Hot Rods Oil Galley Plug Conundrum

Morning fellas,
I got my SBC back from the machinist and did my first round of cleaning last night. The only plug that didn’t get removed from the block is the one that is on the odd (driver) side bank under the cylinder head. I have an earlier block so it is the solid slug that has to be removed by drilling, tapping, and a slide hammer. In what I have been researching, there really is not a direct replacement sold for this slug and the hole is an odd size that is to big for a 1/4” NPT plug and can’t be made bigger for a 3/8” NPT plug and there aren’t really any soft plugs that are the correct size. So….do I just leave the thing in there and take a chance (my feeble brain says not a good idea)? Does anyone have a viable solution for the replacement of this plug? Is my research wrong and I can tap this to 3/8”? Just looking for a little guidance, thanks!

 

Lookup how much of a over size is required for press fit , it will be a few thousand bigger ,
Or can fine thread tap ,sae or mec ,
use hight temp
Pipe Sealant ( loctie ) on threads
Its just a hole drilled for oil galley passage,, Press fit Plug or threaded
About .010 below deck after installed
Brass or aluminum for press fit slug ,
Also maybe race retainer Green

 

Thanks Eddy. So you’re in agreement that I should remove it. I’ll keep looking to see what I can find to fit the diameter. It measured out at .515” inch. Just a complete oddball size, nearest expansion plug I can find is .540”. I’m going to measure up some bolts to see if I can’t make my own plug.

 

.540 way to big , off top of head
.517 .518 , There are charts for press fit,
Another Ideal , maybe where plug
( Not sure off top head)
if goes to main
Maybe small rubber hose & vac

 

Might be something metric that would work.

 

leave tne plug in and drill and tap for 1/8 npt.?

 

Thank you for the help gentlemen. Looks like regular old steel expansion plugs like you would use in the cam galley should fit. Just got some from the local parts store and it think they will do just fine. Sometimes reading about stuff and not working on it gets you in too much trouble. Hopefully, this will help someone like me in the future?

 

that should/ would work ,
Looks to be 1/4 deep wall/ pocket
& Green loctie , install flush thoe,
@ Deck height ,
I wonder why not used originally,

 

If you want to go with something threaded, you're going to be limited to what you can find in a "allen wrench" plug.
For a press-fit solution, I've used a Q-tip to wipe in a skimcoat of Loctite or JB Weld. You don't want to 'snowplow' a lot of either of those into the oil galley.

 

Well…that was a miserable experience and I’m an idiot. But I’m going to share so that it has been documented that I am a moron.
First: Put grease around the hole and on the drill bit so the chips stay somewhat contained
Second: Tried to drill a 3/32” hole for a 1/4”-20 tap so I can rig up some kind of slide hammer to get this plug out. Learned quickly for the 764th time that my drill bits are the dullest in all the land. Proceed to grab Christmas tree bit. Success! (Kind of)
Third: Begin to tap bottom of hole (since I used a step bit). Break tap off in hole. F@#$.
Fourth: We are beyond trying to tap. Screw it…drill the bastard out. Spend lots of time because, again, drill bits are dull.
Fifth: Got the walls of the plug thin enough to bend with a small flathead screwdriver. Now I can slide it out.
I put the pics in order below so that anyone doing this in the future reminds their machinist to do this. By the way. The 1 inch of gallery I was able to access was spotless…but…piece of mind.
Didn’t put the new plug in yet because I’m going to clean the block all over again. Can’t hurt. I’m going to use red loctite because that is what I have. It’s that or Ultra Gray.

 

I wonder why GM would make that special plug?

 

Might want to tighten up your stand bolts before you swing heavy parts into that block.

 

Agreed. Some idiot forgot to put washers on the bolt heads and they crept into the sleeve. There is plenty of thread in the block, I just have to put the washers on the other end.
PS-I’m the idiot that forgot the washers

 

Specifically to aggravate me 50 years later.

 

Tell me again why it was so important to remove that plug-from-hell....just to replace it with another plug glued in with
"liquid-molten steel" to never be removed again.......?! (I know....because it was there)
6sally6

 

Because with my luck, there would be a BB from the shot cleaning process lodged up behind that would come out on initial start and wipe out the engine that I invested ungodly amounts of money in. I complain….but the piece of mind is worth it to make sure that gallery was clean.

