351 c Differences

Curious, what are the main differences between a 1972 and 1973 351 Clevland motor, HP wise ? I have done some research and believe that one motor has closed and one open heads, one being better than the other. Also the compression on the 72 is 8.6:1 and the 73 is 8.0:1. Does all this sound accurate and which one has the closed and open heads. What kind of horsepower do you think each stock motor makes ... is there a difference ? Thanks

Steve

the 73 has open chamber 4 v heads with 2v valves . . i think the cam was advanced 4 degrees also.

the 73 has open chamber 4 v heads with 2v valves . . i think the cam was advanced 4 degrees also.

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I neglected to say that my 72 351 C is installed in my 73 Mustang, not a matching motor. It has the 2 V carb on it.

For HP it all depends on which version that you are looking at.

For 1973: 351C 4V (Q) was rated 248HP net due to lower compression (dished pistons) and smaller valves. There are some that indicate 266 HP on the Mach . For 2V it was 177 HP.

For 1972: 266 is the SAE Horsepower Rating of the 'M' or 'Q' code 1972 351 Cleveland engine. The 'R' code engine was rated at 275 net HP in 1972. The 2 V model was 177HP.

The cam for 351C 4v was retarded 4-6 degrees starting in 1972. I'm not sure about the late 1971 production 351 "CJ". Chuck

I could be wrong but didn't the early build '73 4V have the bigger valves and the late '73's had the smaller valves?....seems to be some conflicting info out there!

I could be wrong but didn't the early build '73 4V have the bigger valves and the late '73's had the smaller valves?....seems to be some conflicting info out there!

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I have read the same thing. Its possible that some of the early 73 motors used the larger valves until Ford used all the remaining inventory from 72. If the heads start with D3 then the smaller valves are there. It would be interesting to see if any members with early 73 builds have heads that start with D1 or D2 casting numbers. Those 4V castings will have 2.19 intakes.

This info is from searching the internet so the accuracy may not be 100%

I could be wrong but didn't the early build '73 4V have the bigger valves and the late '73's had the smaller valves?....seems to be some conflicting info out there!

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I have read the same thing. Its possible that some of the early 73 motors used the larger valves until Ford used all the remaining inventory from 72. If the heads start with D3 then the smaller valves are there. It would be interesting to see if any members with early 73 builds have heads that start with D1 or D2 casting numbers. Those 4V castings will have 2.19 intakes.

This info is from searching the internet so the accuracy may not be 100%

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Thanks all !

I could be wrong but didn't the early build '73 4V have the bigger valves and the late '73's had the smaller valves?....seems to be some conflicting info out there!

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I have also heard the late '73's had smaller valves, not the earlier ones

mike

I could be wrong but didn't the early build '73 4V have the bigger valves and the late '73's had the smaller valves?....seems to be some conflicting info out there!

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I have also heard the late '73's had smaller valves, not the earlier ones

mike

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I have some D3ZE heads that had the small valves.... Pretty sure they came off a 74 GT Ranchero. I put the BIG valves in with some pocket work. Still have them fresh from machine shop....

My mustang still had original small valve 4v heads on it.." showed them to John just the other day" .I'll have to dig up the pics, but yes some 4v's did have small valves late , it was a very short run just to comply with a change due too racing rules in NHRA "and other sports concerning small blocks" From what i can tell they have a smaller combustion chamber too. very rare to find them on 73 mustangs. Some people thought they was myth " including me" Till i compared them too a set of 71 open chambered i picked up.

From what i know there is no horse power report on the diff between the 4v small and big valve in 73...I have a fealing my small valve 4v performed a tad better than the nuttered out 73 4v large valve stock off the factory floor. " with all the emissions crud going on" be neat to see some one build up 2 of the same motors to factory specs and compare.. " who has the money for that experiment? " hehehe

The cam for 351C 4v was retarded 4-6 degrees starting in 1972. I'm not sure about the late 1971 production 351 "CJ". Chuck

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You can't say retarded anymore. The cam had "Special Needs!"

The cam for 351C 4v was retarded 4-6 degrees starting in 1972. I'm not sure about the late 1971 production 351 "CJ". Chuck

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You can't say retarded anymore. The cam had "Special Needs!"

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The notion that I can't say retarded anymore is retarded. Political correctness is an impediment to effective communication and mutual understanding. See political effectiveness of US government over the last

20+ years for examples. Chuck

So an advanced cam went to college and got degreed?

OMG...there's at least 2 puns in there...forgive me for I have no sense of shame.

So an advanced cam went to college and got degreed?

OMG...there's at least 2 puns in there...forgive me for I have no sense of shame.

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Not really. The retarded and advanced cams were equally off center line. They both took a ride on the wheel and are now straight up. However, I do agree that you have no sense of shame. Chuck

The notion that I can't say retarded anymore is retarded. Political correctness is an impediment to effective communication and mutual understanding.

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So its a speech impediment?:shy:

Does this mean that my ignition timing isn't retarded anymore either, it's now "regressed" or "unadvanced"?

"Joe is not "retarded", he is merely "unadvanced"."

Y'all are retarded! rofl

Y'all are retarded! rofl

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Ain't.