Don't rev the **** out of it when it is cold , let it warm up and the pressure will normalize. I stay away from high volume pumps as a rule especially with stock capacity oil pans on high RPM engines. They will pump too much oil to the top end on extended high RPM runs. My pump of choice on a small block is a Melling M55A . The stock replacement pump for the Z28 302 , standard capacity with high pressure relief spring.
One would think that. Will have to check to see what the noise is for sure. I can drop the bottom of the ****tershield and check brg to clutch finger clearance. I'm not one to drive with my foot on the clutch pedal, extra return spring on the fork to push rod to make sure the slave cyl. pulls back in. BCA bearing in it. Maybe a front brg. in the Muncie, although I replaced all the brgs. when I rebuilt the box. Only makes noise when the clutch is disengaged and goes away when you let the clutch pedal out so it sure seems like a t/o brg noise to me. Seems to have free play in the fork. We'll see. Block of wood is when I was fabing it up.
My small journal 327 has about 80-85 psi at cold startup, which drops to about 40 at warm idle, 45-50 at 2700-3000 rpm. I always thought it was a little high, and since I didn't build the engine, I don't know what pump is in it, but it's been that way for 22 years and about 30,000 miles, so I think it might be OK.
The 351 Windsor in my Avatar has about 75 psi on cold start goes down to 25 at idle in gear when warm. It was that way when I got it and I have put a bunch of miles on it with no problems.
There are a lot of variables as many have noted but a rather large issue is the design of the "circuit" the oil takes through a specific engine . The later Poly 318s came from the factory with HV oil pimps.
I guess I go about things backwards. I run a standard volume/high pressure pump in my engines that are going to see high rpms. I do use anti-cavitation pumps. I'm building an engine for a pickup I'll use for daily driving and it will never see 4500 rpms usually closer to 2000/2500 running down the road. I'm using a high volume pump that I put a low pressure spring in to keep a little higher oil pressure at low rpms but not over 55 lbs anytime. Melling sells springs for byp*** pressure from 45 up to 78 lbs. High pressure springs usually hit around 70 lbs when I prime engines.
"I noticed when I was on my way home from Quincy that the oil pressure gauge had a slight deflection while running at a steady rpm on the highway, almost like it was relieving pressure in the system". Any chance you have the pickup too far off the pan? Did it get bumped when the pan went on?
Back in '77 one of my old Cobra buddies gave me one of those old Milodon recessed pump cover kits that "let" you use a huge 534 truck rotor set in an FE pump. So I put it in my stock 406 HP pump with the heavy spring. Made 125 lbs at 2500, and 80 at idle- and always ran hot after a while, was byp***ing a ton and beating the oil to death
Dennis, I just wanted to say that's a very tidy bit of fab on the clutch slave mount, nice work! (right click- saved).
Thought I read somewhere once a standard oil pump takes 5% of the engine horsepower just to run it. I knew it had to cost something of course but didn't know it was that much.
When people ask me where I bought it I tell them "at the s**** steel yard and True Value Hardware" Thank you. D
After reading all the post about a lot of cars with similar oil pressure readings, I have come to the conclusion that I am the idiot they made lights for.
I agree with you that 100 psi at start up is unacceptable even if it smooths out later. I would worry about blowing out the oil filter case or its seal and ruining the engine before realizing it. My thought is this: The pressure relief valve should control the pressure by opening further. Since you changed pumps, I would not believe that both pumps didn't open all the way under that pressure. So, if the pressure relief is opening all the way, something in the circuit "after" the relief must be preventing the oil from flowing/byp***ing. It is possible that there is a burr or high spot keeping the pump from opening till the engine warms and expands slightly, but I would look for some possible obstruction after the byp***. Once the oil and the engine warms up, clearances may open just enough to drop the pressure. You might pull the coil wire try cranking the engine and noticing how much pressure you have when the engine is cold. Then remove the pump and take the byp*** completely out of the pump and reinstall the pump. Crank it again and see if a fully open byp*** drops the pressure or if it remains the same as before. That should tell you if the byp*** is the problem or not.
This was on my mind when I started this thread. I wonder if one of the oil p***ages had an obstruction or, could someone have put too long a galley plug in it causing this. I bought this block from the guy that owned the machine shop had decided he wasn't going to build any more cars. All of the machine work had been done on it when I bought the bare block, and I am sure that he would have taken care since this was going to be used in something of his. I have had other work done there in the past with zero problems. As of now, I'm going to keep a close eye on it and see how it does. I really hate to think about pulling the motor if that is what it comes down to. I just HAD to have a 327 didn't I
I'd just put the thin oil in it and run it. One time years ago, I had a small block mopar drag racer. It was prone to low pressure and oil starvation leading to spun bearings. Working in the hydraulics field at the time, I knew that pumps in general could not tolerate restrictions on the suction side. This thing had a 3/8" pipe nearly a foot long for a pick-up that went with the center sump pan (rear main mounted pump.). I modified a hi-volume melling pump to use a 1" pick up tube with a 3" square pick up body and screen poked directly into the pump cover on the suction side of the gears. Coupled that with a rear sump pan. The first time I fired it up, it pegged the gauge at 100psi at idle, and when I wacked the throttle, it blew the oil filter off. "Well, I guess THAT worked," I sez to myself as I proceeded to clean up 7 quarts of brand new 20/50 Valvoline racin' oil off the garage floor. I used 30 wt after that, and just let 'er warm up. But I never had a bearing problem again!
Dennis , Please don’t overthink this,,,,if it had an oil blockage anywhere,,,it would not have lasted 7000 miles so far . The SBC is one of the finest designed engines there is,,,,,,especially a 327 ! Just warm it ,,and don’t do any high rpm until operating temp . I promise it will be fine . Lol,,,,I feel like Robert Duval in Days of Thunder . “ Now don’t worry Cole,,,,just go up there and drive through it,,,they will be gone by the time you get there,,,”,,,LoL . Tommy
Another point, isn't the byp*** actually located in the adapter above the pump rather than the pump itself? If so, changing the pump wouldn't change anything. You might want to try switching adapters.
I guess you are using a mechanical oil gauge to read pressure!? On my (M-word) SBF it has a H/L gauge but not an idiot light. The CVU on the back of the instrument panel lowers the voltage to ALL the instrument panel gauges...including the oil pressure gauge. So what you may axed!?! A pal made an adjustable CVU so now....I have a higher reading oil pressure reading!!! The take away is........."do I have oil pressure?..........Good, lets go cruise!" 6sally6
To calculate hp for a hydraulic system flow X pressure divided by 1714 or 20gal. at 100 lbs = 1.16 hp
The Jalopy Journal
