Hey Gang. First off I have a 355 sbc swap that I did. Me and a friend did a fresh rebuild on the 355 before hand. I hooked up the stock oil pressure gauge when we dropped it in and it always seemed to have low oil pressure to me. We used a high volume oil pump from summit. I have a stock oil pan on it. What I did was finally change out the stock oil gauge for a mechanical one because I wasn't sure if the stock one was reading correctly and when I did that the mechanical gauge shows no oil pressure at idle. When given a little bit of a rev the pressure increases to around 20 or so when reved a little higher it goes to 40 then starts dropping to 20 and fluctuating up and down. I have been trying to do some research on it and I have read that you cant use a high volume pump with a stock pan, because the pump is longer. I honestly can't remember what pick up we used since we did the rebuild winter before last. I will be yanking the pan off in the next week or so and either replacing the pan/pump/pickup or at least trying to see whats going on. I just recently replaced that gauge and I have driven the car to shows and got on it quite a few times and I didnt even know that my oil pressure was really that bad up untill switching the gauge. Hell I was thinking the stock one was actually reading under what I really had lol. I also read somewhere that you shouldn't weld the pickup tube with just any welder and I dont weld myself, but my friend did weld it on for me and I also thought that maybe he got it to hot and screwed the return part of the pump? I also read that people often install a high volume oil pump and use the stock pick up and bolt the pan up with that pick up and as I said earlier I cant for the life of me remember what pick up we used. So it very well may have been stock. So if that is the case once I yank the pan off and look I read that it would only leave about 1/8" from the bottom of the pan and any oil to pump cavitates and fails to pump oil no matter how much oil is over the pick up. I remember we were checking clearance at one point, but honestly neither one of us can remember what it was at. I just thought I would throw this up in here to try and get some opinions and see if anyone else actually has used a stock pick up with a HV pump (wont know if thats actually what I did till I get my pan off) and if anyone has used a stock pan with a HV pump. Or maybe someone might have a diffrent diagnoses of what might be going on? Thanks for any input. Also as far as an aftermarket deeper pan anyone have a link to one that would fit under our cars with a 350 chevy for a decent price?

 

Well I took a ride out to Summit and picked up a new oil pump and pickup. Got some relatives coming into town tomorrow so I wont be able to get the pan off till sometime in the coming week. What I did pick up from Summit though I hope will fix my issues with the pressure. I got a Moroso Oil Pump and Kit http://www.summitracing.com/parts/MOR-22144/

I read the book on it and it states that this will work for the stock pan. So once I get the pan off and get it changed out I will let ya know how it works out.

 

Well got the new oil pump in pan back on and still have low oil pressure. Though it is better than before. At least now it doesn't drop once the motor is reved. I have very little at idle ( like 5) while cruising its like 20 and when I get on it its around 40 ish. Before when i got on it the pressure would hit close to 40 then drop and fluctuate. Now I am at a loss. Should I go to a HP/HV pump? If I do then I will need a bigger oil pan than the stock one correct? With the way that crossmember looks under there any info on a pan that would fit would be great.

 

OK so I started to research some of the issues and what I think might be the culprit is bearing clearance. Now my question is if I have a high volume pump and a high pressure pump with that help? I know the pump actually doesn't create pressure just flow. the return spring is what controls the pressure. So if I used a high pressure pump wouldn't it still bleed off the bearing clearances and still not help the pressure?

Also if I wanted to adjust the clearance is there any way to do that with the motor still in? or am I gonna have to take it back out to get this oil pressure fixed? I hate to have to pull this thing back out.

 

OK so what I am thinking of doing is putting g the washers in the oil pump return to increase pressure. My only question then would be is the pan size. Do I still have to increase the pan size?

 

In your first post , you mention that you and a friend "rebuilt" this engine . Now , since a rebuild consists of checking all wearing surfaces for excessive wear and excessive clearance due to that wear , and then rectifying any out of tolerance clearances , you should have record somewhere of the written measurements you took while determining whether the wear was within acceptable limits , correct ? Those measurements are the key to whether this is a bearing clearance problem or not . You measure the bearing journal , and then the bearing opening , and do the math to figure out the difference . Too much difference IS the excessive clearance that can result in low oil pressure , and this clearance is measured in the thousandths of an inch .

Please tell me you DID measure this super critical clearance and didn't just slap new bearing shells onto a used crankshaft and call it "rebuilt" , right ? Even if you had the crank milled "ten under (.010 of an inch)" and bought .010 over bearing shells , ya STILL gotta do the measurements as manufacturing processes are seldom 100% accurate . Some take direct measurements of the surfaces using vernier calipers and other precision measuring instruments and do the math , this is the method I prefer . Some use the "plastigauge" method , which produces acceptable results in it's own right . But either way , this clearance needs to be verified during rebuild or you WILL , 100% certainly , end up with an engine whose' bearings are too loose or too tight

 

Yes we did check clearances with a pastigauge. We actually double checked if I remember correctly.

 

What were going to do is put in a few washers at the spring to increase pressure like they do in the loose race engines and go from there.

 

Heres an update on my situation just in case anyone cares :P or has a similiar problem and can't figure it out. I have gotten 2 washers put in the return of the oil pump with the result being no change in oil pressure. So now what I plan on doing is yanking this motor back out and checking Galley plugs and possibly cam bearings if the Galley plugs aren't the issue, but damn-it I am determined to figure this out lol. Cant be taking my TA to Norwalk with no oil pressure!

 

Did you put the little hidden freeze plug in the block under the rear main cap?

