Just got done building a pure stock motor for my pure stocker. Main clearances were .0015-.002. Rod clearances were the same. Use a 75 block. Ran the engine in on a test stand. It ran good. oil pressure 20 psi at idle, and 65 psi at 4000 rpms. now that it is in the car and has around 100 miles on it, oil pressure drops of the gage at idle,and only gets up to around thirty. Funny thing is oil pressure goes up when I let off the gas (around 70 mph) around an additional 10 psi. Crank end play was in specs. I was going to drive it down to the BPG meet to break the engine in. Needless to say I won't be doing that. I changed the break in oil. (Brad Penn) cut the filter apart, it was clean. ran a magnet around the drain pan I had the oil in, only microscopic bits, that smeared when rubbed between my fingers, It felt like break in grease. The oil pump has an adjustable screw for pressure adjustments, but turning it in makes no difference. Is the relief valve staked into place or should it slide easily out, it didn't come out with a magnet. I'm stumped, and tried of one step forward and two back. Help please! Thanks Jim
Jim, I remember JW. I spent a couple of hours talking to you and Jim, and Ted Nagle. Under your tent in 07. I won't be going there this year, I got work to do on Pure Stocker. I'm have never been able to take a day off when I find something wrong. Randy, I'll try to remove the valve tomorrow. If it doesn't slide out.....what is method of removal? I'm really puzzled why it would pick up pressure when I take my foot of the gas, at around 4000 rpm.
The reason I believe you are gaining pressure when you let off the gas is there is excessive clearance between the crank and the main bearings. Where the crank places it's load on the mains changes when the engine is under load versus engine braking.
That is my thought too. The bearing clearances were.0015-.002 when I Plastic gaged them. After gaging I re assemble each main and rotated the crank, to make sure the crank didn't mark the bearings. I also used the TA double grooved cam bearings. I had the crank shaft turned .010 under by the machine shop of the National champ alcohol dragster champion Bill Riechert. Also had the mains line bored. His shop does A-1 work. But that with that thought in mind (crank clearances) is why I drained the oil and cut the filter apart. I found no evidence of bearing failure. I can see though if the check doesn't solve the problem the motor is coming back out. This racing stuff is getting expensive! maybe one day they will come out with a patch to ween me off!
It almost sounds like the sump is too close to the bottom of the pan. Is it possible the oil pan got pushed up a little when the motor was installed?
First Try Flushing The Hole With Some Spray Cleaner While Working Piston Back And Forth If That Dont Work Push It Back In The Hole And Take Some Emery Cloth And Polish The Hole So It Will Slide Out,did You Use A Double Roller Timing Chain? Randy
Randy ...took it out this morning. It didn't comeout with a magnet like the one on my spare engine. But it didn't come out hard with the pick either. But I polished, and cleaned it, and put it back in. 20 psi at idle, but it jumps up as soon as the gas is push to 63 psi. I can live with that if it stays that way. I'll have to see what it does when hot. That's when I seem to gradually lose pressure. I'm using straight 30 weight Brad Penn break in oil. If it does hold, I'm going to pull the engine. The Oil pump clearances are well within the factory clearances. No double roller, using a lighter set up to free up power were ever I can. I have a friend who has used the same setup for several years with no problem. It has 56cc heads. The pistons average around .005 in the hole. Calculates out to close to 11 to 1. I run a Scott Brown cam, within 1% of factory Stage 1 cam specs. This is within the rules we run.
Carson, I agree the last motor I rebuilt for my 4 speed has all the same clearances and holds 60 psi at all rpm's. That's what I would like to have this one run at. I really can't get my head around why the pressure is any different from the last build. This one is blueprinted and balanced. The motor in my four speed is just balanced. I thought this motor would peg the gage all day long.
Jeremy, I pull the pan, loose, couldn't get the $#@%er out even after jacking the motor up saw no reason in the pan, it was clean. Looks like the motor is coming out. The way my luck is going the 4 speed will break before Stanton. Reguardless will see you there!
Pulled the pump apart to check all my clearances again. .0025 between the gear and the housing. .0045 between the gear and gasket surface. using a steel booster plate so there is no scoring. Also using a .005 gasket. Cam bearings are the TA double grooved ones, clock at the proper position. Rod clearances were between .0015 and .002, same with the main bearings. Using a TA adjustable pressure regulator with the standardblack spring. All things seem to check out by the book. Anyone have any new ideas. Jim
No Tuna, I have .0045 of oil pump gears below the surface of the housing. Using a .005 gasket should yield .0005 clearance between the bottom of the gear and the steel booster plate. Thanks Jim
JW, as of now the motor is still in the car. I have to wait til my friend is back in town, he has the pulling crane. We ran it in on a test stand to break in the cam for around 20 mins. Then spent around another 15 minutes or so tuning it. On the test stand the pressure never went below 25 psi. and it would jump up when the throttle was engaged. It went up to over 60 psi. at 4000 rpms. I read one of your post somewhere and you stated you had put in a "window rattler" cam in a pure stock motor. :Brow: Way outside the spirit of the rules Jimbo. But I don't really give a darn. I just race the class to have fun. My wallet isn't deep enough to run with the FAST pure stockers. Thanks for any help in advance. Jim
Jim, Rules and their "spirit" have changed dramatically over time for the PSMCDR. We used to play with cams a bit, but they have clarified the rules for cams now, requiring exact duplicate cams. It used to be that it just had to "sound stock", and not exceed NHRA Stock specs. We complied with that, and what we did back then was well within the norm for PS motors at that time. In fact, we were conservative compared to some stuff out there. Enough so that we had no problem running a dead stock valvetrain. Back then, our work with camshafts was more about killing some low end torque, to be able to launch the car, than it was about building some radical High HP engine. So I will disagree that we were not within the "Spirit of the rules" as you put it. Your judging those motors of yesterday by the today's rules, which is really not fair. Today, we have to use the blueprint STG 1 cam, as the rules specify. Since there is no "grey area" to be played with anymore, as the rules regarding camshafts are clear. As to your engine issues, I would pull the intake off it and see if you can see the cam bearings "peeling out" around the journals. This will cause a loss of oil pressure as you describe, but might not put much junk in the oil right away. If they are ok, then after the motor is out, take the pan off it, and put a catch basin under it.. on the stand, with the intake, valve covers, and oil pan off it, and an old pickup with the end cut off it, a hose affixed to it, run into a jug of oil, spin the pump with a drill and look for the bleed. You won't be able to miss it, it should be squirting oil out like crazy, if the pump is working properly. An oil pressure gauge hooked to the engine will help you diagnose the issue. Pre-heat the oil to 150* and you will really see where it's bleeding. Sneak a jug of 5-30 into the Wife's Microwave when she is not around.. to heat it up. Good luck with it. JW
