carb cleaner ... and vacuum them again. Then wipe everything down with carb/brake cleaner etc.
Le Mans Master
Joined: Oct 2002
Posts: 7,098
Likes: 378
From: Las Vegas - Just stop perpetuating myths please.
Non abrasive wheel - like a scotch pad on a wheel.
Sorry can't recall the terminology. Most are redish brown wheels that look like scotch pad material but a lot coarser and attach into your hand drill chuck.
U want the surface squeky clean but leave the original machine marks unchanged - the block is machine to a specification for roughness.
Yes removing the old gasket material is a job and a half to remove by hand (I've been there) but this should speed things up for u. Vacuum and i clean with alcohol before installing the new gaskets.
Hope this helps,
cardo0
U want the surface squeky clean but leave the original machine marks unchanged - the block is machine to a specification for roughness.
Yes removing the old gasket material is a job and a half to remove by hand (I've been there) but this should speed things up for u. Vacuum and i clean with alcohol before installing the new gaskets.Hope this helps,
cardo0
