351 to 400
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351 to 400
I'm getting ready to pull my blown up 351 out of my 78 F-150 4x4. I'm on a really tight budget so no 460 right yet. I figure I might as well put in a 400. Is pretty much everything the same between the 351 and 400 like motor mounts, wiring, etc. I want to do this quickly and cheaply without a bunch of surprises. How much more power does a 400 have over a 351. They're both going to be left stock except for headers and maybe a carb and intake. Thanks.
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351 to 400
the 400 & 351M share the same block. the 400 will be a direct bolt in and will integrate with the electronics. the distributors will interchange if you happen to find a 400 with a points distributor.
if your truck is an automatic the 400 will be a direct bolt-in. however if your truck is a 4 gear the 351 utilises an 11" clutch where as the 400 utilises a 12". The flywheels will interchange and it is possible to run the 11" clutch with the 400. I have considered this option with my own truck. Personally I would either look for a 400 flywheel or if I am not mistaken you can drill and tap a 351 flywheel to accomodate a 12" clutch assembly (someone correct me if I am wrong).
Fordy
1978 F-250/351m/4spd.
if your truck is an automatic the 400 will be a direct bolt-in. however if your truck is a 4 gear the 351 utilises an 11" clutch where as the 400 utilises a 12". The flywheels will interchange and it is possible to run the 11" clutch with the 400. I have considered this option with my own truck. Personally I would either look for a 400 flywheel or if I am not mistaken you can drill and tap a 351 flywheel to accomodate a 12" clutch assembly (someone correct me if I am wrong).
Fordy
1978 F-250/351m/4spd.
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351 to 400
[font size="1" color="#FF0000"]LAST EDITED ON 23-Aug-01 AT 09:50 AM (EST)[/font][p]First - one could assume that you have a 351M, and not a 351C or a 351W. If you have a 351C (out of an older vehicle), or a 351W then you will have more work and will at least need to change bell housings or the transmission.
If you do indeed have the 351M, yes a 400 should bolt right in place. A 460 would not cost you that much more - as the transmission will work with some mods as noted above if you have stick. Motor mounts are different but are cheap, and you will have to scrounge some accessory brackets and stiffen the springs. You may have to change radiators too - but overall, not much more money - but more work. Since there are more 460's than either 351M's or 400's, you should be able to get a decent one cheaper! You may even luck out and get a 460 with motor mounts and accessory brackets!
As far as difference in power between the 351M and 400 - horspower is close, but the 400 should have perhaps 10% more torque. A 460 would have a boatload more torque...
Tom
If you do indeed have the 351M, yes a 400 should bolt right in place. A 460 would not cost you that much more - as the transmission will work with some mods as noted above if you have stick. Motor mounts are different but are cheap, and you will have to scrounge some accessory brackets and stiffen the springs. You may have to change radiators too - but overall, not much more money - but more work. Since there are more 460's than either 351M's or 400's, you should be able to get a decent one cheaper! You may even luck out and get a 460 with motor mounts and accessory brackets!
As far as difference in power between the 351M and 400 - horspower is close, but the 400 should have perhaps 10% more torque. A 460 would have a boatload more torque...
Tom
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