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Discussion Starter #1
Here is my problem, this past fall I finally got my 1969 chevelle together and had my 396 BB rebuilt and put in a Melling Hi-Volume oil pump and a chrome Morroso 7 quart oilpan. I put about 75 miles on it but noticed that the oil pressure is about 5 to 10 psi at idle and only 40 when driving and it was getting lower everytime I drove it. I took it to a friend to check the exhaust out and put it on a lift and noticed that the oilpan was dented in about a 1/2" right under the oilpump pickup. I know I didn't put a floor jack under it and dent it, there is no scratches, it looks like it just sucked in. Has this ever happened to anyone?. Could the oilpump pickup been too close to the pan and sucked it in?. I have a open breather on one valve cover and a breather/PCV on the other going into the back of the base of my carb. I'm going to pull the motor but would like to know how this happened before I fork out another $150 for a new oilpan.
 

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My personal opinion is that an oil pump could never suck the pan in. The oil pump pickup normally rides about 1/2 inches above the floor of the pan. It might be possible that the dent in the pan is restricting the oil flow to the pump, thus resulting in the lower oil pressure. Have you checked for clearance to the front suspension components?



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'66 Chevelle SS396/375
'71 Karmann Ghia Convt.
'55 Chevy Convt.
'53 Chevy COE
 

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dave
this will sound dumb,but try to find a small toilet type plunger,get her on a lift and try to pull the dented area down,like pulling a dent in a fender.
then start her up and let it get to temp and see what ya have(oil pressure)
if you pull the dent,and the pan pulls toward the pickup,you might have a weak pan bottem that pops up and down,kinda like when you lean on a car fender,pops in-pops out.
did you dent the pan without knowing it?
did someone else dent the pan.
no sups parts should be in the way,your tie rod is in front of the cross member.
although I never seen this,theres a first for all!did you measure pick-up deapth when installing the pan?---67RAT member #199

[This message has been edited by 67RAT (edited 12-20-1999).]

[This message has been edited by 67RAT (edited 12-20-1999).]
 

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I think that it is impossible for the pump to suck the pan in. I agree though that you should check the clearance between the pan and the pump. I am not sure about BB's but a high volume pump in a small block to me is trouble. I uesed to race a IMCA modified and had 400 small block .030 over which is a 406. And with a high volume pump you had to run oil restrictors or all the oil would get pumped to the top and couldn't get back to the pan quick enough. I remember a friend put a HV pump in his w/o restrictors and started it to adjust valves and the oil was shooting clear across the garage. Needless to say the engine lasted about 20 laps. Just my .02 worth.

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Steve
 

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I'm most sure I or anybody else hit the pan with the jack. When I was assembling it there was a 3/8" clearance between the pick-up and the pan. It looks like cheap metal that pulled inward. I'll try the plunger trick. Someone told me I might need the oil restrictors. If I do, were do I put them?. The engine is a 396 .030 over with a 544/567 lift 304/314 duration solid cam.
 

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If all the bearing tollerances in your engine are within specs, a high volume pump will not pump all the oil out of your pan...The pump to avoid is a high pressure pump.

A high volume pump will flow no more oil than a standard pump under most circumstances because both are pressure regulated...When the pressure reaches 60 lbs, the pressure release in your pump (regardless if std or hi-vol) won't allow any more oil to flow to your bearings...At higher rpms (4500+), when your engine needs more oil flowing, a high volume pump can maintain that pressure where a standard pump will begin to lose pressure (esp on a motor with some wear).

Your motor doesn't need oil restrictors unless you want to run a high pressure pump...a high pressure pump (serious applications only) are designed to continue to build oil pressure (and oil volume) as rpms and power build...If you're running 8000+revs and 800+ nitrous fed HP, then a high pressure pump and oil passage restrictors are more applicable.

1st check to see that the dent in your pan isn't pushing up against you pump pickup. That can cause problems.

If you still have a pressure problem after that, it is most likely that someone screwed up on your engines machining...Did you/your builder plasti-gage all the bearings? Were new cam bearings installed? Since your motor is getting worse, you may even have a bearing spinning (bad news)

How could your pan get sucked in? This is a long shot, but I've seen valve cover gaskets sucked in by this...If at somepoint during your engine's initial startup, one or more of your intake valves was out of adjustment, those cylinders will act as a power crankcase vacuum pump. If those valves don't open, or open way late, vacuum can be sucked past the pistons, and if your engine is revved up, could suck in your pan...If you had a breather installed, vice just a PVC and an oil filler cap, it is unlikely this caused it...

