71-73 Engine Performance

[Don C]

Here are the engine performance specs for our cars, based on the AMA specs (where available), in a single, easy to view format.



What made the biggest difference was when they changed from brake horsepower rating to SAE net horsepower rating in 1972. Brake horsepower was measured at the crankshaft without any accessories (water pump, alternator, exhaust, etc.) connected, SAE net horsepower is measured at the crankshaft with the accessories attached.

If you see any errors, please let me know. The one engine that was missing is the Boss 351. Ray (or anyone else), can you help on this one?

Updated to include Boss 351.

Updated to include '72 351 HO.

 

[barnett468]

Here are the engine performance specs for our cars, based on the AMA specs, in a single, easy to view format. The one engine that was missing is the Boss 351. Ray (or anyone else), can you help on this one?

hp 330@5400

tq 370@4000

advertised compression 11.3 - 11.7 depending on the source of the info.

 

[Don C]

Thank you, I just updated it.

 

[Steve73QMach1]

The 73 351-4V is only a 7.9:1 compression ratio? That seems pretty low.

 

[Bill73Ragtop]

Just curious. Where does the 72 'R' code fit in? My assumption has always been it was a de-tuned 71 Boss engine....

 

[secluff]

My sources of info on the 72 "R" 351 show

Horsepower..275@ 6000

Torque.........286@ 3800

Compression Ratio 9.2:1

There may be some different numbers floating around out there, but my info and two other sources show the numbers I've posted!

 

[Boss1Ray]

My sources of info on the 72 "R" 351 show

Horsepower..275@ 6000

Torque.........286@ 3800

Compression Ratio 9.2:1

There may be some different numbers floating around out there, but my info and two other sources show the numbers I've posted!

That's what I've always seen for the 72 351 HO motors. I have seen quite a few Q code folks attach that HP rating to their Q code motors. I have seen it on many showcards at car shows. I try to bite my tongue...

Thx guys. Just FYI these AMA specs are available on our WIKI just not as readable as the engine specs posted here. Funny - If my memory serves me correctly :huh: - one of them lists the gas tank filler as installed on the rear 1/4 panel! See if you can find that reference... LOL

Ray

 

[secluff]

Ray, those folks with the "Q" code's claiming 275 horsepower are dreaming. My 72 Gran Torino Sport was my first encounter with the Q 351. In spite of everything Ford and the Government did to make it an underperforming slug, it still ran fairly well considering it's weight and the lower HP rating (248) when compared to the Mustang (266 HP). But having owned a 70 M code 351 with 11.0:1 compression ratio, I can tell you that compression and a Cleveland makes for a screamer of an engine. Even the slightly lower compression difference with the advertised (10.7:1) on my 71 made a difference I could feel in the seat of my pants. So the 72's with 8.6:1....Like Barney Fife would say, "Nothing to see, move along"! In fact I used to joke that I believed I could take a piece of rope and wrap around the crank pulley of my 72 and hand crank it like an old lawn mower!

Pull their show cards and send them to the timeout out corner Ray!

 

[Stanglover]

OK, Ford advertise 10.7:1 for the '71 M code (4V). I'm curious because, using a basic compression calculator like Summit Racing or United Engine (Keith Black), I only get 10.2 max for a stock 351C 4V engine. Now, I know there are more reliable calculators out there that might get it a little closer, but 10.7 is a stretch as far as I can see. I looked at Wallace Racing, but all I saw was a calc. for a Pontiac. Was this Ford trying to make their engines sound more powerful??

Thoughts?

 

[donkost]

Don't forget Ford played the game underrating certain engines. Like various performance 428 engines being advertised at 335 hp. '71 429 CJ at 370 hp and 429 SCJ at 375 hp. Solid lifters, higher redline, Holley carb, only good for 5 more hp. heh Actually those engines were said to be at around 400 hp for the 429 CJ and over 400 hp for the 429 SCJ. My '71 429 CJ-R was breathed on a little by a past owner with Comp Cams Magnum 292H, Holley carb, long tube headers, MSD ignition box, and is said to be at around 450 hp and 500 lb. ft. of torque. Just by the seat of the pants it feels like this combo would slaughter the stock 400 / 4 speed '68 GTO (not the HO or Ram Air cam) I had decades ago, and I ran that car hard.

 

[c9zx]

What I've seen the last many years is Ford consistently over rates compression ratios. I've never uncovered an official reason for doing so. Speculation is two reasons, marketing and warranty concerns. Ford loved to lower compression by varying deck heights and piston pin locations leaving the piston significantly down the bore at TDC. This condition contributes to detonation, as well as lowering compression, and is most pronounced in the 351M engines. Chuck

 

[Hemikiller]

SUM TING WONG with the 351 4v specs - looks like you swapped the M-code and Q for 71. Also, you're missing the 72 R-code 351HO engine.

 

[Don C]

The '71 351CJ had the open chamber 4V heads.

I updated it to include the '72 351 HO specs.