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Old 07-12-2018, 01:07 PM   #16
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Join Date: Jul 2016
Location: Olathe, KS
Posts: 262
Re: '70 K20 carb options

Check the source of the oil leak at the back of the intake manifold. I had a 1970 350 4 bolt main that had a leak that came from one of the casting holes for the intake manifold gasket. When running, the oil would pump out of the second hole from the left on the rear intake manifold gasket where the intake meets the block by the distributor.

I had to drill and tap the hole and insert an Allen head plug with pipe sealant on it to stop the oil leak. It was essentially a casting problem with the block. I still ran that block 100K miles, so it was not a problem.

First, use a mirror and flashlight to locate the leak while running. If you see it at the seam of the intake, pull the distributor and intake manifold.

Then use an oil pump driver and a drill to pump the oil to see where the leak is coming from. it may take a minute or two of "priming" to locate the source of the leak.
1970 GMC K2500
Dis-use is harder on a car than mis-use.
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