Crafty12

Hey guys, my 70 LT-1 is reading very high on the op guage. Under throttle it is right at or just over 70, at idle it drops down to between the 35 and 70 psi. I am also getting a pretty steedy drip while the car is running comming out of the sending unit on the back of the block. I assume this is due to the high pressure.

I though it might be over full as the stick was reading above full, so I did a 5 quart and filter change last night. When I started it today, same issue including the leak.

Thoughts?

TedH

I have a high volume oil pump and it easily reads close to 70psi at cruise. Drops to about 25-30psi at idle when hot. I'd venture that your rear intake manifold gasket is leaking. Could be the sender and it is easily remedied with some teflon tape. Otherwise, buy a good quality FelPro intake gasket and enjoy your gasket project

cv67

If your sender is leaking its probably shot. Get on it quick before it really heaves oil out. Bet your reading with a fresh one is different.

Mike Ward

If you've got a sending unit on your engine, it and the gauge are not original to a '70. If it's mechanical gauge, Bubba probably did you an un-favour by installing a high pressure pump the last time he played with the engine.

zwede

If the gauge is reading correctly then the only fix is to replace the spring in the pump with a normal pressure spring.

Replacing the spring is real quick and easy. Removing the oil-pan to get to it is not.

tortisevette

The leak is becuase the sender is not tight or defective. Tighen it up. If that doesn't work get a new one. I thought a 70 had a direct oil line to the gauge?

Are you letting the oil get hot before taking the readings. Cold oil is always going to read high. 70 psi at higher RPM is good, so nothing is really wrong.

You could change to a 5w30 or 0w30 synthetic oil to reduce the pressure. The wider viscosity range allows the oil to flow better reducing the backpressure, so its actually a good thing.

Autozone sells a 0w30 Castrol european formula (German) that's supposed to be good stuff. Recommended by Mercedes, BMW etc.

Easy Mike

LT-1s run a higher than normal oil pressure. Do not compare with regular small blocks. 70lbs sounds about right at start up.

gkull

You set your oil pressure with the oil weight.

Teflon tape one thickness solves most leaks

Crafty12

Thanks for all of the input guys. I just put in 5 quarts of Valvoline racing synthetic 10w30. The sending unit it leaking right where the plastic hose goes into the top of it. I will try to tighten and retape it. If that doesnt work I'll replace it.

Solid LT1

Clearances are a little tight on our 70 LT-1 but, with STD volume Melling pump runs 35PSI@idle and 70PSI at any RPM above 3000. This with grooved lifter bores to keep the cam alive, rod bearing clearances are tight at 0.002" and mains are at 0.0023"

Again this is with a STD volume oil pump (Melling M Select) and high pressure relief spring also, no bypass valve on oil filter mount so I am careful revving it while it is cold. about 10K miles on this rebuild now.

Ralphbf

"The sending unit it leaking right where the plastic hose goes into the top of it."

Sounds like a mechanical oil pressure gauge to me.

I'd pull it out re-tape the threads and put a new Farrel with an insert in the oil line it should be good to go.

I run 70psi on mine also but I have a high pressure pump.

Next oil change I'm going with lighter oil because I can.
I believe I'm running 10w30 now.

Ralph

gcusmano74

Had my small block rebuilt by pros a year ago- maybe 3000 miles on it now.
It shows 80 psi at anything over 2000 RPM when the engine is cold. When the engine is fully warm, it shows 60 psi at speed, and maybe 35 psi at idle.
I run the big WIX/NAPA oil filter 1794.