Got a 283 that was running good . Put it in my roadster with mufflers an noticed a knock . Had crank turned , cleaned block and new high volume pump . Start up 80 pluss pounds oil pressure . Hot around 70 . Put a std oil pump now start up 65 and hot 60 . Whats up ? I always liked high oil pressure but this seems to high for a stock 283.
My 327 runs that much pressure. Initial start up it pegged the oil pressure gauge. Ive got quite a few miles on it now and its settled into 80-70 psi range.
I am not a sbc guy but the pressure relief valve should set the oil pressure, not bearing clearances. The bearing clearances are a factor with low oil pressure because not enough flow to cover the loss over the bearings. That oil pressure doesn't seem that high to me. Run it. Neal
I agree with all of the above. If you turned the crank and replaced the bearings, they are probably a little tight. The bypass spring does set pressure, BUT if volume exceeds the capacity of the bypass, there will still be high pressure. It wouldn't scare me unless it runs up over 90 psi at about 4K-5K rpm. Just so you know, some old GM books stated oil pressures as "> 5psi at idle and add'l 10 psi per 1000 rpm above that". That means 5800 rpm could be 55 psi as an expected minimum. I've only seen a few that actually behaved that way because the bypass on a low volume pump will dump anything above about 40 psi, but I have seen a couple of high volume, high pressure pumps deliver 100 psi at 6K rpm.
The Z-28's ran a low volume pump with a high pressure (white stripe) spring. And the specs I've seen for the high performance Chevys was also 10lbs/1000 rpms. I've built quite a few engines that carried 60 lbs. of oil pressure with no trouble. After they run in a while and the oil isn't quite so fresh, it usually drops a little.
Thanks for all the input . I dought its the bypass to totally different oil pumps . I'll just keep dogging it . I had a friend call with some input I will try .
Try another gauge and get a comparison.If it is an electric gauge check Charging output.An over-charging altenator could cause high system voltage and cause electric gauges to give false readings
I think you're ok as it sits, 60-65 is not excessive especially if you wind it up once in a while. Bob
Use thin oil, syntetic or mineral to lower pressure & reduce inner friction. Lower value oilspec 5 or 10 To much PSI just eat ponnies & fuel and stress the camshaft gear.. Kenneth,, from a rainy Sweden
Main seals should no be effected. There is no oil pressure against the seals only crankcase pressure.
sounds like some tight tollerances..as long as you dont spin or wipe a bearing and all stays where it should, I'd say run it
High oil pressure (80-up) on a small or big block chev has a tendency to push the camshaft forward into the timming cover,, the chain will hold it back for awhile but will slowly stretch. The dizzy gear will wear also. I wouldn't run more than 55 pounds hot without a thrust button on the cam,, my 2 cents.
You guys are awsome. I just ran into the same problem last week when we started up my 283. I'm running 45-50 psi at idle cold. Rev it any at all and it shoots up to 70-80. But that's when it's still cold. I'm not sure how much it dropped off once it warmed up. I too had the crank turned...... Justin
As said previous,oil pressure is controlled by the pump relief valve. SBC's don't need a lot of oil pressure,good old Smokey Yunick claimed a SBC can support 500 plus HP at 7500 with just 55 psi.60-65 psi hot and running fast is ok but more pressure just beats up pump drive and cam
Thanx guys... I would have guessed the wrong way. A friend of a friend has a street rod with some half-built, high hp SBC in it. The OP gauge says 100 psi and he also has a rear main leak. So we guessed the fix was to replace the oil pump with a stock one and assume the seal problem would go away at the same time when we replaced that at the same time, too. Guess not, eh? Gary
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