Knocking in a cam bearing, and it's tight

[Paul_G]

I nicked a cam bearing while cleaning the block. So I got a set of Clevite bearings, took out the #2 bearing, Looked it over and knocked it in. Just changed the #2 bearing. Now the cam wont go all the way in. It stops about 1/8" going in to the bearing. very stiff trying to rotate it. Wont turn by hand. I knocked it all the way through. On the bench I test fitted it on the cam and the same thing, it is very tight getting it on that journal. It has no oil clearence at all. Should I use some 3000 grit and open it up? Send it back? What do you do when this happens?

 

[threewood]

There is a specialty tool used to ream a cam bearing. I have also heard of people using an old camshaft with a cut in the bearing journals to ream in new bearings.

 

[Kern Dog]

You didn't specify what type of engine that you're working with.
My machinist told me years ago that big block Mopars were notorious for poor fitting camshafts. He said that the cam bearing bores were not all perfectly centered. The trick was to install all the bearings then line bore the bearings.
Yeah, it sounds strange to me too.
The 440/495 in the red car and 383 in Jigsaw both had tight fitting camshafts that required clearancing with this:

Yeah, diagonal grooves were cut into the journals of an old cam. This was covered in chassis grease, inserted in the block and spun several times. I'd pull it out, try the new cam for fitment and if it still didn't spin freely, I'd put the cutting cam back in and spin it some more.
Good luck.

 

[pnora]

You will have to scrape the bearing down to get it to fit. There are bearing scrapers you can buy. Scraper

 

[Paul_G]

You didn't specify what type of engine that you're working with.

I am refreshing my 505 stroker right now. Had no plans to replace the cam bearings, or any of the bearings. They all were great. It went lean and detonated badly. I am putting a lower compression piston in with new rings and going through the heads.

I measured the inside of this bearing and the cam journal. They are just a few ten thousandths apart. a different journal has .006 oil clearance.

 

[69Bee]

Bearing bores have gouges, raised metal around the drilled holes, etc. I usually ALWAYS have to scrape the bearings to get the cam to fit. One trick I do is to use a ball hone on the bores before the final wash to knock down as much as I can and sand/file any bad spots. The bearing will show the high spots so scrape, test fit, rinse & repeat until it fits. And, under NO circumstances use any sand paper on the bearing.

 

[dvw]

Scraping works find the shiny spots an do a little and fit. It's a slow process. Using an old cam with slits cut in each bearing journal at a forward angle works slick. Press and rotate. It''ll trim off high spots on any one of the five journals in one swipe.
Doug

 

[Geoff 2]

Is it the brg.....or the cam journal that is tight??? If it is the cam, I would be removing metal from the cam, not the soft brg material.

 

[493 Mike]

You will have to scrape the bearing down to get it to fit. There are bearing scrapers you can buy. Scraper

I agree. I have one similar to the McM-C 3797A12. To use in the deeper -in -the-block bearings, remove the blade and install in a old broom/shovel handle for control. Scrape the tight area and repeat where ever necessary. It should be smooth when done.
Mike

 

[roadrunnerh]

Cam was tight after new bearings in my 383, I did the old cam method Kern Dog mentioned, worked like a charm.

 

[padam]

I read the thread title and thought
“how the heck did you diagnose a knock from a cam bearing?”

 

[Doorkicker]

I read the thread title and thought
“how the heck did you diagnose a knock from a cam bearing?”

LOL... me too

 

[toolmanmike]

Cam was tight after new bearings in my 383, I did the old cam method Kern Dog mentioned, worked like a charm.

The original cam from my HP 273 is still at the machine shop. He didn't have a small block Mopar cam to use as a scraper. He does now.

 

[rickseeman]

On the bench I test fitted it on the cam and the same thing, it is very tight getting it on that journal.

"Tight cam" is a common problem. Usually I blame myself. Maybe I hammered it in wrong and "mushroomed" the bearing opening. Even though I cleaned the bore good and oiled the bearing bore and the od of the bearing in hopes of it going in smooth. Now I have to take a bearing knife and feeling with my finger and scraping the front of the bearing until I can get it in. Sometimes trying to put the cam in and turning it back and forth to put a shiny spot on the bearing to help me find the high spot. It's a tough job.
But your situation is a little different. If it was tight on the bench, and you know it will "crush" when you put it in, and this is going to be a bad situation. I would imagine your bearing bore is a little small making the problem worse. I did a video series on "Tight cam". I don't know if it will help.

 

[Paul_G]

I am feeling kind of screwed. Dropping the block off at the machine shop and waiting weeks for cam bearings to get installed is one option. Or, find an old cam I should have here somewhere. Cut a slot in the #2 journal and see if I can cut/resize the bearing with it. I am ordering another set of new bearings. I can practice on this bearing, which has been in and out of the hole now. If it works then knock in a new bearing and resize it.

Thanks for that video series Rick. It explains why this happens. I talked with my friend down the street yesterday, he is mostly a GM guy. They dont have this problem.

 

[Hemirunner]

The cam bearings have the same centers as the cam so it starts into all the bores at the same time so figuring out which one is tight is challenging enough. The cutter cam is typically the best solution.

 

[Slipping727]

Thought I remember from the old days chrysler recommending not to remove the bearings as they were burnished to size and alignment after installation at the factory. Similar to the burnishing tool used for the tower bushing for the distributor.
Could be why there are these problems today.

 

[Cranky]

Is everyone using one of those universal cam bearing installation tools?

 

[Paul_G]

My cam bearing tool is an old "hand me down" universal hammer in tool.

I cut a slot in an old RV cam. Put it in and rotated it. It is amazing how much material came out. Put the roller cam in and it was still tight. Put the reamer cam in again and more material came out. Put the good cam in again and still tighter then I am comfortable with. One more time with the reamer cam and rotated it several times, pulled it back, cleaned the groove and rotated several more times. Now the roller cam goes in and turns easy with just a little help.

 

[Geoff 2]

I never liked the 'hammer-in' method. I made my own threaded bearing pusher tool.