Dumb question here

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1972 Mustang Sprint Sportsroof
What is the difference between a 351C 4v and 351C 4v Cobra Jet? There is a slight horse power variance just wondering where it comes from....what makes it a Cobta Jet? (More dumb questions to follow).

 
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I will give it a "shot."

The 351C initially came out in 1970 in two (2) versions, the 2V and a 4V. The 2V had open chamber heads while the 4V had quench chamber heads. I believe that both versions had 2-bolt main caps.

In 1971, every 351C that received a 4V Carburetor received 4-bolt mains. The 2V and the 4V headed motors were continued. In mid-year (May 1971), the 351CJ was released. It had open chamber heads and 4-bolt main caps. It also had a hotter hydraulic camshaft than the standard 4V motor. There were approximately 144 Mustangs built with 351CJ engines in 1971.

Also released in 1971 was the Boss 351 which was essentially the same as the 351 4V except it had solid (mechanical) lifters and camshaft. It also received the quench chamber heads and 4-bolt main caps.

In 1972, the 4V designation was dropped and all 10,249 4V Mustangs produced were actually Cobra Jets. These motors were essentially the same as the 351CJ that were released in 1971.

Also released in 1972 was the 351 HO (398 Mustangs) which replaced the Boss 351. It differed from the Boss 351 primarily with the use of open chamber heads. It also had a milder camshaft with less duration and a little more lift.

In 1973, the 351CJ continued as a 266HP (Net) unit in the Mustangs.

Hope this helps.

BT

 
I will give it a "shot."

The 351C initially came out in 1970 in two (2) versions, the 2V and a 4V. The 2V had open chamber heads while the 4V had quench chamber heads. I believe that both versions had 2-bolt main caps.

In 1971, every 351C that received a 4V Carburetor received 4-bolt mains. The 2V and the 4V headed motors were continued. In mid-year (May 1971), the 351CJ was released. It had open chamber heads and 4-bolt main caps. It also had a hotter hydraulic camshaft than the standard 4V motor. There were approximately 144 Mustangs built with 351CJ engines in 1971.

Also released in 1971 was the Boss 351 which was essentially the same as the 351 4V except it had solid (mechanical) lifters and camshaft. It also received the quench chamber heads and 4-bolt main caps.

In 1972, the 4V designation was dropped and all 10,249 4V Mustangs produced were actually Cobra Jets. These motors were essentially the same as the 351CJ that were released in 1971.

Also released in 1972 was the 351 HO (398 Mustangs) replaced the Boss 351. It differed from the Boss 351 primarily with the use of open chamber heads. It also had a milder camshaft with a less duration and a little more lift.

In 1973, the 351CJ continued as a 266HP (Net) unit in the Mustangs.

Hope this helps.

BT
Thats a real thorough answer!

 
I will give it a "shot."

The 351C initially came out in 1970 in two (2) versions, the 2V and a 4V. The 2V had open chamber heads while the 4V had quench chamber heads. I believe that both versions had 2-bolt main caps.

In 1971, every 351C that received a 4V Carburetor received 4-bolt mains. The 2V and the 4V headed motors were continued. In mid-year (May 1971), the 351CJ was released. It had open chamber heads and 4-bolt main caps. It also had a hotter hydraulic camshaft than the standard 4V motor. There were approximately 144 Mustangs built with 351CJ engines in 1971.

Also released in 1971 was the Boss 351 which was essentially the same as the 351 4V except it had solid (mechanical) lifters and camshaft. It also received the quench chamber heads and 4-bolt main caps.

In 1972, the 4V designation was dropped and all 10,249 4V Mustangs produced were actually Cobra Jets. These motors were essentially the same as the 351CJ that were released in 1971.

Also released in 1972 was the 351 HO (398 Mustangs) replaced the Boss 351. It differed from the Boss 351 primarily with the use of open chamber heads. It also had a milder camshaft with a less duration and a little more lift.

In 1973, the 351CJ continued as a 266HP (Net) unit in the Mustangs.

Hope this helps.

BT
When I got my 351C 2v the guy had a set of 4V heads in the trunk. I had the rocker bosses (?? rocker bolt points) cut down and installed adjustable roller tip rockers. How can I tell what kind of 4V heads they are?

 
I will give it a "shot."

The 351C initially came out in 1970 in two (2) versions, the 2V and a 4V. The 2V had open chamber heads while the 4V had quench chamber heads. I believe that both versions had 2-bolt main caps.

In 1971, every 351C that received a 4V Carburetor received 4-bolt mains. The 2V and the 4V headed motors were continued. In mid-year (May 1971), the 351CJ was released. It had open chamber heads and 4-bolt main caps. It also had a hotter hydraulic camshaft than the standard 4V motor. There were approximately 144 Mustangs built with 351CJ engines in 1971.

Also released in 1971 was the Boss 351 which was essentially the same as the 351 4V except it had solid (mechanical) lifters and camshaft. It also received the quench chamber heads and 4-bolt main caps.

