What is Factory Torque Rating for M code?

7173Mustangs.com

Help Support 7173Mustangs.com:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.
YellowHorse

YellowHorse

Well-known member
Joined
Aug 20, 2022
Messages
218
Reaction score
212
Location
Michigan, Muskegon
My Car
73 Convertible, c6, yellow
351-2v, power top, power windows.
71 M code being overshadowed by other models and i cant seem to find factory power rating for, for torque.

70 M is 380 ft.lb and since 71 ratings been degraded abit for HP (posibly due to insurance) i would guess around 360 ft. lb. for torque.

Curious to see how much more torque it has over Q. Should have quite abit more unless underated for insurance.
 
For 72 Q
Horsepower net:198.5 kW / 270 PS / 266 hp (SAE net)
/ 5400
Torque net:408 Nm / 301 ft-lb
/ 3600
 
And for some reason, people act like the Q code is the bees knees...next to the R code, of course.
 
detritusmaximus said:
And for some reason, people act like the Q code is the bees knees...next to the R code, of course.
Click to expand...
Because of misleading Ford advertising - they slapped CJ on detuned engine just to sell cars.
71 Q is rare, so i can see it bring more money justlike 72 HO R code.

They all can make similar power once you throw equivalent pistons and heads in the detuned engines.
Performance wise (stock or when modified with cams and carb) it goes like this.

Boss351 > M code > HO R code (72) > Q code.
 
I don't doubt the M-code has higher hp and torque than the Q-code, but above you're comparing gross ratings to net ratings. I'd guess the apples-to-apples comparison would be closer.
Not sure serious people would turn down either engine if offered. You can set either one up to be better performers than how they came from Ford. I'm running M-code CC heads on my Q-code engine. I also changed the cam years ago to a different profile and eliminated the -4° timing of the stock Q-code timing set. And, of course, Hooker SCs, aluminum intake, and Holley carburetor.
 
72-73 Q codes have 4 bolt mains and 71 M codes don’t if I remember correctly.
I would think that is kind of a big deal no?
Ford and everyone else had to play within the rules of more stringent emission standards and it is nice Ford put the important pieces in place so people still had a good starting point. Remember in this time it was still very popular to modify your brand new car.
 
70cobrascj said:
72-73 Q codes have 4 bolt mains and 71 M codes don’t if I remember correctly.
I would think that is kind of a big deal no?
Ford and everyone else had to play within the rules of more stringent emission standards and it is nice Ford put the important pieces in place so people still had a good starting point. Remember in this time it was still very popular to modify your brand new car.
Click to expand...
I have an unqualified line of thought on why 72/73 blocks had 4 bolt mains. For a start, all Cleveland blocks can be drilled and tapped for the extra bolts, but those bolts are (if I remember) only 5/16" and therefore really not doing much to support the crank. I believe the reasoning was to prevent fretting (sideways movement).
Now, when Ford bought out the Boss which had 4 bolts mains from the get-go, Ford probably over estimated how many 4 bolts caps they would use over the life of the Cleveland engine. It begs the question; why didn't ALL 71 351C engines get 4 bolts?? So some of the 72 and all of the 73 engine build simply used up this over supply of 4 bolt caps. The engine line was already set up for the extra operation anyway, so it was a no brainer to use up the extra caps.
Unless the extra bolts are installed on an angle, as in (cough) Chevys, they are adding little to no support to the crank.
Just my thoughts on the subject, but it IS cool to say "I have a 4 bolt mains engine"!! (to impress the Chevy guys)
 
Something that needs to be said outright at the beginning is comparing a 1972 SAE NET rated engine to a 70 or 71 SAE gross rated engine is not apples to apples. Net rating is a flywheel horsepower & torque rating with all accessories, intake and exhaust system components installed as it would be in the vehicle - it does not account for drivetrain losses. Gross is what you'd get on an engine dyno at a machine shop - open headers, no water pump, alternator or air cleaner. Ford also played fast and loose with the HP ratings.

Another factor to keep in mind is that the advertised compression ratios on the 70/71 M-code engines were absolute BS. The only way you'd reach Ford's advertised ratios would be to zero deck the pistons, as they were built .035" in the hole. A factory built 70 M-code will yield about 9.7:1, the 71 with 9.5:1 using a modern .041" Felpro gasket. Once you consider the way they were really built, and ignore Ford's marketing, the 72 Q-code starts looking a lot better with it's slightly lower compression of 8.6:1.

As far as four bolt mains, many Cleveland builders think they're useless. The standard 2-bolt is plenty strong to support the capabilities of the block itself, even more so if you switch to main studs.


