Hi guys, I got this oil pressure problem in my 383 like you wouldn't believe and I need any input possible. Heres what it does.

At idle, 25 psi, at cruiseing speed, 60 psi. It goes right up when I get up to speed, no roblem there. The probelm I have is when I step into it half wayish or full throttle, it goes down to 30 to 40 psi. If I stay into it until 3rd, it it down to like 25 psi. I can try to get into it slowly and it will still drop, if I let off a sec, it will come back up and then I step into it and it goes down again.

Here's what I've done so far.
Back in Nov. the problem started, so I replaced the pump to 3/8's off the pan(M55HV, melling). No good. Replaced the main and rod bearings, no good. Pluged the oil adapter bypass, replace the oil gauage, checked the dist shaft, ran an extra quart of oil, run a pcv set up, and all no good. I just got it back from the engine builder and it is a completly fresh block. Magnafluxed the crank, pressure tested the block, resized the rods, turned the crank .010 under, line honed the mains, honed the bores, new bearing all around, frezze plugs, all of it! Got the engine back in and running today and it is still doing the same thing! This motor has been in my camaro since april and haven't had this problem until last nov.

I've had a few people tell me its my pan, why didn't it do it when I first got it in? Had people say its the high volume pump, but never had the problem before until last nov. I got a friend that has the exact same bottom end. I mean same pump, same oil pan even and he's not having this problem. So where's the problem? I can tell you this much, I'm not pulling this motor unless another ones replacing it. I'm stump! Sorry for the rage, but I'm to the very end of my nerves. I think that it.

Thanks,
Michael

[This message has been edited by Old School (edited 02-14-2003).]

Wish I could help-I've got a 350 with similar problems. I haven't torn it down yet to examine the internals. It's had the same problem for 3 y ears now, and still runs fine-80PSI cold, 55 warm running down the road, but when accelerating, drops to around 20-25. Someone told me this could be something flexing causing the crank clearances to open up, but I figure I'd be knocking by now if that was the case. Oh well, run it till it goes-I need a Big Block http://www.chevelles.com/forum/smile.gif

------------------
Sid Coleman, 71 Ragtop
TC (Gold) #174, MCC #347,
Aces #5457, N3JHV@bellatlantic.net

that is amazing,after all of that work, here is a long shot, try disconnecting the oil line from the back of the oil gauge put your finger over the open end of the hose and basicaly burp all of the air out of the gauge and oil line by running the engine, of course this will leak oil out and make a mess but I had good luck with this on my truck I had an air bubble that would not vent and I've had no problem since- just a thought

Tony Snyder
65 Malibu SS
72 El Camino

I bled my line from the inside of the car, luckily w/out making a mess. Anyone else?

------------------
Sid Coleman, 71 Ragtop
TC (Gold) #174, MCC #347,
Aces #5457, N3JHV@bellatlantic.net

Michael - is the pattern the same cold as well as warm? I was thinking bearing clearences in the mains if so cold you'll find the problem is lessoned or not present. You also haven't mentioned viscosity of oil used. You might try dumping in some 50wt just to help trouble shoot. I think it's mechanical...

As for bleading the oil line to the pressure gauge my opinion is it doesn't matter if there are air bubbles in the line. You could use the same gauge to measure air pressure or oil pressure. Also if you hook the line to the top of the block by the dist some of the oil in the line is going to drain back to the pan when you shut the engine down and you'll get more air back in the line when you fire it back up. The line would have to be extend to below the level of oil in the pan to avoid this...

------------------
...Dennis
The '69 (http://chevelles.com/showroom/ww.jpg), the '96 (http://www.camaroslimited.com/graphics/memcars/96ss.jpg) and The El Camino (http://chevelles.com/showroom/DjD/dsc00016.jpg)
Team Camaro (http://www.camaros.net)
Camaros Limited (http://www.camaroslimited.com)

The oil I have been using is 10-40w. But for right now I am using 10-30w for the break in. The pressure drop happens when its hot or cold. Just when its cold, it hit like 85psi and then drops to 60psi. Of course when it gets hot, then its like 60-65 psi and then 35ish psi.

