1979 Ford 400M engine

My grandson rebuilt his 1979 F150 4x4 400M engine. He put in high compression heads, pistons, new lifters, cam, etc. All new bearings and a high volume oil pump. He purchased a rebuild crankshaft kit from Rock Auto. The oil pressure at startup is about 70psi (manual guage). As the temperature gets to 200 degrees, the oil pressure drops to about 30psi at 2000 rpm. At idle and operating temperature, the pressure is about 12psi. He was told by the crank manufacturer to put 10-40 oil in it. The only change that did was idle is now about 15psi. He originally put in a standard oil pump and had the same results. This oil pressure seems extremely low for a new rebuilt engine. He has about 600 miles on the engine. I don't have any ideas for him to look at. Is this typical for that vintage engine? Any input is appreciated.

What weight of oil was he using initially?

He was using 10-30. Everything is new except for the block. He had the block cleaned by a machine shop.

webengr wrote:My grandson rebuilt his 1979 F150 4x4 400M engine.  All new bearings and a high volume oil pump.  He purchased a rebuild crankshaft kit from Rock Auto.  The oil pressure at startup is about 70psi (manual guage).  As the temperature gets to 200 degrees, the oil pressure drops to about 30psi at 2000 rpm.  At idle and operating temperature, the pressure is about 12psi.  He was told by the crank manufacturer to put 10-40 oil in it.  The only change that did was idle is now about 15psi.  He originally put in a standard oil pump and had the same results.  This oil pressure seems extremely low for a new rebuilt engine.  He has about 600 miles on the engine.  I don't have any ideas for him to look at.  Is this typical for that vintage engine?  Any input is appreciated.

The oil pressure might be lower than your liking but it is within a safe range to operate the engine. If you're seeking increased oil pressure, then I'd stay with the HV pump and try a 20W-50.  Nonetheless, 30 psi at 2000 rpm is acceptable and 12-15 at idle is acceptable.

I realize that without knowing further details about the engine build it's presumptuous for me so say this: next time opt for a personally prepared crankshaft & bearings rather than a generic, production line mail order deal and your oil pressure may be higher.

Thank you for the input. I will pass along to my grandson.

Make sure the new bearings match the crankshaft my ex-brother inlaw had a 351C. He and his new brother in-law rebuilt the crankshaft was turned .010 on rods and.020 on main bearings. They put .010 bearings on both and his oil would drop to 10psi at idle when the engine would get to temp it never knocked with the bearings wrong on the crank. He brought it to me to see if I could find the problem. When I pulled the oil pan and started checking bearings is when I saw what happened. I ordered the correct bearings for the mains put them in he had 60psi hot. Not saying this is your problem but might want to check the bearings and their sizes to make sure.

We did that. Pulled the pan and checked the bearings and even micrometer the journals. The journals were not the same. The crank was turned 20 on the rods. They were between .0005 and .001. We called the rockauto company that turned the crank and he said that was normal and within tolerance. I was surprised as I would have thought they would have all been exactly the same. He was the one who told him to put thicker oil in.

webengr wrote:My grandson rebuilt his 1979 F150 4x4 400M engine.  He put in high compression heads, pistons, new lifters, cam, etc.  All new bearings and a high volume oil pump.  He purchased a rebuild crankshaft kit from Rock Auto.  The oil pressure at startup is about 70psi (manual guage).  As the temperature gets to 200 degrees, the oil pressure drops to about 30psi at 2000 rpm.  At idle and operating temperature, the pressure is about 12psi.  He was told by the crank manufacturer to put 10-40 oil in it.  The only change that did was idle is now about 15psi.  He originally put in a standard oil pump and had the same results.  This oil pressure seems extremely low for a new rebuilt engine.  He has about 600 miles on the engine.  I don't have any ideas for him to look at.  Is this typical for that vintage engine?  Any input is appreciated.

take it back apart,and have it line bored

69F100 wrote:Make sure the new bearings match the crankshaft my ex-brother inlaw had a 351C. He and his new brother in-law rebuilt the crankshaft was turned .010 on rods and.020 on main bearings. They put .010 bearings on both and his oil would drop to 10psi at idle when the engine would get to temp it never knocked with the bearings wrong on the crank. He brought it to me to see if I could find the problem. When I pulled the oil pan and started checking bearings is when I saw what happened. I ordered the correct bearings for the mains put them in he had 60psi hot. Not saying this is your problem but might want to check the bearings and their sizes to make sure.

