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post #1 of 8 (permalink) Old 04-04-07, 01:51 PM Thread Starter
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confused 351m/ 400 in 71' mustang

hi
2 months ago i purchased 71' mustang as a project car, oryginaly car came with 351c 2bbl, last owner changed it to 400 and fmx trans. (i think its not c4 and its not c6) engine is not installed in the car yet its just sitting in the engine bay . i got the engine mounts for 351c.
did someone swap 400 into 71 mustang do i have to change something or its just bolt on, i got also long tube headers for 351m/400 not sure yet if they will fit without modification. i have also 351m i was going to swap into my 68 mustang but decided to leave it # matching car, i can always put 351m into '71 if 400 wont fit
any advice?

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post #2 of 8 (permalink) Old 04-04-07, 02:40 PM
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Re: 351m/ 400 in 71' mustang

last sentence 351M & 400 are the same engine. The '71s had the 429 in them,so a 351M/400 will fit.
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post #3 of 8 (permalink) Old 04-07-07, 04:05 PM
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Re: 351m/ 400 in 71' mustang

Won't be a problem, my mates got a 400 in his 72 'Vert

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post #4 of 8 (permalink) Old 04-14-07, 05:15 PM
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Re: 351m/ 400 in 71' mustang

Quote:
Originally Posted by George1861
last sentence 351M & 400 are the same engine. The '71s had the 429 in them,so a 351M/400 will fit.
Meaning they are built on the same block but have different internal parts. The transmission is an FMX if it has a cast iron body. They are very good transmissions.

I love it when people do things right
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post #5 of 8 (permalink) Old 04-14-07, 05:28 PM
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Re: 351m/ 400 in 71' mustang

Quote:
Originally Posted by Sand1
Meaning they are built on the same block but have different internal parts. The transmission is an FMX if it has a cast iron body. They are very good transmissions.
The crank & rods are the only difference between the M & the 400. Exept for some built in '73, the M/400 have the 429/460 bell pattern.
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post #6 of 8 (permalink) Old 04-14-07, 06:15 PM
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Re: 351m/ 400 in 71' mustang

Just checking, you are probably aware of the number of folks out there (even Ford folks) who dont believe there is such a thing as a 400 cid M block. I had the 400 out of my truck sitting on the floor. I was pointing out the decal that said 400 cid and a guy was still arguing that it was a 351. He kept pointing to the engine class, 351M/400. I finally had to kill him and bury him under the shop floor lol JK.

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post #7 of 8 (permalink) Old 04-21-07, 08:35 AM
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Re: 351m/ 400 in 71' mustang

Quote:
Originally Posted by George1861
The crank & rods are the only difference between the M & the 400. Except for some built in '73, the M/400 have the 429/460 bell pattern.

The rods are the same between the 351m and the 400 ,the Pistons and crank are the difference.
Also the motor was built as the 400 but the stroke ,was changed to the 351,hence 351 Modified, from a 400, because the demand for the 351 cube engine was higher because of the dropped 351 cleveland motor.the Windsor plant couldn't keep up .The 351m crank is a 351windsor crank with different snout.
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post #8 of 8 (permalink) Old 05-03-07, 06:12 PM Thread Starter
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Re: 351m/ 400 in 71' mustang

next problem
first had some problems with engine mounts but welder came in handy...
i ordered full-length hedman headers(#HED-88220 ) from summit racing, passenger side fits fine but the problem is with driver side cant get clearance because of steering box ( car is with power steering) (headers should fit with power steering acording to summit racing) maybe diferent steering box that i can use or different headers, has anyone had this problem or know how to work around it? ( i can take pic if thats gonna help) really dont want to go with stock headers.

any advice
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