Michael

------------------
My 75 Camaro (http://www.geocities.com/oldschoolchevy1975/oldschool.html)
383 with AFR heads.
Old School for life!!!

Again, same symptons as I have. Even noticed it dropping off once or twice as I went up hill, and thought it was related to a possible low oil level or sloshing in the pan. Mine also happens cold or hot.

Wonder if the blocks are the same? I'm runnin an 89 350 4 bolt main block from a 1 ton pickup, supposedly a steel crank too.

Anyone else chime in on this? I've always been bugged about this problem.

------------------
Sid Coleman, 71 Ragtop
TC (Gold) #174, MCC #347,
Aces #5457, N3JHV@bellatlantic.net

I've been running a 383 for about 8 years now. I'm using a 4 bolt block, "turned down" 400 crank, stock 5.7 rods w/ good bolts, etc. Built on a very tight budget, back when "stroker" stuff was really expensive.

I've never experienced the above scenario. The only guages in the car are a Tach and Oil pressure, and I'm fanatical about watching them.

I'm also using a Melling H/V pump, stock pickup, home built/cut crank scraper, and the pan is off a '79 Malibu 305. During assy. did you do the "Play-Doh" trick (I posted it in Tips & Tricks)? Just for grins put an extra 1/2 qt. of oil in it and make a run. The extra shouldn't pose a windage problem for this short time.

I've always wondered just how accurate a stick of metal, in 25 million applications, made by 15 thousand suppliers, could be. You might just be sucking air, due to the inaccuracy of the dipstick, thickness of your pan gasket, crank scraper (if used) etc.


------------------
'64 El Camino
383 - TH-350 - 12bolt - 4wh pwr discs
Bedded down for the Winter.

I believe my block is a 90 4 bolt main, non roller, one piece main seal block. Not sure what it came out of.

"The Play doo" trick, are you meaning the pick-up depth? I had it set to 3/8's and then tach welded.

I have tried the 1/2 quart thing and didn't help. I haven't tried it with the fresh short block, but I will try it again. I am going to try 50w oil and another brand filter to rule out that and see if the heavier oil makes a difference. I will post back on what happens tomorrow.

Michael

Gee, wonder if the same oil pump is used in the pre-86 blocks to the post 86? That's the only similarity I've seen so far.

I also replaced the stock pump with a hv/hp from autozone.

------------------
Sid Coleman, 71 Ragtop
TC (Gold) #174, MCC #347,
Aces #5457, N3JHV@bellatlantic.net

Ok, guys, I changed the oil to 50w and a different brand oil filter and its still dropping. Infact, its drops even worse, to like 20 psi. I am going to drain the oil back and and put in 30w again.

I went today and bought a new oil pressure gauage and tried that again and the results were the same.

Does the pressure drops being worse with the 50w oil tell me anything?

Michael

This is wierd! Pump Cavitation? With the thicker oil it can't pull enough through the pickup fast enough to stay primed/full? It may sound goofy, but what about going to a lighter weight? As long as there's a pressurized supply of oil, the bearings should life.

I'm thinking out loud here, it's your choice.

------------------
'64 El Camino
383 - TH-350 - 12bolt - 4wh pwr discs
Bedded down for the Winter.

I here what your saying, I am diffently going back with the 30w oil. The psi wasn't near as bad. I am thinking about getting a oil pump that has grooves in for anit-cavitation kinda thing. So far, thats the only think left to try besides yanking the thing out and going Big Block. LOL

Michael

Please keep us posted. I'm wondering about changing my oil to 0w30 in mine, just to see if there's a difference.

Thanks for sharing!!

