Cam Bearings

[dantegray]

I'm Mad :mumum:, has any one ever had an issue installing a cam on a 400 block build where the #4 cam bearing was too tight/small? I just tried to install a Lunati roller cam and it would not go in. I know I was being xtra carefull and after getting the cam out there is now the bearing is nicked about 1/8 inch in the bottom of the cam bearing.

Now I have to pull the whole short block apart and go back to the machine shop

 

[805moparkid]

yea when my dad had his 440 built (we didn't have a place to do it) they had to turn a couple of the cam journals down as they were to tight...

this was with a crower tq monster

 

[bOb shingler]

what might help you next time you try to install the cam is a handle for it. jegs, summit, etc. has them. it sure makes it alot easier to keep it off the bearings. you can also try the less expensive way and use a bolt about 12" long.
most of the time the bearing is tight at the edge and with alot of lube and turning it at the same time it will go in. after that keep turning it and it will ease up. after the motor is running the cam will push down on the bearing from all the spring pressure and add a tad more clearance also. cam bearings are babbit and soft so it will work itself out.

 

[Bulldozer]

the first thing I always do is fit the cam first. I do my own bearings and #4 was a little snug so I cut a groove in my old cam and used it for a scraper. a few slow turns and my new cam spun perfectly. if you take it back to the machine shop , take the cam with you and have them make sure it fits.

 

[dantegray]

I just talked to the machine shop and they will fix it, yea they said they want to mic the cam and bearing before removing it.

 

[william]

From Michael Ware's Blog at Muscle Motors



For as long as I can remember, Mopar’s have been known for poor fitting camshafts. I even remember seeing a price sheet in the mid 80’s from a machine shop in Detroit that serviced the Big 3 specifying an additional charge for installing Mopar cam bearings. It even became standard procedure at Muscle Motors to test fit a cam before washing the block for final assembly. The standard solution has always been, “just carve on the bearings to make it fit”. While this mindset works it always bothered me. If it happens to you when you get your block back from your local machine shop and want to put it together, you do what you need to do.

My problem solving nature never accepted the “just carve on them” solution (cure the problem, not the symptom!). I mean they make rod and main bearings within a few ten thousandths, why aren’t the cam bearings just as consistent (PS, they do make cam bearings just as consistent). So in a moment of clarity, I thought, if the bearings are being made correctly maybe I should check the block. I then started measuring the actual bearing bores in the block. This specification, by the way, is in every bearing book in every machine shop on the planet. What I discovered made everything I had struggled with for years make sense. Of the first 10 bocks I measured, not one of them was within spec on ANY bearing bore! Most were ½ to 1 thousands tight!!! To this day I have yet to measure a stock block that doesn’t need at least 2 or 3 housings opened up. The worst example was about 5 years ago when I measured a factory block that the #2 cam bearing was .003 tight!!!

Now the main reason most machine shops don’t measure this dimension is that even if they found something wrong, most shops don’t have the proper equipment to properly hone the cam bearing bores in the block! Due to stock blocks ALWAYS having some level of cam bearing fitment issues, our standard procedure at Muscle Motors is to hone ALL stock block cam bearing bores. This ensures if you get just a machined block or a short block from Muscle Motors, your cam will fit every time with no problem.

If you are having a block machined (at a shop of your choice) PLEASE insist that the shop measures (and corrects) the cam bearing bores BEFORE they install the cam bearings. This will save you time, effort, stress and the need to “carve on them to make ‘em fit……………….