[APACHE]

Took my short block to a friend's shop to have my Comp XE284 installed and degreed in. Had to severly muscle the cam past the 2nd, 3rd & 4th cam journal openings. Once installed the cam was very difficult to turn with a wrench. Dan Whitmore drove over to take a look and the cam needed to come out as it would have wiped cam bearings instantly. Dan "miched" the cam and all journals were dead on. Used a dial bore indicator and some journals were .002/.003 undersized. This was a rebuild of a 455 that I had in operation previously and cannot for the life of me understand exactly what changed....?

Other than Dan's assumptions does anyone else have suggestions on what could be the problem?

[APACHE]

Took my short block to a friend's shop to have my Comp XE284 installed and degreed in. Had to severly muscle the cam past the 2nd, 3rd & 4th cam journal openings. Once installed the cam was very difficult to turn with a wrench. Dan Whitmore drove over to take a look and the cam needed to come out as it would have wiped cam bearings instantly. Dan "miched" the cam and all journals were dead on. Used a dial bore indicator and some journals were .002/.003 undersized. This was a rebuild of a 455 that I had in operation previously and cannot for the life of me understand exactly what changed....?

Other than Dan's assumptions does anyone else have suggestions on what could be the problem?

[PMDRACER]

Just off the top of my head...

1. Bent cam
2. Cam bearings installed slightly askew (but you did say they measured correctly, so...)
3. Slightly wider cam bearings.

I say the latter, because I know of a block that had slightly wider cam bearings installed, and that little bit caught an edge on one or more of the cam journals (possibly casting flash) where the 'normal' bearing would not contact, and it squished the bearing just enough to get the problems you describe.

Just my 2 cents.

TIGER EFI - Electronic Fuel Injection for the Traditional Pontiac Engine. [email protected]

The point to life isn't necessarilly the decimal.

[63Longtop]

Recently had the same problem on my motor! However I did have several journals .002 undersized. I wouldn't rule out the fact of the cam being bent. Have a machine shop check it on a lathe.

[Skip Fix]

My "first" Comp XTreme Energy 262/270 custom grind for my son;s street car had one journal that was only 0.001 bigger than any the other cams I had on the shelf and did the same thing. Second one fit OK, I ended up eating one set of shipping from Comp though in the shuffle.

[Tim Corcoran]

APACHE

Dan you said that Dan's measurements inducated some of the journals were undersize. Good reason would be that is the problem. My guess is that it's the bearings and not the journals them selves considering that you didn't have problems previously. You can hone the undersize bearings or replace them. Sine your short block is assembled honing the bearings would be easier.

Tim C

65 LeMans, 3550lb. D-ports and a flat tappet cam, 10.90@121

[wholio]

What can happen during cam bearing removal is who ever is removing the bearings may have the cam bearing tool to tight when driving out the old bearings. This scores the surface between the block and the bearing. Sort of compressing the bearing slightly, making the bearing tight on the cam. Remove the bearings and feel the surface to find any raised spots. Take a dremel tool and knock them down. They will be across the entire surface under the bearing. Hope this is your problem. Try it before you dump on the cam. It happens in some shops when breaking in a new core man.

[Rob]

You have a block with small and more than likely varying cam bores, the right cure is to re align-hone the cam tunnel, bad news is that's pretty tough to do.

Dial bore gage your cam bores. Cheapest fix is to custom fit the bearings you have by honing each bearing. Might ask Ken Keefer what it cost to make some customs by durabond. Third disaster fix is have comp Grind the cam.

Sorry no easy way out on this one.

-Rob

[Tom McQueen]

Had a similar situation. Turned out to be the cam (bent I assume, but I never measured anything). I had purchased a big hydraulic cam, had second thoughts about it and bought something smaller. The small cam was a PITA to get in the motor. And when it was in it wouldnt turn easily. Actually broke this cam removing it. And the big cam? It slid right in. Never had any issues once it was running. And it wasnt to big after all.

[Rob]

I suppose you could be lucky and have bad cam, measure everything.

-Rob

[Tim Corcoran]

Apache,

I think we have over complicated this for you. Since you didn't have problems with the previous cam I think we can rule out your cam bearing bores in the block being undersize or misaligned. I think worse case scenario your cam bearing bores may have been nicked during cam installation which causes the undersize condition. It could be that your cam journals of your new cam are slightly larger than the previous cam. Everything has a tolerance, if one thing is on the high side of the tolerance and another on the low side you could have a tight fit even though everything is in tolerance. This is called accumulation of tolerances. Also your bearings may be either on the high side of the tolerance or actually oversize (too thick)causing the bore to be undersize. If it were my motor I would just hone the the bearings that measured undersize just enough to get the cam to turn freely in the bores. This would be an easy task for a competant machine shop. Good luck and let us know how it turns out.

Tim C

65 LeMans, 3550lb. D-ports and a flat tappet cam, 10.90@121

[Sporter]

Just had this issue with a new XE284H in my son's 455. It was smooth until the last bearing, then required a ratchet to turn it. Everything miked out fine and the bearings have about 16k miles on them and look great. We just lubed it up and ran it. After about 100 miles we tore it down to advance the cam and it spun freely by hand. The journals and bearings looked fine. If I remember right, my 455 had an issue with a stiff Crane cam too, but turned easily after initial break-in.

[Skip Fix]

Mine was so tight you definitely couldn't turn it by hand.

[Ken -Ace- Brewer]

We see this ALOT! Your best bet is when you are rebuilding the motor, measure the cam bore journals. If they are too tight. We usualy take a brake hone to the bore. Hone it, measure it, hone it, etc! Once your bores are correct, you will NOT get the same crush in the bore. It will be looser! Looser bore make for less crush on bearing, hence more clearance is achieved!
Most comonly the 4, 5 are the problem. Sometimes 3.
Be cool,

ACE-P.P.R.

[tonyk]

The guy at the shop that did my motor showed me a pretty slick gizmo he made to hone cam bearings.he took an old cam and machined a small V-notch into each journal.He said it worked great for lowering any high spots.