Tap type and coolant plugs?

CnC79X19

CnC79X19

True Classic
We bought a 1/8" pipe tap and 2 Allen head plugs to block the coolant passages in our 1500's head. Want to eliminate any chance of coolant into exhaust or intake. The passages appear to be slightly smaller than 8mm or 5/16" in size so I'm wondering if what we are about to do is our best option? The 1/8" pipe tap appears to be much larger maybe 3/8" or better so rather than drill a larger hole to accommodate the 1/8" pipe tap (not even sure of the drill size because the tap doesn't specify?) and risk screwing something up does tapping part way in with a 5/16" or 8mm plug tap leaving a considerable taper and making a couple of plugs out of 2 decent grade bolts with a slotted end to install them might be a better option? We would cost the plugs in JB Weld to seal them well instead of plumbers tape or putty. Also, how can we minimize shavings into the coolant passage with the engine already in the car?? Advice is appreciated
 
I installed 1/2 13 set screw but did not run the tap all the way down. The hole is pretty close to the minor diameter for a 1/2" tap. Then used gasket sealer on the threads and turned in the set screw. As for chips, since the hole is in the exhaust port, just pack the cooling passages with paper towel and you should be okay.

TonyK.

Grimsby Ontario Canada.
 
If you are referring to the two passages in the head that connect to the intake manifold, I used M8x1.25 set screws and RectorSeal with no issues on my 1500. In 1980, I blocked the passages in my 1300 head with silicone. They are still blocked today, although the head is trashed.
 
I also used standard thread set screws rather than pipe thread plugs. This allows you to choose whatever size (diameter) you want, so I found something that could be tapped into the existing hole without any drilling required (sorry I do not recall the actual set screw size I used). The difference in threads is the taper - or lack of it. But with some thread sealant (anything will work fine here) you do not need a tapered plug.

By the way a 1/8" NPT pipe tap uses a "R" lettered bit size, or the closest 'normal' type bit is 11/32". This is assuming you have "NPT" threads up there in Canada, and not one of the others (like BSP, etc).
 
Dr.Jeff said:
I also used standard thread set screws rather than pipe thread plugs. This allows you to choose whatever size (diameter) you want, so I found something that could be tapped into the existing hole without any drilling required (sorry I do not recall the actual set screw size I used). The difference in threads is the taper - or lack of it. But with some thread sealant (anything will work fine here) you do not need a tapered plug.

By the way a 1/8" NPT pipe tap uses a "R" lettered bit size, or the closest 'normal' type bit is 11/32". This is assuming you have "NPT" threads up there in Canada, and not one of the others (like BSP, etc).
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Thanks Doc
 
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