 

could be the oil diversion plug missing or installed wrong. theres some pics and a diagram about half way down the page on this link. hope it helps.
http://forums.chevyhiperformance.com...sure-question/

 

I had a local guy re-do the block as far as Boring it out and installing freeze plugs and cam bearings. He also did the crank and I also purchased the crank bearings through him so I would have the proper ones. As far as the one under the rear main I honestly can't remember if we checked that one. I will find out once I get this thing out of the car. I have a cookout carshow to take it to on the 15th of June then I will be pulling the motor and will dive into finding out the problem then. Thanks for the replies and that link with the pics. I will reply once I find out the problem.

 

I know it's a little late but the spring in the pump only bypasses oil to the pan when the pressure gets OVER the spring's rated pressure so putting the washers in there did nothing as the system pressure never even got near the (probably) 60-ish PSI of the spring that was in there...

You're right in that there is something causing the oil to be able to "flow out" of the system faster than the pump can really pump it and build pressure - Main and rod bearing clearances are first things to usually go so double-check them when you've got it out next time. Also that galley plug is good to check, as well as checking for a cam bearing that may have walked out or gotten gouged real bad during it's installation or the install of the cam.

 

Just to clarify Oil Pump don't create presure they create Volume. The presure are created by the restrictions on the pasages of the engine and you controlle that with the clearence of the berrings. and installing the plugs in the right places.

Have you tried to install an actual gage in place of the Sensor? to read the persice mesure? maybe the sensor is not good.

 

I thought I would give those washers a try before yanking the motor back out. I do remember us checking galley plugs by timing chain, but I definetly don't remember checking the one under the rear cap. When we first fired the motor we hooked up the stock gauge and it was around 20 or so at idle and we thought that was low, but not to bad. We did take into consideration that the gauge is probably off a bit since its stock. What I did think though was once we hooked up the more accurate mechanical aftermarket gauge that I was thinking we would have seen more pressure when in reality we showed less. So yeah Carattini we tried the gauge and yes I knew that about the pump creating volume. I have been doing as much research as possible and once I yank the motor back out I will better know what may be the the culprit and thanks to all of your replies and helping me in doing some of the research and pointing me in the right directions. Thanks again. I will take a little video of the gauges pressure and post it to show what its actually doing.

 

Here is a little video of the pressure.
http://s236.photobucket.com/user/gir...b58ba.mp4.html

 

Well I got the motor out and tore down this weekend. We took a old distributor we made to use for priming the oil and put a drill on it to see what was going on and the front oil galley was leaking a small amount into the timing chain, but it didnt seem to be leaking enough to cause no oil pressure at idle. The plug was in under the rear main cap. So no issue there. we also had a gauge hooked up while we were doing the priming thing and we used a finger to close off the front galley plug with no increase in pressure once the minute amount of oil was not coming through the galley plug anymore with no change to oil pressure on the gauge. Checked all crank bearings they all looked great with nice wear and since we did plastigauge them we think they are fine. So then we pulled the cam and the front cam bearing looks pretty marred and I dont know if that is normal or not. It was getting late so we didnt get a chance to really look inside there at all the cam bearings. What I am gonna do is just start from scratch on this thing and take it to a shop and have them mic everything out and put new cam bearings in and all that good stuff because I dont wanna have to do all this again lol. We did also find a lifter that was blown apart so it was a good thing we took it apart.

 

Depending on what happened to the lifter that could cause a massive oil 'leak' inside the engine and low oil pressure as the lifters are fed with pressurized oil and if one popped out or something it could leak a lot of oil right down to the pan and cause low pressure.

Got pics of the bearings, bad lifter, etc?

 

I work crappy hours so I will get a few pics when I make it back over to the garage. I aint buyin the lifter being the problem though. I am still gonna have the block gone over again. I dont wanna pull this thing back out again for the same problem. The lifter could be the problem. I aint saying it isnt, but I wouldnt be happy unless its gone over completely while I have it out. Once I get this thing ready to go back in I do wanna get a better oil pan than the stamped stock pan. Can anyone point me to one that will fit with our crossmember? I aint to worried about a Y-pipe being in the way I can always reroute that if need be, but I would have to get one that fits with our crossmember.

 

Well took it apart further and found a spun front cam bearing. Attached a photo below. I know one of the galley plugs is out to. We took that one out because it was leaking slightly. Gonna tap those holes and plug them like the rear ones.

 

I was gona say low oil pressure is a classic cam bearing problem. my oil pressure was low (I need new cam bearing or something) but until I can get to it I use 20w-50, fixes the low pressure problem right away, but it is just a temp. fix

 

Well the guy thats putting in my new cam bearings said that I didnt have a spun cam bearing and that was how it was installed from the last guy. He also said that the holes arent supposed to be lined up and that wouldnt have caused my oil pressure problem. So hmm maybe it did have something to do with the lifter. I only drive my car in the summer and I always use 20/50 in it. He also checked all the clearances for me and said everything looked good. I trust the guy I have looking at it because he has a 6 second car lol. So I started doing a little research on the cam bearing holes.
http://www.chevelles.com/forums/showthread.php?t=191727

So yeah maybe it was the lifter as well as that front oil galley leaking a tad. He tapped those front holes for me and gave me some threaded plugs for them.

 

I cant wait to get this thing back together. Finishing up on cleaning up the engine compartment a little more. I also picked up a set of Trick Flow 202 aluminum twisted wedge heads. I thought something was wrong with them when I first seen them not being in a straight line like normal sbc heads. Hence the twisted wedge I guess lol. Also gonna put in a hydraulic roller cam and lifters. .549 intake .544 exhaust. So yeah a little stocked about. Definitely gonna check oil pressure while we have it still on the stand this time around lol.