[gogtogo]

Good afternoon. So, dynoed my engine after freshening and after several pull’s builder was concerned with ideal oil pressure. Melling 80psi pump, 20w-50 oil (aluminum rods). Oil pressure was 76psi @ 7000rpm and 220 deg oil temp. At ideal oil pressure was 15psi. He shimmed the spring but we did not re-dyno. Just fired engine in the car and it barred a Pro Comp 100psi Gauge. I let come up to temp and ideal pressure is 20psi. Bring the rpm up and rap the gas it pressure goes to 80psi. What are your thoughts, something to be concerned with? I told the builder who builds tons of race engines that Pontiac’s typically don’t have much ideal pressure.

[GTOGEORGE]

Your oil pressure was fine to begin with......temp 220 with 15 at idle is ok, 76 at 7,000 is more then enough.


GTO George

[Dragncar]

I had a pump that did that once. Changed it and went back to my old pump and back to 50lbs hot at fast idle.

[Tom Vaught]

Sounds like the Pump has the stock bypass relief ball installed in the 80 psi pump.
A change to the slightly smaller bypass ball and a shim for the spring will bet you back to
slightly lower CONSISTENT Oil PRESSURES from the pump. Lots of posts about this.

Tom V.

[GTOGEORGE]

Originally Posted by gogtogo

Good afternoon. So, dynoed my engine after freshening and after several pull’s builder was concerned with ideal oil pressure. Melling 80psi pump, 20w-50 oil (aluminum rods). Oil pressure was 76psi @ 7000rpm and 220 deg oil temp. At ideal oil pressure was 15psi. He shimmed the spring but we did not re-dyno. Just fired engine in the car and it barred a Pro Comp 100psi Gauge. I let come up to temp and ideal pressure is 20psi. Bring the rpm up and rap the gas it pressure goes to 80psi. What are your thoughts, something to be concerned with? I told the builder who builds tons of race engines that Pontiac’s typically don’t have much ideal pressure.

I had a Butler pump that did the same thing.....drove me up a wall went to a mellings 54ds. All you need is 10 lbs per 1,000 RPM. Mine has less then 70 going through the traps around 6,600 rpm.



GTO George

[Gary H]

Probably bearing clearances a little on the loose side, or a pump with loose clearances. It will be fine with that oil pressure though. Keep an eye on the higher rpm pressure. That's what counts.

[gogtogo]

Thanks for info. I’m aware that I must be very careful with that much cold oil pressure. Builder said just be careful as I don’t want to blow the filter off. Not real sure of clearances on bearings. Just wanted some reassurance that it’s not going to be a issue. I was also thing about a oil pan heater to put some temp in the oil on those spring and fall nights.

[lust4speed]

Scares me that a builder would go and shim the spring to bring up idle pressure. You could weld the ball shut and it won't change low pressure at idle. Spring did activate at 76 PSI and was great. The 15 pounds pressure changing to 20 pounds was only a function of less oil temp and had nothing to do with the spring change.

[taff2]

I've had similar figures with my ali rod engines, 80-100 psi cold start pressures, drops to 15-20 at hot idle, usually around 70-75 at 7000 rpm. Bearing clearances on the rods .0035", crank .003" -.0035", the bearings always look good when checked, has a remote oil filter set up, no factory bypass valve. Just warm up the engine thoroughly before you rev it hard.
ps, I used a Fram PH4825 filter - it doesn't have an internal bypass valve so all the oil got filtered,all of the time.

[flamedabone]

What lifters are in it?

I have the same issue with a 400 I just built and I remember when I primed it before firing I noticed more than the usual oil bleeding past the lifter bores. Also, oil started dripping out of the rockers after about 30 seconds when it usually takes a few minutes to get them all dripping.

At the time I thought huh...that is interesting... but now looking back, I wonder if the lifters are slightly undersize or configured differently than what I usually use. The cam and lifters are a Comp retrofit roller grind.

I know in my mind that 20 at idle is OK, but it always makes me a little nervous.

-Abone.

[gogtogo]

Engine is fresh with ONLY new rings bearings and rods, oil pump and timing set Engine was fare from needing freshening but short block was bought used with just a few dozen passes but was was concerned about the aluminum rods as it was built in 2005. Engine looked like a jewelry store inside with absolutely no wear. Has a solid Roller came with Crower Hippo lifter and block has no restrictors. All clearances fallowed per GRP.

[Todd1035]

You should really have lifter restrictors in that. Having all that oil flow to the top is unnecessary and probably some of the cause of your low oil pressure at idle. Start with .020’s you will still have plenty of up top and it’s better to keep it in the pan where it is needed. JMHO




QUOTE=gogtogo;6214250]Engine is fresh with ONLY new rings bearings and rods, oil pump and timing set Engine was fare from needing freshening but short block was bought used with just a few dozen passes but was was concerned about the aluminum rods as it was built in 2005. Engine looked like a jewelry store inside with absolutely no wear. Has a solid Roller came with Crower Hippo lifter and block has no restrictors. All clearances fallowed per GRP.[/QUOTE]