The Stovebolt Site Forums The Shop Area Engine Shop 355 SBC

OK, I just joined this forum and said in My introductory post that I would be asking questions.

ok my '46 has a SBC 355 in it, and it was in the truck when I aquired it. Here is what I'd like for all of you to comment on with your online diagnosis and prognosis. (I already suspect a couple of things.. I am not new to engines as I can build a BBC with my eyes blind folded.

This engine sounds sweet. After I rebuilt the holley carb on it, it really runs superb- this lil yellow fellow will swap ends when you bury your right foot knee deep in the gas tank, via the gas pedal. It makes NO noises other than the usual stuff. BUT...

when I crank it up it shows about 60lbs of oil pressure (manual guage) and as it gets warmed up the oil pressure steadily declines (and no unusual noise is heard) when the motor is warmed up to approximately 190, the oil pressure falls to about 10lbs at idle but the engine sounds great. I can tap the foot feed and the oil pressure will immediately jump darn near back to 50 lbs....


what say y'all???



(I plan on dismantling the truck down to a bare frame and then going back to my specifications, but havent decided about this particular engine yet..ie- do I tear it down for a looksee or do I run it till it pops... A blower motor hangin out in the shop shadows.)


**EDIT** I forgot to mention that while the engine is idling after it is warm, and when I rev on it gently, the oil pressure will sometimes stay at a higher pressure for a bit then fall of back to around 10lbs. What I mean by 'a bit' is about a couple of minutes.)

Cam Bearings !! I think you will find that the previous owner did a poor overhaul by not replacing the cam bearings. I find that strange because you said it is a 355, so it's been bored .030 over.

yes it has been bored, and rebuilt- I do know that much. There was some paper work with the truck but it is sketchy after 3 or 4 or more owners... Cam bearings is one of my suspects too.

*EDIT* It may have been bored before the PO rebuilt it... Seems likely.

You're describing the problems small block engines have had since we first started doing in-frame rebuilds on 265's in the 55 models when they got a few miles on them. I was the kid running the drill motor on an auxiliary pump in a 5-gallon bucket while my father and his partner looked for the source of the low pressure with the oil pan off a couple of them. The cam bearings leak enough pressure to drop the hot idle oil pressure and make the idiot light flicker at a stoplight, particularly on automatic transmission models.

We stopped doing in-frame rebuilds and started insisting on changing cam bearings on every overhaul, as early as 1960 or so, which was a radical new idea back then. We lost a few customers, but they came back to us after getting a shade tree rebuild from another shop.

The difference now is the fact that high-volume oil pumps are available now, and they weren't back then. To save the day on your present job, drop the oil pan if possible and install a Melling high volume pump. It will flow enough oil at idle to keep the pressure up, and the relief valve will bypass enough oil at speed to prevent overstressing the distributor drive gear or intermediate shaft. If you can get the idle pressure up to 20 or 30 pounds, there won't be any longevity problems at all. Even 10 pounds is enough, but it's worrisome.
Jerry

Hey Jerry, you say you and your dad had a 5 gallon bucket and auxiliary pump to check for pressure loss. We must have been "high tech" because we used a pressureized oil tank and a rain coat lol.

Yep, it gets a little messy, watching the oil squirt out of different places with the oil pan dropped! It's interesting, seeing just how much oil one loose bearing can leak!
Jerry

I would go with the high volume pump, but your not hurting anything. Flickering oil lights were just a way of life 50 years ago and oil is so much better today. But this is 2008 and we don't expect oil pressure to drop that much. Put in a high volume pump, don't worry that you have done any damage so far, and drive and enjoy your vehicle.

Hot Lincon has it right bet I would agree with crenwelge??? what kinda handle is that. Just run it and dont worry about the whole thing. My truck has been doing that for years.

Hey now, I drive around all over town with my 15 pounds of oil pressure! 6-7 at an idle. Sweet...