[HWYSTR455]

I always thought the groove in the cam retainer was to bleed air? Could be wrong though...

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[grivera]

I thought the groove in retainer was to oil the timing chain...

[HWYSTR455]

Could be, or maybe even to reduce plate wear due to cam walk.


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[JSchmitz]

Originally Posted by Schurkey

You guys understand that drilling holes in oil gallery plugs at the front of the engine has NOTHING--absolutely NOTHING to do with lube on the timing chain?

The lil' holes in the oil plugs are to bleed air out of the gallery at start-up, so the hydraulic lifters don't tick.

There's press-in cup plugs with holes drilled in them direct from Chevrolet. Melling sells replacements. If they can do it, I don't know why we can't.
https://www.summitracing.com/parts/mel-mpc-52v

I have to admit, I'm second guessing myself now. LOL! I'm not as close to this stuff as I used to be. I'm positive that the one by the distributor is for positive oil to the gear. I thought that the ones behind the timing chain were same intent. So do the factory plugs, behind the timing chain, have holes?

[Sirrotica]

Originally Posted by JSchmitz

I have to admit, I'm second guessing myself now. LOL! I'm not as close to this stuff as I used to be. I'm positive that the one by the distributor is for positive oil to the gear. I thought that the ones behind the timing chain were same intent. So do the factory plugs, behind the timing chain, have holes?

No, the timing gears oil from the relief cut in the thrust plate, and a drain back hole in the front of the block.

The modification for the distributor gears is a hot rodders trick to supposedly reduce cam gear, and distributor tooth wear, the factory has no hole in the inner plug.

To be truthful I've never done either plug with holes, and my engines never had failures at either end of the camshaft. Since I only have experience with non drilled plugs I can't say that it doesn't work, but I've never had a failure without oil spurt holes in the plugs.

The explanation Shurkey gives to bleed air upon startup to prevent air having to work through hydraulic lifters, and possibly collapse as the air evacuates, is a much better reason to have the bleed holes than aiding in heading off gear wear.

It may be like blocking the by pass valve in the oil filter adapter. Some people feel they have really accomplished something by blocking it, and get a warm and fuzzy feeling for their efforts. But they really just increased the chances of rupturing their filter media, and dumping all the accumulated dirt in the filter right into the bearings. Hydraulic pressure can really do some damage without a relief system. I've seen oil filter media crushed more than once.

[Schurkey]

Another benefit to the hole at the rear of the gallery, ahead of the distributor, is that by eliminating a "dead-end" in the oil system, there's reduced sludge build-up.

Oldsmobile 330--455 engines have essentially the same oiling system as Pontiac. I bought a batch of 425 and 455 Olds cores during my "Toronado" phase. Most had holes in the plug ahead of the distributor gear, at least one did not. The core engine with no hole in that plug, had the oil gallery filled with sludge to the rear lifter. Promoting oil flow in what would otherwise be a blocked passage allows the particulates to "escape" into the oil pan, hopefully they're caught by the oil filter on their next trip past the oil pump.

The front of the oil gallery on the right-side lifter bank which gets the air-escape hole in it's plug isn't a dead end; it feeds the front main bearing, the front cam bearing, and the left-side lifter gallery. The left-side gallery gets a hole at the rear, which happens to spray the distributor gear--and I like that concept--but it also allows the sludge out.

[JSchmitz]

Originally Posted by Sirrotica

It may be like blocking the by pass valve in the oil filter adapter. Some people feel they have really accomplished something by blocking it, and get a warm and fuzzy feeling for their efforts. But they really just increased the chances of rupturing their filter media, and dumping all the accumulated dirt in the filter right into the bearings. Hydraulic pressure can really do some damage without a relief system. I've seen oil filter media crushed more than once.

I digress on my explanation about the plug hole behind the timing chain. My memory/knowledge did not serve me well on that I guess.

The oil filter bypass! I hope we don't beat that dead horse here. I've weighed in on that more times than I care to remember or admit. Blocking it is foolish. Let's see what that starts!

[Cliff R]

It is difficult if not near impossible to drill a threaded NPT plug with a .030" drill bit. First off you will have trouble finding a drill chuck that will hold a bit much smaller than about .060" in the first place. You also need to source out a real USA made 61-80 bit set as most are offshore and they will break if you stare at them too long. HUOT is top shelf, most if not all of the sets you will find are absolute pure JUNK. They aren't even on size if you mic them. Don't be fooled here, I work with tiny bits every single day and none of the Chinese varieties are worth two squirts of duck poop.

Anyhow, what I do here is to drill and tap the NPT plugs for a 6-32" brass set screw. Use a tapered tap and tap only deep enough to effectively set the brass set screws to at least flush and use Red Loctite to make sure they stay in place. Then I drill the set screw with a .030" drill bit with a small hand held drill with a tight chuck that will hold bits that small.

