Head and Exhaust Confusion

digithead

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Hi all. I have a head and exhaust question. I have 73 Mustang with numbers matching 351C Engine.  I understood/believed I had 2V heads and car was shipped with 2BBL carb. When I bought it, it had 4BBL Edelbrock and Hooker Headers. Last fall I spun a low end bearing. I had engine pro rebuilt by very reputable shop and dyno tested (450hp now).  So, before putting engine back in with old rusty exhaust manifolds I thought i would buy new ones. THe Hooker number is clearly stamped on them and when I looked them up it says they are for 4V heads??  Can that be?   When I talked with engine rebuilder about options we talked about aftermarket heads but he agreed that keeping original 2V heads was a good thing??   So I look at engine. On Drivers side I find a single 2 in the head casting at the back of motor.  On Passengers side, I have found two number "4's".    I took pictures of my headers, which are still in car from when we removed motor last fall, and the part number from Hooker Headers is clearly shown.

I am adding pictures to this post as hopefully someone experienced in 351C can clear up my confusion.





















 
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Humm, My heads have the 2 & 4 cast in a different place. They intake runner size is for sure larger on the 4-V heads. There are Australian 302 heads that fit the 351 have the 2-V runner size with 4-V size valves that are said to be the best combo. Not up on the casting number for them but here is a link that should answer your questions.

http://mustangtek.com/heads/Heads.html

This site has the best info I have so far located on Ford Casting and part numbers.

The pictures are of CC 351 4-V head. All of the 351 heads I have has the 4 or 2 cast on the upper two corners like in the pic that tells you 2-V or 4-V. I have seen some with no numbers.

The last picture shows a 2-V casting.

David







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73pony

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Can you post some pics of the exhaust ports and take some measurements? It could be that someone bolted 4v Headers on 2v heads.

 

mjlan

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The '4' identifying the larger 4V heads is in the spot David's picture shows, not where you are pointing. You want to be looking at the front of the valve cover rail, at the front corner of the intake.

You can easily tell by the size of the ports what you have.

I can't remember if the bolt pattern is the same between a 2V exhaust port and a 4V exhaust port. The 2V is an oval and the 4V is more of a rectangle with a corner missing if that helps any...



 
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Hemikiller

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Hooker 6915 are for the 4V head, 6921 are for the 2V. You might have some sealing issues with the 6915 on an 2V engine. If they were working before, they "should" be okay.

ditto to what David and others have said, the casting number you're looking for is up on the valve cover rail.

 

rackerm

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Humm, My heads have the 2 & 4 cast in a different place. They intake runner size is for sure larger on the 4-V heads. There are Australian 302 heads that fit the 351 have the 2-V runner size with 4-V size valves that are said to be the best combo. Not up on the casting number for them but here is a link that should answer your questions.

http://mustangtek.com/heads/Heads.html

This site has the best info I have so far located on Ford Casting and part numbers.

The pictures are of CC 351 4-V head. All of the 351 heads I have has the 4 or 2 cast on the upper two corners like in the pic that tells you 2-V or 4-V. I have seen some with no numbers.

The last picture shows a 2-V casting.

David







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I have a set of Aussie closed chamber (302C) heads on my 351C 2v. Other than being closed chamber, the head casting looks like the stock 2v open chambered heads and they have 2 and 4 as well. The chamber size is small at 58cc, which necessitates using a dished piston to get a reasonable compression ratio for pump gas. The stock 351C 2v, Aussie Square Bore Intake 73DA-9425-AB, or aftermarket 2v exhaust and intake manifolds work perfectly with these heads. I used stock crank, exhaust and a edlebrock four barrel performer 2v intake. 

The combination of the closed chamber heads with the small 2V ports has caused the 302C head to be a bolton-performance upgrade for other 335 series V8s. Having the smallest combustion chamber of the 335 series V8s, these cylinder heads will easily boost the static compression ratio of any other 335 series V8. In addition, the small ports used on these heads are more efficient for a street performance engine (4-5000 RPM), than the large port 4V heads that tend to prefer higher RPM performance.



