[Skip Fix]

I've found even in the same hole NPT plugs or even AN fittings are all over the place in how much they screw in. I don't think many are a standard size so I'l usually tap the hole to match the plug/fitting I am using. I've had a couple of plugs in intake crossovers almost not get tight if tapped too much.

[67cruiser]

After machining and having a block cleaned really no way of machine metal to get out of the areas. So removing the front and rear plugs and running a riffle brush thru them gets you oil galley area clean and keeps oil pressure steady i believe. Remember when you remove rear one to put a .025 to .035 hole in the plug for the distrib. oiling. While your at it have the plug removed next to distrib. usually a square one and pick up your oil pressure there right from the mains!!! Worked for me for yrs.When my block came back from machine shop even with plugs out i washed block down with detergant blew out everything & still got some old oil chunks out!!

[Firebob]

Well I tapped them today. That 3/8 pipe tap was a tough fit. I finally figured out that 5/8-18 tap was easier to get the threads started with. Once I got a thread to bite then switched back to the NPT tap and things went much better. I stuffed a rag in the hole first just far enough to tap the hole. Then cleaned all the chips out with air and a brush before pulling the rag out of the gallery. Clean as a whistle. I'll still go through one more time before I button it up. They ran it through one of those block wash machines after they decked it so it was already clean. I'll probably grab a couple different types of plugs at the hardware store and use the one that fits best.

[GOAT WHORE]

Originally Posted by Firebob

They ran it through one of those block wash machines after they decked it so it was already clean.

Does not mean its clean. You really need to wash that block rifle brushes and all when you get it back from the machine shop.
I got a crank back one time that had some weird rubber pieces in the oil passages even after they cleaned it. Had I not paid close attention and ran a brush thru them I would have had failure for sure.

[Firebob]

Probably a good idea at any rate. I will say it was clean on the outside anyway.

[lust4speed]

Originally Posted by gtofreek

I used to do this until I primed an engine with the timing cover off and saw just how much oil floods out of the cam thrust plate onto the t-chain. It is a TON! Now I don't drill them anymore. Just the one in back to oil the distributor.

I coated the side of my motorhome that was 20' away before I could get my finger off the drill trigger...

[Cliff R]

Just a note on drilling plugs to oil the distributor gear, and timing chain if you choose that deal.

The softer shiny steel plugs from the gasket sets drill much easier than the black hardened plugs you find at most hardware or fastener stores. Even so, it's nearly IMPOSSIBLE to drill a .030" hole thru one without snapping the drill bit.

I drill a larger hole and either tap it for one of our brass screw in Q-jet airbleeds, or peen the hole down and re-size it with a .030" drill bit. Either way takes only minutes vs trying to drill a thick steel plug with a tiny little bit.......Cliff

[gtofreek]

I hold the plug in my fingers and slowly feed it up into the drill bit spinning at a very high speed in a drill press. This way, I don't break drill bits. Trying to use the spindle feed on the drill press to run the drill bit down through the plug will almost always result in broken drill bits. Never broke one feeding the plug up with my fingers. Also, I chuck the bit up until there is only about a 1/2" exposed.

[428GTO70]

Originally Posted by gtofreek

I hold the plug in my fingers and slowly feed it up into the drill bit spinning at a very high speed in a drill press. This way, I don't break drill bits. Trying to use the spindle feed on the drill press to run the drill bit down through the plug will almost always result in broken drill bits. Never broke one feeding the plug up with my fingers. Also, I chuck the bit up until there is only about a 1/2" exposed.

This is what I did also, fed the plug up into the bit while holding it. Worked like a charm and I didn't break any of the bits. And I had spare bits because I was SURE I would break a few

[gene simmons]

Originally Posted by lust4speed

I coated the side of my motorhome that was 20' away before I could get my finger off the drill trigger...

That's funny right there.