Edelbrock heads on a 340 with KB243 pistons

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hemichuck said:
I have a buddy who builds small blocks and is more than a little anal about clearances and Im sure that he can probably give me an hour long lecture on the different gaskets and what they will actually compress to. I guess its time to go by and tell him Merry Christmas.
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That would be good to hear! Please post what he tells you.

BTW, the FME catalog DOES give the gasket thicknesses but the listings are a bit vague at to the meaning:
8553 PT: "Manufactured thickness" => .0468-.0572" (So is that variation part to part, or across a single part, or in various levels of compression?)
1008: "Thickness" => .039"
 
Uh, if "dad" is going to put regular gas in it you're going to have to drop your compression ratio pretty substantially, otherwise it will be detonation city. Even with open chambers and a .039 head gasket I'm at 9.8:1 with the KB243's being .018" out of the hole, and even 91 octane barely gets it done. Sure, I've got iron heads and aluminum buys you some compression because of the head dissipation, but you're going to have to be below 10:1 even with aluminum heads to survive on 87 octane. The cam will play a factor too, my dynamic compression is only 8.2:1, with a smaller cam your dynamic compression will be higher.
 
I just went out to the garage and dig out 8 sets of head gaskets. 3 sets of FelPro 8553 2 new, 1 used, all three measured .050, 2 sets of factory gaskets measured .046 and one was .036. 1 set of Mr Gaskets measured .036
 
hemichuck said:
I just went out to the garage and dig out 8 sets of head gaskets. 3 sets of FelPro 8553 2 new, 1 used, all three measured .050, 2 sets of factory gaskets measured .046 and one was .036. 1 set of Mr Gaskets measured .036
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On a well used gasket, find a spot where the gasket has been pinched and measure there, not the fire ring ;) then account for that .004-.006 crush on the new ones.
 
measured a set of 8553 this morning...got .053.......

since it is not my money...just call cometic and have them make the correct size gasket you think you need...
 
On the used gaskets I measured on the outside edge next to one of the head bolts. I'm thinking about going a little bigger on the cam, I have a pile of them sitting here so I can probably find something with a little more umph
 
Really pretty interesting, all the variations in gaskets and such. Makes me wonder how we got so lucky building motors back when I was a kid, just slapped crap together with very little calculation and most of it ran pretty darn good. I guess the gas was a little better back then and the parts selection wasn't as broad which made not mismatching stuff as easy. I'm going to measure all of the pistons tomorrow and see exactly how much positive deck they have and how much it varies and then decide which set of gaskets I'm going with. I can always fall back on the iron heads if I want, I have plenty of other small blocks I can use the Edelbrocks on if I need to.
 
Before you measure the pistons, you might want to measure the rods. After having mine resized, there was quite a bit of variation. My KB107s were so close it was hard to measure and variation.
Also, after a line-hone,and square decking,plus a crank clean-up,and rod resize, it took me all morning to get everything together with a deck-height variance within about .003 .. This would be no big deal with a fat gasket; but I wanted to run the .028 ..
 
hemichuck said:
Really pretty interesting, all the variations in gaskets and such. Makes me wonder how we got so lucky building motors back when I was a kid, just slapped crap together with very little calculation and most of it ran pretty darn good. I guess the gas was a little better back then and the parts selection wasn't as broad which made not mismatching stuff as easy.
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And we were DARNED happy with 350/350 HP/TQ, and weren't pushing 400-500-600 HP all the time. A true 350/350 would make you "king-of-the-street" in most locales...and will bring all sorts of grins and satisfaction to most people even today.
 
It has Eagle rods so they were new and not resized. So I dig out the old Mopar Performance bible and look up small block piston to cylinder head clearance and here's what it had to say

IMG_0010.JPG
 
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Other than the obvious typo at the beginning [minimal clearance .005] they seem to like a lot of clearance on their motors. I also did a little researching and found that Jegs sells a marine head gasket that is .049 compressed height in stock for about $35 each and Cometics at .051 for $78, the Cometics then jump up to .060
 
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Here's a quick breakdown of some others I found.
Edelbrock 7326 .050
Mr Gasket 1121G .028
Mr Gasket 3211G .040
Mr Gasket 5805G .038
Cometic offers everything from .028 to .051 in .002 increments and then jumps to .060
FelPro 1008 .039
FelPro marine 17050 .049
Oddly enough the only one that didn't have a compressed height advertised was the FelPro 8553 which is the most common one.
 
Is that page from the Direct Connection book? What page?

FWIW, a few decades ago, leaving .100" from coil bind for max valve spring compression was published commonly; now I see .060" all the time. And quench gaps of .040" or less were well known 40 years ago. So the above .055" piston to head clearance is pretty conservative.

