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Discussion Starter #1
Experianceing drop in pressure at high rpm's. Pressure when engine fully warmed up is about 40-45 psi. But at rpm's > 3500, pressure drops to about 30psi. Thermostat opens at 180*. Doesn't matter what the oil temp is, so it's not cooler related.


Autometer electric gauge. Melling high volume/standard pressure pump. Billit pump drive. Canton pick up. Canton 7qt road race pan. 10W-40 dino oil. Remote filter w/ -12 AN lines and russel full flow fittings. Oil cooler with thermostat.

I'm think that the HV pump is sucking the 7 qt pan dry??????? Planning on changing the pump this week end for a standard pressure/standard volume.

Any other thoughts?
 

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Your fine. As long as you have 20psi hot at an idle and 45-50psi hot at rpm you are in good shape. If you are really concerned, switch to Mobil1 15/50 synthetic.
 

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Bob I'm no expert but over the last 4 years everyone has said the HV pump is a NO NO.

BUT Try running the car with an extra quart in it, I have heard many of the racers have done this to counter oil starvation in corners, with wet sump systems.

I see over 55 PSI idle cold start, 25 idle when HOT, and around 45-50 running hot. I do NOT have a remote oil filter on the 351W.
 

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Discussion Starter #4
Originally posted by Gordon Levy:
Your fine. As long as you have 20psi hot at an idle and 45-50psi hot at rpm you are in good shape. If you are really concerned, switch to Mobil1 15/50 synthetic.
Well, that was my concern. When the rpm's go up the pressure drops to about 30psi. I have a case of 15W-50 sitting in the garage. Should I swap pumps to SP/SV? Because of the external lines and stuff I was reluctant to do that.

Zulu, the big concern with SBF's is the High Pressure pump putting a strain on the distributer gears. But the HV pump is recommended by many builders and racers for engines with oil coolers and external filters.
 

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Your oil pressure drop at highr RMP would appear to be oil starvation at the oil pickup. High Volume oil pumps will tend to pickup oil faster than the oil is running back down to the pan. The general experience is don't use HV pump unless you are also using an 8 quart oil pan.
 

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Bob - don't know if you're interested in another opinion.

If so - I Need more input to help diagnose. Does the oil pressure start to drop immediately at the higher RPM or do you have to be at higher RPM's for any period of time?

I.E. It holds fine oil pressure through 1st and 2nd gear but when I get to the top of 3rd gear it starts to drop.

Also - has it always done this or you just noticed it?

Have you changed the oil filter since this started happening? Did it make a difference?
 

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Discussion Starter #10
Good oil pressure at idle and routine driving, 40-45 psi. At about 3500 rpm's it drops almost immediatly to about 30-35 and stays there up to 6,200 rpm's. Just like you said, good pressure until the top of third, then drops.

The engine new, and this has been pretty consistant over the last few hundred miles. Up until then I've been driving it pretty easy, keeping the rpm's and acceleration down to a reasonable level. I've changed oil and filter, which has not changed anything. I use a quality dino oil (for now) and a stock Ford Purolater Pro-1 filter. Once I get all this sorted out and the engine well broke in, I'll switch to Mobile 1.

The engine runs just great, and sounds even better. Not a hint of valve clatter (like I could hear that at 6,000 rpm's).
 

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Bob -

You've replaced the filter and eliminated it from contention.
Your oil lines / fittings are not a significant impediment to the flow.

If, when going through the gears, the pressure increases or stays the same (45 psi) up to 6g in 1st and 2nd gear and then drops when you are in 3rd gear - that would indicate that you are potentially sucking air in the pan. You can verify this problem by overfilling your pan with an additional quart of oil to see if the pressure problem is either delayed or goes away.

If the oil pressure drops immediately in 1st gear (I.E. it never goes higher than 45) then we have another problem as you cannot suck the pan dry that fast.

If the oil pump pickup has been properly spaced from the floor of the pan -and- If the engine immediately (regardless of how long it has been at sustained RPM) drops oil pressure as soon as the RPM's increase to over 3500-4000 RPM - it sounds to me like the oil pressure relief valve in the pump is opening and hanging up. Sometimes they will work themselves free from the burr that is causing them to hang.. sometimes they hang up and stay open which causes a significant drop in pressure at lower RPM's (Need-4-Speed's FE motor did this)..

If the oil pump pickup is too close to the floor of the pan, it becomes a significant restriction to the flow of oil into the pickup. Depending upon the use, I space them from 1/4" (street) to 3/8" (race) from the floor of the pan. Some pans make this a royal PITB to check. I typically put a piece of duct tape over the pickup screen and then a ball of modeler's clay, install pan, remove pan, check thickness of clay, adjust, repeat if necessary.

If the oil pump pickup screen is being restricted by gasket sealer or other debris - it will also cause the problem you are experiencing. From my experience in reading your posts, I would say that you are a relatively fastideous individual and have taken care to not use excessive amounts of sealant which could potentially cause this problem.

Oil:
If you have over a few hundred miles on it - I would not wait to switch to synthetic.


It's my opinion that you don't really need either a HV or HP pump even with the external cooler. We run nothing but SV/SP pumps (although blueprinted) on our engines with -12 lines and aeroquip fittings to the coolers. Never an oil related problem.

Check with precision oil pumps on the web for one of their blueprinted units.

The old Smokey Yunick quote of 10psi for every 1000 RPM is no longer valid with today's oils. If anything I would cut that in half.
 

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Discussion Starter #12
Thanx Randy, that's excellent advice. When I installed the pan the first time, I check pan/pickup clearance exactly as you described. Got about 3/8" clearance, so I left it alone. I have a differant pan gasket, so I'll check it again. I'll also add an extra quart of oil today and see what happens.

One thing I noticed during assembly is that the Canton pick up is pretty heavy duty, with a large box type end and a heavy duty screen, but with bigger mesh than stock. It also looks pretty difficult to adjust. The only way I could see to do that was cut the pipe and weld in an extension. Not sure my welding skills are that good.

Monday I'll start taking things apart again. I have a Melling SV/SP pump on the shelf, so I'll swap that out too.
 

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Bob - It sounds like your clearnace is just fine.
For those who may follow this thread to figure out how/what to do:
Rear sump systems are easier to bend the tube with just a little heat. Front sumps can really be a bear because you don't have as much tube to work with. I've not had to cut a tube yet though - just have to make careful measurements and work the metal gently. I do recall having had to just tip up one end of the pickup "box" to get the right amount of clearance at least on one end.
Let me know how it turns out. If you want to talk - PM me and we can get on the blower...
 
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