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Old 03-10-2009, 08:34 PM
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Rebuilt 355-oil problems

I recently had a good motor shop put a short block back together for me, and I put the top end on. here is a few specs on the motor.
-bored and cleaned to a 355
-all bearing and bottom end parts new
-new vortec heads 64cc
-new comp extream 4x4 cam
-flat top pistons (around 10.2:1 comp.)
-whole motor new.
The problem I am having is with oil pressure. The entire bottom end is new, clean and bored, new oil pump(stock) and stock pan. I have a mechanical oil gauge with the plastic tube line. I made sure there are no kinks in the line. At start up I will read between 40 to 65 pounds at idle and driving. this is when the motor is cold. I noticed that the oil pressure will remain high until i come to a stop where the motor idles down then it will read less than 10 at idle. Then cruise around 30 to 35 pounds, this is after the motor is at operating temp. I had air in the line and I tried bleeding the line but not sure if I bleed it enough or the right way. I took the line off at the gauge and held the motor at different rpm's until solid flow of oil and connected line back into gauge while oil is still flowing. Do i need to fill the gauge with oil before i reconnect the line? i dont hear any knock or ticks by the way. I am running heavy weight oil for break in period. changing the oil and filter for the first time in a few days. After i rule out the gauge I will pull the valve covers and oil pan off. Ive read into some other threads about this problem but wanted to ask myself. Any ideas? Thanks in advance for your time.

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Old 03-10-2009, 10:09 PM
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First off I would suggest getting rid of the plastic line and go with copper. You won't regret it but it will not fix your situation. It will only give you peace of mind. Most motors will operate at different pressures once warmed up and while 10 psi at idle is a little low, it's not bad either. Anything under that I would get worried. There are a number of things that can cause this, one is being worn bearings but since they are new and if the shop used good judgement when building it, you can almost rule that out. Before you pull the motor apart, replace the gauge (much cheaper) and see if that fixes it. Also, if you used a Fram oil filter, get rid of that junk and go with a $6.00 Wix or similar quality filter to be on the safe side. My BBC had NO oil pressure at startup unless I pulled the distributor and primed it first using a Fram filter (scary). I replaced it with a Wix and now instant 70 psi at startup. Just another thing for peace of mind.
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Old 03-11-2009, 03:29 AM
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Drop the pan & check the pickup & make sure it's adjusted ok from the bottom of the pan
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Old 03-11-2009, 04:47 PM
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Yea I have my old gauges and I plan on hooking it back up after I change the oil and filter this week. From everything I have read on this site I see that everyone thinks fram filters are junk, thats good to know. I will change oil and filter, see if that fixes the problem and if not i will hook the old gauges back up since they were working fine before. If this does not fix the problem i will pull the pan and check. If I have to pull the pan I may take it back to the motor shop since it is still under warrenty. Thanks for the posts ill keep ya all updated
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Old 03-12-2009, 09:38 AM
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Fram oil filters junk? News to me, but what do I know. Sounds like "Quaker State oil has water in it" that went around for awhile.

If you take the pan off, you might want to check that the oil pump's pressure relief is moving freely. A partially hung relief can cause what you describe.

As can the bypass that's built into the filter mount that bolts to the block. I always plug it off w/a pipe plug. At least it can be checked or removed and plugged w/o removing the pan- just take the filter off and unscrew the two bolts that secure it. Check that the fiber disc isn't cracked or chipped and that there's sufficient spring pressure. And that there's no junk caught under it.

Likely you just have upper-limit rod/main bearing clearances, and/or upper-limit rod side clearances. This can bleed off a significant amount of pressure. Like was said earlier, 10psi hot at idle is low but not cause for too much concern. As long as the pressure comes up immediately you should be OK.

But I would be wondering why- just like you!

BTW, air in the oil pressure gage line has no material effect on the gage reading.
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Old 03-12-2009, 09:53 AM
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I would check your oil pressure gauge before I get too concerned, I have had faulty gauges give bad readings, the plastic line can get crushed so tightly by the brass Ferrel on the compression fitting it can alter readings! I personally run Fram filters in everything I own, and my silverado has 150,000 trouble free miles on it, my wife's dodge magnum with the hemi has 77,000 trouble free miles,I prefill all my filters with oil before installing them(-as able -if the application has an upside down mount you can't!!) to prevent dry starts, but I would seriously doubt the Fram filter is the reason your oil pressure reads 10# at idle!!
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Old 03-12-2009, 09:57 AM
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check this out