Now if you get a crappy set of recon rods like someone tried to sell me, with .029" center-to-center length variation, then yeah, you had better push that up to .060" or .070" clearance. No, I rejected those rods LOL
 
Lets see...360...block decked and squared...pistons +.018 out of the deck...heads eddy opened cambers ..cut .040...still has .020 depth in the chambers...using felpro .039 gasket...piston to head clearance .040......same clearance I had with the .028 head gasket before things were cut....engine ran for 10 yrs ..shifts at 6500..sees 7000 in the traps..

Keep reading the MP engine manual........
 
I don't have the Edelbrock open chambers, that would make things incredibly simple. That's page 55 in the Mopar engines manual 8th edition around 1991. I went back to my Direct Connection book from 1976 and it didn't even mention piston to head clearance. I just put that on here to show how stuff has changed over the last 20 or 30 years, I wouldn't take anything in either of those manuals as gospel. I'm guessing they recommended the wide clearances because they knew they were dealing with novices or inexperienced engine builders, anybody who builds engines for a living isn't cracking those books open. I also found it amusing that there is no mention of quench in there. I've already figured out how to get either .033 or .042 with off the shelf gaskets, just waiting till I go out and verify how much positive deck I have.
 
another interesting tidbit from the Mopar Engines manual, they say that the Offenhauser Port-O-Sonic is the best intake to run on a small block, they're not bad but I'm pretty sure a Holley Strip Dominator would make more power.
 
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hemichuck said:
another interesting tidbit from the Mopar Engines manual, they say that the Offenhauser Port-O-Sonic is the best intake to run on a small block, they're not bad but I'm pretty sure a Holley Strip Dominator would make more power.
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AT one time it was....just shows how dated the info is....and never updated....
 
OK so I checked my motor and all the Pistons are sticking out .027 so with a Cometic .070 gasket I would have .043 piston to head clearance. The next step down in off the shelf gaskets would be .060 which would give me .033 piston to head clearance. With the .070 gaskets I calculate 9.658 comp. and with the .060 gasket it's 9.892
 
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hemichuck said:
OK so I checked my motor and all the Pistons are sticking out .027 so with a Cometic .070 gasket I would have .043 piston to head clearance. The next step down in off the shelf gaskets would be .060 which would give me .033 piston to head clearance. With the .070 gaskets I calculate 9.658 comp. and with the .060 gasket it's 9.892
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Run the .070's.

I'd bet all I have that no one has done an A-B-A test to see if .040 quench is better than .050 quench.

You won't see a pinch of **** difference. Why squeeze it so tight? To say you did it?

Much ado about very little.
 
.027" over the deck? I would seriously consider switching pistons with that build. Get something close to zero deck and run the closed chamber heads. You've already got the heads, the quench would work out much better, and the swapping the pistons at this point would be cheaper/easier than reworking the heads. The fat head gaskets aren't the way I would want to go unless those compression numbers are really what you want.
 
yellow rose said:
Run the .070's.

I'd bet all I have that no one has done an A-B-A test to see if .040 quench is better than .050 quench.

You won't see a pinch of **** difference. Why squeeze it so tight? To say you did it?

Much ado about very little.
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I'm with you, I don't think on this motor it will make a bit of difference, I doubt I'll be changing the Pistons since it's assembled and balanced, as far as that goes I could run the .028 gaskets and the open chamber iron heads I have. I haven't worked up the compression on that combo yet.
 
hemichuck said:
OK so I checked my motor and all the Pistons are sticking out .027 so with a Cometic .070 gasket I would have .043 piston to head clearance. The next step down in off the shelf gaskets would be .060 which would give me .033 piston to head clearance. With the .070 gaskets I calculate 9.658 comp. and with the .060 gasket it's 9.892
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We were at the same spot with my son's 340 and the decision was to go to the larger gasket step and just not worry about the quench gap going a bit over .040".
 
72bluNblu said:
.027" over the deck? I would seriously consider switching pistons with that build. Get something close to zero deck and run the closed chamber heads. You've already got the heads, the quench would work out much better, and the swapping the pistons at this point would be cheaper/easier than reworking the heads. The fat head gaskets aren't the way I would want to go unless those compression numbers are really what you want.
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I'm not following this.... maybe it's being missed that he already has the closed chamber heads. The CR is being limited by the chamber volumes and piston to head clearance, not by the positional relationship of the pistons to the deck. Just moving the piston tops down and thinning the gasket is not changing anything, right?
 
Right, I'm going to order some of the .070 gaskets from Summit and use the Edelbrocks. Still have to dig through my cam pile and see what looks good.
 
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