Tight cam bearings

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Holy Roller

Holy Roller

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Has anyone had a problem with tight fitting cam bearings on a 383/440 that required additional honing, buffing or machine work. Does a roller fit different than a stock can. I ran into this at the machine shop and wondered if anyone else had this problem.
 
Because the bearings are driven in it's easy to **** them a tiny bit. I have seen quite a few machine shops do it. Sometimes a burr gets kicked up from the bearing driver disc and you need to scrape the front edge a bit for proper fit.
 
toolmanmike said:
Because the bearings are driven in it's easy to **** them a tiny bit. I have seen quite a few machine shops do it. Sometimes a burr gets kicked up from the bearing driver disc and you need to scrape the front edge a bit for proper fit.
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They have the first three bearings in..numbers 5, 4, and 3. But the cam won't go passed the number three bearing.
 
I cut 45 degree slots in my old cam and used it as a scraper to get the cam to loosen up. worked great. if a machine shop can't figure it out .......
 
Holy Roller said:
Is this a problem common to big blocks?
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not any more than any other blocks that I'm aware of. the set of cam bearings I installed didn't go in exactly square and so they moved out of shape a little so my cam was tight. i made a scraper , oiled it up , worked it in and out until it loosened up. (sounds dirty huh lol). I'm going on around 3,000 miles , running strong.
 
Bulldozer said:
not any more than any other blocks that I'm aware of. the set of cam bearings I installed didn't go in exactly square and so they moved out of shape a little so my cam was tight. i made a scraper , oiled it up , worked it in and out until it loosened up. (sounds dirty huh lol). I'm going on around 3,000 miles , running strong.
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Ok, the guy at the machine shop said he was going to have to do some buffing to get the cam to fit right. I was just wondering if it could have been the cam or the bearings.
 
Yes, it's pretty common new cambearings are tight.
Don't know about smallblocks, but big blocks, yes.

I do also what Bulldozer does; use an old cam, grind a few sharp diagonal slits in the bearing-surfaces and use it as a reamer to clearance the bearings.
Make sure the old cam is actually straight first of course.
Use oil in the process and only rotate the old cam 2 or 3 times at a time, clean the slits and check with the new cam if it fits and rotates freely.
 
I am thinking the bearings go in in a certain order, it is like a taper, each one may be a few thousanth smaller etc. I am thinking large to small, front to rear, if on is in a wrong place, it my feel like a "tight fit' like say bearing number five is in bearing number three's place.
 
BigBlockMopar said:
Yes, it's pretty common new cambearings are tight.
Don't know about smallblocks, but big blocks, yes.

I do also what Bulldozer does; use an old cam, grind a few sharp diagonal slits in the bearing-surfaces and use it as a reamer to clearance the bearings.
Make sure the old cam is actually straight first of course.
Use oil in the process and only rotate the old cam 2 or 3 times at a time, clean the slits and check with the new cam if it fits and rotates freely.
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The machinist is going to do the work for me, he has 45 years of experience. So I'm hoping everything comes out right.
 
Dartswinger70 said:
I am thinking the bearings go in in a certain order, it is like a taper, each one may be a few thousanth smaller etc. I am thinking large to small, front to rear, if on is in a wrong place, it my feel like a "tight fit' like say bearing number five is in bearing number three's place.
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I know what you mean Dartswinger 70, he's been doing it for a while. But everyone makes a mistake once in a while. I hope it's just right and not in the wrong order.
 
If a cam is bend it will most likely (when close to the 'bind'-area) just rotate half a turn and bind at the same spot everytime.
 
BigBlockMopar said:
If a cam is bend it will most likely (when close to the 'bind'-area) just rotate half a turn and bind at the same spot everytime.
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How can you tell if the cam is bent, the machinist is going to put the cam in a lathe to polish it. If it's bent , hopefully he'll be able to tell.
 
One thing that helps is to have all of the crankshaft main caps in place and torqued prior to installing the cam bearings and cam.
 
Just roll it on a flat surface or glass plane?
Polishing the camshaft on a lathe to fix the fitment issues raises some questions imo.
How does he know which bearing journal to 'polish'?
I would personally just use the lathe to quickly check the cam for straightness.
The new bearings usually only bind in a couple of small areas, easily seen by extra shiny areas where the cam binds.

Some block distortion could always be an issue over the years, but I think you would notice this amount of offset elsewehere too in the block.

EDIT: Just reread your post about just having 3 bearings in the block installed...
"Usually", with all bearings installed, the cam goes about 5/8" short of all the way in before it binds.
With nr.3, 4 and 5 bearings already in, and not being able to get the cam in any further then bearing 3, feels like he already screwed up the bearing-order, although that would be hard to do I think .
 
Common problem on blocks that have shifted.
If you look at the bearing that is tight you will see a shiny spot. Use emmory or crocus cloth at that spot. Then try it agin. Still won't go? Insert agin, spin it agin an find the shiny spot. You get the idea.
 
I had a machinist for along time do my machine work on quite a few engines, and never had a problem. Then one time on a particular 440 when I picked up the block he tells me to check the cam fit before I install the rotating assy, didn't say why. Got it home and sure as **** I couldn't get the cam in. He tells me to use a bearing knife to get it to fit , oil it and work it till it fits and loosen up. Long story short I took the block back and he put some new cam bearing in and the cam then fit fine. Had the same issue this past build on my /6, took it back to the shop (different shop down here in Florida did my /6 ) had them fix it. I think more often than not it's the shop not getting em in right the first time. Cam bearings are cheap. seized cam is not.
 
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