308 GT4 low oil pressure at high rpm

Don't see how a weak relief valve can only be weak at certain RPM. It can't be strong at low RPM and weak at high RPM. A week spring would just restrict the max oil pressure to some lower value and the max pressure would occur at whatever RPM produced that pressure. I'd suggest it's either a gauge/sender problem OR very low oil level so check that if you haven't already. Low oil can do that because not enough oil remains in the sump at high RPM.

I just re-read that you were racing - did the pressure drops coincide with turns or heavy braking?

 

Hi Johnny,

The first thing that comes to mind is a collapsed oil filter, more pressure just crushes the filter element in further. I was on the track just after a major and things were fine untill late in the afternoon, when i noticed a sudden drop in pressure while out on the track. I tried the pressure relief,it was ok. Then moved on to a known good mechanical gauge and that looked good, so i pulled the filter and this is what i found.

I replaced the fram with a Baldwin and the problem went away.

Needless to say, i don't use fram anymore.

hth,
chris
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Open up the old filter for a look see.

 

There is a lot of opinion that current Fram filters and current Champion spark plugs, are not even remotely related quality-wise to what they used to be. I agree re Fram. We had problems with them similar to what is shown in the pic and quit using them in our engine building in the late '90s, switching pretty much to Baldwin unless they didn't have a filter available for the application. Never had problems with Champion plugs at all but a lot of people claim they are now the worst instead of the best.

 

I think 10W40 is a bit too normal for your use - as you say 10W60 or even Shell 0W60 racing should help especially when the ambient is above 20 deg c

 

How about a bad or going bad sender ? - mine was reading ok at low revs but erratic at mid to high. I guess the sender does spend a lot of it's time at the "high" mark 85 psi so if it's going to deteriorate electrically then high is probably the place. I replaced mine and it read perfect ever since.

Lee

'77 GT4

 

I too had an issue with my sender, replaced it then everything has been fine. Shound you not also be using 20-50 oil. I believe that is what the workshop manual recomends.

Cheers!

 

Yeah, there pretty much a stock Italian car item, similar to Fiat 124, X1/9, 127, 128 ... and they don't last 30 years. I think someone took one apart here and posted pictures. Best to use a pressure gauge which is not a cheap electrical production item and more like a real bourdon style gauge if you really want to trust the reading.

Lee

 

Oil filter

 

+1

I assume you didn't screw the used oil filter back on?

I haven't seen a sender break down in the way described. It'd be nice if you could bench-test it and show a graph of the way it behaves!

I am also running 10W-60: hot climate (most of the time) and we're driving the car hard. Track time whenever it is permitted. Seems the choice to make for the use. Oil temps stay well within acceptable limits with either use, pressure is always fine.

I actually have somewhat of a gripe with using the thinner oils (10w-40, 0w-30) on these cars: The tolerances maintained in these engines weren't designed for them, and IMO the oils are too thin for the application. Others have good tales & experience, so maybe it is all in the stars. I am happy with what I am using, she performs beautifully, and that's the objective.