Breakdown of the 1970 engine options - Mercury based, but applies to the conversation.

1707487415367.png

From the 71 dealer sales manual for the M-code

1707447912466.png
 
I understand the gross vs. net differences. I won't quibble about 20hp, which its already down 15hp from '70. But that doesn't account for a 70ftlb drop in tq. Dished pistons and open chamber heads? The only thing I can see that is 'different' (not 'less') is the cam.
Detuned is still detuned.
So it begs the question, in identical cars, is which has better performance, 71 M or 71/72 Q?
More importantly, which is more enjoyable to drive? More power does not always translate to more fun.
 
Last edited:
Sheriff41 said:
I don't doubt the M-code has higher hp and torque than the Q-code, but above you're comparing gross ratings to net ratings. I'd guess the apples-to-apples comparison would be closer.
Not sure serious people would turn down either engine if offered. You can set either one up to be better performers than how they came from Ford. I'm running M-code CC heads on my Q-code engine. I also changed the cam years ago to a different profile and eliminated the -4° timing of the stock Q-code timing set. And, of course, Hooker SCs, aluminum intake, and Holley carburetor.
Click to expand...
I have an article from an old Car Craft Magazine by Jack Roush regarding the 351C engines and the differences between them. Jack talks about how he preferred the Open Chamber heads as the valves were less shrouded and hence could rev more freely. This is likely why the factory engineers went with the 4-bolt mains. Believe me, they wouldn't have put 4-bolts in unless there was a need, the bean counters would never have never allowed it. Machining costs, the bolts, the labor to install all add up quickly. BTW, the outboard bolts were 3/8-16 grade 8.

Regarding the cam, just for clarification, if you advance the Q code cam 4° it is exactly the same bump stick as the 71's. It was a cheap way to help meet the ever tightening emissions standards. The simply moved the dowel pin. A good set of headers, a 750cfm Holley, and you get a huge improvement. I have a '72 Q code and a '72 Mach 1 with a '70 M code in it, both withe same headers and 750 carb (I have one of the old Ford Buddy Barr D1ZX-D intakes on the Q motor, got it at a swap meet in Indy about 1983 for $100, there was one on eBay for $1750 last year! It's identical to the cast iron square bore manifold except for larger carb bore holes.) The Q does seem to love high RPMs more than the M car. It springs to life at about 5000 RPMs, and God help you if you miss a gear. I typically shift at about 6700 RPM with the Q, and it seems to want more revs. The M car has more at low RPM, but but I shift it at about 6200 RPM as it starts to feel maxed out.

I love both, but for different reasons. Just my 2 cents worth after playing with these things for about 49 years now.
 
t.kohlmeyer said:
I have an article from an old Car Craft Magazine by Jack Roush regarding the 351C engines and the differences between them. Jack talks about how he preferred the Open Chamber heads as the valves were less shrouded and hence could rev more freely. This is likely why the factory engineers went with the 4-bolt mains. Believe me, they wouldn't have put 4-bolts in unless there was a need, the bean counters would never have never allowed it. Machining costs, the bolts, the labor to install all add up quickly. BTW, the outboard bolts were 3/8-16 grade 8.

Regarding the cam, just for clarification, if you advance the Q code cam 4° it is exactly the same bump stick as the 71's. It was a cheap way to help meet the ever tightening emissions standards. The simply moved the dowel pin. A good set of headers, a 750cfm Holley, and you get a huge improvement. I have a '72 Q code and a '72 Mach 1 with a '70 M code in it, both withe same headers and 750 carb (I have one of the old Ford Buddy Barr D1ZX-D intakes on the Q motor, got it at a swap meet in Indy about 1983 for $100, there was one on eBay for $1750 last year! It's identical to the cast iron square bore manifold except for larger carb bore holes.) The Q does seem to love high RPMs more than the M car. It springs to life at about 5000 RPMs, and God help you if you miss a gear. I typically shift at about 6700 RPM with the Q, and it seems to want more revs. The M car has more at low RPM, but but I shift it at about 6200 RPM as it starts to feel maxed out.

I love both, but for different reasons. Just my 2 cents worth after playing with these things for about 49 years now.
Click to expand...
Make sensce, M does not have a cam to rev. and will feel maxed out.
As far as 4 bolts, drag races saw no need for them, maybe road racing abow 8k they wiuld be of a benefit.
 
