Hooray! Oil Pressure Problem Solved! Oil pump install hint.

[Whiplash]

It's been 8 months of slow but sure progress. My 71 one owners now has:

1) New Radiator
2) New Water Pump
3) New Front Suspension
4) New Front Steering
5) New Rear Spring
6) New Shocks All Around
7) Reupholstered Seats
8) New Soft Top (I cheated and had a local shop install it. Chickened out on doing it myself. Great job by the shop however, even if it was a bit pricy.)
9) New Tires

And now Great Oil Pressure!

Since I got it running again a few weeks ago, after fixing oil, steering, and cooling leaks, I noticed my oil pressure was very scary. I went through a lot of trouble shooting for guages, oil level, etc and was able to get 20 lbs at idle and 35 lbs at cruise with oil pressure rising to 40 lbs when revving the engine.

Last week when I went to get the soft top on I noticed that the oil pressure dropped to ZERO when accelerating. Ugggg. It would come back up when cruising but would drop when braking, accelerating, or idling when hot.

There are a lot of things that can cause this from bad oil pump, bad high pressure valve spring, bad bypass valve in oil filter housing, bad positinging of oil pick up.

I don't know what was actually wrong but I replaced the oil pump with a stock (regular volume) pump, new pickup screen, and new shaft with metal sleeve instead of the normal nylon. Replaced filter and filled her up with Castrol High Mileage 10w40 and WOW.

Now I have 40 lbs at idle and 70 at WOT. No problems at all.

A little hint. I think my problem was a combination of old oil pump and poorly positioned pick up screen.

When installing a new oil pump and screen this trick worked great. DO USE the Fel-Pro one piece oil pan gasket. It's the bet $24 you can spend. Really cuts down pain when doing this with the engine installed in the car. To position the screen press it on the pump (I didn't have the special tool for this if you can get it you really want it), install the pump on the motor, tape 3 quarters to the bottom of the screen and gently place the pan on the engine WITHOUT the gasket. The idea here is to have the pan actuall push against the quarters and raise the pick up flush with the bottom of the pan while the quarters are touching. This will give you some gap between the bottom of the pickup and the bottom of the pan. Remove the pan very carefully so you don't bump the screen! Use a Sharpy pen and mark two point on the pickup tube and pump to mark position. Remove the pump and screen as an assembly and tack weld the pickup to the pump at two points being careful not to warp the tube. Reinstall pump, gasket, and pan, prime the pump, start her up and go.

The key to this trick is that the combined thickness of the gasket and 3 quarters will give you about a .365 in gap between the pickup and the bottom of the pan. The tack welds will keep the pickup from moving when you install the pan or while driving. You can certainly use the modeling clay process but I think this cut down on steps. Like I said my problem was probably a combination of a pickup that I bumped when installing the new gasket over the winter and a tired oil pump. I should have done this step the first time and I knew it then and was mad at myself for not doing it.

The good news is that the oil pressure is now great and the motor didn't get too much use with low oil pressure.

I want to thank everyone for the combination of tips on this forum that helped me figure this out. I just wanted to post my experience in one place in case anyone else is having this problem.

Have a great weekend.

Whiplash.

 

[JohnZ]

It's also a good idea to remove the bypass valve spring when you tack the pickup tube to the pump and install it later so the heat doesn't weaken the spring.

 

[JJS]

My oil pressure = 70

Whiplash, the oil pressure in my '71 LT1 reads 70 when warming up, and with my foot just barely to the pedal. It goes back down to about 35 at idle, but right back to 70 as soon as I touch the gas.

 

[Whiplash]

Whiplash, the oil pressure in my '71 LT1 reads 70 when warming up, and with my foot just barely to the pedal. It goes back down to about 35 at idle, but right back to 70 as soon as I touch the gas.

JJS,

Thanks. That's what I've got now more or less. Man you don't realize what a drag your car is when your trying to solve a problem until you get to drive it when it's right. It's a pleasure now.

The only thing that makes me mad is that I had the pan off twice and the pump off once when I replaced the rear main seal. I told myself it would be better to change the pump then but left it alone when the parts weren't in stock and I didn't want to wait. I told myself then that I'd be sorry for not doing it and in the end I'm mad at myself to being impatient and stupid. The good news is all is well now. I don't wan't to drop that pan ever again until it's time to do a rebuild.

I'd like to rebuild the motor this winter but I don't want the numbers milled off when they plane the deck. Every shop I go to tells me that they can't tell if the deck needs to be milled until it's apart and they won't rebuld the motor if it needs to be milled and I ask them not to. One shop even said they'd "restamp" the numbers. NO WAY. If you have advice on how to get the motor rebuilt without losing the stamped original numbers please let me know. I understand the logic in a crate motor and keep the old one in storage but I'd like to have it original. I'm just uptight that way.

Thanks for the feedback.

Whiplash

 

[JohnZ]

If your block deck isn't more than .003" out of dead flat across the corners, it doesn't need to be decked; just use good composition gaskets (Fel-Pro, etc.); most rebuilders don't want to spend $30 per side for good head gaskets, and use the (inexpensive) production steel shim gaskets, but they won't seal unless the block deck and the head surface are dead flat and freshly-surfaced.

 

[joe1975]

Aren't the #'s stamped on the drivers side of the block below the head I think mine are.

 

[GerryLP]

The one thing I would like to caution you all on is that the oil pump bolt torque requirement can be excessive. I broke the main cap that holds the pump when I was almost reaching the torque setting of 65 ft/lbs.

Luckily, at a moments notice, I was able to take the cap to a local engine builder (Bud Long Motors), and he told me that some of the torque values for some Chevy engines are extremely high. He cleaned the cap and placed an ARP stud on the cap. Now the pump is being held by a nut and washer set. He recommended I use 50 ft/lbs on the nut. Alot of main caps are cast iron, and they won't take the extreme torque value. The whole thing only cost me $40 bucks!

So beware!

 

[JohnZ]

Aren't the #'s stamped on the drivers side of the block below the head I think mine are.

Nope, the stamped engine assembly code and VIN derivative are on a machined pad on the front of the block just below the front of the passenger side cylinder head; the cast-in block casting number is on the flange forward of the bellhousing behind the driver's side cylinder head.