Has anyone with a 28-30 plymouth engine had a camshaft bearing pressed into the block?
The cam bearing is bored into the block on these engines. My center camshaft bearing is worn. The only way to repair is to bore it out and press a bearing insert. Also, may need to turn the camshaft journal down some.
Has anyone out there had any experience doing this?
???
It is my understanding that the camshaft bearings need to be line-bored after insertion: It is not just a matter that each one has the right diameter, but the center lines of each has to match up too. It seems unlikely that honing the bearing to size would be sufficient. I guess you could get lucky, but I'd rather not count on that. I'd send the block out to a machine shop that has some experience in older engines to have those bearings installed and line-bored.
The hard part seems to be finiding a machine shop that has experience working on these old engines. I am in lower Alabama. Any recommendations would be appreciated.
It shouldn't matter if the shop has worked on old engines or not. As long as it has the correct equipment and can get the bushings there should be nothing technically different about installation and line boring the U block than the average later model engine. The only problem I can see is the attitude of the people in the shop. They might automaticallyshy away from something unfamiliar.
Brian
My problem is not with their attitudes. None of them can line bore to 1.25 inches in diameter. We are still working on a solution.
Try a shop that rebuilds early sports car engines such as MG, Healey Sprite, etc. They may have small enough equipment.
Brian
John,
I've never had occasion to do cam bearings on a '29 engine, so I need to ask some questions first.
A '29 engine has to be a four, so does it have the same general layout as most other early fours, that is, three cam bearings?
Did the '29 engine have any bearing sleeves at all, or did the cam run in bored holes in the cast iron of the engine block?
Some early fours had a sleeve bearing, steel backed Babbitt, in the front bearing only, some had sleeve bearings on the front and centre, some had no sleeves at all.
How are the cam bearings oiled on the '29, that is, is there pressure oiling to the cam bearings through oil galleries in the block?
What is the over-all length of the block?
What are the diameters (approx or nominal) of the cam bearing bores?
My first impression is that this is a rather straight-forward boring-mill job, and can be readily done if you know someone who has a Lucas or G & L boring-mill. The setup is obvious, after verifying the parallelism of the block 'deck' to the crank centre-line. If the parallelism is good, then the block is simply set up on the mill table and dialled-in on the front and rear main bearing bores.
The spec for the centre distance between the crank and cam bores should be available, but may take some research to find. If that spec is not available, then, with the block dialled-in by the main bores, dialling-in the front cam bearing bore should be reasonably close enough.
If the engine had no bearing sleeves at all, then boring out the casting to a suitable diameter to allow fitting bronze sleeves will be easy, for the front and rear bores.
A suitably small boring-bar of suitable length can be made up to bore for the centre sleeve. The unavoidable flexure and resultant chatter of the boring tool can be minimised with improvised hardwood damping-pads. With care, a sharp high speed tool for the finish cut, and a couple of very light finish passes, a clean, accurate bore can be done.
Unless there are constraints in casting-web thickness in the block, boring for a bronze bush of 1/8" wall thickness should be desirable. Making up the bushes is pretty much self-explanatory. .001 interference fit per inch of diameter is a common old standard, and should work well, but I'd use slightly less myselfl.
Allow for closure of the bush diameter when fitted to the block, so that the resulting clearance between the cam and its bushes is at least .002 on the diameter, preferably .003. Bronzes, generally, should not be fitted as tight as Babbitts. If you miss your guess by a thou or two, just ease the bush out as needed with a hand scraper.
Assuming an oil hole in the block, be very certain to have a corresponding oil hole in the bush, with the bush adequately oil-grooved on its bore. A bit of 'insurance' against the bush 'twisting' slightly in fitment is to make the oil-hole as a slot of 1-1/2 or 2 diameters, so that there is certainly full opening of the oil hole in the bush, relative to the block.
The cam itself, of course, should go to a specialist cam grinder, be straightened if necessary, the lobes touched up as necessary, and the journal surfaces ground just enough to clean up.
There is 'nothing for it' but that the cam must go to a reliable specialist cam grinder. The only good ones I knew of are now retired, so it may take some research to find a reliable specialist in that field.
If you cannot find someone who has a boring-mill and will undertake your block work, there are ways to improvise a boring-bar which can be made to work that centre bore in alignment with the end bores. If it comes to that, ask here again, and I'll explain how that can be done......but you will need, at the least, a good engine lathe and a vertical mill of the Bridgeport class.
cheers
Carla