In 1972, the 4V designation was dropped and all 10,249 4V Mustangs produced were actually Cobra Jets. These motors were essentially the same as the 351CJ that were released in 1971.

Also released in 1972 was the 351 HO (398 Mustangs) replaced the Boss 351. It differed from the Boss 351 primarily with the use of open chamber heads. It also had a milder camshaft with a less duration and a little more lift.

In 1973, the 351CJ continued as a 266HP (Net) unit in the Mustangs.

Hope this helps.

BT
When I got my 351C 2v the guy had a set of 4V heads in the trunk. I had the rocker bosses (?? rocker bolt points) cut down and installed adjustable roller tip rockers. How can I tell what kind of 4V heads they are?
I can answer this one. The combustion chambers are pretty distinctive between the different heads. The head on the left is open chamber (71-73), the head on the right is closed chamber (70-71)

Clevel1.jpg


 
I will give it a "shot."

The 351C initially came out in 1970 in two (2) versions, the 2V and a 4V. The 2V had open chamber heads while the 4V had quench chamber heads. I believe that both versions had 2-bolt main caps.

In 1971, every 351C that received a 4V Carburetor received 4-bolt mains. The 2V and the 4V headed motors were continued. In mid-year (May 1971), the 351CJ was released. It had open chamber heads and 4-bolt main caps. It also had a hotter hydraulic camshaft than the standard 4V motor. There were approximately 144 Mustangs built with 351CJ engines in 1971.

Also released in 1971 was the Boss 351 which was essentially the same as the 351 4V except it had solid (mechanical) lifters and camshaft. It also received the quench chamber heads and 4-bolt main caps.

In 1972, the 4V designation was dropped and all 10,249 4V Mustangs produced were actually Cobra Jets. These motors were essentially the same as the 351CJ that were released in 1971.

Also released in 1972 was the 351 HO (398 Mustangs) replaced the Boss 351. It differed from the Boss 351 primarily with the use of open chamber heads. It also had a milder camshaft with a less duration and a little more lift.

In 1973, the 351CJ continued as a 266HP (Net) unit in the Mustangs.

Hope this helps.

BT
When I got my 351C 2v the guy had a set of 4V heads in the trunk. I had the rocker bosses (?? rocker bolt points) cut down and installed adjustable roller tip rockers. How can I tell what kind of 4V heads they are?
I can answer this one. The combustion chambers are pretty distinctive between the different heads. The head on the left is open chamber (71-73), the head on the right is closed chamber (70-71)

Clevel1.jpg
in this pic the right one is my old 2V head and the left is the new 4V head. is the closed better then to open? I would think so.

carshowjune26 006.JPG

 
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Yes yes and a maybe as far as better, depends on what you are doing. Closed chamber will raise your compression ratio. get the numbers off the head and we can tell you exactly what they are.

 
Yes yes and a maybe as far as better, depends on what you are doing. Closed chamber will raise your compression ratio. get the numbers off the head and we can tell you exactly what they are.
is it the 9L7 on 1 head and 9K20 on the other?

 
Yes yes and a maybe as far as better, depends on what you are doing. Closed chamber will raise your compression ratio. get the numbers off the head and we can tell you exactly what they are.
is it the 9L7 on 1 head and 9K20 on the other?
There should be a longer number on them something like this

D0AE-6090-E 70-74 351C 2V heads In Valve 1.946" 2.046" Ex Valve 1.6495" 1.6595" 78.2cc

D0AE-6090-G 70-71 351C 4V heads Valves 2.195, 1.715 62.8cc Closed Chamber

D0AE-6090-J 70-74 351C 2V heads In Valve 1.946" 2.046" Ex Valve 1.6495" 1.6595" 78.2cc

D0AE-6090-M 70-71 351C 4V heads Valves 2.195, 1.715 62.8cc Closed Chamber

D0AE-6090-N,D0AE-N 70-71 351C 4V heads Valves 2.195, 1.715 62.8cc Closed Chamber

D0AE-6090-R 70-71 351C 4V heads Valves 2.195, 1.715 62.8cc Closed Chamber

D0OE-B 70 302 Valves 1.78, 1.45 58.2cc

D0OE-C 70 - 74 351W Valves 1.84, 1.54 60.4cc

D0OE-6090-R 70-71 429CJ & SCJ Valves 2.24, 1.72 73.5cc Adjustable Rockers

D0VE-C 70-71 429 460 Valves 2.09, 1.65 75.8cc

D0ZE-6090-A 70 Boss 302 Mustang Valves 2.19, 1.72 58cc

D0ZE-6090-B 70 Boss 302 Mustang Valves 2.19, 1.72 58cc

D1AE-GA 71 B0SS 351 Mustang Screw in Studs Guide plates Valves 2.19, 1.71 75.4cc

D2OE-AB 72 460 Police Interceptor

D2OE-BA 72-74 302 Valves 1.78, 1.45 58.2cc

D3ZE-AA 73-74 351C 4V heads Valves 2.04, 1.66 75.4cc

XE-145488 429 Police Interceptor Aluminum Experimental Part

 
Yes yes and a maybe as far as better, depends on what you are doing. Closed chamber will raise your compression ratio. get the numbers off the head and we can tell you exactly what they are.
is it the 9L7 on 1 head and 9K20 on the other?
There should be a longer number on them something like this

