I am looking to buy a 1970 vette with a an L-46 350 engine

I think the temperature was normal, but the car is several hours away, and I am going back tomorrow to see it again and finally make up my mind. I did not drive it on the highway the time before, so I plan to do that this time and look for overheating problems, pulling or abnormal vibrations. I will also put it on the lift and check for leaks and ive read on here to move the back wheels to check for worn bearings. I just remembered I noticed the oil pressure was pointing low at idle. It is all original and has about 90K miles on it

A '70 model has a mechanical/hydraulic oil pressure gauge, so if the reading is low, chances are the actual pressure is also...
One rule of thumb is 10 psi oil pressure for every 1000 rpms is sufficient. Look for the pressure to drop when you get on the throttle hard. If it does, that's a good indication of worn bearings, with too much clearance.
Does it make any noises at idle?
Just having a low reading at idle could simply mean it needs an oil change, or the oil pump might be failing. I would suggest installing a temporary gauge that would give a number readout, instead of a "Low-High" reading, if possible.
I would definitely point this out to the seller, and use it as a bargaining chip.

Good luck on the test drive...hope it works out!

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Joel Adams
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"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"

How easy is it to stab in one of those temporary pressure gauges that you are talking about? Can I get one at the parts store?

You can get one at most parts places. It's fairly easy to install temporarily. Just dis-connect the oil pressure line at the oil filter area, and connect the line from the temporary gauge. Should be able to do this in just a few minutes from underneath, a little longer from the top. Just go ahead and assemble the line on the new gauge before you get there, and that way it'll all be ready to just swap the lines on the fitting...usually takes a 7/16" wrench, but it could be smaller(3/8"), or larger(1/2").Then drive it until it gets warmed up, and see if the test. gauge reads the same as the vehicle gauge did.
Hope this helps.

And be careful of the way you route the new gauge line...make sure it doesn't get around the exhaust, or anything else that may damage it. Adams' Apple2008-10-16 21:35:18

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Joel Adams
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"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"

Thanks for the info

It could be a bad gauge, but it is not too likely.  I have had experience with bad mechanical oil pressure gauges.  They usually work or don't.  If you put in a temporary, just tape it under the hood somewhere and go look at it.  Be especially careful not to get the plastic line close to the exhaust or you will melt it and lose all your oil.

If pressure is low at idle, even if it still acceptable, it means the engine is getting well worn.  If it has good compression and doesn't smoke, you might be able to replace bearings and oil pump, and be all set.  Those can be done without removing the engine from the car.  Materials would be less than $200.00 if you can do it yourself. 

Larry

What he said...

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Joel Adams
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"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"

Joel, just a question....isn't the oil gauge line fitting just beside the distibutor to the driver's side at the back of the motor block top ?

On the older cars, yeah...usually it is...I guess I shoulda mentioned that, but...it all depends, I guess, on if it has been moved, or the engine has been replaced by a later model that doesn't have the tap in the top rear by the dist. It should be on the top side, by the distributor on the '70, tho... Hope that didn't create a problem, Bino....

Good catch there, John!   

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Joel Adams
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"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"

Joel, I always read your comments with great detail, you are one informant guy, glad your here.

Hey guys, thanks for all the information. I did have trouble finding the location you had talked about first down by the oil filter. We agreed to a price, but it was contingent on an inspection by a mechanic who would check the pressure.

Contact your mechanic and ask him how much to change the bearings and the pump, this can be done without removing the motor. (taking my time time it takes me about 4 hrs with another person giving me a hand for about 1 hr during install)Then adjust your offer accordingly. If you buy it... before you do the bearings drop the oil out of it...install new sae 30 oil with a quart of Lucas oil treatment, see what difference this makes, if it increased your pressure to a good reading you can then change the oil later and put in 10w30 synth with a quart of lucas and drive it, top rpm oil pressure is about 35-45 psi stock.

Bino,

If you really like the car, an engine rebuild ain't crap compared to body work, rust, interior, etc. If it is a numbers matching motor, pulling it and rebuilding it will probably run in the 4 grand neighborhood. You're gonna need more than bottom end bearings to put it in top shape.

You can drive it for a purdy long time with a liquid rebuild consisting of a quart of Lucas and another quart of Slick 50 with an oil change. Drive her till she starts making nasty noises then pull the mill and rebuild or replace it.

A worn out mill is not a deal killer if you find a Vette you like otherwise. These things are always a lifelong project.

Dave