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Old 10-16-2012, 12:06 AM
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Head gasket seepage???

I was contemplating getting a car that is supposed to have a dry sump 421 engine and the owner informed me today that he noticed a little coolant seepage where the heads meet the block. He said that his engine builder told him that due to using the thicker Cometic headgaskets and the car sitting for a while they seep coolant...I personally have never heard of this, have any of you? Im thinking blown headgasket or cracked heads.

Is it possible for e healthy motor to seep a little coolant after parked for a while and not run often? I also inquired as if he used a sleeved 400 block and he told me it was a non sleeved 350 block..Is it even possible to get a 421 out of a 350 block? Or am I getting smoke blown up my you know what??

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Old 10-16-2012, 12:17 AM
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biggest engine from a 350 block is 401,that I heard of,,,thats 4.06 bore x 3.875 stroke.
a 421 is 4.155 bore(400 block) and same stroke,,3.875
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Old 10-16-2012, 12:36 AM
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Quote:
Originally Posted by vinniekq2 View Post
biggest engine from a 350 block is 401,that I heard of,,,thats 4.06 bore x 3.875 stroke.
a 421 is 4.155 bore(400 block) and same stroke,,3.875
Thats what I thought..What about the seepage on the Cometic head gaskets? Ever hear of that? I have been reading that they are either hit or miss.
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Old 10-16-2012, 04:17 AM
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head gasket seepage

If he doesn't know what block is being used then the line about coolant seepage is BS too. Cometic head gaskets are one of the best. There must be surface imperfections where the leak is.
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Old 10-16-2012, 04:39 AM
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I had a Z car engine do that after I put on a turbo charger.

So, I loosened and re-torqued each head bolt in the proper ordered.

And that fixed it.
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Old 10-16-2012, 06:29 PM
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Quote:
Originally Posted by Dajerseyrat View Post
I was contemplating getting a car that is supposed to have a dry sump 421 engine and the owner informed me today that he noticed a little coolant seepage where the heads meet the block. He said that his engine builder told him that due to using the thicker Cometic headgaskets and the car sitting for a while they seep coolant...I personally have never heard of this, have any of you? Im thinking blown headgasket or cracked heads.

Is it possible for e healthy motor to seep a little coolant after parked for a while and not run often? I also inquired as if he used a sleeved 400 block and he told me it was a non sleeved 350 block..Is it even possible to get a 421 out of a 350 block? Or am I getting smoke blown up my you know what??
He sounds like the same guy I bought my S10 drag truck from when we first got it. Wonder if he moved to your area? Hope so cause I sure would like to see him again Don't believe any of this crap and walk away unless you can get it for a price you set. Quiz the guy on the bore and stroke and see if it all adds up.
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Old 10-16-2012, 10:35 PM
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Quote:
Originally Posted by cdminter59 View Post
If he doesn't know what block is being used then the line about coolant seepage is BS too. Cometic head gaskets are one of the best. There must be surface imperfections where the leak is.
My thoughts exactly.
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Old 10-17-2012, 06:45 AM
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Whats the casting number on the back of the block????????
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Old 10-17-2012, 09:32 AM
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Well I actually called the guy that built the engine and he clarified that it is a 389 engine and that they sonic tested the block and it was really thick so they punched it out and used a long stroke,he did clarify that the engine was indeed a nice piece and that since they built this one they have been using a layer of copper on the Cometic gaskets. He said that they did find that when the car sat for some time and if the surface of the block and heads werent a certain finish the Cometics would seep slightly. He suggested a Re-tourqe of the heads and if that didnt do it try the layer of copper seal.

When I told the guy that he said his calculations with the heads he used (Brodix) it came out to a 421. But he said if the engine guy said a 389 then thats what it is. The guy seems very honest and even offered to send the motor back to the builder and checked out for piece of mind and he would fix anything if there was any issues with it. He is pretty straight up. The pictures he sent me it looks like the bolts on the outside of the heads were rusted a bit which would indicate to me the water seepage was at the head bolts themselves or perhaps above them from a coolant line..

I will keep you posted of what I decide..
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Old 10-17-2012, 07:42 PM
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I guess we should have asked if it was a 350 "chevrolet" engine?
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Old 06-29-2013, 02:28 PM
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Just to revive this thread and get a few opinions before I proceed. I had some leaking head studs so I decided to remove the engine, replaced the head gaskets (which were fine by the way)and re seal the head studs. I cleaned the hell out of the studs and the block threads with lacquer thinner and re sealed them with ARP thread sealant. I spent hours cleaning it and doing it right. However some time passed between installing the studs and the torquing of the heads.

Now Im getting coolant seepage after 2 or 3 heat cycles, on one side from 2 or three of the lower bolts. I have a cast iron block and aluminum heads. I did check the TQ on one easily accessible head stud and it did go 1/4 turn before re TQing at 80 ft lbs. I originally TQed all studs to 80 ft lbs in a 3 step sequence, 25,50,80.

How should I proceed to fix this issue? My thoughts were:

1) Re TQ all the studs
2) apply sealer to the top threads of the ones that are leaking and Re TQ
3) add the GM coolant pellets
or
4)Bars leak....

Any advice and reasoning why?

Keep in mind, removing each stud one by one and resealing the bottom is NOT an option at this point due to room under the hood of my set up..Heck I cant even remove the headers without pulling the engine..And Im NOT pulling the engine again.. It is a high performance 383 SBC that will see mostly street use.
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Old 06-29-2013, 03:30 PM
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5 years ago when I put my 388 together , I had a little seepage show up ,,along the same area, 1 bottle of bars leak... been dry ever since & it did not adversly affect the cooling system.... just my experience.

dave
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Old 06-29-2013, 03:37 PM
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Quote:
Originally Posted by 2old2fast View Post
5 years ago when I put my 388 together , I had a little seepage show up ,,along the same area, 1 bottle of bars leak... been dry ever since & it did not adversly affect the cooling system.... just my experience.

dave
Times 2 on the Bars Leak. Been using since I was a kid. Not too keen on chemical fixes, but this stuff works.
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Old 06-29-2013, 04:14 PM
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Times 2 on the Bars Leak. Been using since I was a kid. Not too keen on chemical fixes, but this stuff works.

So skip the Re TQ? How about the GM pellets? Same stuff? Also how long does it take to work?
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Old 06-30-2013, 08:49 AM
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All good anwers

Hi all

If you are not doing a tear down.I would go with silver soder seal.Bars leak and GM pellets are also good .Silver soder is just finer particals.And do not install the hole can.Just a little at a time till the leak goes away.The same is also true for bars leak and gm pellets.


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