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  #1  
Old 05-22-2009, 11:21 PM
sasquatchgeoff's Avatar
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Head Gaskets and Block Surfacing

I was having a jovial discussion with my machinist of choice today while I waited for my camshaft bearing caps to be cleaned and polished. He had rebuilt my '86 OM602.911 head last week, and I forgot to include the caps when I initially dropped the head off. He knowledgeably went over the issue of block parting surface and the common error of mechanics to overlook subtle but substantial evidence of corrosion. He described that the dissimilar metals (aluminum/iron) and dielectric effect due to lack of coolant maintenance, and sometimes electrical issues left unrepaired, created a condition that allowed the block to deteriorate to the extent of detriment. This for me was an alarming wake-up, since I am in the process of rebuilding the top end of my engine. He stated that when torqued down, the head presses the gasket, and if the imperfections are enough, allow combustion gas breach and ultimately grossly premature failure of the gasket. In my case on the aluminum head parting surface, there were two areas of corrosion build up that required welding. This allowed surfacing of the head to render a perfect mirror finish. However, on the block side of things, there only are a few areas of discoloration. I suppose I could get a straight-edge and feeler gauge to see if these areas amount to relief enough to cause problems.

Here is a close-up shot of the block after cleaning, and here is another

My question to any of you that care to contribute: How many of you had your block surfaced when performing routine replacement of head gasket, and if not, did any of you experience premature gasket failure as a result of not having the block surfaced?

Thanks for any input,
- geoff

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327K on 1986 W201, 602.911, 722.414 2.5 190D ("The Red Baron")
139K on 1993 W124, 104.942, 722.433 2.8 300E ("Queen")

http://farm5.static.flickr.com/4081/...0bb92d3c_m.jpg http://i370.photobucket.com/albums/o...g?t=1325284354

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Last edited by sasquatchgeoff; 05-23-2009 at 08:00 PM.
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Old 05-22-2009, 11:51 PM
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Location: Bay Area No Calif.
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I have been involved with the rebuilding process on two 603's. In both cases I sent the head to an experienced head shop where the aluminum was skim cut for flatness and a pressure check was done (but in the reverse order).
I went over the block with a razor blade to remove all the build up right to the lip around the cylinder liners (that was dealt with by another fellow who came in and honed and removed the stuff). Incidentally my head guy, Mark DeGroff in Northridge CA, who has done many hundreds of these heads, said it is against his policy to routinely cut until its like a mirror, he stops short and there are visual signs of whatever left in the metal but still quite flat, so I trusted him on that. He offered to polish it if I wanted but had something against too much cutting. I also would worry about reducing hardness after any kind of welding on aluminum.
I re-ringed one and wish I had done the other engine but they are both daily drivers w/ no head gasket problems at all. Cleaning the ring grooves is something I will remember forever (I did it in my laundry room and stunk up the hose with liquid wrench, the solvent I chose.).
You want to get the best gasket set available. I read there was an improvement in the head gaskets by using some silicon stuff at key points and there are metal areas that crush down and make a seal when the head is torqued down, I think it fills small indentations OK so I wouldn't worry about the head surface unless it is really bad. If your pulling the engine and can send it to be checked at a machine shop (for cylinder maintenance or replacement) they can check it closely. Machining it down would raise compression however and the PC chambers would have to be shimmed to maintant the same compression ratio.

Some small things I did would probably never be done by some mechanics, like cleaning the threads and blowing air into the holes in the block using a long needle valve attachment on an air hose. I like things clean
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Last edited by dieseldiehard; 05-22-2009 at 11:58 PM.
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  #3  
Old 05-23-2009, 12:23 AM
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Thanks DDH,
Since I am only rebuilding the top end, I have not been able to take the block into the shop for surfacing since most of the engine is still in the car. I like the idea of cleanliness and liquid wrench. I added a couple of photos to my post to better illustrate the discoloration I am referring to. I will get back to the razor blade and use a rag with Liquid Wrench. I can't imagine that the block could get too clean.

