[Fot] Oil Pressure Conundrum

[marty]

I could use some opinions. Some history. Spitfire small
journal 1296 engine, rebuilt 6 race weekends ago included all new bearings. I tore
it down this spring to check it over prior to last weekend PVGP event. Cam and crank
end floats were to spec. Rod and main bearings checked between .002 and .003
clearance. I do not have the actual numbers in front of me at the present. Cam
bearings appeared to have some slight visual wear at the bottoms but I did not
actually measure them. I run Brad Pen 20W50. Oil temps run 210 and water temps
run 190. EGT are 1200/1250 range on track. I was fighting low oil pressure at running temps all
weekend. Once my oil temps come up on track the pressure drops down to 35psi.
If I add enough springs to the pressure relief valve I see over 125 psi cold so
I am thinking my pump is putting out enough pressure. I tried shimming to get
50/60 cold at idle and it drops to 35 at operating temps at 7000 rpm. I tried a
new pressure gage over the weekend and the numbers did not change. I am
currently running an auxiliary oil line to the head, I removed it at one point
over the weekend and it had no effect. I tried a new pressure relief valve assy
and it had no effect.  I believe this
situation actually started a season ago because I added a washer to the
pressure relief valve last season.  I’m
thinking it most likely is cam bearing wear even though all the bearings were
fresh 6 events ago. Any guidance? One thing I did learn this weekend is my accusump
pressure gage is incorrect.  It was
reading about 30 psi higher that my dash gage. I was thinking it was probably
correct and my dash gage was wrong until I replaced my electric dash gage with a mechanical gage and its
reading matched the gage I just disconnected. Oil pressure readings are taken
at the port below the distributer. 

 

Side note. Car ran awesome. I ran a 2.22 at PittRace Sunday
and that was 6 seconds faster than my previous best lap there. 

 

Thanks,

Marty 

 		 	   		  
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