351c stroker kit with 4v open chamber heads?

[cazsper]

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

 

[mikleins29]

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

 

[cazsper]

So, the 4 with raised simple was open or closed? Or it depends on the year?

 

[Don C]

I believe it depends on year and casting number. Apparently the dimple was used on both open and closed chamber heads.

 

[TommyK]

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.

 

[cazsper]

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..

 

[nosdelacruz]

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.

 

[Jeff73Mach1]

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.

 

[kidwithfastback=fast]

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 anyway

P.S. Ford was really sloppy with casting numbers back then on heads and blocks, i wouldnt necessarily trust the markings.::thumb::

 

[cazsper]

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.

 

[johnwanzel]

If you are really serious about the 408 stroker, the 4v heads will compliment the build. Decent sized carb like a 750 or 800 and a cam with about 240-245 duration at .050 lift, and compression around 10 to 1, you're looking at around 450-500 hp with very good street manners and pump gas. If you were to stay with a traditional 351c .030 over, then the 2v heads would be the better choice IMHO. That 408 will LOVE those 4v heads and you will too. It's an air pump, more air in, more air out.

Sent from my iPhone using Tapatalk

 

[cazsper]

Hmm..

 

[nosdelacruz]

i have read to not use modified heads, there is a big difference in the ex. port form the 2v head from the modified head. as stated above, if you are doing a 408 stroker what not put some 4v's or some good alloy heads at least? wouldn't make sense to build a sweet bottom end that can take a beating and top it off with a weak top end package... In my opinion.

 

[cazsper]

That totally makes sense. I was just concerned that I would have issues with open chamber 4v heads (if that's what I have).

 

[cazsper]

If you are really serious about the 408 stroker, the 4v heads will compliment the build. Decent sized carb like a 750 or 800 and a cam with about 240-245 duration at .050 lift, and compression around 10 to 1, you're looking at around 450-500 hp with very good street manners and pump gas. If you were to stay with a traditional 351c .030 over, then the 2v heads would be the better choice IMHO. That 408 will LOVE those 4v heads and you will too. It's an air pump, more air in, more air out.

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Concerning a 408c with a 240'-245' cam. How street able would that be?

 

[Totalled]

Yeah, M heads suck.

http://www.7173mustangs.com/thread-351m-heads-info

Here is the "hump" that blocks the exhaust port in an M head.

 

[Jeff73Mach1]

2V heads are only better for the street if you are building an engine designed to work best with 2V heads. 4v Heads do require a matching cam and compression ratio, but so does any combination. Open Chamber to closed chamber conversions are worth about .75 point added to your compression ratio. I have a set of open chambers standing by in case my closed chamber heads lead to too much compression to run on available gas.

build with the open chamber heads if that's what they are, they are fine and will not detonate any different than the 2V heads as the chambers are the same.

 

[turtle5353]

If you are really serious about the 408 stroker, the 4v heads will compliment the build. Decent sized carb like a 750 or 800 and a cam with about 240-245 duration at .050 lift, and compression around 10 to 1, you're looking at around 450-500 hp with very good street manners and pump gas. If you were to stay with a traditional 351c .030 over, then the 2v heads would be the better choice IMHO. That 408 will LOVE those 4v heads and you will too. It's an air pump, more air in, more air out.

Sent from my iPhone using Tapatalk

Concerning a 408c with a 240'-245' cam. How street able would that be?

My 408C cam is running 243 int./257exh. at 050. all roller. I am running AFD 4v aluminum heads, have around 10.5 compression., a quick fuel 850 carb and msd ignition. Around 550hp and I love it on the street. Probably not the best daily driver because of the single digit MPG. But I wouldn't hesitate to drive it anywhere. The cam isn't too crazy and idle sounds great. Its a big Mutha thumper cam.

 

[Phil429boss]

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 anyway

P.S. Ford was really sloppy with casting numbers back then on heads and blocks, i wouldnt necessarily trust the markings.::thumb::

2v open heads are prone to detonation not the 4v closed you have your wording backwards which confuses everyone who reads your thread bud! backwards

 

[SteveO_71]

I hope in 10 years he got it all figured out!