Plugging Timing Case Holes

gtiller said:

@swooshdave as I mentioned on your Facebook post, I really don’t like what I’m seeing here.

A tapered plug will not fall in to the crankcase, but please confirm that you plan to carefully deform the junction between plug and tapped hole to stop it from backing out?

Feel free to plug from the other side where you feel there is not enough material to drill and tap.

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I don't like it either, but the set screw is pretty long. You're just seeing a little cracking where the material is really thin. If I pack some JB Weld behind the screw it should be fine. I have another set of cases that has a similar screw.

Sure I can punch around the plugs. I can tell you that there is no way they can move once I drive them in. A dab of locktite would be enough. The brass and aluminum should expand at similar rates so it would be pretty impressive if they backed out.

swooshdave said:

You try to tap that hole and let me know how it turns out. Not much material on that top part.

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Yes, I know. I've been staring at it now for two weeks. I haven't seen anyone jump in here and post their grub screw tap.
It's a tough one.
After looking at yours and my abilities, I'm considering injecting it or filling it.
Silicone may or may not be OK. The thought of it or some of it breaking loose and causing carnage bothers me.
I also have an extreme dislike of silicone, but that's me.

JB Weld is up next. Thinking of using one of the injection tubes so I can lay it in there and back it out, then tool it off.
Or mix up some regular JB Weld and tool it in there with a stick, knife, screwdriver or whatever.

MichaelB said:

Yes, I know. I've been staring at it now for two weeks. I haven't seen anyone jump in here and post their grub screw tap.
It's a tough one.
After looking at yours and my abilities, I'm considering injecting it or filling it.
Silicone may or may not be OK. The thought of it or some of it breaking loose and causing carnage bothers me.
I also have an extreme dislike of silicone, but that's me.

JB Weld is up next. Thinking of using one of the injection tubes so I can lay it in there and back it out, then tool it off.
Or mix up some regular JB Weld and tool it in there with a stick, knife, screwdriver or whatever.

Click to expand...

I think a bottoming tap might work better. But I used what I had.

I will definitely punch around the set screw regardless.

There should be a blanking plug at the front of the gallery, accessible from the outside of the case?

Perhaps it might be possible to replace it with an extended plug that would blank off the opening into the crankcase?

L.A.B. said:

There should be a blanking plug at the front of the gallery, accessible from the outside of the case?

Perhaps it might be possible to replace it with an extended plug that would blank off the opening into the crankcase

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Yes there is. I was looking at it earlier, but hadn't thought of extending it.
It should match the upper one which is a 5/16 UNC or 5/16 x 18.
I'm going to look into that.
Thanks!!!

MichaelB said:

Yes there is. I was looking at it earlier, but hadn't thought of extending it.
It should match the upper one which is a 5/16 UNC or 5/16 x 18.
I'm going to look into that.
Thanks!!!

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You'd have to tap it pretty deep to extend that plug.

swooshdave said:

I'm not putting silicone there! I'd sooner fill it with JB Weld.

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Why?

Re JB Weld - I know the thought of using JB weld for repairs may sound decidedly shade tree as opposed to something more "professional," both in appearance and concept. BUT I have seen JB weld 'repair' some rather impressive holes/cracks. I did what I thought was going to be a temporary repair on a holed auto transmission back in the late '80's with JB Weld. I had never heard of it but a friend told me about it so I bought some and tried it. Turned out I never got around to buying a new housing/case and that JB Weld fix had lasted nearly 20 years when I donated the car to a local trade school - still running fine - in 2003.

NOT saying you should use it over a more mechanically 'pleasing' method but you could use it temporarily, while you wait for a new part. If you don't happen to order the new part for the next 20 years...well it'll probably still be working fine1

@MexicoMike +1 from me

It’s superb stuff:

• A smear around a new drive side oil seal
• Used to drive in blanking plugs when sorting engine breathing
• Used when inserting timeserts in those three head bolts
• Fixes in place the pushrod caps

Used for the correct applications, I really rate it highly!

Stick with the Original and avoid the MinuteWeld and KwikWeld as they seem to set up more brittle, are prone to cracking out and are not as stable at very high temperatures for sustained periods of time.

Taper threads can be good, and they do indeed ‘lock in’ well... provided the host material can take it.

They have their downsides though. Screwing a taper thread into a hole not designed for it, and / or screwing in too tight can create huge stress on the areas it’s being screwed in to. This could cause distortion or cracking or both. This is especially the case on soft alloy cases where the holes were never intended to take tapered threads.

That hole next to the cam bush comes to mind, if the taper is too tight it could cause the bush to oval.

Not withstanding the issues you’re having with the oil pick up hole.

Contrary to an earlier post, pipe thread do come in parallel threads. I once mistakenly put a tapered thread (of the correct thread type) into a Triumph timing cover that was designed for a parallel thread, it split the cover and rendered it scrap.