------------------
Sid Coleman, 71 Ragtop
TC (Gold) #174, MCC #347,
Aces #5457, N3JHV@bellatlantic.net

i have seen this a couple of times the end play on the crankshaft. thrust juornal is bad and the other was bad camshaft bearings are wrong clearances. just a couple things i have seen. and try going back to standard oil pump it uses less horsepower most engines on the street dont need hv pumps. and 30-45 is what you should see on a hot engine

Michael,

Were any modifications made to the top of the block to restrict the flow of oil back to the pan? I experienced a similar problem on a 400 SB when I plugged the valley holes above the cam and placed screens on the oil drain backs on top of the block. This was to prevent any debris from getting back to the pan if something broke top side. My pressure would drop to almost zero and I got caught up in similar try this and that activities (pump, pick-up, bearing check, etc.). I just back tracked and realized the change points. I removed the restrictor plugs and screens at the top end and the problem went away.

I'm not sure this is what could be contributing to your problem, but worth a try.

------------------
Ed C.
------------------------
70SS 396/350 4speed
70 LS6 4speed under resto.
00 C5 6speed

I have been asked to see if I have made any changes when this problem started and I can't think of any.

Heres some thougth, the pressure doesn't drop when I am in park/neutral(reving it to the moon). It only seems to drop when there's a load or I am moving, so I thought to maybe try and powerbrak the car, so its under a load, but the car isn't moving. This would tell me something right? Tell me that my shirt block is messed up somewhere? I would be highly p'ed off ifs it the short block since I just got it worked on.

Michael

Years ago I had this very problem. It was seen in a factory crate motor, an L-79 327-350 HP Corvette engine. No "Speed Racer" modifications had been done whatsoever. Outta the crate and into the car. After a while....I don't know how long or how many miles, it started do exactly what you describe. I tried all the stuff outlined here...more oil, different oil...endless guessing and theorizing about the pickup angle and the guage and and and and.....

Finally i just got up one day pulled the pan down and put in a FACTORY 365 HP 327 oil pump and pickup. New pump and pickup installed ....problem gone!!! If indeed this engine has no modification like oil flow restrictors or other "racer" stuff CHANGE the PUMP and the PICKUP. Chevy oiling systems are as close to perfect outta the box as you can get.

Put in a STOCK Chevy pump and pickup and more than likely your problem will go away. Leave the racer stuff for the real racers ...stock stuff almost ALWAYS is superior on the street.

Its so wild you say that. A friuend of mine is thinking the same thing. He also says that a stock oiling system is more enough for us street motors and such. I am really thinking about going and getting a stock pump and pick-up.

Here's somemore thougth, I see with aftermarket pans, they have pick-up tubes to go with the pans. But they have standard volume pick-ups, and High volume pick-ups. Maybe my pick-up isn't matched to the pump? The very 1st pump that I had was one that was bought from summitt, it was a summitt specail, but with melling name on it. The pick-up was already welded tot he pump, and matched to the pump. This would be the only thing different that I could see in the 3 pumps I have used in the last 4 months. Any thoughts to this.

Michael

Something is worng WITH THE PUMP. Why not accept that? Most likely it is bypassing oil when the RPMs get to a certain level. I Like I said this "Speed Racer" stuff is JUNK on the street. You don't need it.

Millions upon millions of dollars and engineering hours went into engineering GM oiling systems, GM had to stand by the warrantee for MILLIONS of these engines. Why oh why do people wanna believe that this go fast goodie stuff from Joe Dokes Engineering is better?

In a lot of cases this go fast stuff is not even any different than the GM stuff. I don't know about Melling but did you know that there is one or two hydraulic lifter manuf. companies in the US?? All the stuff, ALL OF IT, comes from the same one or two sources. Then we have TRW and Speed Pro....same stuff. Do you think Summit grinds Summit cams....I doubt it: they BUY them someplace and put their label on the parts.

What I am saying is the stock stuff...oil pan, pump, pickup and the windage trays are great for street driven engines. All the aftermarket stuff does is cause problems.

What was the specific reason for buying that stuff as opposed to going with GM offerings? I mean what FEATURE(S) did you have to have that GM stuff did not offer??? Bet ya can't tell me right? Then why use that hodge podge of stuff? Even IF the problem is elsewhere than the pan [and I still think it is the pump] you have introduced possible sources of trouble with an unknown, possibly never ever before run combo of parts down there in your oil pan.

