I picked up a 400 engine with low miles on it. When I pull the valve covers the rockers have some slop on the rockers with the valve lifters on the bottom of the cam lobe. This motor has never been apart and I'm wondering if that's the norm without the lifters pupmed up. Now I pulled a 351M out of my truck, and the rockers are so tight there is no movement at all on the rockers that are at the bottom of the lift. These heads look rebuilt. If the heads were milled, aren't the pushrods supposed to be shortened? I pulled this motor cause the bottom end is weak.
If the 400 sat for a long time the lifters bleed down....I started my 67 Caddy 429 after it had been sitting for 25 years without being run and Holy Cow!!! It sounded like a washing machine full of nuts and bolts for about 30 seconds before quieting down !!!...Then it was fine...Give it a go...It might do the same as the Caddy and be OK.
If the heads were milled, it would probably be only like a .010" clean up and the lifters have enough plunge to make up for that. If they were cut a bunch, like say .050" or more, then yes shorter pushrods would be advised since these motors had non adjustable rockers (unless it was a solid lifter cam version)
Cool, I just wanted to make sure on that. When i got the pan off the 351, the oil pickup was flopping loose. It defintely was worked on, I see the marks from a pipe wrench on the pipe itself. So whoever changed the oil pump goofed that up and I think the motor was starving for oil. So I'm gonna assume the mains and rods are junk. No wonder it rattled when you increased the rpms I asked the question about the pushrods cause I'm thinking of putting the heads from the 351 onto the 400, since they are rebuilt already. I just didn't want to put them on and when I get it running, find out the valves aren't closing all the way cause the pushrods are too long.
Hey all, I'm rebuilding the 351M in my cougar and I don't think it's ever been apart since 1970. I'm learning as I go. Am I better off just putting all new pushrods in while i'm in it? And second, every parts catalog I look in has parts for 351windsor or 351cleveland. Do the parts of either one work in the M? Thanks for any help
The difference between a 351M, and a 400 is the 351M is a 400 block with a 351W crankshaft (.500" shorter stroke) along with different pistons (a .500" taller compression height) than a 400 piston. Ford had a shortage of 400 crankshafts in the mid 1970's thus the 351M was born.
If it's the original '70 engine it's a 351 W or C, not an M. Actually they killed the C and then couldn't produce 351Ws fast enough to keep up with production schedules.
The Jalopy Journal
