"Moby" is coming along nicely - here is the latest detail I MUST take care of soon.

When I first start it up and the engine is not at running temp the oil guage reads strong at about 60% of the guages range (whatever that is). As the engine warms up oil pressure slowly declines until finally at normal running temp there is NO PRESSURE. I can get the guage to move by jumping on it a little or driving on the freeway, but for the most part it is low to none.

I hope it's not the oil pump. My mechanic tells me to replace we pretty much have to pull the engine and turn it over. Is this true?

To refresh: 1977 F-250 supercab with 400.
Just in case it helps I have newly installed the follwing modifications: Edelbrock cam, lifters, non-EGR intake and 600 carb. Water pump and double roller timing chain, new four core radiator, new hoses, thermistat and belts.


Thanks for any help,
BOB

 

Could be your sending unit. I'd get a real gauge on it quick. If you really had no oil pressure you should hear the lifters clattering at least.

Bear Tracks

 

i believe there is a whole post somewhere on this site dedicated to this problem. i know a lot of guys with old fords that have this problem. i have read a bunch of "fixes" but it seems as though you need to get an after market gauge on there and see what happens. those stock ones sometimes arent the hottest. a lot of guys have this problem and just drive their trucks with no apparent problems. but your oil pump might not be the problem, it could just be the age of your engine. i would put one of those after market gauges on there before ripping the whole engine apart.
i think you can replace the oil pump w/o removing the engine but you still have to jack it up to get access to it because of the cross memeber!

just my two cents,
nick.

 

i had that problem with one of my trucks. i changed the gauge to a mecanical type, instead of the stock ford electric type that is in the dash. it fixed my truck. so try it first. gauges are fairly inexpensive. mudder trucker.

 

There is never any clattering of lifters ever. Even when the guage shows ZERO pressure.

I should order a mechanical gauge from Summit ASAP and see what it says.

Thanks... any more ideas would be welcome.

BOB

 

[updated:LAST EDITED ON 20-Apr-02 AT 01:41 AM (EST)]I have been having that same problem. When I got my new mechanical gauges it would drop to 0 after it warmed up with strait 40 weight oil. Then i replaced the oil pump with a high volume oil pump and I had to clean my pickup filter because it was very dirty. Now with the new oil pump I have zero at idle but if i am driving it down the road now i have 20 psi and I have been told that with older fords that it is normal and if my lifters don't clatter then i shouldn't worry about it.

 

Had the same thing happen on my 77 F100 302. Changed the sending unit,everything OK now.

 

hehhe..I think I was the one who started the aforementioned "previous post" a couple of months ago....I have a 460 in my truck, and I have the exact thing happening to me....I have been lazy and have not a mechanical guage in yet....however, other than my slightly increased heart rate everytime my stock gauge bottoms out, I have had no ill side effects on my motor, and I have had this truck for about 4k miles.

One poster on my thread said he talked to a Ford dealer mechanic who said that at temp, and at idle, the oil pressure is only about 5-7PSI, which he said was acceptable.


The other advise was to just leave it alone until I got ready to rebuild, then replace the pump with a HIGH VOLUME (not high pressure) pump.

 

I think I'm going to leave it be for now... from every thing I've read in this forum it sounds pretty normal for an engine with some normal wear and tear.
It runs great, no smoke, no clatter, strong... and whenever I'm at highway speed the pressure stays at 40% to 50% of the gauge. It's only around the city, at idle, stopped at a light that the pressure drops off to zero.

So... on to the next issue.

 

Gobstopper ......

I purchased my 77 F-150 4x4 in 1986 with 35,000 miles on it. It has a 351M in it. In 1989-91 as I built my new home, I put some miles on it and in 1991 I got a deal on a Shopsmith located 500 miles away in Atlanta. My oil pressure showed about half range then when the motor got hot, the truck then had 74,000 miles on it.

Well, about a third the way into the trip down, I notice the oil pressure was a little under 1/2 range, and thought it odd in November. a while later, I notice it down near "zero" but the motor sounded fine ... so on I went. Well, I arrive at the home of my brother in law, I go to Napa and get a sending unit to put on ... and no help! Motor still quiet, so I figure its the guage. I drive the truck to the speedway while there (Richards last race, Alan wins Championship, and Bill won the race) and after a few days stay, load up the Shopsmith and stuff, wife & dog, and take a long scenic detour coming home through the Smokies ... you know ... UNCONCERNED to say the least.

I get home, unload the next day, "chill out", drive down to my favorite home away from home where my best buddy and mechanic works and he suggest a "Ford" sending unit. I get one ... still no pressure.

We install a manual oil pressure guage just for kicks. I have exactly 4 psi at 2500 rpm! Damn ... I drive home very gently.

Being a 4x4 ... I am able to drop the panhard rod with the truck on stands, then remove the oil pan, then remove one rod cap and one main cap ... the mains are almost completely gone in the bottom ... solid copper! The rod bearing isn't too bad though. I take the bearing shells to Napa (after Ford guy says he has no idea what size they are by numbers) and the machinist miked the shells over toward the side where they aren't worn, and I have standard bearings. I replaced the mains and rod bearings one by one laying on my back, removing the upper main shell by using an old shell to "push" it back around till it would drop straight down. I put a new standard oil pump in there too. did it all in an afternoon. The Crank looked great with only the most minor wear pattern showing on the front main journal only.

The guys at Napa and several other mechanics here said that it wasn't uncommon for 351M/400 to wear the bearings out before the rest of the motor when I related this story. The motor uses no oil, has a crane fireball cam, holly 600, Edelbrock, roller timing chain with cam straight up, and I did have the heads rewaorked completely at 60,000 miles. She has 98,000 now, still runs great, and carries 55-60 psi when hot (mechanical guage now too, but stock works too since I purchgased the Ford sender ... just used a tee). When first put her together, she had 75psi hot, but I guess as it broke the new bearings in, she dropped or that front main journal is wearing that bearing.

Fix it before it gets really expensive.