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08-13-2018, 02:14 PM | #1 |
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21 stud big bore gasket
Does anyone make a big bore head gasket for a 21 stud engine? I've got a 36LB that is going to 3 3/16 + .020.
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08-13-2018, 02:49 PM | #2 |
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Re: 21 stud big bore gasket
made mine from a 239 24 stud gasket. Just punch in the 4 stud holes
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08-13-2018, 02:51 PM | #3 |
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Re: 21 stud big bore gasket
What are you doing to keep the rings out of the water jacket?, LB blocks get thin at 0.060
Ron talks about using later gasket and making needed holes |
08-13-2018, 03:33 PM | #4 |
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Re: 21 stud big bore gasket
Will be interested to see if it works for you. I bought a '36 sedan that came with a '36LB block that was made into 3 3/16: cylinder walls bored completely out and machined for sleeves. New cam and valve train was already installed. i assembled the rest of it and put it in my '36 coupe. Got hot right away and spit water out the left header. thought it was a head gasket so tried a couple snake oil "fixes", that didn't work. Tore it down and one of the sleeves was split top to bottom. Bad sleeve??? I don't know, but I later found some info on boring 221 blocks to 239 and it was done with later blocks that had thicker cylinder walls. Good luck. Rod
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08-13-2018, 07:13 PM | #5 |
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Re: 21 stud big bore gasket
This engine was already bored to 3 3/16 +.010 with very little wear. Sonic testing showed that with a slight shift in a couple bores, it is doable. I'm not doing the work, just suppying parts. Where do you find a LB block these days? Too bad, I had sold one last month and my other one didn't pass the pressure test.
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08-13-2018, 08:35 PM | #6 |
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Re: 21 stud big bore gasket
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In the last five or six years, 36LB engines, with good blocks, seem to be coming out of the woodwork for me, and another local friend. I've stumbled over four, and a friend has found at least three. Prior to that, I couldn't find one good enough to rebuild, or buy one at a reasonable price. Two of mine were basically gifts, and two were in cars I bought.
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08-13-2018, 08:39 PM | #7 |
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Re: 21 stud big bore gasket
I'll see if I can get the sonic test results.
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08-13-2018, 09:53 PM | #8 |
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Re: 21 stud big bore gasket
Cometic can do 21 stud gaskets 3.188 bore Part number : H2428SP2040S That is .040" thick, but they can make any desired thickness.
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08-13-2018, 10:00 PM | #9 |
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Re: 21 stud big bore gasket
With my 3 3/16 bore 21 stud engine, I'm using gaskets that were as big as I could get- not 3 3/16 but...I think from memory I had something like a .007" overhang around top of cylinders. I chamfered the pistons a tad; sufficient to clear, and it works; have not blown any head gaskets. Possibly, using those Cometic gaskets, you'll have in the region of .010" overhang, judicious relieving of edge of piston crowns could get you outta trouble. What are the existing gaskets with the +.010" bore?
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08-13-2018, 10:11 PM | #10 |
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Re: 21 stud big bore gasket
Brian is correct with Cometic
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08-13-2018, 10:49 PM | #11 | |
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Re: 21 stud big bore gasket
Quote:
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08-13-2018, 11:06 PM | #12 |
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Re: 21 stud big bore gasket
John, It's a 37 block. According to the sonic test performed, it'll go another .020" yet [safely]. Running pump in head heads on it.
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08-13-2018, 11:31 PM | #13 |
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Re: 21 stud big bore gasket
Okay, thank you Brian.
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08-13-2018, 11:43 PM | #14 |
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Re: 21 stud big bore gasket
With MLS gaskets everything has to be dead flat or they leak so surfacing block and heads is a must before using them.
Solid copper and a waterjet cutter maybe...probably cheaper then the MLS from Cometic. |
08-14-2018, 02:33 AM | #15 |
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Re: 21 stud big bore gasket
Murre, Have you such a machine?- waterjet cutter
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08-14-2018, 03:14 AM | #16 |
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Re: 21 stud big bore gasket
Nope but there is a company in the next town with one.
I just send them a CAD file and they cut what i need. Best would be to O-ringing the engine going for solid copper but that takes CNC macining both head and block...and pinning the head to block for keeping it centered. Been a lot of questions about bigbore 21 headgaskets lately...wonder what kind of order it would take to make some of the big dragons do a custom gasket run...probably more then hundreds of gaskets... |
08-14-2018, 08:44 AM | #17 |
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Re: 21 stud big bore gasket
I need some for .100 over, was planning to repunch 24 stud gaskets.
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08-14-2018, 06:50 PM | #18 |
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Re: 21 stud big bore gasket
We need Tod to cast a run of these blocks, where is Tod?
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