351W oil pressure

[madmaxx]

Rest assured 20W50 will have substantially more pressure than 10W30. Why would anyone set bearings loose??? especially on a high performance engine. I imagine your mains are .002-.003" KC knows how to build engines.

Its a double edge sword, sure if you are going to race for 60 minutes straight and run your oil temp up 20W50 might not be to heavy. If you start and run around town 10W30 is the answer. Heavier oil just overflows instead of penetrates. You can wear your engine out with 20W50 with day to day starting.

[zrayr]

Originally Posted by madmaxx

"......... You can wear your engine out with 20W50 with day to day starting.

not true, at least not in my case.

Using 15w-50 Mobil 1 for 9 years, nearly 40,000 miles. No measurable wear on rod or main bearing checked recently. Piston/cylinder clearance unchanged. Car started and ran 4 to 7 times a week, minimum 30 miles, usually more. Longest trip 1700 miles over a 3 day period.

I do agree that it doesn't seem right that someone would set up a high perfmance engine, a street engine that is, with loose bearings.

Z.

p.s. no leaks either

[DAVID GAGNARD]

I do agree that it doesn't seem right that someone would set up a high perfmance engine, a street engine that is, with loose bearings.

It all depends on the way the engine will be used, this is usually decided bewteen the owner and engine builder.......

daily driver cars will have a certain bearing clearance,basically the same amount you would find in any production engine....

High performance engines that will see track duty usually have a "little" more clearance and I mean a little more, as in a thousandth or less......this promotes oil flow and the more oil flowing over the bearings,the more they are lubricated and produce less friction and less heat will be generated....a by product is a little less oil pressure....

There is a big difference in oil pressure and oil flow, more oil pressure does not mean more oil flow....

I would prefer oil flow and a lower oil pressure than high oil pressure and less oil flow in a motor......

Also, oil temp has a big impact on oil pressure.....my 65 Fastback (351-W) using 15/40 conventional oil,oil pressure is 60 psi on start-up with cold oil at 900 rpm idle, once the oil is up to 180 degress, my idle oil pressure is around 35 psi, on track, I've come in from a 15 minute run with the oil temp in the 200 to 220 range, at idle rpm,oil pressure is from 25 psi to 30 psi........this engine has near 30,000 hard miles on it right now........

BTW: NHRA Pro Stock cars have been know to run as little as 10psi of oil pressure at speed, of course they only run for 6 seconds at a time at speed......

I have a 351W with 6000 miles on it and over the last year or so the oil pressure has been slowly dropping after a long run (40-50 miles). On short runs (15 miles) it seems ok, the engine is at temp (185) in both cases. Originally it was around 55 at 2500rpm and 30 at idle (850rpm). It is now at 45 and 18. I pulled the oil filter, cut it open (what a pain) and found some tiny metal flakes in it, about 1-2 per pleat in the paper filter

I'm guessing wear from the bearing is causing the lower oil pressure since you have found metal flakes in the oil filter,1-2 per pleat is a lot to me anyway.... I don't think I've ever seen that many in an oil filter from a "good" engine.......

David