I was thinking the same thing ... maybe wrong size main bearings.

Have the crank cut by a competent shop and get new bearings to get your clearances correct

Also make sure your rods a round and have the correct side clearances.



Me personally id shove that crank up rock autos ass......

Did he change the cam bearings?

The mains are within tolerance and was lined bored. I am not sure how you "line" bore rods? I am starting to wonder if there is any "competent" shops to have a crank turned. There are only two shops in Montana that do it. This is his second crank. The first one turned at a shop in Montana who had a good reputation came bad and way out of tolerance. That is why he ordered one from Rock Auto. I would assume they would use a "competent" shop. He did put in a new cam and cam bearings and had the machine shop match the bearings with the cam. He is getting pretty frustrated and I don't blame him. Since the majority feel that the pressure is acceptable, he is going to drive it and watch to see if it gets worse. Thanks for all the replys.

On my 408 Windsor, the brand new oil pressure sending unit went bad within a few hours of running. I thought I lost all oil pressure for a few minutes...

webengr wrote:The mains are within tolerance and was lined bored.  I am not sure how you "line" bore rods?  I am starting to wonder if there is any "competent" shops to have a crank turned.  There are only two shops in Montana that do it.  This is his second crank.  The first one turned at a shop in Montana who had a good reputation came bad and way out of tolerance.  That is why he ordered one from Rock Auto.  I would assume they would use a "competent" shop.  He did put in a new cam and cam bearings and had the machine shop match the bearings with the cam.  He is getting pretty frustrated and I don't blame him.  Since the majority feel that the pressure is acceptable, he is going to drive it and watch to see if it gets worse.  Thanks for all the replys.

UPS or FedEx run every day.

Performance Crankshaft, Inc.

I will second if the quality of work that comes out of Performance Crankshaft, Adney knows his s**h!!!

I wouldn’t worry about it for a truck. I haven’t dealt with a 400 too much but the Cleveland is notorious for shitty oiling top to bottom. They have low pressure at idle and the rods will starve for oil at high rpm.

Sounds like there may be some loose clearances somewhere, but have you considered using the Roush high pressure spring in your oil pump? I had very good results when I was into Clevelands with that and ARP oil pump drive.
Sheldon G.

[quote="webengr"]The mains are within tolerance and was lined bored.  I am not sure how you "line" bore rods?


noone does, You recondition them , or some guys say rebuild,You line bore block.

stanger68 wrote:I wouldn’t worry about it for a truck.  I haven’t dealt with a 400 too much but the Cleveland is notorious for shitty oiling top to bottom. They have low pressure at idle and the rods will starve for oil at high rpm.

Yea, pretty much the same shitty oil layout used in the 429/460. Sucks huh.

Your cold pressure is in line, hot pressure is not bad but probably should be in the 25~35 range with a 195 thermostat and fully warm. If the mains are correct clearance, then there could be issues with rod side clearance and such. 351C-400 types are also a bit sensitive to lifter bore clearances on the right side. I run .0025 on the main and rods in my 393C dragster engine, 55 PSI @ 6800, 25~30 at idle @ 180F with 10w30 VR-1. No weird oiling mods - HV Melling pump, restrictors in the main to cam passages and to the left side lifter gallery. Hundreds of rounds, bearings are fine, thanks.

webengr wrote:We did that.  Pulled the pan and checked the bearings and even micrometer the journals.  The journals were not the same.  The crank was turned 20 on the rods.  They were between .0005 and .001.  We called the rockauto company that turned the crank and he said that was normal and within tolerance.  I was surprised as I would have thought they would have all been exactly the same.  He was the one who told him to put thicker oil in.

. Between .0005 and .001 is to tight. You can buy a Eagle stock stroke crank new probably as cheap as you can have one ground.

Sorry was thinking your working on a 460. Scratch that idea

That is tight, but close to stock specs. The next check I'd be doing would be lifter bores. Thats where you are most likely to lose oil volume and pressure.

those blocks had a bad oiling issue... they have a passage drilled right into the main bearing that is off to the side of the oiling hole. I guess that main bearing is supposed to "stop" theoilfrom leaking around between that bearing shell and the block. I mod the oil galley in mine with a allen drive pipe plug 1/4" MNPT. I agree that the oil pressure is likely acceptable, but to mod that thing you need thecrank out. if you mod the block, the pressure will comeright up.