Try replacing the sending unit , that may be where your problem is.
Russ

 

Does this happen at idle or while at cruising RPM's? How did you secure your oil pick up tube? How far from the pan was it set? What kind/brand of oil filter are you using? I had the same problem a few years ago and it turned out to be a bad solid roller lifter. It wouldn't happen all the time and the car ran fine, I figured it was a bad oil pump, so I went to replace it and found needle bearings in my pan.

I don't think it is your bypass, even if is stuck open you will have full oil pressure, the oil just won't get filtered. If it's plugged (whicjh I always block mine off), you will have oil pressure unless your filter is completely plugged. I have heard of several times that a Fram filter caused a zero oil pressure problem, which is why I asked what kind of filter you are using. You might want to try to swao out the filter and see if that makes any difference.

 

Thanks for the reply. It happends at full throttle and while crusing, I am not thinking it is the filter bypass but the oil pump bypass. It is interesting that you had the same problem and found a roller lifter was the problem, I just installed a new set of solid roller lifters (Crower). The oil pickup is bolted to the pump, so I doubt it has fallen off. It is intersting the pressure comes back full on after a short time.

 

Try replacing the sending unit , that may be where your problem is.Russ

Thanks Russ, it is a mechanical gauge, so there is no sending unit.

 

Bypass or not, you should have oil pressure. It sounds like the oil pump is starving for oil. The pick-up may be bolted to the pump, but how far off the bottom of the pan is it positioned? I think your pick-up tube needs to be looked at.
Chris

 

WOW!! Lowcamaro, guess what brand roller lifters I was running? Yep, Crower. Your symptoms sound exactly like mine. Check your valve lash, it's easy and free. If you have any that are out of adjustment I would recommend digging a little deeper. Have you had to adjust them lately? Keep an ear out for any unusual noises. If you do have to adjust your lash, pull your lifters and look for tiny little cracks near the axle.

Hopefully that is not your problem but, if so you want to catch it early it will save you an engine.

 

Thanks Camaroman, never would have thought of this, I will chech the lash tonight

 

I would check your oil level also. I had the same setup and was a couple of quarts low and my opil pressure would go up and down. Added the oil and pressure stayed the same.

 

I am having a similar problem, I installed a new autometer gauge and it shows pressure but when I give it gass, the gauge seems to freak out and loose pressure. the oil pump is original (73' Z28 22k miles) so maybe the pump is bad?

 

I think so, I checked out the lifters and all seems well there... I have run at least 10 runs since the last time I adjusted them, but thay gapped out ok. I think I will go with my first thought and replace the oil pump, if that doe not solve the problem that motor is coming out.

http://i33.photobucket.com/albums/d84/lowcamaro/DSC00082.jpg

 

I un oil pressure guage AND the idiot light tieed off
I also do the same for temps...
One doesnt always glance at gauges every few secs or minutes, a RED idiot light catches ones attention real fast

 

When you roll the rollers in your fingers do they feel smooth or gritty? If they feel gritty you might want to replace them or have them rebuilt (if they are rebuildable). Glad to hear yours weren't failing. Might want to double check your cam gear and oil pump drive shaft as well.

 

A pump bypass that is stuck open won't usually give you zero.

A stuck open oil filter bypass won't effect pressure, just bypasses the filter.

A pickup that fell off would do it, you can tell by overfilling a quart or two and pressure comes back.

A plug falling off or popping out from the front of the cam tunnel (the outer two plugs) would also kill your oil pressure.

A lifter popping out of its bore due to a broken pushrod or rocker arm would kill your oil pressure.

A broken oil pump driveshaft would do it, but would not be intermittent.

A stripped distributor or cam drive gear would kill your oil pressure but the engine would not run either and they usually die with a very loud backfire out the carb.

Very loose bearing clearances would cause low or no oil pressure at idle but pressure would come back when you rev the engine.

A missing plug in the block under the main bearing cap would just bypass the filter, it would not cause no oil pressure.

Hope that helps.

 

Also, if you have a mechanical pressure gauge a pinched oil pressure line would do it.

A bad electric gauge sending unit would be a likely culprit if the problem is intermittent. In my experience electrical problems can often be intermittent but mechanical problems seldom are.

 

Thanks Eric, we will be pulling the pan on Thursday night and replacing the pump, seems to me to be the most likly cause, I don't think the oil pressure did hit zero because when we swithched to aother gauge and line the pressure bottomed out at 7 to 9 psi. the second gauge is a 0 to 80psi while the dash gauge is a 0 to 100psi unit. We will also be able to check the oil pikup at that time.

 

I have never seen an oil pump fail like that . . . unless something went through it (like needle bearings or metal from a flat cam)