oil pressure problem
 

I have a 434 sbc. with a motown block. i ran this car last year and when i let off at the end of the track my oil pressure would drop to 10lbs. so i put a new pump in this year with a copper gasket and it wouldnt hardly carry any pressure at all when it warmed up. so i put another new pump in and removed the gasket. same problem still. i was using a bolt on pump screen, so i removed this pump and brazed the screen. i dont think its sealed 100% but its prob pretty close. so today i take it out and it will carry 60lbs of pressure for a good while, if i get on it or cont. quick reving it it will drop down to almost 0 then climb back up to 20lbs and may hit 40 but if i rev on it it drops down as soon as i let off the throttle. im stumped. i run 20/w50 lucas oil with a wix racing filter. and yes ive tried a different gauge. any help will be greatly appreciated

Re: oil pressure problem
 

A couple of things come to mind after reading your post.
1. Have you tried a different oil filter. I know it sounds crazy but there are people who let a car sit all winter without changing the oil and filter. If the filter was collapsed and you never changed it just pumps well you get the idea
2. Did you remove the bypass spring before you brazed the pickup on? If it gets too much heat while brazing the inlet on it will get weak and can cause low oil pressure
3. Define pretty close. If there is a leak couldnt it pull air instead of oil? I could be wrong but I would think it would be easier to pull air through a gap than 20W50 through the pick up.
4. How old is the engine? could it have been built with loose bearing clearances and now that its got some wear on it its way too loose. Sounds kind of like when the oil is cold its ok but when the oil gets hot and thins out a bit its loosing oil pressure couldnt that be a sign of too much clearnace somewhere.
I am no engine builder by any means but thought I would throw it on here. I am sure if I am a idiot someone will tell you in a minute. LOL

Re: oil pressure problem
 

the engine has prob 75 passes on it. it is a new filter just put it on at the initial start up this year. no the bypass spring was still in it when we brazed it. it is the same problem as before the brazing though. i ordered a new pump from competition products with a bolt on pick up i guess i will try this to. im sure it would suck air easier than pulling the oil. when we brazed it we sprayed some soapy water and shot air into the pump to see how well it was sealed and it only had a couple of small leaks. but im for sure not ruling that out. im honestly stumped.

Re: oil pressure problem
 

Have you pulled some caps and looked at the rods and mains to see how they look and check some clearances? Another thing that comes to mind is this scenario.

Something was not right from the get go (IE not enoughf oil in the pan, pan that could not controll the oil ect) So when you crossed the finish line the pan was already low on oil or the pan could not controll it. You hit the brakes to slow down and whats in the pan goes forward away from the pickup uncovering it and oil pressure went low and hurt one or more bearings.

Re: oil pressure problem
 

I have had exactly what Rob is desribing. It hurt 1 rod bearing and was very low on pressure once warm at a idle. Never made any noise just lost oil pressure and this on a car with exhaust so I would have heard it knocking. When I dropped the pan the bearings all looked fine but one had lost it's tension in the cap, I almost reused it it looked that good. I put new bearings in with the old pump and it was back to idling hot at 40psi in gear again just new and went all last season like that.

Re: oil pressure problem
 

X2

Yeah, I'd be pulling some caps and checking bearings and crank. I had a Z28 that did that very same thing about 3 months after a rebuild with a new crank. I pulled the motor out and apparently the crank had not been tuftrided. It looked like it had 200,000 miles on it. GM warrantied the crank and I was back in business.

Re: oil pressure problem
 

i checked the bearings over the winter, just visually when i put the first new pump in. they all still looked brand new. i didnt get this motor in my car until late in the season and it still looked great.

Re: oil pressure problem
 

You might want to check the cam bearings. Have seen the same problem after it warms up goes low on pressure. Phil

Re: oil pressure problem
 

cut the old filter open and see whats in it. See If there is bearing material in it. If there is pull it apart and start looking for where it came from. If a cam bearing was coming apart there would be some in the filter.

Re: oil pressure problem
 

Since you're pulling the pan again anyways I would plastigauge all the bearings. High (good) pressure while cold falling off to little pressure warm is a sure sign of excess bearing clearance.

Re: oil pressure problem
 

This might not solve your problem but here are two things you might think about. # 1 Do you have the proper gap between the pick-up and the bottom of the pan ? #2 Do you have a couple of coils in your oil pressure line going to your gauge? Kenney Kelley

Re: oil pressure problem
 

What kind of oil pan do you have...some oil pans are really bad and will let the oil go to the front of the pan as soon as you let off and hit the brakes...how many quarts does it hold and how many do you use?...just trying to eliminate things...Luke

Re: oil pressure problem
 

ok heres what ive found. we took the drain plug out of the oil pan. ran a clear 1/4" hose into a threaded adapter and installed it where drain plug goes, measured normal oil level, then i started it up and kept quick reving it to get the pressure to drop. when the pressure dropped the oil level in the tube droped to. when we measured the difference its only leaving a 1/4" of oil in the pan which is how far the pickup is off the bottom. it also starts pumping air into gauge. ( we put a clear tube on it to) so. Im going to throw a std volume pump on it. and remove the trap doors in my oil pan. if that dosnt work i will remove the plugs out of the lifter valley. at least it appears to be a cheap fix. not bearings.

