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Author Topic:   Oil pressure to high?
51racing
Dirt Maniac

Total posts: 138
posted April 14, 2005 08:49 AM  
I put my new motor together for my pure stock, pretty basic motor, 307 with 416 heads, and a isky hydraulic cam. I used a melling 55A oil pump in it but I think I may be getting too much pressure from it and don't know why. I've even gone down to using 10w30 oil in it to try to cut it down some. Idling, it's pretty normal when warmed up, about 25 pounds. As I rev it up, it starts to go up, then when I get to around 4,000 it really jumps, like up to 100 lbs. Anyone know why that might be?

supwitchew
Dirt Maniac

Total posts: 122
posted April 14, 2005 10:03 AM  
If you can rule out a faulty gauge, then the first thing that comes to mind would be the relief valve is stuck closed.

51racing
Dirt Maniac

Total posts: 138
posted April 14, 2005 11:25 AM  
Yep, we can rule that out as I just stuck a new one in it last night. Relief valve in the pump, or what do you mean?


dirtbuster
Dirt Forum Champ
Total posts: 2007
posted April 14, 2005 11:58 AM  
What were your bearing clearances when you put it together?

The 55A is a high pressure pump, so I would expect on a tight engine the pressures would be higher. A stock pump in a good engine will make 60psi at 2500 or so, so a high pressure pump that has a stiffer sping in it could possibly make 100 psi like that. A standard pump prob would have worked better for you. Really 60-70psi is more than you whould ever need.

Or the relief valve could be stuck like mentioned above. Did you weld the pickup tube to the pump?

[This message has been edited by dirtbuster (edited April 14, 2005).]

supwitchew
Dirt Maniac

Total posts: 122
posted April 14, 2005 12:16 PM  
There is a pressure relief valve in the pump. Sometimes it can get stuck in the closed position. Since you just put the motor together, it's possible that you have some debris causing the valve not to open. A restricted or blocked main oil gallery, or tight bearing clearances can also cause high OP. Anyone else?

supwitchew
Dirt Maniac

Total posts: 122
posted April 14, 2005 12:19 PM  
You beat me to it, dirtbuster.

51racing
Dirt Maniac

Total posts: 138
posted April 14, 2005 01:43 PM  
Actually, I don't know what the clearances were when it went together. Long story short, it was new last year, only had a few races, I took it apart to put new bearings rings, cam and such in it and didn't check them. I don't think anything is plugged, I'm getting oil up top, and plenty of it. Assuming it's just got tight clearances, is this going to hurt anything? I would assume it'll get lower over time right?
And yes, the pick up tube is brazed on.

dirtbuster
Dirt Forum Champ
Total posts: 2007
posted April 14, 2005 01:59 PM  
If the bypass is stuck it wont affect oil getting to the top end. Normally once pressure in the oil passages reaches say 60psi that vavle opens and lets some oil back into the pan. If your is stuck and never opens then the only place for the oil to go is into the motor, which is why the pressure spikes. All the oil has to go to the motor.

Like the previous poster said, blocked oil passages, tight bearings, etc will increase preassure and if the bypass doesnt work it will spike the guage reading.

The reason i asked if it was welded is because if you didnt remove the spring when you welded or brazed it, that heat could distort it enough to make the valve stick shut.

51racing
Dirt Maniac

Total posts: 138
posted April 14, 2005 02:08 PM  
OK, I think I understand. So if the bypass is working correctly, where does the oil go? If the pressure is high enough, does it just pump it back into the pan or what?

supwitchew
Dirt Maniac

Total posts: 122
posted April 14, 2005 02:23 PM  
That's where it goes. Also, I don't think I would assume it was tight bearing clearances. I would rule out the pressure valve. If you take your car on the track with it stuck you can hurt your car. You can build enough pressure to rupture your oil filter.

nvracer
Dirt Maniac

Total posts: 127
posted April 14, 2005 02:44 PM  
Alot of times oil pumps come with 2 springs for the bypass. 1 high pressure, 1 for a lower pressure.
You might be able to change the spring in the pump bypass.

shifty8
Dirt Maniac

Total posts: 123
posted April 17, 2005 09:09 PM  
i run the high pressure pump in mine and have ran that style for a few years it is the same at idle it is around 20 30 lbs and when u get on it it jumps up to 85 -100 lbs i have never had a problem with it only worry when it gets below 10 lbs then i know somethings wrong..lol

ringo2882
Dirt Roller

Total posts: 14
posted April 17, 2005 09:43 PM  
ran 75 to 100 lbs last year and didnt have a problem.

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