crank question
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crank question
After reading some other posts in this forum I have learned that the whole knocking at higher RPM and only under a load but not when at an idle is a continues problem for the 400. I have had the same problem in my 77 f-250 w/ a 400.
I am going to just do the crank and bearings, top half is still ok. Just rebuilt everything 50,000 ago.
I was wandering if i need to go with the crank from the 400 or if I can go with a crank from a different motor or even a different year 400 with out having to change a bunch of things. If I can do this, what are the bennifits if any?
One more question is, does anybody know the cure for this ongoing problem?
I am going to just do the crank and bearings, top half is still ok. Just rebuilt everything 50,000 ago.
I was wandering if i need to go with the crank from the 400 or if I can go with a crank from a different motor or even a different year 400 with out having to change a bunch of things. If I can do this, what are the bennifits if any?
One more question is, does anybody know the cure for this ongoing problem?
Hotshot
Joined: May 2003
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From: south louisiana
A 400M is a 400M, there's no difference in the early vs the last 400's built when it comes to the crank and rods. To convert a 351M to a 400, you need the 400 crank and pistons. Rods are the same between the two. But if you're experiencing a knock with your 351M, then I suggest changing the rods too. Get another set and have them resized with new bolts installed. Or at least have your rods done the same way, that way, if you do have a rod problem, the machinist should spot it when he works them over.
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I have the 400. The problem is that either the crank was machined wrong from the beginning of the rebuild or when we replaced the head gasget when it over heated we got something down inside the engine that caused the oil pump to fail due to a clog on the screen, which in turn deprived the bearings of oil causing them to get all out of wack. We are going to redo just the crank and bearings everything else is still okay.
So what you (baddad457) are saying that there is no difference in an early 400 compared to a late 400 crank, they are all the same thing?
Is the 351 cleveland interchangable on that with out having to do anything but the bearings and crank? If so is there a difference in the performance/ stroke and so forth???
So what you (baddad457) are saying that there is no difference in an early 400 compared to a late 400 crank, they are all the same thing?
Is the 351 cleveland interchangable on that with out having to do anything but the bearings and crank? If so is there a difference in the performance/ stroke and so forth???
Hotshot
Joined: May 2003
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From: south louisiana
The Cleveland had smaller main bearings so the cranks are not interchangeable. The 351W, M and 400 all shared the same main bearing diameter. Only difference there was either of the two (351W or M, I don't recall which, offhand ) had a shoulder just forward of the #1 Main journal to space the timing set differently.
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From: chicago burbs
resizing the rods will do little good if the crank rod journals are worn wide and need to be welded up. check the rod side clearance, if it's not within spec new bearings and resized rods will not repair the situation. sometimes a new(wider, not worn) set of rods will bring the side clearance back into spec but the rods don't usually wear thin, it's the crank. 72 manual lists connecting rod side clearance @ .010"-.020" and a wear limit of .023" max.
the Cleveland and M/400(335's) have an integral shoulder on the crank, if a Windsor type crank is used in a C or M/400 a spacer or special timing set is required to locate the crank sprocket. the 72 factory manual lists the thrust journal width of the302, W, M and 400 as identical @ 1.137"-1.139", and the C thrust journal is narrower @ 1.124"-1.126".
the W and M/400 share the same main bearings up to 76, then a different number is listed and they share the new set from 77 on. i'm not sure what the difference is, 1/2 grooved for the later style?
the Cleveland and M/400(335's) have an integral shoulder on the crank, if a Windsor type crank is used in a C or M/400 a spacer or special timing set is required to locate the crank sprocket. the 72 factory manual lists the thrust journal width of the302, W, M and 400 as identical @ 1.137"-1.139", and the C thrust journal is narrower @ 1.124"-1.126".
the W and M/400 share the same main bearings up to 76, then a different number is listed and they share the new set from 77 on. i'm not sure what the difference is, 1/2 grooved for the later style?
Last edited by grclark351; Jun 18, 2006 at 11:17 PM.
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In '77 the Truck blocks were strengthened with a reinforced main web area to compensate for the forward forces generated from the T/O bearing pushing against the clutch. Same thing for '78 & up Passenger blocks. This may have something to do with the different part #.
