I have a 1978 f-150 4x4. it has a 400 in it and it seems to like oil. it does not smoke and runs really well, no engine noise. i have some leaks at the oil pan and i am going to replace the gasket. my pressure on my guage shows on the L of normal on a cold start but ends up on the N after about 20 mins of driving at idle. would it be a bad thing to put in a high volume oil pump when i am in there. dont know the miles on the motor. thanks for your input

 

Check out the search function for oil pressure options on these motors. It is quite common for these engines to show lower oil pressure with age. A higher volume pump may help if you replace the rod and main bearings while you are in there.

 

I'm assuming your not pulling the engine. Bearings will be a major pain in the truck, and if you got the right tolerances you don't need the HV pump. The HV pump is around $30.00 and will, without a doubt, make some add'l pressure for you and get some more time out of the engine, IMHO. GL, welcome to FTE.

 

thanks for the information, not sure about the right tolerances though, but was conserned about hv pump spinning a bearing, does that happen? do oil pumps wear out? i would like the truck to last awhile but have spent about all money i can fixing the rest of it. thanks again for anyone and everyones advice. this is the coolest site i have found in a long time......keep up the good work....

 

Re: spinning bearing w/ HV pump
I know an old man who was setting speed records at Daytona before I was born and he told me once an HV pump will "wash your bearings out" take it for whatever you want.... IMO I would look at ( & measure) one rod and one main when I did the oil pan. You can look up the spec, if it was at the upper limit you don't have a lot to loose going HV.
Yea, everything wears out. (There are some tolerence published somewhere on pumps, you may want to inspect your old one and in conjuction with the bearing info make a desicion on whether to go HV or just replace it.) GL

 

When I rebuilt my 351C I installed a high volume oil pump. I built this engine with tolerances a little on the looser side. It gets about 75 - 80 psi when cold and 40 - 50 when hot at idle. If I rev this engine to around 1500 rpms the oil pressure spikes around 90 - 95. Oil pressure at highway speeds when hot is around 70 psi. I would think the maxium oil pressure is preset by the oil pump manufacturer.

I have been running this engine for about 3.5 years now and 35K miles and the oil pressure has stayed where it is right now since the first week on the road. I have pressure tested it so to speak many times. So far, I can't complain about this engine. I have heard of the bearings being washed out before too. One day in maybe the next ten or fifteen years I may take it apart for a rebuild and see what the bearing look like. I'll be interested to know if the bearings do actually wash out with high volume pumps.

 

The bearings do not wash out with HV pumps. What will "wash out" bearings is grit in the oil.

FWIW the std volume oil pump I pulled out of my 400 looked like it had been pumping sand inside. It was worn out. I did not change the bearings out because it was plain toooo cold outside. The HV pump gave me a few more pounds of pressure at idle (~5) and the truck ran another few years b4 I retired it for a rebuild.

The oil pressure relief valve is built into the pump. I believe It is a single stage valve and for that reason pressure is affected by oil viscosity, and volume. A piloted two stage valve is much more stable but also more $$$.

 

thanks guys i will do some checking when i am in there. i'll try and find those specs on this.

 

Yes, oil pumps wear out.

The following are M-block (351M/400) oil pump service specs from a Ford shop manual:

Gear backlash: 0.0

Rotor end clearance: 0.0040" (maximum)

Driveshaft to housing clearance: 0.0015-0.0030"

Outer race to housing clearance: 0.0010-0.0030"

Relief valve to housing clearance: 0.0015-0.0030"

Relief valve spring pressure: 20.6-22.6 lbs @ 2.49"

These are factory-recommended service limits for OEM-spec oil pumps. If you use a non-stock type of oil pump (such as a high-volume unit), you need to get these service specs from the pump's manufacturer.

If you're checking a used pump, look first at the gear backlash. It's the easiest thing to check, and it should be zero. When a pump wears out, noticeable gear backlash is the most obvious sign. If the gear backlash is good, then go on to checking the rotor end clearance, outer race to housing clearance, and relief valve (piston/disc) to housing clearance.

IMO, if you replace the oil pump, it's smart to take the extra time to verify the service specs of the new pump. I've seen a few new oil pumps that were out-of-spec, and I've heard several horror stories about brand new pumps with bad clearances, particularly with defective pressure relief valves that jammed up in the bore.

A bad pressure relief valve can cause either excessive pressure (possibly rupturing the filter case), or catastrophic loss of pressure (dumping all the oil pressure when you need it most, and burning up the crank).

The weird thing is, after I first heard about a problem with pressure relief valves, I checked the next pump I bought and found that exact problem (pressure relief piston/disc sticking in its bore).

I've had enough experience with "new" parts failing that now I am wary of any new part, and the more critical the part, the more wary I am.

 

you say your oil pressure is low when cold and gets better when warm.this is a sign of a plugged screen on your pickup.as the oil gets thinner more can get through.be sure to check this when changing the pump.

 

78oldsmokey said the other way around... Read the post again.

Always check and clean the screen or buy a new pickup. Check pan clearance also.

 

My Custom 300 has a 351c and I used a high volume oil pump since it puts out around 350+ horses and it helped with my oil pressure problem. Im about to do the same the F-100's 400 since it gets a little valve noise every once in a while.

 

thanks guys, ya'll are the best. i sure wish the rest of the world were as helpful as you folks on this site!!!!!

 

I have a hi volume oil pump on my 400. I have to run 5-20wt oil to keep my oil filters from blowing out the rubbber o-ring. Idle oil pressure hot is about 20psi now, was at 35psi with 30wt oil. Running anything above idle and it pretty much pegs out at 80psi regurdless of oil used. I could realy get away with a stock pump, but when I was building it, I thought I needed the extra insurance. Either way my 400 runs like a scalded ape, and thats with the stock intake and a 500cfm 2V! Boy I can't wait for the 4V and a manifold!!Sorry for the long post.

 

I lost a 350 chevy to a brand new napa h.v. pump that had .010 end clearance from the factory. It spun every bearing in the rods and block in about 5 minutes of break-in. Last time I ever make that mistake again. I still have all the bearings and the pump sitting in my storage to remind me.

You can't wash a bearing out from high pressure. Not nowadays. Maybe back in the 40's when bearings were made of pure lead you might have had something like that happen, but not now.

As for too much pressure. With FE fords, I like to see 70-80 hot at 1500 rpm and 90-100 at 6-7K rpm. Unless you've done oiling mods, anything less and they seem to eat the rod bearings out.

Excess pressure only hurts if you start blowing oil filters off, or you are looking for that last 3 hp and .25 mpg. On the other hand if you don't have enough pressure at low rpms with a standard tranny, the compression pressure can actually push the oil out from between the crank and bearing and give metal to metal. This is easily observed when you pull the rod caps and the center of the top bearing shell is pounded out to the copper.

Any of these engines with more than 80K miles will probably need new bearings at least in the rods and the top front main bearing. Bearings are available by special order from most of the manufacturers in undersizes other than the typical .010/.020/.030. If you have a standard crank and you don't need to turn it, but you need to tighten the clearances, you can get. .001 and .002 undersize bearings for a lot of applications.

With the lifter-bore wear and camshaft bearing wear inherent in many 335 engines I like to see a h.v. pump put in to compensate. A standard pump will do the job in a good tight engine, but in one that is half or more worn out, the h.v. is easy insurance and it's only another 10-15 bucks.