View Full Version : Ford 351 Cleveland Guroos…. Please Help
24-10-03, 10:41 AM
Hi party people,
My cousin just bought a 1970 Ford Capri.
It has a 351 Cleveland in it.
My question is that, when you first start it the oil pressure goes very high (100psi) and stays like that till it warms up then drops slightly (80-85psi).
I believe this is not normal, my experience with cars tells me that there might be something wrong.
I don’t know much about Ford v8 engines.
Does anyone know what the problem could be, is this common?
We think it could be the oil pump, but before we start ripping it apart, we would like to know what our options are?
I don’t have any other specs on the engine, other than it’s a Solid Engine, and has all the goodies on it. We believe that the engine has a substantial amount of work done to it, approx 500+ flywheel HP.
24-10-03, 02:14 PM
Anyone Please .
it could be the main bearings are a little worn, or as you say the oil pump or relief wearing out.
what will happen is you get good oil pressure when the oil is cold and nice and thick, but as the motor warms up the oil thins out, losing a bit of oil pressure.
an old trick was to fit a few washers or a nut (or stronger spring) between the spring and housing of the oil pressure relief valve in the oil pump.
But i'd start with a fresh oil change of good oil and recheck the pressure. Who knows, previous owner may not have changed the oil for ages if they were selling the car.
24-10-03, 04:52 PM
The relief spring may be too strong. Although it is normal to have higher pressures when a motor is cold. Mine was 90psi then went down to 70psi when warm.
24-10-03, 04:54 PM
Although the engine may be purposely built like that, apparently the rear bearings on Clevlands (this is one of its weaknesses) can get oil starvation under high rpm. They may be trying to ensure the rear bearing get adequately lubricated.
Sorry, I misread it as low, not high :rolleyes:
also to add to mopar lovers comments what kind of oil does it have in the sump.if it is heavy grade 50 race oil or 40/70 type then high oil pressure is quite normal.
sounds fine to me, maybe a little bit high, might want to keep an eye on the oil filter, put a hose clamp around it in the middle to stop it from bulging out..
Depending on the engine - some oil pumps don't actually pump higher than necessary (volume wise) when hot. The pressure relief spring is there because when it's cold and the oil is thicker, it ends up putting too much strain on the the oil filter seal, the pump drive shaft/gear - whatever. So once it warms up, in some cases, the spring tension is high enough that it actually never unseats the pressure relief valve.
If the guage is accurate, then the pressure you have is actually bloody good from what (admittedly not a hell of a lot) I know of clevelands.
The 'rule of thumb' used to be 10psi for every 1000rpm the engine normally sees. Now on a cleveland, the oiling system is not the best in the world, and to actually have a cam etc that would support >7,000rpm, would require mods to the oiling system (in very broad terms the problem is that teh oiling system goes out of it's way to provide for the valvetrain, but the main bearings are secondary. Hence the creation/use of upper oil restriction kits/modifactions.
But from the pressures you quote - unless it's a really high rpm piece - I'm sure it will be ok.
As an example of the opposite - holden 6 oil pumps - you don't need a higher volume oil pump for them as the valve unseats even when warm. A heavier spring (or a shim behind the existing one) will up the pressure. Running a higher volume one is useless - as it is already capable of supplying more than is needed - even by a race engine.
Hemi oil pumps are weird too. The gears aren't super strong. The pressure relief valve hardly ever 'seats' - even at idle. The thing is, the bypass passage is a fair way up the 'tunnel' the pressure relief valve/bucket travels in. the spring has practically zero seat pressure. It rides off the seat all the time and has to move a long way to uncover the bypass hole. If you give enough preload to seat it hard, you can guarantee it won't break the pump gear - as it'll blow the oil filter seal out immediately after starting. The reason it's designed to ride off the seat so far is to act as a cushion - so that each 'pulse' of the pump is damped and it lowers the stress on the drive gear.
27-10-03, 07:53 AM
Thanks for all you help gents,Maybe this week end we'll get a chance to check it out properly.
Couldn't see any dramas there.
If as you say it is a perf engine, I dare say it will have oil restrictors, etc.
The Relief has been played with to help compensate for, as posted, cleveland's problems with oil circulation.
I wouldn't touch anything. find out from the previous owner/ engine builder what they did, and change the oil/ filter.
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