Just not worth the aggravation for my money. Leave the Speed Racer stuff to the racers. It always worked for me...might not be your cup of tea but like I said....something is wrong in that pump, all the guessing and what if'ing ain't gonna fix it.

I went back and read some of the prior posts again and found this......From Ed Carpentier: "I removed the restrictor plugs and screens at the top end and the problem went away" .......Doesn't that tell you something ????? Restrictor plugs are supposed to keep oil out of the top end and screens are supposed to keep stray pieces outta the bottom end. Net result...oil pressure fades away as the engine runs thru the gears. Take out the Speed Racer stuff and what happens?????????? Everything works OK. I rest my case. You better think about what other go fast stuff is in that 383. Anyplace the "hot parts" are installed could be a source of this and or other problems.


[This message has been edited by oman (edited 02-18-2003).]

[This message has been edited by oman (edited 02-18-2003).]

Oman, I respectfully disagree. When his (and my) engine is revved up with no load, oil pressure is fine. When the engine is under load is when the pressure drops.
If it was just a pump problem, wouldn't it occur regardless of load?

My engine has no mods other than the cam, hi-volume, hi-pressure pump. I picked that model because it was a backyard rebuild and was worried the clearances may be a little high, so the extra oil might help.

------------------
Sid Coleman, 71 Ragtop
TC (Gold) #174, MCC #347,
Aces #5457, N3JHV@bellatlantic.net

most oil pumps are mellings even factory gm the part number tags on the pump on a oil pump start out with hv or hp even the trw pumps are mellings even moroso pumps ect. the pump and the pickup is a very good start. and i would use a moroso pickup with stock pump the factory pickup lets dirt get by it on cold start up.and anything above 50 psi. the bypass is built in to the factory pickup. thier is nothing wrong with any of the other speed parts but they have thier place

most oil pumps are mellings even factory gm the part number tags on the pump on a oil pump start out with hv or hp even the trw pumps are mellings even moroso pumps ect. the pump and the pickup is a very good start. and i would use a moroso pickup with stock pump the factory pickup lets dirt get by it on cold start up.and anything above 50 psi. the bypass is built in to the factory pickup. thier is nothing wrong with any of the other speed parts but they have thier place i still would look into the cam and crank clearance. if pump does not fix proublem crank end play is easy to check even with engine in the car.

So you have a "hi volume hi pressure" pump. Ok. I guess I always thought that they were eather hi volume or hi pressure but whatever.

I don't know what clearances you have in your bearings so I can't really comment on the need for a bigger pump. I will say that if your bearings are high enough on clearance to require a Jerry Rig answer like a special pump then that is a bearing problem that needs to be solved with new bearings not with a different pump.

Did the engine knock when you had the old pump? Was the oil pressure lower than the accepted 10/15 lbs per sq inch per 1000 RPM? Is that why you determined you needed supplimental oil pressure and flow? You might indeed have bad / loose bearings and that might be indeed causing this problem. On the other hand your high volume high pressure pump might be pumping the pan dry or possibly it is blowing oil out thru those same warn bearings and starving the down stream bearings Beats me. Is it a stock pan? Is it a stock pickup? Do you have some kinda windage tray in there? Can't really diagnose what is going on in your engine but that aside you are missing my point.

Most of the time when all the engine components are in good condition this go fast stuff is just plain not needed. People end up with XYZ oil pan and DEF oil pump and HIJ oil pickup and some other brand windage tray and of course a screen then the fun starts. People just seem to want to have all that stuff cause the big name racers all have it so they need (want?) it to.

Whatever happened to the idea of matched components that are designed to work together? I firmly believe that the stock GM stuff is WAY beyond adequate for street performance or occasional racing applications. When these cars were new they took tremendous abuse over and over every Friday night, sometimes also every Sunday afternoon at the track oh and by the way they were daily drivers too. They did not have Moroso this and Melling that and restrictor this and screen that and Glyptol paint in the lifter valley. Just outta the box stock stuff. Stock stuff that worked.

