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78 620, L20B foreign matter in combustion chamber.


Atikin9000

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You should be able to see your reflection. :lol: :lol: :lol:

 

Not really, if you can run your had over it and have it feel smooth then your likely alright, but you have to be honest with yourself,

if you think you felt anything then your not done yet.

 

Everything is smooth but there’s clearly residue spots that are smooth and flat, I even went at some of the tougher spots with a razor blade. I just don’t know when it’s good to go.

 

 

K6RmaD0.jpg

 

6BdAB2Z.jpg

 

9TeI1ng.jpg

 

Xpj4heZ.jpg

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The only way to get rid of the stains is to have it decked, and I would not do that unless it was not level.

It's etching from the gasket and two different metals. Notice the rust in the coolant holes? Make sure you use a good quality antifreeze/coolant.

Should be good to slap a gasket on, and check on good coolant.

 

Also I might add, i used a can of permatex gasket remover and just went over it with a plastic scraper, then hit a couple of spots with a metal razor. The can I bought was expired or something came out all runny, went back and exchanged for another, same thing. Still did a pretty good job.

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Looks like a rough surface finish to start with, then corrosion set in over time.  It should pretty much pass the razor blade test as well as the white towel test with brake cleaner.  You can even knock down high spots around stud holes with a fine file if you are VERY careful!  I use a scraper that's got a solid carbide edge and it will shave cast steel if you're heavy handed.  

 

Due to the condition of the block deck, I'd use Permatex #2 sealant around all the head stud and water jacket holes on the deck and the head.  Don't apply gasket sealant to the fire rings on the head gasket, and don't use enough for it to squeeze out into any of the holes.  Lett it just help bond where gasket pressure may be a little light from corrosion and age.  

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Looks like a rough surface finish to start with, then corrosion set in over time. It should pretty much pass the razor blade test as well as the white towel test with brake cleaner. You can even knock down high spots around stud holes with a fine file if you are VERY careful! I use a scraper that's got a solid carbide edge and it will shave cast steel if you're heavy handed.

 

Due to the condition of the block deck, I'd use Permatex #2 sealant around all the head stud and water jacket holes on the deck and the head. Don't apply gasket sealant to the fire rings on the head gasket, and don't use enough for it to squeeze out into any of the holes. Lett it just help bond where gasket pressure may be a little light from corrosion and age.

Just gonna stick to my little thread, ventured to Facebook and the 620 group and all I got was people pointing out #1 piston lol.

 

Anyway I’m gonna give some scotch brite a try as well.

 

Thanks guys.

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Thanks man, happen to know the length of the spacing in the middle part?

 

It really depends on how far the stud screws into the head, the exhaust/intake gasket is 1/16th of an inch thick, the stock exhaust manifold is 7/16ths of an inch thick, and the washer is a 1/16th of an inch thick, so is the lock washer, so if the stud threads all the way in to where you cannot see any threads a 1/2 inch would sound about right but I have some studs and it appears to be 5/8ths of an inch, anyway you look at it the stud should start having threads about a 1/2 inch away from the head surface.

If you don't have threads till 3/4s of an inch from the head surface you will have to start using thick washers or start stacking them which you do not want to do.

Here is a photo of a couple studs I have, the end with the most threads goes into the head.

DSCN7324.jpg

Here is the stud in the head.

DSCN7325.jpg

 

DSCN7327.jpg

Here is the stock manifold on the head, with an exhaust/intake gasket less threads would show.

DSCN7332.jpg

 

DSCN7334.jpg

Here is the washer and lock washer in place, with a intake/exhaust gasket in place it would be better.

DSCN7336.jpg

And here is the nut in place, it is not quite tight, but with another washer to simulate the gasket it is tight.

DSCN7328.jpg

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It really depends on how far the stud screws into the head, the exhaust/intake gasket is 1/16th of an inch thick, the stock exhaust manifold is 7/16ths of an inch thick, and the washer is a 1/16th of an inch thick, so is the lock washer, so if the stud threads all the way in to where you cannot see any threads a 1/2 inch would sound about right but I have some studs and it appears to be 5/8ths of an inch, anyway you look at it the stud should start having threads about a 1/2 inch away from the head surface.

If you don't have threads till 3/4s of an inch from the head surface you will have to start using thick washers or start stacking them which you do not want to do.

Here is a photo of a couple studs I have, the end with the most threads goes into the head.

DSCN7324.jpg

Here is the stud in the head.

DSCN7325.jpg

 

DSCN7327.jpg

Here is the stock manifold on the head, with an exhaust/intake gasket less threads would show.

DSCN7332.jpg

 

DSCN7334.jpg

Here is the washer and lock washer in place, with a intake/exhaust gasket in place it would be better.

DSCN7336.jpg

And here is the nut in place, it is not quite tight, but with another washer to simulate the gasket it is tight.

DSCN7328.jpg

Thanks for the pics, that’s exacltly what I needed.

 

 

Also mike is this what you’re talking about ?

 

 

kC7mdS1.jpg

 

I found some of these in m8 1.25 but I thought the manifold would beat up the threads from hanging on it.

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Thanks for the pics, that’s exacltly what I needed.

 

 

Also mike is this what you’re talking about ?

 

 

kC7mdS1.jpg

 

I found some of these in m8 1.25 but I thought the manifold would beat up the threads from hanging on it.

It might but you'll never use that part of the stud anyhow.... And once tight nothing will be moving around so you should be just fine.....
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The Z-Store has a set of studs and nuts for $31. I can't remember where I got my stud

set, but they even came with Allen wrench holes in the end for screwing them in. Used the studs for all my intake/exhaust clamping and had some left over. They worked excellent. You can put a bit more torque on them when you aren't afraid of stripping out the aluminum threads.

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I’m missing these two johnnies too, timing cover bolts, and a lower manifold bolt.

 

Wondering if local hardware store will have something similar? Any suggestions for hardware?

 

BQhFeoX.jpg

 

 

What happened to that #1 piston?  Was that from the broken valve?

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