'66 L-79 Block Cam Plug Replacement (Engine Out)

[Bob S.]

My freshly rebuilt '66 L79 engine came home recently after a comprehensive "stock" rebuild followed by as much as 2-3 hours of running on a dyno primarily at moderate speeds and loads. Another reason for running besides break-in was to check for leaks. None were seen at the time, but now after sitting in my garage for 2 weeks, it's clear there's a slight oil leak from the cam plug in the rear of the block.

Is it possible to remove the plug without partial engine disassembly first to remove the cam?

Thanks in advance for any input!
Bob

[Timothy B.]

Re: '66 L-79 Block Cam Plug Replacement (Engine Out)

Hi Bob,

I don't think you will have any problem removing the plug, it's just there to close the cam bore hole and performes no other function. Your biggest problem is removing the plug without getting anything near the rear cam bearing.

Try removing it like a freeze plug by driving it slightly sideways and pulling it out, make sure your machinest did not stake it in place. When you install the new plug use #2 sealer around the perimeter.

[Michael G.]

Re: '66 L-79 Block Cam Plug Replacement (Engine Out)

Bob,

If indeed you've determined the cam plug is leaking the fix is easy. Don't see a need to remove the freeze if there is no seapage. The cam plug typically will be a screw in plug with a recessed allen head. Locate the appropiate size allen wrench, unscrew, clean up the threads, place sealent on threads and screw back in.....ez....breezy.

Bob....you don't indicate.....is the leaking plug one of the screw in plugs or the large diameter drive in plug?

[Clem Z.]

Re: '66 L-79 Block Cam Plug Replacement (Engine Out)

if you mean the large diameter push in plug it will be better to just clean up the area around the plug and use a good 2 part epoxy to seal it up. there is no guarantee that the one you put in will not leak and by then you will have the engine in the car

[Edward J.]

Re: '66 L-79 Block Cam Plug Replacement (Engine Out)

Bob, Im with Clem, Ive used a sealant called the right stuff made by permatex, ( like RTV sealer only better)works well with engine oil, epoxy may not like the oil and may break down over time. use alittle brake cleaner solvent to remove any oil and take alittle sealant on you finger tip and smear it on the plug and let it set for a few hours.

removing the plug and putting sealant on the plug may push the sealant in the rear cam bearing, (Not Good), as the factory I believe never put any sealer on the rear plug.

[Clem Z.]

Re: '66 L-79 Block Cam Plug Replacement (Engine Out)

Bob, Im with Clem, Ive used a sealant called the right stuff made by permatex, ( like RTV sealer only better)works well with engine oil, epoxy may not like the oil and may break down over time. use alittle brake cleaner solvent to remove any oil and take alittle sealant on you finger tip and smear it on the plug and let it set for a few hours.

removing the plug and putting sealant on the plug may push the sealt in the rear cam bearing, (Not Good), as the factoryI believe never put any sealer on the rear plug.

i always use permatex non hardening sealer on the OD of the cam plug just to be safe.

[Bob S.]

Re: '66 L-79 Block Cam Plug Replacement (Engine Out)

Thanks for the ideas! It's the welch plug; not a screw-in.

Hi Timothy, I was worried there wouldn't be much room between the plug and the cam.....pretty much the same concern you expressed. At least if it becomes necessary, it sounds like replacing the plug should be possible if approached carefully. As Clem suggested, some careful inspection would be needed to identify the root cause of the weep and correct it so a replacement plug would seal.

I plan to verify the leak (it's more like a 'weep'....but admittedly after only a short operating period) by driving the oil pump with a primer, and then check the leak is gone before installing the engine.

Clem / Edward, I like your idea too. Has anyone successfully used a 'fix' like this for a leak from the large diameter push-in cam plug at the rear of the block?

'Just want to get this fixed once-and-for-all before installation....I want to minimize the chance of debris getting into a fresh rebuild and obviously don't want oil on the clutch, garage floor, etc..

Regards,
Bob

[Clem Z.]

Re: '66 L-79 Block Cam Plug Replacement (Engine Out)

Thanks for the ideas! It's the welch plug; not a screw-in.

Hi Timothy, I was worried there wouldn't be much room between the plug and the cam.....pretty much the same concern you expressed. At least if it becomes necessary, it sounds like replacing the plug should be possible if approached carefully. As Clem suggested, some careful inspection would be needed to identify the root cause of the weep and correct it so a replacement plug would seal.

I plan to verify the leak (it's more like a 'weep'....but admittedly after only a short operating period) by driving the oil pump with a primer, and then check the leak is gone before installing the engine.

Clem / Edward, I like your idea too. Has anyone successfully used a 'fix' like this for a leak from the large diameter push-in cam plug at the rear of the block?

'Just want to get this fixed once-and-for-all before installation....I want to minimize the chance of debris getting into a fresh rebuild and obviously don't want oil on the clutch, garage floor, etc..

Regards,
Bob

getting the plug out will be hard because there is very little space between the end of the cam and the plug. i have never tried to remove one with the cam in place. there is very little oil pressure on the plug because the rear cam bearing journal is drilled to relieve the pressure back into the engine. i would just clean the area good and reseal the outside and then check it with a oil pump primer.

[Edward J.]

Re: '66 L-79 Block Cam Plug Replacement (Engine Out)

Bob, if engine is still out of the car and on the dyno, nothing to loose with the sealer, its works very well.

[Joe L.]

Re: '66 L-79 Block Cam Plug Replacement (Engine Out)

if you mean the large diameter push in plug it will be better to just clean up the area around the plug and use a good 2 part epoxy to seal it up. there is no guarantee that the one you put in will not leak and by then you will have the engine in the car

clem------


I agree. Clean up the area THOROUGHLY to remove every last trace of oil and carefully apply JB Weld to the complete perimeter of the plug at the interface with the block.