A great case for illustration of my point is the fuel pump. People want electric pumps on carbed engines or they want high presure fuel pumps feeding their "ground pounding BBC monster". After all their combo is sooooo freakin hot that it gobbles up gallons of fuel / per seconf...far more than the stock systems could ever supply. Right? Usually all those gadgets do is blow the needle valve off the seat and flood the engine. People also add bigger fuel lines, I read questions like "Will a 3/8 fuel line feed my ......da da da....engine. In most cases the practical real world answer is USE THE SMALL LINE AND THE STOCK PUMP and you are home free. Might need that racer stuff with a 700+ cube or bigger motor but the average street car being talked about here just plain does not need all that glitzy stuff on the street. That stuff feels cool to have it and it shows great at the burger joint but all you are doin is lining the manufacturers pocket.

In the case of my L-79 something was wrong with my original pump, the spring was weak or broken or I don't what. What I do know is that the problem went away with a new pump. I chucked the old pump and ran that engine for over 75K miles with no additional oil related problems. I only changed one thing, the pump, I did NOT weld the pickup on even though the racers all do it, I used the right tool to assemble the pickup and the new stock pump just like the factory does it and it just worked from then on. Welding the pickup can, if done wrong, warp the pump then you get other problems ....see where I am going? If It ain't busted don't screw with it. If it is busted fix it right.



[This message has been edited by oman (edited 02-19-2003).]

I've had the same problem with my 94' chevy pick-up. Your problem is that you maybe overful on oil by 1/2 qt. Try running 4 quarts. I've also installed a factory oil pump/w 3\4 inch pickup and factory windige tray. I have fixed two motors that way.

Ok, I am going to try a standard type pump with a matching pickup. It really isn't that hard to pull the pan and do it. Changing out the pump should tell me something anyways.

Michael

Oman, that was one of the reasons I used the HV/HP pump (how it was advertized.
In my defense, this was a CHEAP re-ring, was very low on cash when I got this. Engine was dumped out of the back of a pickup from it's previous owner. All I knew was that it had approx. 100K on it and it smoked when pulled (got in trade for a cb radio). I plasigauged the bearings and the mains & rods came out a little on the high side of normal according to an older chiltons (the BIG one), but still within specs. I honed the cylinder walls, got .005 over rings, checked end clearances which were OK, and slapped it together. Yeah, redneck backyard rebuild, but it runs OK other than the oil pressure issue.

I do get your point, and happen to agree with you. If I'd had all my parts freshly machined and verified, I'd probablly go with a stock pump. I'd stick with a stock fuel system unless I was going REAL fast.

Thanks for the input.

Old School, like to hear if it fixed your problem. Thanks!

------------------
Sid Coleman, 71 Ragtop
TC (Gold) #174, MCC #347,
Aces #5457, N3JHV@bellatlantic.net

Ive heard that a high volume pump will suck the pan dry.sounds like youve tried everything.Go back to the stock setup and let us know! Good luck.

I am going to try another brand oil pump, but a standard type. It might be a week before it happens, got some other things going on, so I will diffently let you guys know what happens either way.

Michael

On a plus in my mind, I took the car out today and had it in neutral and held the rpm at 5000 and alittle more and the pressure did drop, like 45ish, but not any lower. So I think this is a good thing maybe, it says that it just doesn't drop under a load like I thought. Maybe its not my block. Could be the HV pump cauing my problem. I did put 30w oil back in today.

Is Moroso oil pump made by them, or is it made by melling's? I want to stay away from melling.

Michael

Michael,

When you put the stock pump and pan in here is an easy way to set the pickup tube: Spin the engine on the stand so that it is bottom side up. Install the oil pump gasket. Put the tube loosely in the pump. Orient it so that the pickup will hit the pan slightly. Drop the pan into place. The pickup will swing out of the way slightly. That is "0" clearance. Now, remove the pan. Move the pick-up 1/4"-3/8" closer to the crankshaft. Tack in place. Perfect clearance every time!

Mike

p.s. please keep us posted.


