90 over 318 Head Gasket info needed !!

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SS Lancer

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Fixing to do the boring for my 318 and just have an unusual situation kinda !!!
90 over 318 is a 4" bore and its LA block so couldn't I just order a Cometic MLS gasket for a LA 360 since it has a 4" bore and all be well ???
 
Fixing to do the boring for my 318 and just have an unusual situation kinda !!!
90 over 318 is a 4" bore and its LA block so couldn't I just order a Cometic MLS gasket for a LA 360 since it has a 4" bore and all be well ???


Most of the small block Chrysler head gaskets I’ve seen usually have over a 4” bore. But I’ve always used pretty common generic felpros.

I think Jason’s on his 318 we’re felpros with a 4.08 bore.

Hope this helps. Eric
 
Most of the small block Chrysler head gaskets I’ve seen usually have over a 4” bore. But I’ve always used pretty common generic felpros.

I think Jason’s on his 318 we’re felpros with a 4.08 bore.

Hope this helps. Eric
Thank you Sir
 
I have Felpro 1008 for the 340. Bore is 4.180. Buy them at dodge store under MP#, way cheap and the only way to buy in pairs. Cant remember the MP#
 
Is .090" over on a 318 even doable? Just curious, as I have only done big blocks. We usually go .020, .040 or at the most .060, but 60 is pushin it! How much overbore will a 318 take? Is 90 the max? Thanks.
 
Is .090" over on a 318 even doable? Just curious, as I have only done big blocks. We usually go .020, .040 or at the most .060, but 60 is pushin it! How much overbore will a 318 take? Is 90 the max? Thanks.

From what I understand earlier 318 blocks can be sonic checked for wall thickness, and often bored to a 4.00 bore.
 
Is .090" over on a 318 even doable? Just curious, as I have only done big blocks. We usually go .020, .040 or at the most .060, but 60 is pushin it! How much overbore will a 318 take? Is 90 the max? Thanks.
Shane @ Crower Cams has went beyond 90 over
Im using a 68 model block that has been sonic tested and block will have a partial fill also.
 
From what I understand earlier 318 blocks can be sonic checked for wall thickness, and often bored to a 4.00 bore.
I have the following
68
70
(2) 1974 blocks
They are cheap to purchase and works for me .
My recent purchase/ project 66 Dart has a nice 70 340 in it but Im trying this format first with the 318 blocks and my custom crank with 3.20 stroke.
 
From what I understand earlier 318 blocks can be sonic checked for wall thickness, and often bored to a 4.00 bore.
Makes sense, I would definitely get it checked before I bored it that much. I am more and more impressed with the A engine as time goes by. Saw a Duster with a 408 run a 10.75 last summer, at 5400 feet! Wiki stated the LA engine is just a lighter version of the early A motor. So LA stands for Light A. Like 40 pounds lighter. They may not take as much of an overbore.
 
Makes sense, I would definitely get it checked before I bored it that much. I am more and more impressed with the A engine as time goes by. Saw a Duster with a 408 run a 10.75 last summer, at 5400 feet! Wiki stated the LA engine is just a lighter version of the early A motor. So LA stands for Light A. Like 40 pounds lighter. They may not take as much of an overbore.
Older the block normally the better this engine is going in a 66 Dart which will be run in the Super Stock division and with a Jerico.

20160518_0621221.jpg
 
Shane @ Crower Cams has went beyond 90 over
Im using a 68 model block that has been sonic tested and block will have a partial fill also.
What displacement do you end up with a 318 bored 90 over? Then adding the 3.20 stroke crank, what do you have? Is that a shorter stroke than a stock 318?
 
What displacement do you end up with a 318 bored 90 over? Then adding the 3.20 stroke crank, what do you have? Is that a shorter stroke than a stock 318?
Crank is special
Bob Glidden unit from late 1978
It uses small journal Chebby rods machinist is using a 6.200 H Beam and custom pistons to be ordered soon just getting started with shortblock
321 CI on the build
Super Stock class Im running in is 9.5 lbs per Cubic inch
 
I’ve got a steel shim 4.06 bore
Fixing to do the boring for my 318 and just have an unusual situation kinda !!!
90 over 318 is a 4" bore and its LA block so couldn't I just order a Cometic MLS gasket for a LA 360 since it has a 4" bore and all be well ???

6AD3B318-A119-4A4C-9007-B66D2DB0F65E.jpeg


E1CAC2C8-A1BE-4A9B-8D37-430CF289698B.jpeg


156D695C-F25F-4DCF-BB88-6F656927093C.jpeg
 
Don't use a 4" bore gasket on a 4" bore block the fire ring will over hang the cylinder bore after chamfering the block to drop in the rings. I'd recommend a 4.08 gasket.
 
I'd have to chk my set, but pretty sure they are bigger bore than what summit lists...I hope so my 340 is 0.030" over lol.
Summit shows those gaskets fitting all the wedge small blocks from 273 to 360, up to a 4.060 bore. Good luck with your SS engine!

Thank you
Great info
 
Don't use a 4" bore gasket on a 4" bore block the fire ring will over hang the cylinder bore after chamfering the block to drop in the rings. I'd recommend a 4.08 gasket.
Yes, I went to 4.125" with a set of Cometics on a 340 over bored to 4.060". There will also be some small mis-registration of the chambers on the bores that will require a slightly larger gasket bore hole. So the 4.080" recommended above is the most suitable size for your use here IMHO.

The Cometics can be had in quite a variety of thicknesses and bore sizes too, starting at .027" thick.

Go here:
https://www.cometic.com/c-1280258-automotive-domestic-mls-head-gaskets.html
Then enter your engine type and it will pop up a whole list of MLS head gaskets for the LA with their whole variety of thickness and bore hole sizes.

Be aware that the head and block surface finishes need to be in a certain range for these MLS head gaskets. So keep that in mind. The info is somewhere on the Cometic site.
 
I may be mistaken but I believe the early 318's (67-69) have thicker walls and forged cranks . Don't throw away those old 318's folks .
 
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