D0AE-6090-E 70-74 351C 2V heads In Valve 1.946" 2.046" Ex Valve 1.6495" 1.6595" 78.2cc

D0AE-6090-G 70-71 351C 4V heads Valves 2.195, 1.715 62.8cc Closed Chamber

D0AE-6090-J 70-74 351C 2V heads In Valve 1.946" 2.046" Ex Valve 1.6495" 1.6595" 78.2cc

D0AE-6090-M 70-71 351C 4V heads Valves 2.195, 1.715 62.8cc Closed Chamber

D0AE-6090-N,D0AE-N 70-71 351C 4V heads Valves 2.195, 1.715 62.8cc Closed Chamber

D0AE-6090-R 70-71 351C 4V heads Valves 2.195, 1.715 62.8cc Closed Chamber

D0OE-B 70 302 Valves 1.78, 1.45 58.2cc

D0OE-C 70 - 74 351W Valves 1.84, 1.54 60.4cc

D0OE-6090-R 70-71 429CJ & SCJ Valves 2.24, 1.72 73.5cc Adjustable Rockers

D0VE-C 70-71 429 460 Valves 2.09, 1.65 75.8cc

D0ZE-6090-A 70 Boss 302 Mustang Valves 2.19, 1.72 58cc

D0ZE-6090-B 70 Boss 302 Mustang Valves 2.19, 1.72 58cc

D1AE-GA 71 B0SS 351 Mustang Screw in Studs Guide plates Valves 2.19, 1.71 75.4cc

D2OE-AB 72 460 Police Interceptor

D2OE-BA 72-74 302 Valves 1.78, 1.45 58.2cc

D3ZE-AA 73-74 351C 4V heads Valves 2.04, 1.66 75.4cc

XE-145488 429 Police Interceptor Aluminum Experimental Part
Thank you, I pulled out the old 2V head and found a strange # D1AE CE and the 4V looks like in the pic DOAE N

If you click on the pic I put up and click it again you can see the #'s on both

 
is it the 9L7 on 1 head and 9K20 on the other?
There should be a longer number on them something like this

D0AE-6090-E 70-74 351C 2V heads In Valve 1.946" 2.046" Ex Valve 1.6495" 1.6595" 78.2cc

D0AE-6090-G 70-71 351C 4V heads Valves 2.195, 1.715 62.8cc Closed Chamber

D0AE-6090-J 70-74 351C 2V heads In Valve 1.946" 2.046" Ex Valve 1.6495" 1.6595" 78.2cc

D0AE-6090-M 70-71 351C 4V heads Valves 2.195, 1.715 62.8cc Closed Chamber

D0AE-6090-N,D0AE-N 70-71 351C 4V heads Valves 2.195, 1.715 62.8cc Closed Chamber

D0AE-6090-R 70-71 351C 4V heads Valves 2.195, 1.715 62.8cc Closed Chamber

D0OE-B 70 302 Valves 1.78, 1.45 58.2cc

D0OE-C 70 - 74 351W Valves 1.84, 1.54 60.4cc

D0OE-6090-R 70-71 429CJ & SCJ Valves 2.24, 1.72 73.5cc Adjustable Rockers

D0VE-C 70-71 429 460 Valves 2.09, 1.65 75.8cc

D0ZE-6090-A 70 Boss 302 Mustang Valves 2.19, 1.72 58cc

D0ZE-6090-B 70 Boss 302 Mustang Valves 2.19, 1.72 58cc

D1AE-GA 71 B0SS 351 Mustang Screw in Studs Guide plates Valves 2.19, 1.71 75.4cc

D2OE-AB 72 460 Police Interceptor

D2OE-BA 72-74 302 Valves 1.78, 1.45 58.2cc

D3ZE-AA 73-74 351C 4V heads Valves 2.04, 1.66 75.4cc

XE-145488 429 Police Interceptor Aluminum Experimental Part
Thank you, I pulled out the old 2V head and found a strange # D1AE CE and the 4V looks like in the pic DOAE N

If you click on the pic I put up and click it again you can see the #'s on both

That 2V is actually D1AE CB. The B just looks funny.

Here is a page with just about all of them I think.

http://home.comcast.net/~jelerath/mustang/Specs/heads-fr.html

That page has some good basic info too.

 
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D0AE-6090-N,D0AE-N 70-71 351C 4V heads Valves 2.195, 1.715 62.8cc Closed Chamber

Are nice heads
Yes they are, and since they are already machined for an adjustable valvetrain, they might as well be Boss 351 heads.
thank you, that is what I was thinking but did not know for sure. The cam I put in is a little better then the 351 boss also.

 
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