Hemikiller said:
Something that needs to be said outright at the beginning is comparing a 1972 SAE NET rated engine to a 70 or 71 SAE gross rated engine is not apples to apples. Net rating is a flywheel horsepower & torque rating with all accessories, intake and exhaust system components installed as it would be in the vehicle - it does not account for drivetrain losses. Gross is what you'd get on an engine dyno at a machine shop - open headers, no water pump, alternator or air cleaner. Ford also played fast and loose with the HP ratings.

Another factor to keep in mind is that the advertised compression ratios on the 70/71 M-code engines were absolute BS. The only way you'd reach Ford's advertised ratios would be to zero deck the pistons, as they were built .035" in the hole. A factory built 70 M-code will yield about 9.7:1, the 71 with 9.5:1 using a modern .041" Felpro gasket. Once you consider the way they were really built, and ignore Ford's marketing, the 72 Q-code starts looking a lot better with it's slightly lower compression of 8.6:1.

As far as four bolt mains, many Cleveland builders think they're useless. The standard 2-bolt is plenty strong to support the capabilities of the block itself, even more so if you switch to main studs.


Breakdown of the 1970 engine options - Mercury based, but applies to the conversation.

View attachment 85592

From the 71 dealer sales manual for the M-code

View attachment 85578
Click to expand...
I see that all years mustangs had inconsistent heads volume and the true measurement will vary by car. They are all lower in compression then advertised by roughly same amount.
CJ heads varies (76.9cc - 79.9cc)

End of the day, throw CJ/ford performance cam (as it was referd to in 1970) and larger carb on M and you be making good power.
Or throw closed heads on Q or R and you will have the same.

And if totaly rebuilding go for boss spec compression ro make music. This video shows differences between M code and Boss cam (Boss cam is fairly close to CJ)
 
Last edited:
The torque ratings are also net, for 1972 and up, gross in 1971.
The M code makes 25 more ft-lbs of torque and 5 more horsepower than the '71 CJ (Q code), both at 400 less revolutions, which means it is likely more responsive on the street. Here is a chart I compiled of the performance of 71-73 Mustang engines
71-73 Mustang Engine Performance-V4.jpg
 
t.kohlmeyer said:
I have an article from an old Car Craft Magazine by Jack Roush regarding the 351C engines and the differences between them. Jack talks about how he preferred the Open Chamber heads as the valves were less shrouded and hence could rev more freely. This is likely why the factory engineers went with the 4-bolt mains. Believe me, they wouldn't have put 4-bolts in unless there was a need, the bean counters would never have never allowed it. Machining costs, the bolts, the labor to install all add up quickly. BTW, the outboard bolts were 3/8-16 grade 8.

Regarding the cam, just for clarification, if you advance the Q code cam 4° it is exactly the same bump stick as the 71's. It was a cheap way to help meet the ever tightening emissions standards. The simply moved the dowel pin. A good set of headers, a 750cfm Holley, and you get a huge improvement. I have a '72 Q code and a '72 Mach 1 with a '70 M code in it, both withe same headers and 750 carb (I have one of the old Ford Buddy Barr D1ZX-D intakes on the Q motor, got it at a swap meet in Indy about 1983 for $100, there was one on eBay for $1750 last year! It's identical to the cast iron square bore manifold except for larger carb bore holes.) The Q does seem to love high RPMs more than the M car. It springs to life at about 5000 RPMs, and God help you if you miss a gear. I typically shift at about 6700 RPM with the Q, and it seems to want more revs. The M car has more at low RPM, but but I shift it at about 6200 RPM as it starts to feel maxed out.

I love both, but for different reasons. Just my 2 cents worth after playing with these things for about 49 years now.
Click to expand...
Correct on the fact many racers preferred the open chamber heads. Some actually considered them a "Semi-hemi" or near hemi design.
 
t.kohlmeyer said:
I have an article from an old Car Craft Magazine by Jack Roush regarding the 351C engines and the differences between them. Jack talks about how he preferred the Open Chamber heads as the valves were less shrouded and hence could rev more freely. This is likely why the factory engineers went with the 4-bolt mains. Believe me, they wouldn't have put 4-bolts in unless there was a need, the bean counters would never have never allowed it. Machining costs, the bolts, the labor to install all add up quickly. BTW, the outboard bolts were 3/8-16 grade 8.

