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Hi everyone, my 79 f150 has had the engine replaced with either a 400 or a 351m. Now I know there is no way of telling which is which other than checking the stroke but my casting number is 2d10 on the back of the block near the oil press sender. Does that mean it was built in 1972? and if that is the case was there any 351m's in 1972? If not that would make it a 400 right? Any info would be appreciated.
Also is there any reason not to rebuild this engine assuming it hasn't been rebuilt already?
If it runs good and carries decent oil pressure there's no need to rebuild it. IMO. Why fix it if it's not broke? lol. I'm not sure whether its a 400 or 351m by the #. But, no 351m were made in '72. 351m started in '77 for trucks. Altought 400's could be had in '72 in bigger passenger cars.
I run 15-50 in several different engines
Don’t know what your using now but put 15-40 in and try it, if oil pressure is still low change the 20-50
Neither one will hurt the engine
Hi everyone, my 79 f150 has had the engine replaced with either a 400 or a 351m. Now I know there is no way of telling which is which other than checking the stroke but my casting number is 2d10 on the back of the block near the oil press sender. Does that mean it was built in 1972? and if that is the case was there any 351m's in 1972? If not that would make it a 400 right? Any info would be appreciated.
The 2 is the last number of the year, and iirc, 351M/400 were used through 1982, so based on that one date code alone, it could be either 72 or 82. It should be easy enough to tell as there were a lot of changes made between the years and there will be other parts and other casting codes to narrow down the correct decade. Look around for other casting markers and let us know what you find.
I know that a casting date on the block behind the intake on my March '77 built F-150 is "7A7" and it means the 351M's engine block was cast 1977, January 7th.
I know my 400 on the stand is from a '79 F-350, it's "8M20" for 1978, December 20th. I believe it was the "I" they didn't use for month, so M is the 12th month.
Following that, I'd say "2D10" would be 1972, April 10th ... but the "2" might mean 1982 since you think it's been swapped in?
Clean the block real good and look on the passenger side, front face of block, there beside the timing cavity / water pump for stamped in numbers / letters and that's where mine are stamped with the build date, not the casting date. My 400 was coded for January 4th, 1979 as an example, like 9A4 as I recall. If you ever have the intake off, look at the lifter valley walls. Before March of 1977 they were smooth. After wards they were corrugated.
I know it says "crack prone", but most don't crack. Overheating is the cause.
you can pull pan and look at crank. post pics here. I am certain someone will identify if you are wanting to get parts or a plan, 351m and 400 have different counterweights so I would be able to identify by picture. I am sure others could as well. pan would have to come off though.
