Oil Question

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rod7515

rod7515

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I have a 408 that has a roller cam with solid lifters and roller rockers. It may have about 1000 miles at most on it since it was built and during that time it’s always had 20-50 penn grade oil. The last oil change I had to buy partial synthetic oil. I’m noticing that oil pressure is lower with this oil. Probably 15 lbs cold and 10-15 lbs once warmed up to normal operating temps.
Is this a normal thing and what happens if I go to full synthetic 20-50?
Thanks Rod
 
Synthetic oil tends to be thinner than traditional oil. I just went to a synthetic 15-50 from 10-30 dino oil in my Mazda B2600.
Pressure went up a little but is much more stable once hot .
20-50 seems pretty heavy for a new build . Was it built with bearing clearances on the high side ?
 
If I remember it was .0015. I’ve run the 20-50 from the first start. I haven’t had any issues and when going to the partial synthetic noticed the slightly less oil pressure. I do think you are correct as it seems to keep a more constant pressure once warmed up and at a stop light/sign. What changes would I see if I went to full synthetic and should I be using any ZDDP additive with synthetics ?
Thanks Rod
 
there is nothing to worry about there. The first power pull of my 340 it was at 102 PSI on the Penn 30wt BR oil. I changed it to 10-30 Penn partial syn, and now about 70 PSI cold and 50 psi hot at idle. I would just stick with the partial 20-50. For the Cosworth racing engines my brother builds, (60’s/ 70’s tech engines) he runs .0008 mains and .001 rod/ cams bearings, we run 20-50 Penn in all of them.

These pics are right before the teardown. This motor was about 10 minutes from blowing up as we found some dumb **** from the last builder. When one of these blow up, it’s a 100 grand of ****…

IMG_3684.jpeg


IMG_3683.jpeg
 
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Go to the Penrite.com. website & look for the description of 'Friction Modified' oil. FM oils are 'thinner' to give better economy. Penrite make oils that are NOT FM'ed, which is what I use in my engines & engines that I build.

Not saying that the above is the reason for the oil pressure loss [ between different oils ] , cut it certainly could be. Usually a 10-15 psi loss at idle, hot; applies to syn & non-syn oil.
 
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