Regarding the cam, just for clarification, if you advance the Q code cam 4° it is exactly the same bump stick as the 71's. It was a cheap way to help meet the ever tightening emissions standards. The simply moved the dowel pin. A good set of headers, a 750cfm Holley, and you get a huge improvement. I have a '72 Q code and a '72 Mach 1 with a '70 M code in it, both withe same headers and 750 carb (I have one of the old Ford Buddy Barr D1ZX-D intakes on the Q motor, got it at a swap meet in Indy about 1983 for $100, there was one on eBay for $1750 last year! It's identical to the cast iron square bore manifold except for larger carb bore holes.) The Q does seem to love high RPMs more than the M car. It springs to life at about 5000 RPMs, and God help you if you miss a gear. I typically shift at about 6700 RPM with the Q, and it seems to want more revs. The M car has more at low RPM, but but I shift it at about 6200 RPM as it starts to feel maxed out.

I love both, but for different reasons. Just my 2 cents worth after playing with these things for about 49 years now.
Click to expand...
So there is some contradicting info even in this thread on the cams being the same or not. Regardless, since the original question is in reference to M and Q code engines there is an implied idea that we are talking about stock, factory motors. I think that once you start swapping parts there is absolutely no relevance of the factory code. Nevermind apples to apples, it's not even apples to oranges, it's a fruit salad!
 
YellowHorse said:
71 M code being overshadowed by other models and i cant seem to find factory power rating for, for torque.

70 M is 380 ft.lb and since 71 ratings been degraded abit for HP (posibly due to insurance) i would guess around 360 ft. lb. for torque.

Curious to see how much more torque it has over Q. Should have quite abit more unless underated for insurance.
Click to expand...
As I recall, the 70 closed chamber heads had a slightly smaller chamber than the 71 closed chamber heads. Just a couple cc's and a little extra compression ratio, but maybe enough to account for 15 hp/10 ft-lbs, along with any carb changes.

I do suspect that many people get excited about the Q code because it's a Cobra Jet (which sounds cool) and the M is just a 4V (not as cool sounding).
 
YellowHorse said:
I see that all years mustangs had inconsistent heads volume and the true measurement will vary by car. They are all lower in compression then advertised by roughly same amount.
CJ heads varies (76.9cc - 79.9cc)

End of the day, throw CJ/ford performance cam (as it was referd to in 1970) and larger carb on M and you be making good power.
Or throw closed heads on Q or R and you will have the same.

And if totaly rebuilding go for boss spec compression ro make music. This video shows differences between M code and Boss cam (Boss cam is fairly close to CJ)
Click to expand...

I had watched a few of his videos before. I was a little disappointed that he used the 11.0-1 pistons for both runs. At that point, with the 750 Holley and long tube headers, it's really no longer an M-code.
 
detritusmaximus said:
I understand the gross vs. net differences. I won't quibble about 20hp, which its already down 15hp from '70. But that doesn't account for a 70ftlb drop in tq. Dished pistons and open chamber heads? The only thing I can see that is 'different' (not 'less') is the cam.
Detuned is still detuned.
So it begs the question, in identical cars, is which has better performance, 71 M or 71/72 Q?
More importantly, which is more enjoyable to drive? More power does not always translate to more fun.
Click to expand...

71/72 Q-code used flat tops, same as the 70-71M and 70-72 H code engines. Dished pistons came in '73.

The only apples to apple comparison I'm aware of is by Chevrolet, who published gross and SAE Net figures in some of their 1971 brochures. The 454 in the Corvette showed a difference of 100hp, the Camaro engines differed by 50~60 hp and similar amounts of torque.

In comparison, the 351CJ showed a measly 14hp difference between 71 & 72 - which tells me it was under rated to begin with. There are also HP variations depending upon the chassis. The intermediates had a lower HP rating at 248/299.

detritusmaximus said:
I had watched a few of his videos before. I was a little disappointed that he used the 11.0-1 pistons for both runs. At that point, with the 750 Holley and long tube headers, it's really no longer an M-code.
Click to expand...

He also stated he used an M-code camshaft from Elgin - which they do not and never have made. Dollars to donuts it's a CJ cam in that engine.


1707513916553.png


1707513857433.png
 
Last edited:

Similar threads

Don C
I'll Be Back on the Forum
Replies
8
Views
1K
Bill Perkins
B
7
  • Article
How to Rebuild a Ford 9 inch.
Replies
0
Views
2K
72HCODE
7
Boss1Ray
Some excerpts from a book about our cars
Replies
3
Views
2K
Boss1Ray
Boss1Ray
O
Question about 1971 engine codes
2
Replies
23
Views
7K
OPN PONY
O
Boss1Ray
1972 Mustang brochure/specs Venezuela
Replies
6
Views
3K
Boss1Ray
Boss1Ray

Latest posts

Back
Top