- geoff
__________________
327K on 1986 W201, 602.911, 722.414 2.5 190D ("The Red Baron")
139K on 1993 W124, 104.942, 722.433 2.8 300E ("Queen")

http://farm5.static.flickr.com/4081/...0bb92d3c_m.jpg http://i370.photobucket.com/albums/o...g?t=1325284354

Do not worry about your difficulties in Mathematics. I can assure you mine are still greater.
- Albert Einstein

take a walk down memory lane...
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Old 05-23-2009, 06:40 AM
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Quote:
Originally Posted by sasquatchgeoff View Post
Thanks DDH,
Since I am only rebuilding the top end, I have not been able to take the block into the shop for surfacing since most of the engine is still in the car. I like the idea of cleanliness and liquid wrench. I added a couple of photos to my post to better illustrate the discoloration I am referring to. I will get back to the razor blade and use a rag with Liquid Wrench. I can't imagine that the block could get too clean.

- geoff
The problems discussed here are endemic with older Citroens because they were made with aluminum from the 1950s. When rebuilding an engine, I routinely clean the block top with a rag and xylene in a well-ventilated area or outside to remove all discoloration.

I also spray a BIT of spray copper on both sides of the gasket to reduce the possibility of dielectric reaction as much as possible. I also put a super thin coat of antiseize at the very top of the block drillings only so that they don't make it all the way down the bolt hole and hydraulic the block.

Maybe not necessary but all my redos have lasted at least 5 years (so far) of reasonably constant driving.
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  #5  
Old 05-23-2009, 07:50 AM
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In the second picture that shows #1 cyl, is that a crack running from the front of the cyl to the front of the block? It sure looks like one in the picture.

If it is, I believe you have a problem.

Paul
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  #6  
Old 05-23-2009, 09:39 AM
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Quote:
Originally Posted by pmckechnie View Post
In the second picture that shows #1 cyl, is that a crack running from the front of the cyl to the front of the block? It sure looks like one in the picture.

If it is, I believe you have a problem.

Paul
Paul,
Thanks for noticing. I promptly ran out to the car to take a look, and fortunately it was just grease. A cracked block would have seriously ruined my day.
__________________
327K on 1986 W201, 602.911, 722.414 2.5 190D ("The Red Baron")
139K on 1993 W124, 104.942, 722.433 2.8 300E ("Queen")

http://farm5.static.flickr.com/4081/...0bb92d3c_m.jpg http://i370.photobucket.com/albums/o...g?t=1325284354

Do not worry about your difficulties in Mathematics. I can assure you mine are still greater.
- Albert Einstein

take a walk down memory lane...
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  #7  
Old 05-23-2009, 05:53 PM
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I am reallllly glad to hear that. That would make anyone have a bad day.
Other than that, I think you will be fine if you clean it as good as you can and use good quality gaskets.
Paul
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  #8  
Old 05-24-2009, 10:22 PM
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Quality gaskets are discussed, any suggestions as to brand?
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  #9  
Old 05-24-2009, 11:28 PM
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Dieseldiehard
 
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I use and recommend Elring. You can also get a gasket from the dealer, but ask them NOT to procure it from World Pac, something some dealers are tending to do lately! Definitely avoid Autozone, POOP Boys, Kragen and so on!
http://www.elring.de/en/02en/09_spezialanfertig.php

Victor Reinz is a good alternative.
http://www.reinz.de/root/eng/index.php
Anything else is to be avoided!
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  #10  
Old 05-25-2009, 03:13 AM
sasquatchgeoff's Avatar
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Quote:
Originally Posted by dieseldiehard View Post
I use and recommend Elring. You can also get a gasket from the dealer, but ask them NOT to procure it from World Pac, something some dealers are tending to do lately! Definitely avoid Autozone, POOP Boys, Kragen and so on!
http://www.elring.de/en/02en/09_spezialanfertig.php

Victor Reinz is a good alternative.
http://www.reinz.de/root/eng/index.php
Anything else is to be avoided!
Elring is what I have - I will post pics of the process as it advances...still cleaning that freakin block!

__________________
327K on 1986 W201, 602.911, 722.414 2.5 190D ("The Red Baron")
139K on 1993 W124, 104.942, 722.433 2.8 300E ("Queen")

http://farm5.static.flickr.com/4081/...0bb92d3c_m.jpg http://i370.photobucket.com/albums/o...g?t=1325284354

Do not worry about your difficulties in Mathematics. I can assure you mine are still greater.
- Albert Einstein

take a walk down memory lane...
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