drilling a .030 hole in the hidden oil gallery plug
 

I noticed my old machinist buddy was assembling a Pontiac engine for someone about a week ago. Yesterday I asked him if he had finished it and he said "yes, it was gone". He mentioned that the guy had insisted that he drill an .030 hole in the hidden oil gallery plug
because he (the customer) had read that this would prevent any lubrication problems with the distributor gear, so he did it. I told him I have been into Pontiacs for years (which he knows anyway) and have never heard of this before.

Has anyone here ever heard of this?

During this same conversation my friend also mentioned that early big block Chevys (396s and 427s) were having problems wiping cam lobes and the problem turned out to be air being captured at the end of the lifter galleries and the fix, which did solve the problem, was to drill .030 holes in the gallery plugs at the end(s) of those galleries; we didn't get into which ones or how many.

Anyone ever heard of this one?

Yes,, normal practice with Pontiacs,, especially if you run a bronze Dist. gear.

Never have done it on a stock gear,only bronze.Tom

Who has 0.030" drill bits? That is smaller than 1/32", and 1/16" is the smallest you'll typically find in a drill bit set. 1/16" is 0.0625", and I'll admit I've drilled many with a 1/16" and never had a problem.

Not only does the hole help to bleed air out of the system, it also helps to flush out trash in the passage, so I don't worry about the hole being a bit bigger. I've torn down blocks myself, removing the galley plugs, and have often found all sorts of sludge, grime, CRAP collected behind that plug - stuff which could eventually work its way into the #8 lifters, and cause them to have problems.

You can easily find a 1/32" (0.03125") drill bit or around a #68 (0.031") drill bit. These are a little delicate to use for hand drilling, so you need screw the plug into a pipe fitting and do it in a drill press.

what about a composite gear?

I thought all Pontiacs came from the factory with a .020 hole there, no?

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The H-O galley plug sets used to come pre-drilled I thought, and believe you can find plugs pre-drilled, any machine shop should have them.

Drilling one of those plugs is not fun.

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Much easier to do in a lathe

You will have to move to the numbered bits. or machinists bits. Very helpfull on carburetors. Here s a chinese set i purchases. Average chinese quality. So mic the bit for sizing before you use them. I had to return my first set of another brand. The first 4 bits were's all the same size.
http://www.ebay.com/itm/61-80-MICRO-...item4ab6500f81

I use an aluminum plug for easy'er drilling. Some will freek about dissimilar metals. But in the grand scheme, the aluminum plug install will out last the build.
If using a steel plug, pre drill thru 80% of the plug with a larger, more durable bit. Then finish with the .030 or .025 bit.

Well I'll be darn. Thanks for the responses.

Also....not all Pontiac engine builders believe in drilling the hole.

Oldsmobile uses essentially the same oiling system as Pontiac. There's a thread-in plug ahead of the distributor, and most--not all--Olds engines received a drilled plug from GM. Many of the aftermarket plug kits include a solid plug rather than drilled.

One of the Olds blocks I inspected was filled with crap up to the rearmost lifter on that bank. Had to pull the plug out and force the sludge out.

I'll never build either engine (Olds or Pontiac) without a bleed hole in that plug.

I have absolutely no idea why anyone would mount a campaign to NOT use a vented plug there. Better distributor gear oiling, no dead-end oil passage...what's not to like?

Ken Crocie turned me on to this in the mid 1980s. As stated earlier, H-O plug sets came with the 5/16" plug pre-drilled. It serves two purposes: 1) Provide extra lubrication of the distributor gear 2) Helps stop the sediment that can block the RH oil gallery.

Not a campaign
 

He's the builder with over 30yrs experience....not me and no issues with engine, also my engine is a street/strip only, not a race engine.....if that matters?

My engines get 2. One for the rear of the RH galley to oil dist gear and one for the front of the LH galley to balance the oil pressure and oil the timing chain.

I always drill them. I've found the easiest way to drill them is in a drill press, spinning very fast, then hold the plug in your fingers, and, while bracing your hands, slowly feed the plug up into the drill bit. I have drilled many plugs this way and only broke one drill bit.

I used to do the same thing until I primed an engine with the t-cover off, and saw how much oil squirts out that little hole. Also how much oil comes out the factory hole in the cam thrust plate. That made me realize that the t-chain gets absolutely flooded with oil from the factory hole, so I no longer drill the gallery plug in the front. Only the rear one.

I do the same here, one hole to spray the distributor, another to spray the timing set.

It's nearly IMPOSSIBLE to drill a .030" hole thru a standard steel plug, and not really very practical anyhow.

I drill them with a slightly larger bit, then peen the hole closed, and finish size them to .030". I can make one in about the time it took to type this.

Another very good option is to drill them and tap for a small brass set-screw, which drills really easy compared to steel.....Cliff

I had a Warrior set I used that was supposed to be 0.030. When I prelube blasted a LOT of oil out. Pulled off the freeze plug and it was 0.055 so peened it smaller and reduced the giant spray down to what to me looked more normal.