Author Topic: 351C vs 351M ID  (Read 3478 times)

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Offline ablue69

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351C vs 351M ID
« on: September 02, 2012, 01:08:19 pm »
Is there a way to 100% ID a 351M?  When it's still in a car?  When it's out and on an engine stand? 

Bought what I thought was a 351C that someone had put into a '66 Ford pickup.  Junkyard markings said '73 Mustang and I noticed D2AE-CA casting # on 2V iron intake, D3 # on the Ford carb, etc.  All had me convinced it was an early 70's Cleveland.  What has me confused is the assembly date code I found stamped into the blocks front face when I removed the sheet metal cover to replace the timing chain.  It was stamped 9J17T, at least I think it's a 9 the curl is missing from the bottom.  Since it couldn't have been assembled in 1969 I'm thinking 1979.  But if that's the case wouldn't it have to be a 351M?

Dazed and confused as per usual.  :-\                        ;D
'64 1/2 Convertible
'64 1/2 hardtop
'67 Mustang Junior!
'69 BOSS 302  9F02G196425
'73 Bronco
'89 Saleen (bought new, never modified!)
'03 Jaguar XJ8
'03 Volvo Cross Country
'03 Sprinter van
'08 F 150
'08 Sprinter van
Norm

Offline ablue69

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Re: 351C vs 351M ID
« Reply #1 on: September 02, 2012, 01:13:32 pm »
May have figured out a sure fire way to tell them apart.  I believe I read the 351M uses the 385 series (429/460) bell-housing pattern.  So a tape measure across the top two bell-housing bolts on mine are less than 6" apart and then I measured across a C-6 from a 429 and it was close to 8" across.  So am I right in saying for sure I have a Cleveland?
'64 1/2 Convertible
'64 1/2 hardtop
'67 Mustang Junior!
'69 BOSS 302  9F02G196425
'73 Bronco
'89 Saleen (bought new, never modified!)
'03 Jaguar XJ8
'03 Volvo Cross Country
'03 Sprinter van
'08 F 150
'08 Sprinter van
Norm

Offline BLAZN BOSS

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Re: 351C vs 351M ID
« Reply #2 on: September 02, 2012, 02:43:11 pm »
you're correct, M has the bigblock patern for the bell housing.  I also believe that the cylinder heads for M's have thermactor ports in each end of the cylinder heads on the intakmaifold sealing surface.  The M block has a raises area for the thermostat and most of all a C has 2 bolts for the motor mount and the M has 3.   

Offline hotrodford

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Re: 351C vs 351M ID
« Reply #3 on: September 02, 2012, 03:47:32 pm »
The 351M is a destroked 400.  It is a taller and wider block.  The intake ona 351M is a 400 intake, therefore wider than a cleveland intake.

Offline Nitro

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Re: 351C vs 351M ID
« Reply #4 on: September 02, 2012, 04:08:37 pm »
The M engines that Ford put out were nothing but junk !!!
I think all of them were under 200 HP and had no Hi-performance
potential..
Truck engines..
How long did they make them ? Two years or so.
Nitro.
NITROâ„¢

Offline BLAZN BOSS

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Re: 351C vs 351M ID
« Reply #5 on: September 02, 2012, 04:20:15 pm »
The M engines that Ford put out were nothing but junk !!!
I think all of them were under 200 HP and had no Hi-performance
potential..
Truck engines..
How long did they make them ? Two years or so.
Nitro.
I Bought a 79 F-150 4wd pick new in 79 when I worked at the dealership............Pulled the enginge after the warranty went out............flat top pistons like come in a C........shaved the heads .040, .579 lift cam lifters and springs, Holley single pleneum strip intake, 750 double pumper headers.   That truck would boil a set of 38 and 1/2 inch tall tires with only the stock 3.50 gear.  MANY cars fell prey to that truck.......including many mustangs small and big blocks.   Dont count out a motor just cause they were not HP new.

Offline sportyworty

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Re: 351C vs 351M ID
« Reply #6 on: September 02, 2012, 05:08:15 pm »
The 335 series 351M was produced from 75-79 and has a lot of potential as noted above. They were produced during the big gas/emissions crunch so the heads and low compression were not a high HP engine. They did however make torque on the low end so were used in trucks/broncos and heavy passenger cars/wagons of the day.
"To steal ideas from one person is plagiarism; to steal from many is research."

Offline okcmustangresto

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Re: 351C vs 351M ID
« Reply #7 on: September 02, 2012, 05:18:51 pm »
  In a nutshell, 351M and 400 use the same block. The difference is in the 1/2" shorter stroke crank.
67 GT500 428 2-4's 4 spd. inboards, dark green
71 Mach I 429 SCJ 4 spd, 4.11 fully loaded power windows etc.
71 Mach I 351C 4V auto power windows, etc. loaded
72 Mach I Q code 351C 4V 4spd.
65 coupe 289 4 spd. 4.11's street car
71 Maverick drag car 351C, C6 5500 convertor, 5.14 gears
3 70 Boss 302's in varying states of repair, none in show car condition
All but one of the above have been sold. Getting older changes priorities, at least for me.

Offline BLAZN BOSS

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Re: 351C vs 351M ID
« Reply #8 on: September 02, 2012, 06:13:00 pm »
Only problem I had with it was push rods..........they are long and with canted valves and high spring pressures the didnt like it.  Nobody made any hp ones so I kept a few in the glove box......shifted it at 7800.......push rods would kinda bend..........wasnt a valve to piston problem.....just weak pushrods.

Offline Fairlane514

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Re: 351C vs 351M ID
« Reply #9 on: September 02, 2012, 08:30:17 pm »
The M engines that Ford put out were nothing but junk !!!
I think all of them were under 200 HP and had no Hi-performance
potential..
Truck engines..
How long did they make them ? Two years or so.
Nitro.

