Need help homemade engineering fix

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Time Warp said:
I'm surprised no one has posted saying they have never needed to ream a cam bush in 40 years. ;)
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When I pulled my newly bought 850 apart to fix a loose valve guide, I found a cam that ad very worn lobes and a mm or so play in the cam bushes (other than that, it was fine :cool: )
I ended up sending the crankcase to Steve Maney to get it fixed - it was just too complex for me to do.
 
Any ideas how this was addressed when the engines were assembled in the factory?
I would have thought that the cam bush bores would be jib bored at the time the cases were machined, resulting in two bores in axial alignment.
Then the two cam bushes would be driven in the bores.
The cam bush ID would shrink, but this would be a standard change in dimension, addressed by minor lapping when needed.
In other words, no line boring of cam bushes at factory.
If so, why line bore bushes now?
Is there not a simple method of lapping the one bush that has the undersize bore?
 
Stephen Hill said:
Any ideas how this was addressed when the engines were assembled in the factory?
I would have thought that the cam bush bores would be jib bored at the time the cases were machined, resulting in two bores in axial alignment.
Then the two cam bushes would be driven in the bores.
The cam bush ID would shrink, but this would be a standard change in dimension, addressed by minor lapping when needed.
In other words, no line boring of cam bushes at factory.
If so, why line bore bushes now?
Is there not a simple method of lapping the one bush that has the undersize bore?
Click to expand...
I have no idea, but I know this. I've never changed a drive side bush but I have changed the timing side a few times. The last one I did the bushing fit the new cam perfectly before being installed. Heated case and pushed the bushing in - not much force. Once cooled, the bushing was tight and out of line about 1/2 degree with the drive side. My *GUESS* is that the factory bushes were properly oversized so they were a proper fit once installed and possibly loose enough to allow slight misalignment, or that the factory ran a reamer through them (probably not line bored).

On the other hand, the workshop manual (06.5146), section C17 says: "In our experience the camshaft bushes have an extremely long life and renewal cannot be accomplished without extensive machining facilities."
 
swooshdave said:
Most people will either know how to do it themselves, take it to a machine shop or just leave the bushes alone.
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Have located a retired local mechanic who claims he can do the job has already sorted a new pressed in tight Bush in kickstart will turn down reamer and fabricate a sleeve for timing side I suggested I could purchase prefabed bush for Tside his words were not accurate enough! (like his attitude) I will make it ,and doesn’t mind me observing while he does the work.will take a few days will post results.now for slipping main on crank and loose main shaft bearing in gearbox case .
 
jseng1 said:
There are easier ways to do this.

Adjustable reamer for reaming timing side (add extended pilot bush in drive side hole).
Need help homemade engineering fix


For reaming drive side (add pilot bush for timing side hole and driver slot to turn reamer).
Need help homemade engineering fix
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I can say the fit I got with the newly reamed bushes was to my liking but took the time to go through all the spare engine cases I have using three camshafts known to be good (measured) one being NOS.

All of those cases have original bushes in perfectly usable condition surface wise.
The camshaft journal to bush fit (T/S to D/S) went, nice fit, excessive, to tight, to loose, would not fit so maybe you could get a Monday morning or Friday afternoon engine.

Maybe there was a skip of cams and if it fit it was deemed good to go.
 
If you have to buy new bush/es, do you HAVE to ream them? If so, is it because they are "under sized" when you get them, which I don´t understand the reason why, I mean the cams should all be the same diameter? Or when they are pressed in do they rarely, or never line up correctly to each other? One more: How do I check if I have to change a bush or two?
 
fiatfan said:
If you have to buy new bush/es, do you HAVE to ream them? If so, is it because they are "under sized" when you get them, which I don´t understand the reason why, I mean the cams should all be the same diameter? Or when they are pressed in do they rarely, or never line up correctly to each other? One more: How do I check if I have to change a bush or two?
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Always something to worry about. Or not. I've only ever changed out a 750 timing side cam bush and it wasn't much necessary , just wanted to upgrade to another year one and get rid of the 72 type using the bent over tabs securing washer. A known issue. But the new 850 type Frozen) went in fine to hot case. No more tab washer so the cam went in snug and fine. The drive side bush seemed fine so it's a bugger so leave it alone. Same for the layshaft bush.
 
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