273 HEAD GASKETS

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A/MP

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I have 3 273/high compression motors that will be building, starting in November. I'm ordering 4 MLS sets with standard 318 bore. Anyone interested in my ordering extras?
 
Why 318 bore on a 273? Loss of compression from the 273 and this puts the fire ring back a bit. I agree with Dana67Dart. “What’s so special?”
Syleng1
 
Building a 273 and making 318 head gaskets for it doesn't make much sense to me. The OP must have something going on we don't know about.
 
Using the correct 273 gaskets makes more sense to me. Back when I was running 273's on the street and strip, I always ran the 273 spec gaskets. When I went to much higher compression, I had Hamburger o-ring my heads and ran the copper head gaskets he suggested. Once I did things to Ed's suggestion, I no longer killed head gaskets.
 
Unfortunately, Cometic didn't exist back in the mid to late 60's when I was running my 67 Dart 273 car. Back then, Ed Hamburger was the small block guru. LOL
 
3.910 I can get easily. the 3.62 is more of a special order. Once I get down to the head prep and block decking, I'll know better. If you might be interested, let me know what you will be want. One motor is for stock eliminator, one radically street and the other a procharged 273.
 
The gasket bore needs to be large enough to clear the chamber diameter of whatever heads will be used.
 
I wonder how much Power my rebuilt 273 makes with her Brand New Mr. Gasket 1121G Head Gaskets (4.060) in place? lol
Makes 150 p.s.i. per Cylinder tho. So, I'm guessing 150HP...

1121G.jpg
 
That's a .285" difference between the 318 and 273 standard bores. That's over 1/4". I would be looking for the smallest bore gasket I felt comfortable with running on a 273. @toolmanmike Mike, weren't the original 273 gasket bores "unround" so to speak and kinda followed the contour of the chambers, or am I imagining that? In any event, in the picture @eekvonzipper posted up there, ^^^^^, that's a TON of block deck that's now part of the chamber. You have to wonder how much effect it would have had on cylinder pressure had a smaller bore gasket been used. When I'm shopping for head gaskets, I don't look at the thinnest compressed thickness. I look at the smallest compressed volume.
 
If anyone actually knows of a 273 head gasket with the correct bore diameter other than special order, really expensive, Cometic gaskets please speak up. My understanding is that you have to use a 318 gasket now-days on a 273 because they no longer make 273 gaskets other than really expensive special order . I am building a bone stock 273 and would love a cost effective 273 size gasket but can't find one.
Thanks.
 
D/Dart man said:
If anyone actually knows of a 273 head gasket with the correct bore diameter other than special order, really expensive, Cometic gaskets please speak up. My understanding is that you have to use a 318 gasket now-days on a 273 because they no longer make 273 gaskets other than really expensive special order . I am building a bone stock 273 and would love a cost effective 273 size gasket but can't find one.
Thanks.
Click to expand...
It has been over a decade ago but there was none when I rebuilt mine. I used the MP composition gaskets. Thinnest and smallest bore size I could find at the time. (MR Gasket 1121G) Mr. Gasket 1121G Mr. Gasket Head Gaskets | Summit Racing

Here's the stock ones. The bores are not perfectly round. There are a few members here that have found NOS gaskets and that's the only ones I know of that are correct. Cometic is the only brand that can make the smaller bore size. All the rest will be 4" bore or larger.

Try AMS Obsolete for the original's
.


stock head gasket on 920.jpg


273 head gasket.jpg2 A3.815 B3.975.jpg
 
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D/Dart man said:
If anyone actually knows of a 273 head gasket with the correct bore diameter other than special order, really expensive, Cometic gaskets please speak up. My understanding is that you have to use a 318 gasket now-days on a 273 because they no longer make 273 gaskets other than really expensive special order . I am building a bone stock 273 and would love a cost effective 273 size gasket but can't find one.
Thanks.
Click to expand...
"Really expensive" Considering how much an entire engine build costs, that's a cop out.
 
With your typical 318/340/360 replacement head gasket, its been calculated by several people to losing 3/4 to 1.5 of compression. These last 273 builds that I'll be doing will need all the sealing and compression, especially the stock eliminator motor. The procharger, I just want the best sealing I can get.
 
A/MP said:
With your typical 318/340/360 replacement head gasket, its been calculated by several people to losing 3/4 to 1.5 of compression. These last 273 builds that I'll be doing will need all the sealing and compression, especially the stock eliminator motor. The procharger, I just want the best sealing I can get.
Click to expand...
So, Where do you get these 318 Gaskets? This has gone on for long enough...
 
Not that this is a good idea but....

Would it be possible to use a stock 340/360 head gasket but make an insert to fill the gap between the larger bore and the stock 273 bore and shape?

Just thinking outside the box!

And yes I can see 100 issues that could be a problem
 
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