I had my block machined about a year ago and had cam bearings installed at that time. I started assembling it last month and discovered the cam is too tight, will not go into the journals. The bearings are Dura-Bond High Performance Coated Bearings PDP-17T, I tried the cutter cam idea since they were probably coming out anyway and had no success. Ordered new bearings and talked to the shop I was going to have look over my Eddy RPMs, they use a different cam bearing installation tool/method and sounded like the quickest way to proceed. Just got done talking with him and found out he is having the same issue. He says the bearings fit on the cam journals, the block journals measured out fine and the bearings still measure fine after installation but the cam will not go in all the way. He says its as if the journals need to be align honed but he has never had to do that before. Anyone ever see this? Any ideas how to fix it? I hate to think I might have to eat the $2K I've already put into this block.
Cam Bearing Journal Issues
- Thread starter Boris7K
- Start date
R413
Well-Known Member
Find the tight area On the bearing. There should be rub marks. There is a bearing scraper to use to scrape material off the cam bearings and make the cam fit and spin normally. The block should be fine after that.
So scrape the tight side of the bearing surface the cam is riding on? I assume the Durabond Coated bearings are not prefered when scraping either.
Not uncommon to scrape the bearings quite a bit for the cam to fit.
When you drop the block off at the machine shop, you should give them THE cam or A cam to check
the bores for being straight. If the machinist finds out like you did, that the bores are a little wacky,
he will do the "Shaving" to put clearance into the tight bearing. Check your cam for runout on a pair
of V-Blocks first!!!! It may be a bent cam causing your problem.
the bores for being straight. If the machinist finds out like you did, that the bores are a little wacky,
he will do the "Shaving" to put clearance into the tight bearing. Check your cam for runout on a pair
of V-Blocks first!!!! It may be a bent cam causing your problem.
Just google scraping cam bearings.
He does have the cam to be used as well as the cam I removed and turned into a "cutter". He said the cam is definitely not the problem.
I have ran into a couple cams that I had to machine the the bearing journals of the cam. Comparing then to a oem cam they were 5 thousands oversized. I used a lathe and turned them to spec. Quality control is not so hot these days.
Usually a burr on the oil hole is the culprit for tight bearings.
Usually a burr on the oil hole is the culprit for tight bearings.
Lefty71
Well-Known Member
Not a bad idea to ask the machinist to check it again with his cam blank.... Those guys usually have one at the shop for just such cases where the customer hasnt provided them with one. You may get a clue whether your new cam is a part of the problem or not.
Lefty71
Well-Known Member
Part # ?? Thx
steve340
Well-Known Member
I talked to a guy here who owns an engine rebuilding shop. I recently had this job done on my own engine.
He said they measure all the journals - find the tight ones and grind down the cam journal.
They prefer not to replace cam bearings unless you supply the camshaft you want to use in the engine.
He said they measure all the journals - find the tight ones and grind down the cam journal.
They prefer not to replace cam bearings unless you supply the camshaft you want to use in the engine.
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