1967/1969 Bonnie Rebuild Desert Sled Project - Any Advice

fitting new bushes will require a trip to the machine shop

- get hold of a drift kit. this will keep you from damaging the cases or new bushes.

https://www.lowbrowcustoms.com/products/cam-bushing-driver-tool-for-triumph-unit-pre-unit-500-650

-- you will warm the cases and tap the timing side bushes out with a drift. the drive side bushes need to be pulled out using a huge tap, with a penny or something in the bottom of the bore to prevent gouging the case.

-- use the drift to tap the new bushes into timing and drive side cases.

-- the drive side bushings are delivered overlong. you can have the machinist cut the new ones to match your old, or tap them in and then have the machinist mill the ends of flush with the aluminum

-- the bushings will need to be sized and reamed. there are kits for this:

https://www.classicbritishspares.com/blogs/news/triumph-camshaft-bushing-reamer-kits



cam bushes these days can be sintered bronze or solid bronze. the more common solid bronze is much harder to size correctly. but most suppliers seem to sell pre-sized bushings now, which i have found to be on the outside of the range. i prefer to size em myself, but theyre hard to get.

if the cam doesnt turn when its all together, you'll have to reduce the thickness of the thrust surface on the timing side bushes. this is easy to do carefully with an ordinary whetstone and a set of dial calipers.





so you can do bushes, but its something of an art all by itself.

 

yes. unless you have a lathe to do it yourself.

the sintered bronze bushes are apparently hard to get these days. most places seem to carry the solid bronze ones. once installed, the timing side bushes are sized by tapping a hard 7/8-inch (0.875) ball bearing through the bush. with a soft sintered bush, this spreads out the metal to the factory size of 0.874 to 0.875-inch. with the solid bronze bushes, you can tap the stinking ball through over and over and the bush will stretch out and then relax back to the undersize. takes a long time. i might have used emery cloth on the last one i did. with a sintered bush people tell me that particles of grit get lodged in the bush, but the solid ones seem to be immune to that.

once the timing side is done, you slip in the reamer guide and use the straight-fluted reamer to carefully cut metal from the the inside of the drive side bushes. using the timing side as the centering point means that the two bushes are lined up correctly. you dont take off much metal.

you have to have the cases spotlessly clean and correctly torqued together to do this. i also put on the cylinders and torque the base nuts.

the issue with the cam seizing up has to do with the thrust surface on the top-hat timing side bush. if the thrust surface is too thick, the cam shaft will not protrude far enough through the right side case and tightening the nut on the cam wheel will lock the cam wheel against the bush:





see how the step on the cam is incorrectly recessed below the end of the timing bush? when the cam wheel nut is tightened, the camwheel will lock against the bush instead of the step on the cam. and the cam will not turn. this problem will not fix itself.

you have to do one of two thing. either machine the inner thrust surface of the camshaft back so that it sticks out farther, or grind the inner surface of the timing side bush back so that the same occurs. you need a lathe to do the cam, but the bush can be done on a whetstone.

the camshafts need to turn perfectly freely in their bushes. if they don't, you ll spin a bush and destroy the cases

 

ive done bushes several times, but only had to grind a timing side bush once.

you have to have a good set of calipers to do this. 0.001-precision is good enough.



the way to see how much metal you need to remove from the bush-- if any-- is to measure the length of the camshaft between the timing side of the camshaft thrust surface and the step on the camshaft where the camwheel will tighten against:



then you measure the length of the bush that you have:



specs are 1.010 to 1.020. ^^^ this one was too long, as the picture shows the cam doesnt protrude into the timing chest enough for the step on the cam to clear the right side of the bush. so i ground it down on a whetstone, using oil and a figure-eight motion. rotating the bushing frequently and measuring across the thrust surface in different directions frequently. doing this i was able to keep the surface i was grinding square. by the time i was done, i had the bush shortened to 1.092 inches, which is what is shown in ^^^this photograph.

these are aftermarket megacycle cams. ive had megacycle cams lock up when the camwheel was tightened twice. the first time was because the megacycle cam was machined with the bush distance too short. i mailed it back and they cut a bit more metal off it. the second time was here, where the cam was fine but the bush was too long.

there is no spec for how much the camshaft needs to protrude out of the bush. i just ground away enough of the thrust surface of the bush that the step on the camshaft stuck up maybe three-quarters of a millimeter above the bush. the cam and the camwheel are steel, so a small clearance is enough.

 

slip the bush over the camshaft first and just look at it. if the step on the cam sits outside the bush youre good to go. if the step is sitting inside the bush youre looking at modifying what you have

 

I only use a few torque settings but 5lbs to 80lbs for engine work would do.

 

1060 was megacycles hot street cam from the 1970s. they still sell that grind, but call it 510-65.

try mitch klemph for bushings. he will have advice if nothing else.

http://www.klempfsbritishparts.com/triumph

 

the 1060 was specced to use the R tappets. is there an "R" stamped on the side of your lifters?. people used those cams for street bikes and for mild road and drag racing. its got more duration and somewhat more lift than a stock cam, but was intended to work with stock pistons and head.



btw i was looking at CBS and kyle writes there that he sells sintered bushings. mitch klemph has the solid ones, which wear longer but are hard to ream. his were all pre-sized at the very outside of the specs when i last had him measure some, which is how the manufacturer manages the reaming difficulty. frankly, the cam bushes last so long that worrying about longevity is pointless. i have the solid ones in one motor, and they were a pain in the ass to size.

https://www.classicbritishspares.co...camshaft-bushings?_pos=2&_sid=6623a92a3&_ss=r[/img]

 

shouldnt matter but its odd that it was done that way. theyre generally sold in sets

obviously at least one was replaced at some timeundefined