I’m not being a party pooper, and I’m not saying don’t do it, just trying to urge caution.

Personally, I’d scrap plans to try and tap that oil pick up. I’d use silicone, but I agree that JB weld would indeed work well. Either will do the job of sealing the hole without putting any undue stress on the surrounding material.

swooshdave said:

You'd have to tap it pretty deep to extend that plug.

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I don't think the extended section would necessarily have to be threaded but only a 'pin' of sufficient diameter to block the gallery, however, I don't have a '72 case so this is no more than an idea.

Fast Eddie said:

Why?

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Because I don’t trust that it won’t breakdown, come loose and get sucked into the oil pickup and destroy the engine. Is that a good enough reason?

swooshdave said:

Because I don’t trust that it won’t breakdown, come loose and get sucked into the oil pickup and destroy the engine. Is that a good enough reason?

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It’s your engine Dave, so any reason is good enough.

But, FWIW, if you use the right stuff, and clean the area properly first, that won’t happen.

Dave , I have used a mix of steel & aluminium plugs in both my race bike and road bike.
Race bike has had a good hard thrashing for 5 years with the current cases, all plugs are tapped and JB weld(ed) in place no issue.
They are easy to check on the race bike periodically as I have no ignition at the end of the cam cavity , so can take the timing cover off without any hassle.
Road bike has had two years of constant use since the plugs put in and JB weld(ed) and no issues so far.
The steel plugs I used in the smaller holes like the breather hose barb that the 850's have out the back of the timing chest pointing towards the g/box and the old drain back hole.
Just my two cents worth
Regards Mike

What is the deal with the Jim Comstock reed unit in the sump plug location on an 850 and the stock breather hose off the timing chest ?
I should just ask, but on Fast Ed's post it looks like both are retained which might reduce the reed performance unless the T/S was quite well sealed with only the one 1/4" oil level return hole. ?

SD, you are getting there but am reminded how lucky I am to have plenty of taps and machine tools (small lathe and mill/drill) which make a lot of jobs very easy. (and enjoyable)

Time Warp said:

What is the deal with the Jim Comstock reed unit in the sump plug location on an 850 and the stock breather hose off the timing chest ?
I should just ask, but on Fast Ed's post it looks like both are retained which might reduce the reed performance unless the T/S was quite well sealed with only the one 1/4" oil level return hole. ?

SD, you are getting there but am reminded how lucky I am to have plenty of taps and machine tools (small lathe and mill/drill) which make a lot of jobs very easy. (and enjoyable)

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The Timing case hose is probably an external drain back from the head, not a breather.

MichaelB said:

The Timing case hose is probably an external drain back from the head, not a breather.

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I see in another pic the stock head drain is in the Maney case so have asked FE/N, but yes could be of course.

No its a breather hose barb on the 850 as it was designed to go back to the oil tank.
Once the holes in the TS chest are blocked and a reed Vv installed , that outlet becomes redundant, hence the need to block it off.
The hose that would normally go there is connected to the now installed reed Vv whether in the bottom of the c/case or at the back of the c/case. Standard cases.
Regards Mike

Time Warp said:

I see in another pic the stock head drain is in the Maney case so have asked FE/N, but yes could be of course.

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For the benefit of others, TW is referring to pics of my 920 build: TW, that’s not a breather you’re looking at on the rear of the timing case, that’s the oil return from the cylinder head. This has to be done on a Stage 3 Maney head cos he breaks into the stock oil return hole when he opens the inlets ports, so it has to be welded up in the head. So, that’s also one potential head gasket oil leak cause removed!

It says ‘breather fitting’ in pen as that was simply my instructions to my machinist who had to drill and tap the hole for the fitting.

Engine breathing WAS gonna be taken care of by a cNw reed valve bolted to the back of the crank case ‘Combat style’ but this gave clearance issue between engine and box, so I’m using the Comnoz sump type that I used very successfully on the 850 motor.

My VERY limited understanding about this reed valve topic is thus:

No, you definitely do no want to keep the original breather position as well as one of the aforementioned, that would screw up the functionality.

The theory is to get the reed valve as close as possible to the source of the pressure, to avoid any ‘air cushion’ or delay in the pressure pulses acting on the reed valve. The theory behind blocking the timing cover etc is similar, the idea is to prevent an plenum chamber acting as a ‘cushion’. At revs the breathing happens as very short / sharp pulses, it’s not really ‘breathing’ as we might envisage. So, blocking the timing cover, siting the reed valve as close as possible to the crank case chamber, all helps to keep these ‘pulses’ clear and sharp.

As I said, that’s my very limited ‘lay persons’ understanding.

But what I do know with practical certainty, is that they work exceedingly well !