• Hi Guest!
    You can help ensure that British Car Forum (BCF) continues to provide a great place to engage in the British car hobby! If you find BCF a beneficial community, please consider supporting our efforts with a subscription.
    There are some perks with a member upgrade!
    **Upgrade Now**
    (PS: Subscribers don't see this gawd-aweful banner
Tips
Tips

74 midget 1275 oil galley plug

Share this page

dingleberry3343

dingleberry3343

Freshman Member
Offline
I am rebuilding a 1974 1275. Does this block lend itself to tapping the oil galley holes for installing tapered pipe plugs?

If so, what size is used? 3/8 npt?

If not, where can I get the oil galley plugs? I cannot find them anywhere.

Thanks

Tony
 
I think you can order galley plugs for the 1275 from Mini Mania or Seven Enterprises. However, on the Mini (very similar 1275 turned sideways) I used pipe plugs. I don't think any of them were 3/8". I remember some small ones being 1/8"NPT and one or two being 1/4"NPT.
 
Yup, Doug. I do that on all my engines, and 1/8 & 1/4NPT it is. I use a tapered reamer to prep the holes prior to tapping, and use AN plugs that are internal wrenching.
Jeff
 
Thanks,

Looks like the machinist drilled the galley to 1/2" so he could use a standard 1/2" press in plug.

Guess I will Not be tapping these.

tony
 
dingleberry3343 said:
Thanks,

Looks like the machinist drilled the galley to 1/2" so he could use a standard 1/2" press in plug.

Guess I will Not be tapping these.

tony
Click to expand...

The factory oil galley plugs are 1/2" O.D., two on the front of the block, two on the rear of the block. You tap them NPT 1/4" which taps into a 1/2" hole. Sneak up on them, all they need to do it set them flush with the block, so they don't interfere with the engine plates, but you don't really want the NPT plugs counter sunk very much.

To do this job right, you need two 1/4 NPT taps, a normal starter tap and a bottom tap, I made a bottom tap by very carefully grinding a standard starter tap down. The bottom tap will allow you to tap in the hole deeper when the starter tap has bottomed out.

NPT sizing can often times be confusing because it reflects the size ID of the pipe it would be use for, not the OD of the hole you have, so 1/4" NPT is correct for a 1/2 hole, a NPT tap is tapered so it gets bigger the more you tap into something. 1/2 hole is about a big as you want to go to tap 1/4 NPT, but that is what size the factory oil galley holes are from the beginning. What you do is use 1/2" drill bit preferably on a drill press or mill to get a good straight drilling, then carefully drill out the factory brass plug, then you can tap, always make sure you get all the plug out of the oil galley, the very bottom piece of the plug sometimes likes to play tricks on you and stay in the galley bore. Some people will drill and tap a smaller hole in the center of the factory brass plug and use a puller to yank the plug out, that never worked well for me, so I use the 1/2 drill bit and drill press routine. All the other plugs on the block can be done 1/8 NPT, all but one can be got on the drill press, one on the side of the block has to be hand drilled.
 
expanding on what Hap said above.......

when your prepping a case (engine block) it's important to remove those spun in brass plugs as well as the plugs in the rear and above the pan rail as there will be a lot of packed grit and sludge in these galleys that only hand bore brushing will remove.

Follow Haps' method above...and when examining the oil galley after you remove the two brass plugs at the front and rear, examine the hole...you will see that the galley is stepped larger in the front/rear. This means that where you are using the bottoming tap, that the bore is larger than the tap drill size for the first 3/8" or so. There are intersecting holes so you cant run the tap in too far or youll sink the 1/4 male npt plug, and will go too far in the hole blocking the intersecting galley. Use the .460" long internal wrenching (hex)pipe plug and not the shorter one so as to gain more thread grip area.

So getting the correct tap depth the 460" long plug will almost be flush with the face of the case at the hole with the plug tightened and no deeper. Not too tight as the threads might strip out (remember the step and not much thread depth there). What you want to use as a sealer is Seal-Lock "Fluid Weld" on the threads and let it set up for a day... if your cheap, use 2 part epoxy.

This can be a real leaker if it isnt done right. BTW, a 3/8" npt plug wont work as there is not enuff o.d. to work with.

In the oil pump galleys and the smaller galleys use 1/8" pipe.
 
Thanks,

The drill size for the 1/4 npt is 7/16. I figured 1/2" was pushing it so I pressed in new plugs.

If I have to do it again I will go ahead and tap the 1/4 npt in the existing hole.




Tony
 
Back
Top