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Old 08-22-2007, 09:29 AM
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low oil pressure...

I have beat my brains out over this one. I have a .040 over 400 small block ex-circle track engine that I ponied off of a guy that I trust knows his *****. I have been fighting low oil pressure and valve noise since the beginning with this engine. I have changed out the pump with a new Mellings m55 oil pump and a steel sleeve for the pump rod. pressure has improved a little, but still noise. The next thing I thought was bad lifters, replaced lifters and pushrods, as well as rocker arms. Once again, slight improvement, no fix. I also thought about cam bearings misaligned, checked with the original owner, he sent that engine to the builder three different times for the low oil pressure problem. I would think that even a mediocre engine builder would check gallery plugs and cam bearings after the same engine comes back three times.

To make a long story short, the engine actually runs fine, it oils the rockers, and was ran for an entire season with the oil pressure problem. (he got rid of it because he couldn't keep it cool. New head gaskets after every race gets old. I fixed that.) I don't want to remove the engine ( it would be the third engine I have tried in this car, I just can't settle on the engine that I want)
I love this engine, and I want to keep it forever. Any advice?

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Old 08-22-2007, 09:34 AM
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Have you removed the oil pressure sending unit and screwed in a hose with a mechanical pressure guage on it and checked your pressure? Thats the way I check.....you could just have a bad sending unit. How low is your oil pressure?
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Old 08-22-2007, 10:24 AM
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some numbers would be a help, idle and 3,000rpms...

where on the motor is the pressure reading from, up on top?

our shop has (winning) sportsman circle track racers...every motor build has more than normal crank bearings clearance (=lower pressure) for max HP/less friction at 6800rpm...
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Old 08-22-2007, 10:57 AM
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sorry, forgot that numbers help.

10-15 psi at idle,cold, 3000+ barely touches 20psi.Hot idle is about 5psi, 3000+ 10-15psi. tapped right from the back of the block

Last edited by gearhead81; 08-22-2007 at 11:03 AM.
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Old 08-22-2007, 12:32 PM
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low oil pressure

what weight oil are you using??go to a thicker oil. i bought an airplane with only 5 lbs of oil pressure,i drained the oil and filled it with 80 wt. i flew it 1600 miles home,no problem.
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Old 08-22-2007, 12:55 PM
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because it is a "used" circle track motor...my gut feeling is telling me you need to check the main bearings for enlarged oiling slots and see if it has a cross drilled crank...another circle track trick is to use extremely narrow bearings which allows more flow and pressure escape at the mains....

with any wear on the bearings from being used to race, any combination of the above will show low pressure

the oil gpm flow thru the motor is a major contributor to cooling....less psi is less gpm....was contributing to the overheating before

do test the guage...stick it on another known good psi car?

air getting into the oil (frothing) can make psi alot lower....drain 1.5 qts from your pan and see if pressure is better

heavier oil can help indicate if it is worn bearings....buy 4 qts of store brand straight 40wt and see if pressures aren't alot better warmed up (bet they are)

bottem line, based on 5psi and 20psi.....crank bearings are behaving like the motor has 200,000 mile on it....to much oil is escaping at the crank

do wait for more replies.....I'm not a 400 pro for sure
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Old 08-22-2007, 01:24 PM
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the gauge works. I ihad it in with the other two engine swaps, and it worked then, and they were all this summer.(my wife says I change engines like some people change socks,lol).

As for the bearings, that makes sense. It's getting to be winter time here, so it looks like I now have something to do. It is going to be a helluva lot easier to just pull the engine and rip it apart. I was hoping to at least get through the summer with it, and I did, so I'm happy. I have a warm, spacious garage w/ a newly built clean room, waiting for an engine. At least I know what engine I want now, lol. Now it's time to make it mine. I was wondering about the bearings, but I knew it ran, so I just threw it in the car after cleaning it.

The darnedest thing is that the engine has done that since he had it built the first time.
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Old 08-22-2007, 05:19 PM
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make sure the galley plug under the rear main cap is there, occasionally it gets left out and causes low oil pressure
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Old 08-22-2007, 09:39 PM
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on my list. thanks alot guys.
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Old 08-23-2007, 04:40 AM
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gearhead,
a gift?
on this link, check out the tech articles and how to's on the left margin for alot of insite for what it takes to build a winning bomber or sportsman motor (and stay within the rules or lose the motor to a competitor's $500 tear down challenge for cheating*)

http://www.stockcarracing.com/

I expect you will find most changes have been done to your motor, correction to my post above:"less heat" not less friction at the crank...

*my favorite true "cheating story"....the guys car was way way to strong to be legal race after race, challenge after challenge showed it was legal and he walked away with the $500 and the 1st place $$$....they do always measure max allowed cam lift at the rockers....they guy (smart!) had noticed they ALWAYS measure on #1 cylinder......he had a cam ground with only #1 cylinder legal!!!!!

ps: click on the primemedia automotive group small link at the bottem for the page to all the car/truck/mc magazines...Prime Media publishes most
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Old 08-23-2007, 05:21 AM
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lol------We used that SPECIAL GRIND CAMSHAFT trick for NHRA drag racing way back in 1970. This brings back memory's.

454 RATTLER
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Old 08-23-2007, 07:27 AM
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Quote:
Originally Posted by red65mustang
*my favorite true "cheating story"....the guys car was way way to strong to be legal race after race, challenge after challenge showed it was legal and he walked away with the $500 and the 1st place $$$....they do always measure max allowed cam lift at the rockers....they guy (smart!) had noticed they ALWAYS measure on #1 cylinder......he had a cam ground with only #1 cylinder legal!!!!!
LOL I'v heard of this, some tracks also only allow a over bore of .010, and always measure on the #1 cylinder, so some racers would over bore all cylinders to .060 and leave the #1 .010, then have the rotating Assembly balanced.

Theres lots of tricks out there, Smokey Eunuch (spelling?) was one of my favorites, beating out floorboards to make them into air pans and painting intake and exhaust runners smooth.
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Old 08-23-2007, 08:00 AM
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Wow.That's a lot of info. Got me some readin' to do...
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Old 03-12-2009, 06:54 PM
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jmmc

As red65mustang stated many different things are done to the c-track engines. One of them is that the easy cylinder to pump is normally correct as far as compression but not the others. First is first, take that engine apart and check it over very carefully. Check the deck on all cyls piston in the hole depth, take plastic gauge and measure all mains and rods. Looking at a lot of posts i do not hear much about clearances in these engines. Gauge clearances are going to tell you everything about the oiling going on down below. Remember that uyou can have high volume pumps but if all your clearances are not right it will not matter.
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