Thread: Small block race motor odd problem

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I have been having this odd problem and am hoping someone on here may have some ideas. Here is the motor
4.030 bore 4 bolt main
Eagle 4340 forged crank 3.75 stroke
6" H beam rods
SRP Forged 12.9:1 pistons
Total seal gapless rings
Cleavite H bearings
Comp cams 4/7 swap Mech. Roller cam
Comp cams roller lifters w/ rev kit
Oil restrictors in back of block.
Lifter galley's have been plugged and screened.
World products heads with + .100 valves and pushrods to correct geometry

I can give more detail if necessary. this motor runs on Methanol and puts out around 640 HP.

now the problem.. The first night out i had great oil pressure. then my warning light came on. it was down to around 10 psi. i took it home and measured all bearings etc. every thing was fine and looked good. I put a new Moroso racing oil pump on, new pick up tube ( and set it to 1/4" from pan bottom, and a new oil pan. this is a circle track car. The next race it was golden. 8000 rpm's and oil pressure to spare. then this last Saturday night the light came back on and i was at zero oil pressure. I pulled into the pits and we started looking. pulled the oil line and no oil was pumping out. I pulled the dist. and turned the oil pump shaft with a long screw driver. Oil squirted out of the oil hole. scratching my head i stabbed the Distributor, set the timing and had 65 psi at idle. then i went out and ran the entire main event with plenty of oil pressure. This motor is spotless inside, Distributor to oil pump drive shaft has plenty of engagement. I was thinking maybe the bypass was sticking open on the pump. but 2 brand new pumps? I run HP4 oil filters and change them every race along with the oil. Myself and all the engine guru's localy are all scratching our heads. so if anyone has more idea's let me know. I will try everything. also, i checked and the rear cam bearing was installed correctly.

the pump bypasses at 80 psi. about 5000 rpm's it hits that.

Lifter galley's have been plugged and screened.

Possibly got em plugged and screened too good, may be filling the valve covers with oil and starvin the pan. also check for a sticking gate in the pan......

i have thought about that screening. I plan on pulling the intake off this week and yanking those screens out. But due to the way the problem was, i am still thinking something else. it sat for a couple minutes when i came off the track. when i fired it back up it still had zero pressure. the motor was 180 deg, so the oil was plenty thin. it should have had plenty of time to drain back to the pan. I have been running that expensive synthetic oil in it due to the problems. I dont know how much longer the budget can aford to dump $50 worth of oil every week. My next option is to yank this thing out for the back up motor. I would really hate to do that. This thing flat screems. if this motor wasnt so damn good i would have yanked it out weeks ago. but i want to work this out now. Keep the ideas coming please. and thank you for the replies so far. This message board seems active with some sharp guys.

its one of the Moroso HV race pumps. the one that was on it before was a Melling HV pump. being honest here when you set the $29.95 melling pump next to the $79.99 Moroso pump visually they look identical. Casting numbers are even the same. when you tear them apart you can see that Moroso Deburs everything and changes the bypass set up. Keep in mind 2 pumps, same problem. both were new.

i appriciate the ideas you have. and i think your in the right direction with your thinking. The spring in front of the plunger is a good idea. I may try that one. This is in an IMCA type Modified, and pulling the pan is a breeze.

your secret is safe. I just want to keep that thing on the track so i can throw more mud at the guys behind me. those hoosiers really fling it!! I am hoping that one of these fixes cures my woes.

I've had the mechanical gauge go bad.

What oil pan are you running on it, and how much oil is in the engine? As others said, with the screens installed, maybe your oil isn't draing back to the pan and what little is in the pan runs away from the pickup..... Another thing to check, is the carb way too fat and methanol getting into the oil and thinning it out to the point it won't register pressure???? Had a stuck injector do that to me once. I'm sure a carbed motor could do the same thing.....

is the oil pump drive gear pinned on the shaft . on the by pass i hone them a bit with a BRM guide hone and polish the by pass piston some times . have you check to make sure the pump plate is not getting cut in by the pump gears from the dist being to long and pushing on the oil pump plate. i would do like said .look at the drain back . were do you have the line for the oil gauge. line some were is it getting pinch . are you using no -4 or -6 if not i would and i do .have you tried a new gauge? look at the pump see if it laying flat on the main cap ?do you have a cam bearing that is spun ?will the oil psi go up after it sits . if so it is a drain back or mains and rods are to big on the oil clearance and the pump can not keep up when oil warms up.

to answer a couple of the questions. Pan is a 7qt Hamburger dual kick out.
Distributor to oil pump drive shaft length is good. the Oil pump drive shaft is an ARP pinned. The oil pressure guage is plumbed with -4 an Braided stainless line from the rear of the block, the idiot light ( comes on when pressure drops below 20 psi ) is plumbed in the front oil galley. Oil looks good. does not have the white Methanol washed out look to it. I know the oil system on these things are a simple hydraulic system. Still scratching my head on this one. i had a problem a few years back colapsing Fram oil filters and loosing pressure. But it flat lined and would not come back. This one is a little different. I guess my next step would be to pull the pump and everything else and start measuring. But first i am going to run the car this saturday. Keep in mind my oil pressure came back and has been fine since last saturday night. I fired it up last night in the garage and it was 65psi at idle. after the woes last saturday night i ran a 20 lap main hitting 7500 rpms without a problem. plenty of oil pressure.

had a big block with .003.7 on the mains and.004. on the rods had good oil psi cold and would hold oil psi but was a bit low. but it went to 8000 rpms all the time with a 70 +pound crank. never got supper psi hot. but it would build oil psi at rpms and the rods and mains look good so that 10 pounds for every 1000 rpm .is BS

When I have a problem like this, I turn up the radio.

Sorry for the smart-a**ed reply but it looks like the other folks have given some good suggestions for not being there touching the motor.

mike in tucson

Originally Posted by robot

When I have a problem like this, I turn up the radio.

Sorry for the smart-a**ed reply but it looks like the other folks have given some good suggestions for not being there touching the motor.

mike in tucson

my engine is my radio

well it sounds good ? seen this some were on the 10 psi for every 1000 rpms ? but my old crank grinding friend and i have shot this to hell on many big blocks chevys and small blocks. i like to see some oil psi but 80+ psi cold may be a bit much