 

I have never removed those plugs when having a block hot tanked.

 

I wish I was near I would have turned you a slug on the lathe to fit perfectly . It’s been a while since have touched a GM engine , but I’m sure it could be threaded a bolt thread and set screw type fastener could have been threaded in . Later blocks had a threaded hole that the freakin plug always leaked requiring removing a head to repair the leak

 

If you've been a good boy, maybe Santa will bring you a Drill Doctor.

 

This has been a learning experience for you, and the more frustration involved, the more you learn. Not trying to be a smarta**, I mean that in a good way. Although it's too late now, here are some suggestions/opinion.

I would have rotated the block upside down to do any drilling and maybe hooked up some air that would blow thru from the inside as you drill. That way chips would tend to go away from the hole instead of into the hole. If not completely upside down, at least on a downward angle . I wouldn't have used grease to catch chips, because any that did fall into the hole would want to stick inside the hole, whereas just plain chips should blow out more easily. Now that you have done the deed, I would flush the oil passages with diesel fuel (kerosene costs too much). Remove the engine from the stand and try not to turn it sideways or nose down.....that way any possible chips should stay at the rear of the motor, then sit it in the diesel fuel rear face down. Flush fluid thru from bottom of that passage if possible. Then raise out of fluid and blow air while rear of engine is still downward. The diesel fuel should dissolve any grease and the flow and air should wash it out well.


When tapping a hole, cast iron usually taps easily. Just use a little oil. Also, tap a thread or two and then back the tap up to clear the chip and make tapping easier. Clearing a chip is a touchey/feeley kinda thing. Don't force the tap backwards. Turn it back and a little force should clear the chip. If it doesn't, turn forward slightly and back it up again. Sometimes you have to do it a couple times to clear the chip out. Then continue tapping deeper and backing the tap to clear the chip every couple of turns or so. If a tap feels like its taking too much force to make a thread, back it out and start again. If that doesn't help, get another tap. Something people don't consider is that taps do get dull, and hard to tap holes are often caused by slightly dulled taps. I find that using a drill that is slightly larger than the one specified on the tap chart often alleviates hard tapping. Maybe up to .010 on a medium size tap or larger. Try it on a test piece of steel by drilling 2 holes and tapping them with the same tap.

 

And when tapping a hole, always keep the T-handle bar centered over the tap. That keeps you from pushing or pulling sideways on the tap... a sure fire way to break one. Tap sockets that allow you to turn them with a ratchet are really handy but you need to be careful with them for the same reason.

 

Thanks guys! Really good information here, not just for me, but for everyone. Like I said, I hope my buffoonery helps someone else out

 

Hahaha…funny thing is I had one. Broke before I ever used it!

 

Asking for information to solve a problem usually shows two things about the person..........

1: He lacks experience with doing the problem he is trying to fix..........just like we all did the first time we tried.
2: He is intelligent enough to realize that people can /will give him the benefit of their experiences.

In no way is attempting to arm yourself with info before doing battle with some problem Buffoonery........IMHO

 

Like @ekimneirbo has mentioned in a few post above, One that is a learning
Trial and Error , is when you brake a tap
Then time getting it out , You learn to tap a few turns @ a time , lube , clean flutes & threads.

 

Was the plug under the rear main removed when the block was cleaned...? That one is often overlooked too...

 

I have seen a few engines assembled ,
Oil leak spraying out because not install @ machine shop ,
I have even seen on sbc where bottom end was assembled & turned over set to TDC, then heads installed & torqued.
Engine lock up / stuck ,
Dome piston's up side down!!

 

Had to think about the upside down pistons for a minute…

 

I was almost able to put my pinky finger
Between block & head , I was surprised
That Intake was able bolted up,
When I was called to check out ,
When I seen engine ,, lying on ground there was a 4 ish foot cheater pipe ,
24 inch 1/2 drive , crank bolt was rung off !! They just did not know about things

 

For those thinking of threading the hole, 9/16 NF would work well.