I'm replacing the oil pump in my '71 400 and I am also replacing the rear main seal as it looks like it has been slightly leaking. My book says to loosen the caps by 1/32" in order to pull the top portion of the rear seal. My question is, is there a torque sequence for retorquing the caps back in, or just go ahead and torque them to specs, (95-105 ft-lbs)? I assume there isn't, as there is no info in three of my books . Thanks
AFAIK the pin is to keep the old rope seal from turning. I pulled the pin and used a regular two piece seal on my 390 with no problems. Unfortunately I do not remember if I filled it with any sealer or if it was drilled all the way thru. I may have just ground it down and put it back in to fill the hole or even left it out. The OEM manuals do not mention filling the pin hole with anything. Apply sealer to the rear main cap as specified in the locations shown in the manuals.
The tightening sequence is kind of the reverse of what was mentioned above...
351M/400 Main bearing cap bolts are torqued to 35-45 lb-ft.
-Install the rear main cap with the rear surface flush or slightly ahead of the rear of the block.
-Install the other caps except the thrust cap #3 and tighten to specifications.
-Install the thrust bearing cap with bolts finger tight.
-Pry the crank forward against the upper half surface of the thrust bearing.
-Hold the crank forward and pry the thrust bearing cap to the rear.
-Retain the forward pressure on the crank and tighten the thrust cap bolts to spec.
-Force the crank to the rear and check crankshaft end play which should be 0.004-0.008".
I got the rear main cap ready and a few other things. I put silicon in the pin hole and punched the pin back in until it was flush on the inside. It's a real tight fit, so I shouldn't have any problems. When I pulled out the old seal I found the source of my leak. My previous gasket tore, (about an inch) across the pin as the new one was installed. So, I was doomed from the beginning and I didn't even know it. I was using an old Chilton's manual from the mid 70's when I assembled this engine years ago and it made no mention of removing the pin, as I believe people were still using the rope style back then. Either way, my new books DO mention removing the pin for the split seal, which is what I have. This is interesting, I'm glad I found the source though. So, first thing in the morning the cap gets put back on. I got the standard oil pump and everything ready to go. I move slow...."measure twice, cut once", you get the idea
One question though, are you sure about the torque specs you gave me? I think those are for the rods, not the crank bearing caps?
That seemed low to me but it is right out of the 1977 OEM Ford truck manual I have. I rechecked and that is what it says. I will check some other sources.
A Chilton's lists 35-45 for a 1977 but 95-105 on a 78-80.
It also lists 35-45 for a 77-86 351W.
A 73-9 Haynes manual lists TWO main bearing cap bolt specs:
3/8"-16 as 35-45 lb-ft
1/2"-13 as 95-105 lb-ft
It does not differentiate between years.
My old 1974 Motors manual that covers cars but not trucks lists the following for the 400:
3/8"-16 as 35-45 lb-ft
1/2"-13 as 95-105 lb-ft
My loose-leaf 78 OEM truck manual lists 95-105 for the 400.
A website that does not differentiate for years calls out 95-105 for the 351C/M but does not have a listing for the 400.
Did the machinist machine (line-bore or line-hone) the crank bore? If he did you will need to use the torque values he used for the machining process. Check with them and see what they used. I would use 95-105 for the 1/2" bolts that should be there if they did not machine the crank bore. Personally I have never seen 3/8" main cap bolts on these engines but I have only torn down 4 of them.
Just for reference the 390 and 460 is listed in the 77 manual at 95-105 lb-ft
Torque values listed are for clean and lightly lubricated threads.
Torque is a terribly inaccurate method of setting fastener preload...
Machining the crank bore changes the crank to cam centerline distance and throws off the transmission alignment. It can also change the deck height. Normally they try to barely touch the top of the crank bore but that produces an out-of-round crank bore. Changing the cam centerline distance requires a custom timing chain set. So many chances for a FUBAR...
BTW- "measure twice, cut once" is the best policy.
A 1974 Chiltons which covers American Cars from '67-'74. In the Ford section, it has it at 95-105 lb-ft for the mains. Two other books I have are, Tom Monroe's book, or should I say the 335/385 Ford owners Bible and another Chilton's covering '76-'86 Ford trucks. Anyway, all three specify torquing the mains at 95-105 lb-ft. I went ahead and torqued the mains at 100 lb-ft. I'm not sure what to say about the numbers you have in the Ford book for the '77. I'm thinking it's either a mistake or that year used 3/8" bolts for the mains. Mine are the 1/2"-13, and the crank bore was not machined, so I went with 100 lb-ft and got them torqued in there today. Again, thanks for the info, I appreciate it.
No problem! I just pulled out all my books and found the strange numbers in more than one. The 77 OEM manual did not mention anything about bolt sizes but others did. 4 different brands of manuals had the strange numbers for different years, check out the post above. The 74 Motor's manual came out in 74-75 way before an error in the 77 OEM manual... Someone here may have an explanation tho.
the 400 engine that the factory 4bbl intake came from was a 4 bolt, according to the guy that had the intake. and there are a few other "old codger reports" of the 400 4 bolt block, that'd really be cool for one of those to surface.
Last edited by grclark351; 05-23-2006 at 09:42 PM.