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http://www.1962to1965mopar.ornocar.org/ml-pitchercastingheadarticle.html


photo http://pub31.bravenet.com/photocenter/album.php?img=48846&usernum=2614635276

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According to that chart you only give up 2.5 cc of chamber volume on the 920 versus the 302 but the port volume advantage goes to the 920. I know I kept the heads off my 67 318 because someday I would like to port and polish them and stick a set of stocker 1.88/1.60's valves in them and see what they will do. They do need opened up for more flow in my opion but just a side by side comparision to my gasket matched J's they dont look like they have enough meat in the intake gasket area to open all the way up to 340/360 gasket size. Man those compbustion chambers on the 302's must be tight to be less volume than those 920's though. Those 920 chambers are postage stamp size compared once again to the 915 J's. Well unless the valve size/configuration is accounting for that 2.5 cc's of volume. Those valves in the 920's were cupped a bunch if I remember right.


http://kb-silvolite.com/calc.php?action=comp

Dave using that KB calculator with what I believe is your engines specs of Felpro .039 thick gasket with a 4.06 bore, 3.94 piston diameter, 5 cc KB 167's piston volume, .005 down in the hole, 62 cc's for the 302 heads chambers, and a 3.31 stroke it spit out your comp ratio right now at 9.673. Change to .028 Mopar gasket which are on national backorder right now by the way and it brings that number up to 9.948! Almost a 1/3 of a point with a gasket change alone. With what you got now no wonder it wont drink anything but 93 octane.

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Change to .028 Mopar gasket which are on national backorder right now by the way and it brings that number up to 9.948!

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I currently have 302 heads and KB167 flat tops .005 below deck and felpro .039 gaskets.

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I have asked on here before and most guys say they are more like .028 to .030 compressed.

I have tight piston to wall clearances, I don't remember the number but it was the KB minimum. That should give keep piston rock to a minimum. Also since it never goes over 5000 rpm I figure it will be fine. Also the hypers expand less than other pistons.

A note on your head gasket measuremennt the curent felpros have more like a 4.16 bore vs the mopar gaskets 4.06 bore. That means it will be a bigger increase than you stated.

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why are 70' 318"'s rated at 9.0 compression, but dont make it?

what will happen with the national backorder? arent they discontinued due to moparPerformance.

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Summit, Mancini and Jegs told me they expect the Mopar SB head gaskets at the end of the first week of June or so they are being told anyhow. I couldnt wait so I ordered a set of Mr Gasket .028 head gaskets through Summit, the part number is 1121. I got them today, and I tell you what I will almost swear to it that they are the same gasket as the MP's. They are white embossed sticky material on a steel gasket just identical to the set of Mopar ones I had to remove off an unfired engine because I forgot to have the inner step cut off the valve guides area of my J heads for the double springs. I called Mr Gasket in Cleveland before I called Summit to see if they had them on shelf in their warehouse and they said yeah got plenty. Summit doesnt stock them and they call them special order. Same goes for Jegs. Summit then had them dropped shipped to me direct. Only problem is they charged like $48.95 for the set of Mr G's versus the $35 they charge for the MP's. Though dollars to doghnuts says they are the same gasket. They look IDENTICAL.