 

digithead

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Humm, My heads have the 2 & 4 cast in a different place. They intake runner size is for sure larger on the 4-V heads. There are Australian 302 heads that fit the 351 have the 2-V runner size with 4-V size valves that are said to be the best combo. Not up on the casting number for them but here is a link that should answer your questions.

http://mustangtek.com/heads/Heads.html

This site has the best info I have so far located on Ford Casting and part numbers.

The pictures are of CC 351 4-V head. All of the 351 heads I have has the 4 or 2 cast on the upper two corners like in the pic that tells you 2-V or 4-V. I have seen some with no numbers.

The last picture shows a 2-V casting.

David

Thanks David!  I see now, all your numbers are up higher, right under where the valve cover would sit. I wonder what the heck the numbers I'm pointing at in my pixs signify?







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digithead

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So the plot thickens!! thank you all for your help. I called motor rebuilder and he is adamant I have 2V heads. So I called Hooker about my headers. He said they didnt have headers for 2V with power steering, which is me! So he guessed that previous owner put on the OTHER HEADERS for 4V heads as they do support PS. I didnt realize the bolt pattern was the same! So you guessed it, my PO could have put 4V headers on 2V heads! Hence my mass confusion.

So what should I do for replacement headers? Hooker tech support says the one listed on website for 2V 351C cannot have PS????

 

73pony

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I believe the hookers fit with power steering. I am running Headmans on my 2v with PS and they fit just fine.

 
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The 1972 vert I parted out has power steering and it had a set of ceramic coated headers on it. I can get the number off them since they are off the car. I took the gasket from them and laid on the 351 4-V closed chamber heads i have in the picture. There is some overhang of the gasket into the exhaust opening. I was going to use them on my Q code when I built but sounds like they are smaller but might be 4-V anyway since they were on a PS car. Now I am confused, lol. I am that way most of the time.

David





 

Hemikiller

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So the plot thickens!! thank you all for your help.  I called motor rebuilder and he is adamant I have 2V heads. So I called Hooker about my headers. He said they didnt have headers for 2V with power steering, which is me!  So he guessed that previous owner put on the OTHER HEADERS for 4V heads as they do support PS. I didnt realize the bolt pattern was the same! So you guessed it, my PO could have put 4V headers on 2V heads! Hence my mass confusion.  

So what should I do for replacement headers?  Hooker tech support says the one listed on website for 2V 351C cannot have PS????

Your Hooker rep was confused, there is no issue with fitment in a 71-73 around the power steering box. The 65-70 had an external ram that was usually in the way and required a drop bracket.





6915 - 4V heads

6921 - 2V heads

end of story

 

digithead

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Can you post some pics of the exhaust ports and take some measurements? It could be that someone bolted 4v Headers on 2v heads.
Thank you. Turns out thats what the previous owner did! I didnt know they would even bolt up. Learned something new.

 

digithead

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So the plot thickens!! thank you all for your help.  I called motor rebuilder and he is adamant I have 2V heads. So I called Hooker about my headers. He said they didnt have headers for 2V with power steering, which is me!  So he guessed that previous owner put on the OTHER HEADERS for 4V heads as they do support PS. I didnt realize the bolt pattern was the same! So you guessed it, my PO could have put 4V headers on 2V heads! Hence my mass confusion.  

So what should I do for replacement headers?  Hooker tech support says the one listed on website for 2V 351C cannot have PS????

Your Hooker rep was confused, there is no issue with fitment in a 71-73 around the power steering box. The 65-70 had an external ram that was usually in the way and required a drop bracket.





6915 - 4V heads

6921 - 2V heads

end of story

WOW! Thank you!!  Do you have these headers by chance?  I thought it was weird thats why I called them!!!!  Maybe the PO just ordered wrong damn things!
 

Hemikiller

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Sure do. I have run the 6915s on all of my 71-73 4V cars. They fit great, don't hang too low and are very good quality for the money. First set I bought were actually sold under the Casler brand. Same as and/or made by Hooker at the time. 

If the 4V headers sealed on your 2V heads in the past, then I'd just run them as is.

 
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