tgensel

Rebuilt my 72 numbers match 350 last winter and when runing it hard today I noticed that the oil pressure will drop from 60 psi to 34 psi between 4000 and 4500 rpm. Not sure if its related but it will smoke when I back off, again at 4000 t0 4500 rpm. Heads have new bronze guides and I don't see smoke any other time. Need some help with this one!

'75

What oil pump are you using? Is it a hi volume?

Gordonm

4000 to 4500 rpm is not hard at all. It should not be dropping oil pressure at any time when you increase the rpms. You might be emptying the oil pan is you have a high volume pump.

tgensel

I believe its a stock pump.

0grandmastercorvette

What area of the country are you in, your profile didn't state anything. Because you may be having a oil issue concerning the grade of oil. The only reason I say that is that if you live in Alaska, your oil grade will be different than what I am using where I live. Also the draining of the oil pan can be an issue, like earlier posted, that I have encountered in some of the "hot" engines I have built in the past. I have used the restrictive push rods that still oil the top end enough, but make it so more oil stays in the pan so it does not become starved. Trust me, I have adjusted enough valves on a stock engine while the engine was running to say that there is alot of oil that makes it to the top end. What grade of oil are you using and how many miles are on your new engine? Your oil viscosity can be an issue. Do you know what your connecting rod and main journal bearing clearances were at the time of assembly. That can also make a difference if the clearances are to great and you are using a low weight mulit-grade oil. It appears that with having 60psi oil pressure they are close but I am just throwing out issues that I have encountered in the past. I gotta ask... did you change the oil pan or dipstick indicator and or is the dipstick tube fully seated to the engine block and not away from being fully seated?? If so, did you add 5 quarts of oil and run the engine, then let it sit a while and then check your dipstick? Often times the aftermarket dipsticks are not indexed correctly and that may throw you off on oil volume in the pan. I know it does not deal with your oil pressure problem but is the oil filter you are using a crossover to the now non-existant PF-25 AC Delco oil filter. I know the ones that GM sells as its replacement are smaller. I use the PF-35 filter which is longer which I and add extra oil to make sure there is the correct amount in the pan because I like the larger filter. It is about the size of the canister oil filters on the 63-67 vettes and is a screw on type and does not hang down below the oil pan. I like more filtration myself, especially on a new engine. Funny how the oil FILTERS keep get smaller from the early days. I guess they want parts to wear out faster. Keep us all informed, because none of us want to hear that something "bad" happened to your Vette.

tgensel

every thing is stock. Not sure what the clearances were since I didn't put together the rotating assembly I had an engine shop do it. I called them and at this point they dont have an answer. I'm using Brad Penn 10w 30 oil. Sure do appriciate the help!!

tgensel

When the engine is cold the oil pressure is 35psi ( probably 700 to 800 rpm) and will go to 70 psi when I rev it up. When its hot and Idle goes back to 600 rpm it has around 15 psi and 55 to 60 at speed. I'm using a wix filter. The lifters get noisy when it gets hot also and when I adjusted them on the stand I only went a half turn past zero lash so I was planning to adjust them running.

0grandmastercorvette

I assume that they are hydraulic lifters. And when you set the valves, you performed the cold setting like what is stated in the GM service manual where you can set 8 valves on the number 1 TDC firing position and then rotote the engine one revolution so that you are on number 6 TDC firing position and set the other eight. How many miles on your engine?????

tgensel

Right on the valve adjusment. The engine has about 600 miles on it.

tgensel

Yes hydraulic lifters

0grandmastercorvette

Did you properly "break in" the camshaft at the intial running of the engine? If the engine was "broken in" as required, what grade of oil did you use during "break-in"??
After the cam break in and the engine running to the current 600 miles, has the oil / filter been changed. What is the air temp where you are at? If it is warm where you are at , try replacing the oil / filter. Use Rotella T 15w-40. Rotella oil has lubricants that are being removed from many of the conventional oils and for many engine builders, like mine. He specifies that he wants me to use it do the quality of the oil during the first few thousand miles. The gov keeps removing ingriedents and adding more ethanol to our fuel and many of the people do not even know about these changes. But Rotella t does not get pulled into these changes because as I have been told it is the oil for the diesel industry and that they don't mess around with that. Is your dipstick indicator correct? Please let me know or call me tomorrow if you wish. "DUB"

427Hotrod

The Brad Penn you are running is likely better than even the diesel oils. They are still better than regular stuff, but they ARE being reduced in phosporous and zinc. Brad Penn racing oil is great stuff.

Your problem sounds like oil control or drainback issues. I'm thinking drainback because of the smoke when you let off. Maybe the valve covers are full of oil and getting past guides at that time. I'd look real close at the drain back holes for no obstructions. Some head gaskets overhang enough to partially restrict one or both holes.

HV pumps don't cause issues really. Think about it...all a HV does that a stock won't do is get to max pressure earlier. You can get 100+ pis with a stock pump easily with a few shims...but the HV will get to whatever pressure at a lower rpm. Your pressure is determined by clearances and oil viscosity. Even 20/50 is pretty thin when it gets to 200+ degrees...so it will flow well. 10/30 for sure shouldn't have any issues. If you're getting 60+ psi at RPM hot...that is no big deal. Sounds like a stock pump with the Z-28 spring maybe.

I wonder if there is a loose oil pump pickup sucking some air? Or if there is either too much or too little oil in pan. Too much will aerate early and too little will starve it. Maybe try an extra half qt...or drain a 1/2 qt out and see how it acts.

JIM

tgensel

Jim: I have five qts in the pan and the oil pickup tube was welded in when the motor was done! I'm stumped !! I'll pull the valve covers off tonite. Cam was broken in properly all oils have the propper zddp
Tim

Michel B

Just an amature here,, but before tearing apart,, try some synthetic 10/30 or 1040,, it will illiminate the thining possability. I to was thinking pick up tube,, but if its welded ??,, I had mine drop in the pan once,, you can tell very quickly everytime you brake, the pressure drops to 0.
good luck