You said that they replaced all the bottom end bearings. Did they replace the cam bearings as well? Have seen alot of people with this same problem and were mad because they replaced "all the bearings". Loose cam bearings won't chatter or give anything to tell you that they are loose except low oil pressure until they get really bad. If they were replaced then like they said i would check the over pressure bypass in the pump and make sure that the wafer were the oil filter goes is not cracked or hung up or missing. Just to confirm, you said 355. If you used a 400 block and 350 crank (377 destroke) there are a few other things that it could be as well. Good luck
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Old 03-18-2009, 10:03 PM
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Alright well have changed the oil and filter. this didnt have any effect on my oil pressure being low. i pretty much ruled out the gauges because i took the valve covers off and saw that there was almost no oil getting to the heads, it was barely oozing out of the push rods and when i gave it gas it didnt change that much. When i did this the motor was still a little warm and reading around 20 pounds at idle. as i said before the motor has no pressure on the gauge at idle when completely warmed up. today i pulled the valve covers off when the motor was cold. the truck shows over 40 pounds when cold but there was absolutely no oil coming to the heads. The motor is cold and at 40 pounds - no oil. when it is warmed up and showing almost no pressure the oil barely oozes out to the heads. The oil pressure gauge is on the top of the block behind the intake so there is obviously some oil getting the the top end. I have new lifters and pushrods in the motor from comp cams. it is hydrolic flat tappet. Any ideas?????
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Old 03-18-2009, 11:25 PM
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I had a small block that did that... it eventually destroyed the valve train from the lack of oil.. never did figure out why.. it spun a rod bearing, and the cylinder walls were badly scored and the block was already .030 over.. so I sent it up the river to the metal recycler
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Old 03-19-2009, 12:41 AM
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You don't mention what distributor you're running but if it's equipped w/o-rings (like some MSD) and the block wasn't chamfered to allow the o-rings to pass, an internal oil leak could have been created.

A loose/missing gallery plug (some are "hidden") is another possibility.
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Old 03-19-2009, 12:50 AM
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my block wasn't chamfered... (never overbored, so I assume it's not chamfered) and I dropped an MSD pro Billet in with the o-rings and it makes awesome oil pressure

40psi @ 3000 rpm.. idles on 19psi @ 700 rpm after an hour on the freeway *shrug* (stock type oil pump)
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Old 03-19-2009, 12:58 AM
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The chamfer Iím talking about isnít the bores, itís HERE, page 5.

Damaging the o-rings might only happen 1 out of a hundred- but if you're that 1...
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Old 03-19-2009, 01:37 AM
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Quote:
Originally Posted by cobalt327
The chamfer Iím talking about isnít the bores, itís HERE, page 5.

Damaging the o-rings might only happen 1 out of a hundred- but if you're that 1...
The o rings are optional when installing the MSD - they are not necessary. The instructions state that if you use them you should chamfer the hole.
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Old 03-19-2009, 08:00 AM
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Quote:
Originally Posted by Chevy355
I recently had a good motor shop put a short block back together for me, and I put the top end on. here is a few specs on the motor.
-bored and cleaned to a 355
-all bearing and bottom end parts new
-new vortec heads 64cc
-new comp extream 4x4 cam
-flat top pistons (around 10.2:1 comp.)
-whole motor new.
The problem I am having is with oil pressure. The entire bottom end is new, clean and bored, new oil pump(stock) and stock pan. I have a mechanical oil gauge with the plastic tube line. I made sure there are no kinks in the line. At start up I will read between 40 to 65 pounds at idle and driving. this is when the motor is cold. I noticed that the oil pressure will remain high until i come to a stop where the motor idles down then it will read less than 10 at idle. Then cruise around 30 to 35 pounds, this is after the motor is at operating temp. I had air in the line and I tried bleeding the line but not sure if I bleed it enough or the right way. I took the line off at the gauge and held the motor at different rpm's until solid flow of oil and connected line back into gauge while oil is still flowing. Do i need to fill the gauge with oil before i reconnect the line? i dont hear any knock or ticks by the way. I am running heavy weight oil for break in period. changing the oil and filter for the first time in a few days. After i rule out the gauge I will pull the valve covers and oil pan off. Ive read into some other threads about this problem but wanted to ask myself. Any ideas? Thanks in advance for your time.
The general rule of thumb for a Chevrolet is 10 psi of oil pressure per 1000 rpm. Anything less and you're asking for trouble. Anything more is a bonus. What does the shop tell you that built your engine? You might consider taking it back to them before it's too late.
ZAPPER
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Old 03-19-2009, 03:20 PM
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The distributer i have is an Accel Hei supercoil. i am planning on getting a new one very soon the old motor i had would fall on its face when i put my foot in it so that is why i have the motor i have now. when i took the old motor apart the cam had a tooth chiped off on it where the distributer rides. the bottom end of the distributer didnt appear damaged so i put it in my new motor. The new motor falls on its face and backfires. we tried timing it and never could get it right got a new vacume advance and all. the truck starts and runs fine unless i put my foot in it or let out of the gas and let the gears take it down then it backfires. so i plan on getting a new distributer very soon. the truck starts and runs so i dont think that would stop all oil getting to the heads
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