Hey Nitro,

What is your experience with these motors, sounds like you really hate them. 
63 Fairlane big block
76 Bronco 347 3 speed
70 Boss 302
65 GTO tripower/4 speed

Offline randy

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Re: 351C vs 351M ID
« Reply #10 on: September 02, 2012, 11:53:02 pm »
Is there a way to 100% ID a 351M?  When it's still in a car?  When it's out and on an engine stand? 

Bought what I thought was a 351C that someone had put into a '66 Ford pickup.  Junkyard markings said '73 Mustang and I noticed D2AE-CA casting # on 2V iron intake, D3 # on the Ford carb, etc.  All had me convinced it was an early 70's Cleveland.  What has me confused is the assembly date code I found stamped into the blocks front face when I removed the sheet metal cover to replace the timing chain.  It was stamped 9J17T, at least I think it's a 9 the curl is missing from the bottom.  Since it couldn't have been assembled in 1969 I'm thinking 1979.  But if that's the case wouldn't it have to be a 351M?

Dazed and confused as per usual.  :-\                        ;D

actualllly, the 9J breaks out to September, 1969 which is perfect for the new for 1970 351 Cleveland.  I am pretty sure (Marti can confirm) that they were punching out 351C's as early as July, 1969 for the upcoming 1970 model year which were typically introduced in the September/October timeframe.  You didn't mention (or I missed it) the actual casting part number on the block itself which would also lend credence to a September, 69 casting date.  I would think the block would probably be DOAE or some such animal.  I am also a huge Cleveland fan and not so much with the 351M (was told the M stood for Midland or Modified, not sure) as there was pretty bad core shift in these blocks and they also had problems with cracking in the lifter galley area.  I am pretty sure that when the Cleveland stopped production sometime in 73 or 74, all the dies, molds, machining, etc were sent to Australia.....

randy



1970 W code Boss 302
2009 GT500   SOLD
2002 WS6 Trans Am Convertible
1999 Camaro SS 6 speed
1997 LT1 Firebird Formula 6 speed
1996 Firebird V6 5 speed     SOLD
1970 Boss clone convert
1969 Mustang convert
1970 H-code Mach 1
1969 M-code Mach 1    SOLD
1970 F-code fastback
1969 H-code coupe      SOLD
1965 C-code fastback (X-tremestang)

Offline Daryl

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Re: 351C vs 351M ID
« Reply #11 on: September 03, 2012, 07:22:31 am »
The easiest way for me to tell the difference between the 351C and the 351M/400 engines was the 351M/400 (I think the M = modified) has approximately a 1" rib cast onto the block along side the distributor from the front of the block back to the intake manifold.

Here is a link to a photo with a good comparison of the 351C and 351M/400 that clearly shows the rib and other differences between the two.

http://www.fordmuscleforums.com/attachments/all-ford-techboard/1527d1194606890-ways-tell-351c-351m-400blk.jpg

Here is another website that has some useful info on how to ID Ford engines.

http://www.fordification.com/tech/engineID-V8.htm

Offline ablue69

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Re: 351C vs 351M ID
« Reply #12 on: September 03, 2012, 07:59:16 am »
Thanks guys for all the info!

Randy - yeah the block casting number is DOAE-J and has a cast in date code of
9 H 19 which I believe is August 19th of 1969 !

Daryl - Great information! 

Soooo... Bottom line is two SURE FIRE ways to tell the difference are -

1  Ridge on top of block on drivers side of distributor that runs to front edge
2  Width of two top bell housing bolts is approx. 6" for a 351C and 8" for a 351M

                                    Quote from one of Daryls links -
       Top 2 bellhousing bolt holes are 5 inches apart on a 302, 7 3/4 inches on 400.

       
       Says "302" but same for Cleveland and says "400" but same for 351M as per
        okcmustangresto

This site is the best!   Norm
'64 1/2 Convertible
'64 1/2 hardtop
'67 Mustang Junior!
'69 BOSS 302  9F02G196425
'73 Bronco
'89 Saleen (bought new, never modified!)
'03 Jaguar XJ8
'03 Volvo Cross Country
'03 Sprinter van
'08 F 150
'08 Sprinter van
Norm

Offline okcmustangresto

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Re: 351C vs 351M ID
« Reply #13 on: September 03, 2012, 08:21:10 am »
As Blaznboss stated, the M will respond to the same mods as a C. And the 400 will also respond to these mods. Saw a 400 in a 69 that was running 12.00's. Not bad for a "truck" engine.
67 GT500 428 2-4's 4 spd. inboards, dark green
71 Mach I 429 SCJ 4 spd, 4.11 fully loaded power windows etc.
71 Mach I 351C 4V auto power windows, etc. loaded
72 Mach I Q code 351C 4V 4spd.
65 coupe 289 4 spd. 4.11's street car
71 Maverick drag car 351C, C6 5500 convertor, 5.14 gears
3 70 Boss 302's in varying states of repair, none in show car condition
All but one of the above have been sold. Getting older changes priorities, at least for me.

Offline JoshBolger

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Re: 351C vs 351M ID
« Reply #14 on: September 03, 2012, 12:47:48 pm »
May have figured out a sure fire way to tell them apart.  I believe I read the 351M uses the 385 series (429/460) bell-housing pattern.  So a tape measure across the top two bell-housing bolts on mine are less than 6" apart and then I measured across a C-6 from a 429 and it was close to 8" across.  So am I right in saying for sure I have a Cleveland?

Unless you find a extremely rare 1970-71 400 that had the standard small block bell housing bolt pattern...
Josh Bolger
(*1T113044)