- Joined
- Nov 20, 2008
- Messages
- 1,362
Lesson in making an Intermediate Shaft support tool (cut away timing cover)
In actuality this is more a lesson in How NOT to make a cut away timing cover (t/c). I thought I would share so others don't make the same mistakes I did.
After recently rejoining the CNOA I met Gary Parker the local rep. As it turns out he lives 1/2 a mile from me and invited me to drop by which I did. I found him busy working on a commando and using the cut away timing cover he’d made. I’ve always considered them to be not a necessity but still I think I was inspired. I bought some parts on ebay and the guy also had a ratty looking t/c so I picked it up for cheap thinking I could make a cut away t/c from it. Cut away t/c's are useful to support the intermediate shaft during torquing the camshaft nut and for getting accurate timing chain adjustments.
I recently found my self tearing into a 71 commando engine and was confronted with some heavily torqued nuts that seemed far tighter than anything I could remember. Maybe they had hardened into place from sitting so long. The intermediate pinion shaft became more an issue than it ever had some 25 years ago since I last did this and I found myself imagining a ruined right side crank case from stressing the pinion shaft too much and putting it's bore in the crank case out of round. But then maybe it was the empty drawers in my new roller cabinet speaking to me...
I grabbed the beater T/C I’d bought and went at it using the illustration in a norton manual as a guide and drawing an outline with a felt pen.
Here’s another version from an earlier Dunstall book:
I had to struggle with my inner feelings to bring myself to cut up a commando t/c but this was really a junker that had been chromed and the contact breaker plate had spun Or the concentric weights had flown off wearing a groove right into the breaker plate bolt threads. Still, I went about it taking off as little material as possible (and doing twice the cutting as the ones pictured in the books). After a while I had it! Now I could start tearing down the engine again, but wait, ......it doesn’t go on all the way! .......Of coarse, the pre 72 engines with the distributor had a longer intermediate pinion shaft to accommodate the extra sprocket for the distributor. (Duh)
Also the boss in the earlier timing cover is inset 1/2” deeper from the mating edge of the cover.
Now I had to cut the boss back 1/2” to match the older style T/C’s. This isn’t that easy to get at with a hack saw but finally I’d cut it down and time to get on with the real job.
But wait! It still doesn’t fit all the way on. Not even the locating dowels reach yet! Turns out the boss on the newer style T/C’s are not drilled as deeply as the older style and now the pinion shaft bottoms out inside the boss. Oh man this is getting to be a bummer.
Out with the drill and bore the boss out another 1/2” deeper and finally success! (the hard way) My cut away T/C catches the end of the 71 and earlier pinion shafts by 1/2” and it catches the end of the 72 and onward pinion shafts by 3/8” so it works for both (just like one made from the old style T/C would have).
The morrow of the story - If you plan to make one of these start with an old style T/C, (the one without the Norton name cast in the side) and you’ll save yourself 2/3rd’s the work..
In actuality this is more a lesson in How NOT to make a cut away timing cover (t/c). I thought I would share so others don't make the same mistakes I did.
After recently rejoining the CNOA I met Gary Parker the local rep. As it turns out he lives 1/2 a mile from me and invited me to drop by which I did. I found him busy working on a commando and using the cut away timing cover he’d made. I’ve always considered them to be not a necessity but still I think I was inspired. I bought some parts on ebay and the guy also had a ratty looking t/c so I picked it up for cheap thinking I could make a cut away t/c from it. Cut away t/c's are useful to support the intermediate shaft during torquing the camshaft nut and for getting accurate timing chain adjustments.
I recently found my self tearing into a 71 commando engine and was confronted with some heavily torqued nuts that seemed far tighter than anything I could remember. Maybe they had hardened into place from sitting so long. The intermediate pinion shaft became more an issue than it ever had some 25 years ago since I last did this and I found myself imagining a ruined right side crank case from stressing the pinion shaft too much and putting it's bore in the crank case out of round. But then maybe it was the empty drawers in my new roller cabinet speaking to me...
I grabbed the beater T/C I’d bought and went at it using the illustration in a norton manual as a guide and drawing an outline with a felt pen. Here’s another version from an earlier Dunstall book:
I had to struggle with my inner feelings to bring myself to cut up a commando t/c but this was really a junker that had been chromed and the contact breaker plate had spun Or the concentric weights had flown off wearing a groove right into the breaker plate bolt threads. Still, I went about it taking off as little material as possible (and doing twice the cutting as the ones pictured in the books). After a while I had it! Now I could start tearing down the engine again, but wait, ......it doesn’t go on all the way! .......Of coarse, the pre 72 engines with the distributor had a longer intermediate pinion shaft to accommodate the extra sprocket for the distributor. (Duh)
Also the boss in the earlier timing cover is inset 1/2” deeper from the mating edge of the cover.
Now I had to cut the boss back 1/2” to match the older style T/C’s. This isn’t that easy to get at with a hack saw but finally I’d cut it down and time to get on with the real job.
But wait! It still doesn’t fit all the way on. Not even the locating dowels reach yet! Turns out the boss on the newer style T/C’s are not drilled as deeply as the older style and now the pinion shaft bottoms out inside the boss. Oh man this is getting to be a bummer.
Out with the drill and bore the boss out another 1/2” deeper and finally success! (the hard way) My cut away T/C catches the end of the 71 and earlier pinion shafts by 1/2” and it catches the end of the 72 and onward pinion shafts by 3/8” so it works for both (just like one made from the old style T/C would have).
The morrow of the story - If you plan to make one of these start with an old style T/C, (the one without the Norton name cast in the side) and you’ll save yourself 2/3rd’s the work.
.
