Just got my new eng. running and have an oil pressure question? Using 10/w/30, bearing clearance ok, hv oil pump, new mechanical gauge, cold 60 psi hot 40 psi But hot in drive 750 rpm I am just under 20 psi. Seems a little low for a new eng. ?????
Also when i shut it down after running for a while it tries to continue running for a few seconds. Timing is set for now at 4 degrees, idle 750 in drive, and about 1100 in park. I have yet to hook up the vacumm advance, because when i do the problem gets worse. (Once i solve this problem I think i can fix vacum advance thru adjustment screw). I had some low grade gasoline in it when i pulled the engine, with this 10-1 comp or better, I just added 5 gallons of 93 octane and a can of octane boost. If I am not mistaken octane will cause run on??? But that gas I am sure hasnt gotten thru the system yet. I still need to adjust the valves and fine tune the carb , but these are the only 2 questions i am scrathing my head on now. Thanks in advance for any help. new eng in sig. below

 

82Z,

The run-on probably means trhe chambers are hot. That likely means that the engine and engine oil are hot. Heated oil will certainly be less viscous and hold lower pressure. Heated oil also breaks down faster and won't produce teh same pressure the next time you run. Once the engine cools, your pressure should increase again. Fresh oil will probably help a little bit more, too.

To answer your initial question, any oil pressure over 10 PSIG per 1,000 engine RPM is safe. A fresh engine is usually expected to hold more than that, but some of the factors mentioned above could explain that.

 

What would cause this???Timing????Fuel???? As for changing the oil...It has only been run with this oil in it for the 20 minute breakin and maybe about ten more minutes after that. Would break in temps be enough to break the oil down that quick? The oil pressure immediatly goes to 40-45 soon as the rpm's come off of idle so I guess that is as it should be. I do need to figure out this run on problem. I have the timing set at 4 degree's btdc without the vacum advance hooked up. That little advance wouldnt cause this problem would it? I plan on final adjusting the valves tomorrow...would this cause run on or hard starting till they are adjusted?

 

If you are running in the engine (presumably with a new cam) at higher RPM to break in the cam, the engine is making quite a bit of heat with very little throttle opening. The low air flow through the engine is not doing much to cool the chambers, so they naturally would get hot. Run-on (dieseling) is just a consequence of that. I'll bet the exhaust valves were cherry-red and the spark plug side electrodes were warm enough to glow and light a fuel mixture with no problems.

What you experienced on your break-in run is completely normal. Your timing is probably not excessively advanced at 4° BTC. Of course your oil will break down faster at higher temperatures, but is probably still adequate for the rest of your break-in tuning. Once you put it on the road, I'd advise new oil and a fresh filter. That's as much to clear out the cam break-in debris and lube as anything else. If the lower than expected oil pressure problem persists, then I'd wonder a bit.

During your run-in, the oil was probably so hot that is flowed like water, so lower pressure isn't really abnormal for those conditions. The next time you start it and allow it to run normally, I'll bet the pressure is fine.

 

That's why you have run-on. That's way too high. That sucker will drive down the road at 35 mph with your foot off the gas, set like that.

Aim for something more like 800-850 in neutral and 650 in gear.

I had that cam for a while in a motor of mine, I really liked it. It ran pretty hard. People who heard the motor described that the motor sounded "angry", like it wanted to jump up out of there and kill something (Mustangs I hope). Another guy that has a big block race car said he had been thinking about building a street car again, just because he liked that sound. Get it dialed in. I think you'll enjoy it.

 

I dont have everything fine tuned yet. I do like the sound of it. I am wondering if i dont have a vacum leak somewhere. For it to drop that much btw park and drive?? I am sure it will all come around i just need time to tune it.
You arent the first person to tell me i will like it

 

Are you sure you are looking in the right direction?
First, If your timing is to retarded you will create allot of heat due to the cylinders firing before the pistion is top dead center. So your engine will fight itself to run smooth. This will also cause not all the fuul to burn in the combustion chamber, this will lead to fuel getting by your new rings that are not seated yet and mix with the oil. this will cause low oil pressure at idle. It will seem fine when it is cold but it will drop fast as the oil and gas keep mixing and breaking down the oil.
Also timing is the major cause of run on. If you canot even hook up your vacuum advance you really have a timing problem. At an idle the port you hook your vacuum advance to should not even have any vacuum. It should only have vacuum as you increase the RPM - hince the name "vacuum advance"
If this is stock to mild motor you should run about 8-10degrees timing at idle and max total timing after the advance has kicked in at about 28-32 degrees.
If you have a big cam you need to set idle at 18 degrees and your total should be around 36-40 degrees.
You will have to set your timing curve in your distributer. My suggestion is to get a MSD mech. advance dist.
Good luck

 

I solved the timing problem and run on problem today. RB83L69 hit it dead on. The idle was to high in park and drive, this enabled there to be a little vacum on the advance at idle, also caused the run on problem. I adjusted my idle to 650 in drive/850 in park, no more run on and no vacuum at idle till i crack the throttle.
8NOJOKE---you might be right about the fuel in the oil though. I changed the oil today, It seemed thin but it was definatly not clean---- I would suspect the moly assembly lube that i used had mixed with the oil is to blame for some of the color. I cut the filter open just to make sure nothing else was going on and it was pretty clean.
Also the choke was way out of adjustment. so now on to adjusting the valves/timing/carb. A freind of mine is bringing a air/fuel gauge and a dial timing light, so hopefully in the next day or 2 i will be in good shape.
Anybody have any suggestions on oil weight/type to use after break in is accomplished. I have been doing some reading and some are using 15w50 syn. and others swear by 5w30 non- synth.????????Thanks for all your help guys

 

Well, recommended oil in my hawk was 5w30, but the crappy LS1 PCV system burned that. For a while, I ran that in both the LS1 and the ZZ4, and the ZZ4 never burned a drop.

When I converted the LS1 to 10w30 to combat oil burning, I switched the ZZ4 as well. Only difference I noticed was slightly higher cold pressure.

 

your timing should be around 8-12 degree.

thats to retarded (only do that when your looking to pass emissions.)

-- oops, i didn't see that you fixed the timing, oh well, cheers.

 

yeah I set the timing to 8-9 degrees and drove it wow what a difference.
As for my original oil press question---I found the exhaust was touching the oil pan> I suppose that was transfering a lot of heat . So I took it off today and lightly maletized it and now I have about a 3/8" gap btw pipe and oil pan. My oil pressure after 30 min. of driving is now 28-30 in drive(650 rpm) and 55psi. at normal cruise. I am getting it there slowly but surely.