I have a running 540", i am swapping the cam.

I pulled the motor and pulled existing cam out. The new cam will not slide into the engine all the way. It stops at the last cam journal. I am sure i can force it in, but it will not slide in. I tried putting my orginal cam in and it slides in just fine, all the way in. Tried the new cam again, and it stops at the same spot, about 1" from being installed.

I have read all about how cam bearings can do this or that once installed, but they all address new engine builds where the cam does not fit. Not a running engine and a cam swap.

What do I do?

Is it a bad cam?

I would measure cam journal size on old cam & new cam, so you have a comparison. Just in case there was incorrect machining/grinding performed on new cam.

Should be no reason why new cam does not fit, other than size interference

Measure old vs new bearing journals

Check the cam to see if it’s bent/a lathe and an indicator or V blocks and indicator

Really all you do is try to find out why

People forget that when new, the factory installed the cam bearings then actually "line bored" the whole she-bang. New bearings take you back to square one.
I've had this same situation happen. I pulled out a '509 to put in a Lunati Solid and while the '509 fit easily and spun with almost no resistance, the Lunati would not fit. I had to make THIS:

That was an old stock cam. The diagonal grooves were packed with wheel bearing grease. I installed the white cam, spun it slowly and removed it to clean the shavings. I did this numerous times until the Lunati spun as easily as the '509 did.

Been there, done that

Maybe the 200 dollar SnapOn hammer.

It doesn't fit for a reason, find it

been thru this a few times. used to do the "bearing sizing" with an old cam but would rather not anymore. i think the issue is journal run-out or size on the camshaft. the only way to really know is check size and run-out on the new cam. the last one i did for myself was a little odd. i had 3 cams i could use for one engine and the first i tried wouldn't go in but the second fell in. i didn't want to cut the bearings so i just ran what fit. the bearings are soft and have a lot of conformabilities. checking the new and old camshafts journals and run-out will tell the story if cams or bearings are the issue.

Once you find the interference by measuring you will know. Although the old cam with grooves trick works it makes I cringe for a number of reasons. Unless you pull down the engine that is likely to be your solution if you dont find iszue with the cam journal size. In my experience there usually a few tight cam journal bores towaed the back of the block.

I hear that undersized cam housing bores and bearing scraping is common on mopar big blocks.
And just for reference, my old mega block had the 2nd and 3rd bores .001-.0015 undersized and had to be corrected.

AG.

The first engine I ever built had a tight cam bearing but what did I know. Bolted up the motor and away I went. A year later I had reason to tear it down again ... and found the bearing seized to the cam and spinning (quite freely) in the block.

I don’t like the idea of scraping off one side then leaving a big gap on the other side, how do you know the cam with the cutting grooves is not bent?

Has the OP even measured the journals against a "known good" cam yet to determine if the cam is an un- finished cam? He had a cam in the block already that turned smooth so why do so many people think the block or the bearings are at fault ? All we need to do is whip out even a cheap HF digital caliper and check it out
Have seen more than one cam with wrong size journals

Gus

[u][/u]

Yep….I wouldn’t be cutting on cam bearings that are already used and known to be good with a previous cam.

im going to take it to my machinst to check for run out, and see if the cam bearing journals are the correct size.

I had this problem also. Took out my older Hughes cam to swap in a new Comp cam and it did not fit. Grabbed a used Mopar 484 cam I had on the shelf and it slid in no problem just like the Hughes cam. Started measuring the cam journals and found the older cams were at the low end of the spec. and the new cam was at the high end. Also found the new cam was slightly bent. I took it to the machine shop and had him straighten the cam and polish the journals and after that it fit good. Just cause it is new don't mean it correct, I would be checking your new cam over good before I would start messing with the bearings.

Saw a recent build on a guys YouTube channel and the journals on the new Comp Cam were oversized. Tech support reviewed the records and admitted to this mistake. The journals were corrected for free all though the builder obviously was out the time for having this all corrected.

I just got a comp solid big block cam, that was nitrided and it also would not slide in the block. The block has new coated cam bearings, every other new cam I have did fit, comp was about a .0012 too big, it was straight just too big.. Common problem now it seems like.

Too big a cam might be the way to go on rebuild, now each bearing can be centered and cut true if block journals are off.

It amazes me with the machining tools available today any engine part needing precision isn’t with in .000x. Like buying a new $6000 block that needs line hone , deck, and other tune ups.
Doug

i agree with Doug.
as a former machinist, [45yrs worth, and still practicing !] the object is to make items to blueprint spec.
the newest and best machines out there [even five years ago] brag about how great they are at finishing items to the 0.0000 tolerance, and even self correct for tool wear as well as detecting tool breakage, stopping the machine when breakage is detected, or tool wear is at the limit of the tolerance.
my opinion is there is absolutely no reason reworking of items should be needed if bought from a reputable source with modern tooling.
mistakes can, and will happen, but there is just too much reworking needed anymore on a lot of different items, that should absolutely not be needed.
the only thing a guy should need to do is clean, inspect, and install. [unless you are like me, and try to save everything cast off by others, like abandoned dogs. i like dogs better, that's why i didn't say cats. ]
just a crabby old man mumbling in his oatmeal.
your mumbling will vary..............

I wouldn't tough the bearings in the block. measure the old cam that fit versus the new cam that won't. I bet you'll find the new cam has one or more journals that are too big.

When I hear myself saying it in my head, it’s seems pretty obvious....... to me at least.

You wouldn’t install a new crankshaft without measuring the journal sizes...... would you?
And if you didn’t...... well you could still plastigauge it.

Of course, plastigauge isn’t an option for a full round bearing..... so at a minimum you’d want to at least measure the journals and make sure they’re to size.

Same goes for straightness. I always check it...... on cranks and cams.

Factory BB Mopar blocks are fairly notorious for having screwed up cam tunnels........ so when a cam won’t go in, it’s 50/50 which is the culprit. If the cam is straight and to size..... the problem is the block.

In cases where one cam fits where another doesn’t....... its a safe bet the problem is the new cam.
But..... you gotta measure it to know for sure.

Probably the best analogy that could be be made - crank versus cam - measure them both.

Up until I stopped visiting the engine plants at Chrysler in the early 2001 time frame, we machined ALL the cam bearings after they were pressed in to the block.
They were called “green” bearings because they were unfinished.
We did this at the trans plant too on ALL the bushings in the auto transmissions.

Any updates yet? I have had to carve up a lot of cam bearings in the past to fit many camshafts
i have return maybe one instead of all of them. I do check the cams first for runout on the #2,3 and 4 cam bearing journals for run out to see if they are bent, if they are bent, they go back unless they're a steel roller cam
It is usually the block not machine to the proper I.D making the cam bearings to small

Once you understand this is how it was done at the factory, the poor fit and finish of the cam tunnel becomes somewhat of an “ah ha” moment.
At least, it was for me.

Measuring the cam bore sizing got moved way up near the top of the list of things to check for determining the viability of the block as a buildable core.
I had gotten screwed by that a couple times.
Block is all done and ready to assemble, and a cam bearing slips right through the bore.
At the time that happened, the repair to the block cost more than a core 440 block was worth.

Just a preliminary few measurements were taken at. The shop. The new cam is big. 3 of the 5 journals were 2 thousandths big. Compared to my old cam. They will polish the cam down to the same size as my original. Shoukd get it back in a few days.