Camshaft bush dimensions for reaming

Hello Can anybody give me dimensions of camshaft bushes fitted 73/850 commando I need to get my 7/8 reamer ground to size to install cam. I would like to know the correct size to fab reamer so I end up with the right tolerances ,I am installing new standard camshaft,timing side is a good tight fit primary needs opening up. I have had reamer machined down to fit a bush fabricated wich fits into timing side to keep alignment to bore primary blind hole and hex cut on the end to turn hope this works.i have been bogged down with to much info on the subject and need a positive dimension to aim for .would be a great help if somebody could give me the size to actually grind reamer to so the cam has correct tolerance once fitted. Thanks

Use exactly .875"
The cam journals should come new as undersized at .873" with .002" clearance.

jseng1 said:

Use exactly .875"
The cam journals should come new as undersized at .873" with .002" clearance.

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Absolutely same as jseng...
However:
In 30 years I have never had to ream cam bushings. I have an engine, just dropped off for cam bushing change, that hopefully will NOT be the first.
Be careful and do not use poor quality and mis sized aftermarket bushes

I have had to get a cam journal ground as it was oversize and then it fitted a cam bush reamed with a standard sized reamer but hardly any material was removed, more helpful for alignment as I piloted it off the other case bush.

Still the same, new out of the packet AN bushes, 7/8" reamer.
The same reamer did the swing arm bushes.
It is only used on bronze type materials.









Measure the journal, calculate the bore to suit clearance as a check.

The NOS camshaft I tried in this bore was to tight by a few tenths but rotated, trying it in other engine cases with factory bushes was hit and miss so I do not doubt K for a second.

Maybe that is part of the reason the TS journal and bush was corrugated and needed replacing (a poor factory running fit )

Dynodave installed new cam bushes in a '73, 750 for me; no reaming was needed.

Best.

RoadScholar said:

Dynodave installed new cam bushes in a '73, 750 for me; no reaming was needed.

Best.

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DD states up the page he gets that done outside (farmed out) which if so has little to do with reaming bushes and the simple question asked by the OP.
#
Its very simple.
You can take a brand new AN bush out of the sealed packet.
You can fit it to the cam journals and it will have a nice sliding fit (without measuring)

You then chamfer the oil feed hole at the OD.
Check the bore in the engine cases.
Heat the cases, use a guided mandrel to fit the DS bush and another fixture to pull the TS bush in.

The bush is an interference fit in the engine case to hold it in place (The TS two bush set up on the Mk111 was somewhat of a step backwards for that reason (imho)

It is not uncommon, once the case is back to room temperature that the bush has reduced on the ID due to the interference fit which holds it in place at running temperatures and above, it would then need light reaming to restore it to a correct running clearance (including round)

Easy to say when you have the fixtures to rectify by reaming over using sandpaper (maybe even a flapper) as has been a common practise for decades as a generalisation .

I machine the old bushes out so there can be no possibility of compromising the camshaft bore in the engine case.
Dragging (DS) or beating out (TS) the old bushes out cold is also common it seems.
It was obvious the factory beat the bushes in cold from what I have seen including a furrow from the non chamfered oil hole at the OD.

There is no good reason to use those production line yesteryear techniques these days and who knows what has been done when you do not do it yourself.

step one is to measure the cam, and verify what the OD on the bushing ends is. also if getting a "new" cam need to verify that in fact it is ground to the correct dia. I purchased a "new" cam which had bearing about 0.005" undersize. so ended up having to do new bushings to suit.

Time Warp said:

DD states up the page he gets that done outside (farmed out)

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dynodave said:

I have an engine, just dropped off for cam bushing change

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NO!
A (club member) customer just dropped it off at my shop for ME to do his bush change and my combat oil pick up mod

I look forward to the installation pics then.

You also misquoted me.

DD states up the page he gets that done outside (farmed out) which if so has little to do with reaming bushes and the simple question asked by the OP.