------------------
BDE 327:
Bored .030", balanced, TRW 9.35:1 pistons, Crane Energizer cam .454" 216 @ .050", Trick Flow heads, Edelbrock Performer, Quadrajet.
Home page: http://home.peoplepc.com/ppages/viewpage.asp?MemberName=mbey
327 photos: http://photos.yahoo.com/bc/unclepennybags_2/lst?.dir=/My+Photos&.src=ph&.order=&.view=t&.done=http%3a//photos.yahoo.com/

Just a thought but it is possible that your HVHP
pump is pumping oil to the top of your engine
faster than it can flow back to the pan and you
are starving the pump and bearings for oil. :(

Ok guys, I haven't forgotten about my problem, just tried to put it off while I got moved all in in my new place. I got a Moroso Standard Volume pump and a matching pick up and am going to try to get it out on friday. I'll let you guys know if it helps any. I am hoping!!! Keep your fingers crossed.

Michael

I have the exact same problem with my 406. I am going to have pull the motor and change the pump. Rev it to the moon and the pressure is fine in park. Stomp on it and when it hits about 4500rpms and the pressure slowly drops. Let off of it, goes back to 60lbs. It got worst this year for some reason. Someone told me a valve might have got stuck in the pump.

Know I chimed in on a previous post, have the same problem with my 350. Looking forward to seeing if those changing pumps end the problem.

I have seen hv/hp pumps suck the pan dry under hard acceleration mostly with hydralic lifter engines a good portion of the oil ends up in the top of the engine and flowing towards the rearof the valve covers not much of a drain back hole back there so there the oil stays for quite some time I recommend stock pumps for street apps.solid lifter engines can restrict the oil to the top of the engine so it stays in the pan also smokey yunick recomended 10 psi per 1000 rpm's as rule of thumb so 6000 rpm =60 psi and so on with max pressure not to exceed 80 psihigh pressures tend to blow the top main bearing out of the block and causing catastophic oiling problems like large rotating parts exiting the car have fun make noise graemlins/clonk.gif graemlins/thumbsup.gif

This may sound stupid, but I either read or was told a story about someone who found that their pan was being sucked up against the pick-up and blocking it at higher rpm's. Obviously, the fix is to move the pick-up further from the pan.

Peter

i had the same problem. I switched oil weights and it is alot better now graemlins/thumbsup.gif

Michael the 50w oil introduces the possibility of a suction problem. That is the only side of the pump that could cause that problem. I bet that if you checked the clearance of the bottom plate of the pump and the gear faced it would be too much.
Makes ya go HMMMMMMMM. A lighter weight oil would display the same effect to a lesser extent. If That does turn out to be the case the solution would be to sand the pump housing with sandpaper on a piece of thick glass. Best wishes

Well guys, no good on the pump change out.

I got the new moroso stand volume pump and it reads 18 pnds at idle, and 45-50 cruiseing. These numbers are worse than before with the HV melling. I kinda expected this, but the psi drop is really bad now. It drops to 20 psi. I was highly p'ed off and so I held into it through all 3 gears and it read about 18 psi when I got done. I never did hear any valve trane noise taching high like i did. So now I am not sure were to go. I don't have the means for a new motor or the place to do it, so I kinda got a cruise/show car on my hands for now. No more racing it seems.

Michael

Dang Michael, was hoping to hear different news. :(

Did you check any of your bearings while removing the pump to check for any abmormal wear?

Man I hate to hear that. :mad: I have the same dang problem. I was ready to take the engine out and I thought I would try to change my oil filter adapter. I currently have one that has a plugged off bypass and I put one in with the bypass installed. It still does the same thing but it is not as bad. Instead of going down to 25-30 psi it goes down to 30-35 psi. The oil pressure also went down to 25-30 :mad: psi at idle warmed up instead of 35-40 psi. Now since you changed pumps and seen no change I am second guessing pulling it out right now. graemlins/clonk.gif I still want to drive it. I guess I will have to build another short block and keep this one running for a while. graemlins/sad.gif

every now and then I here about somebody who lost 15 psi oil presure in a given criteria, send in a oil sample, or check a bearing, as long as coolent temp is good and oil pres. above min. spec for a given rpm all is well, I would go pump or reg. if I had to know.