How much horsepower does 351 have?
 

This question has been haunting me ever since I had my 1972 351c 2v engine swaped into my 71 Mustang sportsroof. I have been searching websites over and over, but have not yet confirmed how much horsepower this engine has. HOw many different versions of the 351 were made from 1971 to 1973? I noticed some 351s were 330,280,266hp, and so on each year going down more and more by horsepower. If anyone would please help me out I would greately appreciate it. Thanks in advance

The following codes/hp ratings were issued from '71-73

1971
H 351cid 2V V-8 240 hp
M(Q?) 351cid 4V V-8 280 hp (Cobra Jet)
M 351cid 4V V-8 285 hp
R 351cid 4V V-8 330 hp (Boss)

1972
H 351cid 2V V-8 177 hp
Q 351cid 4V V-8 266 hp (Cobra Jet)
R 351cid 4V V-8 275 hp (High Output)

1973
H 351cid 2V V-8 177 hp
Q 351cid 4V V-8 266 hp (Cobra Jet)

Got the above numbers, and most of my classic tech stuff, from
Brad's Mustang Site
Hope it helps.

Also remember between 71 and 72 engines went from gross HP rating to net ratings. The changes between 71 and 72 were minimal, but the numbers look horrendous because of the change in ratings.

yeah thats true. But what changes did the factory do to the engine for it to lose the power anyways? Milder cam?

i know the compression went down to 8.5:1, but what causes the compression to lower?

those were some tricky years for musclecars, emissions hit hard, muscle car era died off...

I don't know all the specifics here but some of the changes (all done for emisions) were switching to unleaded fuel (hardened valve seats) lower compression by using dished pistons. Other changes were advancing the cam two degrees, great for top end power but lowers torque. I wouldn't do it in a street engine, but as I said, emisions. The boss 351 motor lost its solid lifters, got a milder cam(I think so on the cam, not sure) and became the 351 HO. That was about it for internal changes between 71 and 72 that I can remeber. Someone else probably remembers a few more.

I don't know if they might have messed with the ignition timing.

haha then i have an RV cam in there. probably weaker than stock lol. Thanks for the info too. Im learning alot from this website!