Another possibility, if this is a brand new fabricated pan (vs stamped steel pan), is that the expansion of the metal, when your engine reached operating temperature for the first time, caused you pan to "pop" in. In that case, its just an unforseable manufacured flaw in your pan.

-Good luck!

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68 El Camino...Slow, Much Work Required
98 Z28...Fast, No Work Required
Goodfellow AFB, San Angelo, TX -- Where? That's what I said..
 

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Well i just got my engine in about a month ago and i drove it home ok then when i took it out on the freeway to get some freeway miles i am seeing tons of white smoke behind me so i pull off the road and see oil all over the headers. Well i limp it home and take alook underneath and i have a 8 quart Morosso
well i see this hole about 3/8" in diameter but i do not remember this being there when i put it in. So we get a fine thread screw and a rubber washer and put it in there i asked a guy that has been into racing for years and can't figure out how that hole got there considering it was from the factory becuase it was a smooth indent and also a perfect hole. Mine was on the risen part of it. If its a perfect hole stick a bolt in it and check it for a few weeks then forget about it
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Dave, Chevrolet's will not tolerate oil pressure that low, continued operation with that condition will spell doom for your 396. Fix the obvious first, the plunger trick was an excellent suggestion, if that doesn't work, weld a sheet metal tab to the bottom of the pan and snatch it out with a slide hammer, (I know that option sucks with a chrome oil pan, but you gotta do whatcha gotta do). See if this restores sufficient oil pressure, if it doesn't, your going have to go back into the engine and see what the malfunction is. BTW, current thinking about oil restrictors among some of the leading engine builders is..DONT. Rational is to put oil on the valve springs to keep them cooler and extend spring life, of course this thinking is involving high pressure springs seen in racing applications, but us street guys can always benefit from their R&D. Hope this helps. Rob
 

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Sorry, I am wrong, it was a high pressure pump that I was talk about not high volume. I have also heard of valve adjustment causing a valve cover gasket to be sucked in. Sorry for the wrong type pump. :0 good luck

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Steve
 

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There's "no way" I'd believe the oil pump sucked the pan in. Simply because the engine produces pressure in the crank case, not vacuum. Even if you could suck in the oil pan it would take an extreme amount of vacuum.


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Lowered '67 Elcamino
ZZ430 eng / 4L60 trans
"Canyon Carver"
 

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Hey Dave, I am going through the same thing right now with my rebiult LS5 (I have about 100 miles on it). I used a Melling high volume pump also. I have good oil pressure at an idle 55-60 lbs but my oil pressure drops as the rpms get above 2000 RPM (drops to about 20lbs). I drained my oil and looked into the pan and saw my pickup tube resting tight against the bottom of the pan and the pan looks concaved or sucked in right under the pick up tube. I figure I set the pickup tube too close to the bottom of the pan for starters and it got worse as the pump started to starve for oil. As I said I get good oil pressure at an idle so I hope I didn't do any dammage to the engine. I will be pulling the motor next week.
 

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Is it possible, either of you guys set the oil pan on the front cross member while installing the motor,and that could have dented your pan??? just my 2 cents


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Bob West
Monett,Mo.
1972 Malibu,461 cid.
 

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Dave,
I just went through this whole mess with my 70 Nova (350 SBC) and it turned out to be something I didn't expect. I too thought my oil plan looked indented, but I think that is pretty normal since we all have a tendency to let the motor rest on the pan at one point or another. i finally just pulled the plug and with a flashlight, double-checked that the clearance was correct. It was, and was actually really easy to do (except for draining out some new oil). I kept searching, and finally took it back to the machine shop. They unhooked my new Autometer pressure guage at the block and put their's on. Bingo, perfect oil pressure. I never use that cheap nylon line they give you, have always upgraded to 1/8" copper line and never had a problem. I don't know what was different about this particular line, but I finally swapped it out for the nice steel braided line Autometer sells for it's gauges and now everything is great and looks good too. This may seem too simple, but believe me, I went over about everything before the machine shop found the problem quickly. Again, you should be able to pull the oil pan plug and check your clearances without even dropping the pan. (You might need a mirror if you have headers that hang down as far as the ones on my 71 Chevelle SS)

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Bill C.
'71 SS (now with 468BBC)
ACES #2780
Colo Spgs, CO
 
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