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- My Car
- 73 Mustang Convertible
Born an I-6, spent the teenage, 20 and 30 years as a 302, but at 40 will reach full potential as a 351C.
Updated 3/25/2012
My main interest was to build my motor a little cockier than the 351 BOSS, but not much. I wanted to start with it's cam specs and beef it up just a tiny bit from there.
No one has been able to post a Ford published specification for the
351 BOSS Cam. People have posted values, but no one could post a page from a Ford document. People have reported the existence of engineerign specs/documents, but I haven't seen a single page. That means we can only come close to matching the values.
For what it is worth, the 1971 351 BOSS cam is supposed to match the cam for the 1970 302 BOSS. From my 1970 Ford Shop Manual:
1970 302 Boss
Tappet: Mechanical
Lobe Lift: .290*
Theoretical Lift: .477*
Rocker Ratio: 1.60:1*
Duration: Not Listed
Interestingly, my 1971 Ford Shop Manual lists a 302 BOSS/302 HO:
1971 302 Boss Mechanical Tappet
Tappet: Mechanical
Lobe Lift: .290*
Theoretical Lift: .477*
Rocker Ratio: 1.73:1*
Duration: Not Listed
For 1971, a 351C 4v(Boss not listed) shows the following:
Tappet: Hydraulic
Lobe Lift: .247 Intake, .262 Exhaust
Theoretical Lift: .427/.453
Rocker Ratio: 1.73:1
Duration: Not Listed
*There is a dispute regarding the factory numbers. Many sites list the lobe lift at .295. The rocker ratio in all likelihood is a typo for 1970 and should be listed at 1.73. As a result, some say the theoretical lift should be increased to 1.73x.290=.502. However, an "expert" named George Pence believes the .477 number is correct taking into account the fact the Boss utilized a mechanical tappet(He takes into account valve lash with the 1.73 rocker arm ratio, ...but NO ONE is sure the Ford engineers took these same factors into account because 1.60x.290 just happens to matche the .477 published value).
If you are interested, further in this thread are listed part numbers for the original BOSS cams, as well as a SCHNEIDER BOSS CAM. However, at this point, I do not know there are numbers that can be trusted.
I sure would like to have an OEM BOSS cam to measure...$$$$$. Anyone got one on their shelf?
=======================
I have a 1971 OFFICIAL Ford Engine Car Shop Manual, and it has nothing in it about the Boss 351. Does anyone here have one, or is the 351C 4V in the manual I have THE Boss 351?
I have looked online for a Car Shop Manual for the Boss, but didn't find any Ford manuals.
Specifically, I am interested in the SPECIFICATIONS section for the motor. The cam I purchased for my motor is supposed to be a BOSS cam, but I had someone challenge the lift/duration numbers I was using. So I am seeking some clarification.
For what it is worth, I have service manuals for 70, 71 and 73 Fords if anyone ever needs anything.
My main interest was to build my motor a little cockier than the 351 BOSS, but not much. I wanted to start with it's cam specs and beef it up just a tiny bit from there.
No one has been able to post a Ford published specification for the
351 BOSS Cam. People have posted values, but no one could post a page from a Ford document. People have reported the existence of engineerign specs/documents, but I haven't seen a single page. That means we can only come close to matching the values.
For what it is worth, the 1971 351 BOSS cam is supposed to match the cam for the 1970 302 BOSS. From my 1970 Ford Shop Manual:
1970 302 Boss
Tappet: Mechanical
Lobe Lift: .290*
Theoretical Lift: .477*
Rocker Ratio: 1.60:1*
Duration: Not Listed
Interestingly, my 1971 Ford Shop Manual lists a 302 BOSS/302 HO:
1971 302 Boss Mechanical Tappet
Tappet: Mechanical
Lobe Lift: .290*
Theoretical Lift: .477*
Rocker Ratio: 1.73:1*
Duration: Not Listed
For 1971, a 351C 4v(Boss not listed) shows the following:
Tappet: Hydraulic
Lobe Lift: .247 Intake, .262 Exhaust
Theoretical Lift: .427/.453
Rocker Ratio: 1.73:1
Duration: Not Listed
*There is a dispute regarding the factory numbers. Many sites list the lobe lift at .295. The rocker ratio in all likelihood is a typo for 1970 and should be listed at 1.73. As a result, some say the theoretical lift should be increased to 1.73x.290=.502. However, an "expert" named George Pence believes the .477 number is correct taking into account the fact the Boss utilized a mechanical tappet(He takes into account valve lash with the 1.73 rocker arm ratio, ...but NO ONE is sure the Ford engineers took these same factors into account because 1.60x.290 just happens to matche the .477 published value).
If you are interested, further in this thread are listed part numbers for the original BOSS cams, as well as a SCHNEIDER BOSS CAM. However, at this point, I do not know there are numbers that can be trusted.
I sure would like to have an OEM BOSS cam to measure...$$$$$. Anyone got one on their shelf?
=======================
I have a 1971 OFFICIAL Ford Engine Car Shop Manual, and it has nothing in it about the Boss 351. Does anyone here have one, or is the 351C 4V in the manual I have THE Boss 351?
I have looked online for a Car Shop Manual for the Boss, but didn't find any Ford manuals.
Specifically, I am interested in the SPECIFICATIONS section for the motor. The cam I purchased for my motor is supposed to be a BOSS cam, but I had someone challenge the lift/duration numbers I was using. So I am seeking some clarification.
For what it is worth, I have service manuals for 70, 71 and 73 Fords if anyone ever needs anything.
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