Second option and easier for most reading this is to drill a slightly larger hole, then "peen" it nearly shut with a small machinists hammer. After the hole is peened almost closed "size" it with a .030" drill bit held in a pin vise.

All of my engines, Chevy and Pontiacs for sure get a .030" hole in the front of the block. Be careful if tapping a Pontiac block for an NPT plug as the plug can sit too deep cutting off oil flow. You may have to do some grinding on the back of the plug with some engines.

By design the timing set gets adequate oil with the stock set-up, but I see no negatives anyplace drilling a small hole in one of the front plugs to vent the system a little more and put some additional oil on the timing set........FWIW......

[HWYSTR455]

I still say it's easiest to just buy the dang plug with a hole in it.


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[Cliff R]

Correct. I sell a couple a month, mostly to Forum members who contact me via PM or email. Although pretty easy to make your own by the time you round up what is needed you could have bought three or four of them and paid the shipping and came out ahead of the game......

[JSchmitz]

Holding a small drill bit in a large chuck is easy. It's called a pin vice. That along with good drill bits and proper speeds and it's no problem. Tough, or uneven, materials can be started with a center drill also.

https://www.amazon.com/Starrett-S162...a-570866993943

[JSchmitz]

Wanna drill a tapered pipe plug? Thread it into a pipe coupling and chucking that up in the lathe.

[mgarblik]

The way I drill tiny holes in plugs and other stuff without a lathe is crude, but it works fine. I purchased a pin vise and the tiny drills in wire sizes all from McMaster Carr. The drills are high speed steel, made in USA by Cleveland Twist Drill Co. They are pretty inexpensive, but you have to buy packs of 10. The pin vise, I cut the end off with a hack saw to make it shorter and just chuck it in a cordless drill. When I was making lifter restrictor plugs by the hundreds for Dick Ducklow for the IA blocks, that's how I did it. I could do about 32 plugs with a single bit in brass. About 8 in steel. Drilled some as small as .016" while experimenting. What size do you guys recommend for the rear and front gallery plugs?

[HWYSTR455]

I think the 'standard' for the hole by the dizzy gear is .040, but the one in the front is up for debate. I think the range is like .025-.065, or at least what I have seen.

I vaguely recall the ones H-O used to sell were .030, but am not 100% sure.

I suspect the practice of adding the one in the front, if not careful, could impact idle oil psi, but not sure by how much.


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[Cliff R]

Using a pin vise will not guarantee the bit will spin exactly on center but it is often the only way you are going to hold a tiny bit for any type of drilling operation. Most of the pin vises sold are offshore manufacturer, some or decent, others not worth two squirts of duck poop.

Brass is your best bet here with bits smaller than about .046". I also buy #60-81 drill bits in packs of 10, USA made but they still break relatively easily drilling steel, so make sure you have a couple of extra plugs available. One thing I do when drilling steel plugs is to drill most of the way thru with a larger bit, then finish the operation with .030" bit. I have one .018" bit out there right now that's drilled at least 100 holes without breaking, but with that said it will probably break the next time I stare at it too long!

I'll also mention here that the dark black plugs can be very difficult to drill as they are hardened. The shiny colored mild steel plugs are much easier to drill.......FWIW.....

[67Fbird]

yes not many folks are going to have a micro chuck,, pin vise or 00 chuck in their arsenal to hold a .030" drill. Most are going to be .060-.375 or .125-.500 chucks.. Being in the trade for some 30 yrs we do and see things differently than EVERBODY and "feel" is essential. Just one of those things.. One thing is for certain...if you drill a hole in one of the galley plugs....OIL IS COMING OUT of it. known fact.

[JSchmitz]

It is true that some black oxide (Holo Krome type) fasteners are VERY hard. As hard as a quality drill bit. Tried to extract quite a few broken off ones in my day. Not fun. Carbide time. The gorillas at work can butcher bowling balls and the like. Need to saw some of their wrenches in half!

If the chuck that you are using will not work with the bit size, it's likely that the drilling device won't go the right rpm either.

["QUICK-SILVER"]

Originally Posted by JSchmitz

Also worth mentioning is making sure to drill a hole in your front oil gallery plug to ensure plenty of oil gets on the chain.

Read that many years ago in the directions for a Cloyes tru-roller timming set.

Think it said warranty void if you didn't
Clay

[JSchmitz]

Originally Posted by "QUICK-SILVER"

Read that many years ago in the directions for a Cloyes tru-roller timming set.

Think it said warranty void if you didn't
Clay

So it's possible that I haven't completely lost it! LOL

[Dragncar]

The factory 3/8 pipe plugs with the 5/16 square hole are not so bad to drill.
harbor freight sells a set of small drill bits, 6$. They are metric. I checked them and they are roughly .040,.035, .029 and .023.
I drilled a .029 hole in the plug in front of the distributor gear and a .023 hole in another factory plug in the opposite, front galley for the timing chain.
The oil does not know its going through a metric hole.