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351c stroker kit with 4v open chamber heads?
#1
I've been back and forth about a motor for my '73 Mach-1 and am leaning towards a 4v Cleveland stroked to a 408 (Eagle kit). Looking at my heads, (on the corned) is a 4 with a raised "dimple" or half circle. I have been told that this means "open chamber". Is this true? If they are open chamber heads, I've also heard (and read) that they are prone to detonation with high compression applications. What do "they" consider high compression? I assume the open chamber heads with this kit will give me 9:1 compression. Closed chamber heads seem to be about 63cc and should give me about 10.17:1. I fingered a 408c, 232/240 @ .050", Air Gap intake, 750cfm (holley or Demon), 3.5:1 and a TKO-600 would make for a nice daily driver. Any opinions? I'm especially concerned about the heads..
Thank..
Mike
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#2
I believe the ones made after may of 71 are cobra jet open chamber but prior to may they are the closed chamber with a 4 and a raised dimple in the corner of the 71heads prior to 71 they just had a 4 in the corner

This is more than a hobby, its a Passion, its a way of life.
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#3
So, the 4 with raised simple was open or closed? Or it depends on the year?
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#4
I believe it depends on year and casting number. Apparently the dimple was used on both open and closed chamber heads.



“If you can't explain it simply, you don't understand it well enough.”
--Albert Einstein
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#5
cazsper;162902 Wrote:I've been back and forth about a motor for my '73 Mach-1 and am leaning towards a 4v Cleveland stroked to a 408 (Eagle kit). Looking at my heads, (on the corned) is a 4 with a raised "dimple" or half circle. I have been told that this means "open chamber". Is this true? If they are open chamber heads, I've also heard (and read) that they are prone to detonation with high compression applications. What do "they" consider high compression? I assume the open chamber heads with this kit will give me 9:1 compression. Closed chamber heads seem to be about 63cc and should give me about 10.17:1. I fingered a 408c, 232/240 @ .050", Air Gap intake, 750cfm (holley or Demon), 3.5:1 and a TKO-600 would make for a nice daily driver. Any opinions? I'm especially concerned about the heads..
Thank..
Mike

With a flat top piston using a 76cc chamber volume for open chamber heads I come up with 10.7:1 at 408 ci and 12.3:1 for closed chamber using 64cc chamber volume.

This is with the Summit calculator.

73 conv. 460, D0VE large valve heads, Performer RPM manifold, Voodoo 227/233 cam, Holley 950 HP carb, C6 trans, 3.25 trak-loc.
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#6
Thanks. I used the Eagle site and that's what it gave me. I'll have to call. I guess I have to see what heads I have anyways..
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#7
i have d1ae GA 4v heads that had the little dimple above the 4. most of the time they are open chamber though. you'll just have to get under the car and find the numbers for yourself.

THE HOOFBEAT IS LOUDER THAN THE HEARTBEAT!!!!!
SINCE 1964


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#8
Open chamber heads should be fine. There is an advantage to Open chamber heads in that they can be ported and polished to exceed the flow of closed chamber heads as a result of there being less valve shrouding. (and even though Cleveland heads all flow respectable numbers, more flow on the exhaust side is a good thing.) They may be slightly more prone to detonation, but they aren't going to cause detonation in an otherwise properly built engine. What I have been seeing with OC heads is a trend to use a piston dome or even a dish that is a reverse match of the chamber.

[Image: 1_01_07_15_8_53_18.png]

"I love my Hookers!" and "Get some Strange" probably have a different connotation to non automotive enthusiasts!
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#9
Honestly 2v heads are best for street. you get a way better bottom end, they dont load up like the 4v ones, they get better gas milage(if you care) and they dont typically have the detonation problem like you stated.
BUT,
4v heads do have bigger horsepower and a stroker would be awesome, its really whatever you want that matters anywayBig Grin

P.S. Ford was really sloppy with casting numbers back then on heads and blocks, i wouldnt necessarily trust the markings.thumb
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#10
Well, would 2v heads with 10:1 be better than 4v open chamber with 9:1? I have a 400M in storage and they came with 2v heads.
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