Re: oil pressure problem
 

High volume pump? There might be your problem it sounds like its sucking the pan dry faster than the oil can return. I dont know about removing the trap doors though. thier job is to keep the oil in the sump on deceleration to prevent uncovering the pickup just make sure they are working properly ( IE they are not stuck shut). You might just fix one problem and create another if you completely remove them. If it were me I would try one thing at a time untill you figure it out. And it sounds like you are doing this in the car. But if you have it on a stand dont roll the engine upside down and then install the pan. Reason being on some pans it will cause the trap doors to open and stick. Moroso and others recomend the eninge be sitting up right when the pan is installed to prevent this. Good luck and let us know what you find.

Re: oil pressure problem
 

i already pulled the doors out. i really think that as sticky as the lucas oil is it was holding the doors a little. i went ahead and removed them because its so hard to drop the pan on this car with it in. i still have plugs in the lifter valley if this dosnt cure it i guess i will remove some of them or go to a thinner oil. i really think the std pump will help a lot if not fix completely

Re: oil pressure problem
 

Your original problem sounded like oil getting away from pickup,Your next problem sounds familiar,you did'nt say what pump you put in when you changed,but I ran into problems w/ 3/4 pickup hex drive pumps that melling has,they idle good and drop pressure when rev'd.I sold several and everyone has been took back out& replaced for that reason,replaced with 5/8 pickup HV melling select pump and fixed it.
It acted like cavatation,but could'nt get to stop tried different pickups,clearances on pickup,overfill w/oil, just switched to 5/8 pickup pump and fixed everytime.
Years ago we used run 3/4 pickup bbc pumps in sbc without any problems,so I don't know why we could'nt get those pumps to work,I remember comparing pumps and could see no difference other than pickup diameter.
Mike Taylor 3601

Re: oil pressure problem
 

Take those nice screens out of the drain backs in the block as well as the vent pipes you screwed in the lifter valley. I bet it has a vac pump on it too. The oil rope that builds up around the rotating assy can keep the oil out of the sump. Get a good windage tray & pan combination on it that scrapes the oil back to the sump.
Those long stroke SBC's need the "right" pan and windage control.
Keep in mind your 434 has a lot more movement above the oil pickup than a 327 or 350.

Re: oil pressure problem
 

Yall better listen to Adger
I just got two 434 SBC off my dyno. Both wet sump, one with vacuum pump other without. Customer furnished both oil pan systems. Both blowed a hole in the oil as RPM went up. We dont run any screens as we have seen this problem a number of years ago. Ya got to get the oil off that rotating assembly. Spend time getting oil back too sump. Ya better look at windage, cause it is for real, both above the crank and below the crank.
reed

Re: oil pressure problem
 

my pan has a scraper on it. its for my setup. i havnt tried a windage tray though

Re: oil pressure problem
 

Clarification - A loss of clamp load does not "spin bearings". When you see a spun bearing, you also see it extrude out from the sides. This is not because something was loose, but because everything was tight. In other words, the loose cap and spun bearing is a symptom of a larger problem.

A loss of clamp load will result in a bearing that retains its original width, but flattens out and has "bite / chomp" type witness marks. This is from the cyclic load on the rod journal...open, close, open, close...bite, chomp, bote, chomp....

Re: oil pressure problem
 

I can not imagine anybody putting a high volume oil pump in a SBC. Don't know why they even make them.

Re: oil pressure problem
 

What happens if you put another half quart or more above " measured normal oil level"?

Re: oil pressure problem
 

I agree with the others....could be a pickup to pan clearance issue or a windage issue. Another thing that wasnt mentioned is this...I have seen pipe pugs with tiny holes drilled in them for BBC to oil the chain....is it possible you didnt install an oil plug or you have put one of thses plugs with the tiny hole in it by accident?

If u have to try a new pump get a Mellings M55A pump...the best afordable alternative to a high dollar race pump. Thats what I have in my 377 Street engine with a Mowtown block and crossed drilled crank.....60+ psi of oil pressure and ive turned it well past 9000 RPM.

Also check the clearance between the front main cap and the timing cover...if its too tight oil will get trapped in the cover and not drain back to the pan. Mowtown blocks have a super thick main cap and some aluminum covers (even tin covers) come close to the cap. I know on a jesel front cover we actually had to machine a relief in the cap and the cover to allow the oil to pass by.

I also know that my oil pressure is as responsive as my tach.....when I rev it up the oil pressure moves just as quick but I always thought that was because of the priority oiling built into the block. Also not sure what pan you are running but there is a 1/4 pipe tap on the pan rail that is not level with the pan rail...im assuming if you didnt have this plugged you would have zero oil pressure but who knows. It doesnt go in all the way and the pipe plug actually needs to be ground down a bit to get the pan on...ive seen some big "bath tub" superstock pans that would cover this but im just brainstorming. Hopefully you can figure this out. One more thing...Usually if the filter is colapsed the oil pressure gets locked at a certain psi or is very sluggish and low...Ive had this happen with a Fram and a Quakerstate filter.....switched to a wix race filter and now I put them on everything.