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915 heads CR

67charger383

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Can I get away with 12-1 dome pistons in a .30 over 383 with 915 big valve heads?
It will eventually get aluminum heads.
 
No, the dome on the piston will smack the closed chamber head. U can use an open chamber 906 head amongst others. All aluminum heads are closed chamber also so u would need a flat top piston. Ok, I stand corrected. Kim
 
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Can I get away with 12-1 dome pistons in a .30 over 383 with 915 big valve heads?
It will eventually get aluminum heads.

I think you can. If you have the 2293 pistons, I think the compression height is 1.905 and will sit about 0.025 below an uncut block deck.

Even with the valve notches in the pistons, if you have a big cam, you might still have valve to piston clearance issues.
 
No, the dome on the piston will smack the closed chamber head.

No, it won't. That combo can work. I just did that build with old Manley (TRW) pistons last year. I can dig out the compression data for you, but in reality you will need to measure everything to come up with meaningful info on your own, since we dont know who's pistons, how much your heads are cut, what head gasket you are planning, desired gasoline octane, etc...... The videos of me goofing off with the Orange Dart are that exact build, 30 over 383, big pop-up pistons and 915 iron heads.

 
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All depends on which piston. compression height & dome configuration. Piston to valve is always an issue depending on the cam profile. I used a "13.2" domed piston in my 400/452 with extensively milled 915's.
 
If you plan to drive it on the street, my suggestion would be to keep it under 10:1.
Short term it might be ok, but as soon as you get some carbon in there it will ping.
 
If you plan to drive it on the street, my suggestion would be to keep it under 10:1.
Short term it might be ok, but as soon as you get some carbon in there it will ping.

The 2293 piston with the 915 head can be an honest 12:1 motor. Of course the devil is in the details. But even so, there is no way that combo will run on pump gas, IMO. I've taken 0.300" off the dome of that piston and used 906 heads and it still will not run on pump gas.
 
I'm not worried about pump gas because I am gonna set it up to run on E85.
I've already got hardened valve seats in my 915s.
This motor's gonna have some trick stuff on it, check out my Weiand tunnel ram
KIMG0217.JPG
 
I do not like one carb trs
i'd go with small primary TQs if they fit a dual quad top
 
Did this build 10yrs ago to put in a Omni chassis car, but ended up going nostalgia racing with a front engine dragster (zoomies!) instead. My pistons were .060" over L2293Fs, and when I mocked it up with 915s (fully ported with 2.125x1.78" 11/32"stem valves) and a Lunati 261/271*@.050" .576/.563" lift solid FT cam, it had inadequate clearance (block and heads were milled about .060" combined), so we made asymmetrical valve reliefs for adequate clearance +.050" so I could easily go roller later. I did a bunch of messy cc'ing of the .500"-down volume and chamber cc's, and got a touch over 12.5:1 even with the deeper valve notches (which quickly eats dome volume). The car ran 8.70s all day, for several seasons, and we only changed the plugs ONCE, before a race at Bristol's "Thunder Valley." Used an Offy tunnel ram with 2x660 Holleys (1:1 linkage) and shifted at 7200rpm. MAN did that thing sound awesome!!
 
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Did this build 10yrs ago to put in a Omni chassis car, but ended up going nostalgia racing with a front engine dragster (zoomies!) instead.

Useful tidbit (for me)... Can you remember what the car weighed?? TIA, Lefty71
 
Useful tidbit (for me)... Can you remember what the car weighed?? TIA, Lefty71

1700lbs. 197" w/b 1969 rail, we found a chassis tag from 1971 certification for top fuel. 8.75 rear with 4.30 gears (we tool 3.91s out) and 32" slicks, Powerglide trans with 1.76 gears and brake, 8" 5000 stall PTC converter.

 
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No, it won't. That combo can work. I just did that build with old Manley (TRW) pistons last year. I can dig out the compression data for you, but in reality you will need to measure everything to come up with meaningful info on your own, since we dont know who's pistons, how much your heads are cut, what head gasket you are planning, desired gasoline octane, etc...... The videos of me goofing off with the Orange Dart are that exact build, 30 over 383, big pop-up pistons and 915 iron heads.


I know this is old, but what are your cam specs
 
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