cam replacement
- Thread starter redbloke1956
- Start date
Talking about cam timing ,an interesting thing happened to me when i was building my Comet engine, to set the valve timing I lined the marks up as suggested in the bible,and then decided to check everthing with a degree disc,WOW the valve timing was way out, much gnashing of teeth and head scratching,and genarally moving gears around failed to resolve the situation,luckily I had made a note of the the timing figures at my first attempt , then looking through the bible again, I happened on the figures for a Grey flash ,yep, sometime in the distant past had fitted the flash cam.Very confusing
Somewhere in the literature I have read that Comets with the timing marks in the wrong place are not uncommon. I've just got my Comet cam back from Gary R, so although I will time it (Mark II 105) for equal lift 4 deg BTDC, expect that his IO 42 deg BTDC will come in perfectly, on the marks. My twin (same) cams did.
I suspect - too soon to say - that GR 105's work better with a straight through (Armours') silencer - which is what Ian Hamilton who played a part in the development, was after.
If you feel the need to adjust them see MPH for January 2003...
I suspect - too soon to say - that GR 105's work better with a straight through (Armours') silencer - which is what Ian Hamilton who played a part in the development, was after.
If you feel the need to adjust them see MPH for January 2003...
If you are considering welding pinion to cam, be sure to remove the Oilite bushes first. The heat will boil the oil out of them and render them useless.
And when they "become one" they unscrew from the nut which is trapped by the timming cover and push a nice circle shaped dent in the sleeve where the piston goes up and down..........
No comment on how I know this.
Cheers, John
Perfectly true. I had a case with an open D where the engine started to labour during a test ride. Fearing a possible piston seizure, I lifted the heads and barrels-nothing wrong there. Off with the timing cover-Oh! what's this? The nylon inserts in the cam spindle nuts had melted and the spindles were a delicate shade of blue. Sure enough the camshafts had been bushed with phosphor bronze. The clue is in my copy of KTB p.111 where EMGS mentions the need for greater running clearance when using PB.
I'm thankful for the advice, but a friend in Shetland told me a story. He had a Chater-Lea, which has an overhead face-cam. The numpty (a person of low competence, see under "Westminster, recently elected") to whom he gave the cam spindle to fix, thought the 0.005" increase in diameter where the cam fits was a mistake, so he ground it off. "If you don't know, just bash on", as Andrew Lansley would say.
Even outside Shetland, Chater-Lea cams 0.005" undersize are rarely in stock in B & Q, so he had recourse to Captain Loctite, heavy-duty bearing fit company. Two years later, his Chater-Lea was still running perfectly. You may object that the ambient temperature in Shetland is low. I wouldn't argue. But it isn't low inside a Chater-Lea cylinder head.
Besides, Gary R sells good stuff.
Even outside Shetland, Chater-Lea cams 0.005" undersize are rarely in stock in B & Q, so he had recourse to Captain Loctite, heavy-duty bearing fit company. Two years later, his Chater-Lea was still running perfectly. You may object that the ambient temperature in Shetland is low. I wouldn't argue. But it isn't low inside a Chater-Lea cylinder head.
Besides, Gary R sells good stuff.
1) See MPH 648 for an article by Neville Higgins on moving cams within camwheels. Not advised for those of a sensitive disposition. Both shaft and pin will expand at the same rate, so don't heat.
2) Who knows? Suck it and see... but DO try to get sight of MPH 648, January 2003.
3) Silver steel ones should be hardened already, stainless ones work-harden, so in both cases the answer is no.
Older readers may skip this. If I were you, I would set the timing to equal lift at 4 deg before TDC. Even if I weren't you, I would certainly check that that's what I had if I'd timed them by any other method. And if I didn't have EL at 4BTDC, I'd go and make a cup of tea, and think about why not. While perusing MPH 648, p. 12, et seq.
2) Who knows? Suck it and see... but DO try to get sight of MPH 648, January 2003.
3) Silver steel ones should be hardened already, stainless ones work-harden, so in both cases the answer is no.
Older readers may skip this. If I were you, I would set the timing to equal lift at 4 deg before TDC. Even if I weren't you, I would certainly check that that's what I had if I'd timed them by any other method. And if I didn't have EL at 4BTDC, I'd go and make a cup of tea, and think about why not. While perusing MPH 648, p. 12, et seq.
