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Fitting cam bearings?

Posted By: 47hudson

Fitting cam bearings? - 12/20/09 08:43 PM

My favorite machinist has retired. I tried a new guy I had good luck with in the past, on chevy engines, but left feeling a little uneasy. He had to "fit" my cam bearings. The cam was too tight and would not install and turn. I had to take the block back along with a cam for him to "fit" the bearings? I have never had this issue before so is this just an issue with some blocks or do I need to take my next block down the road? your appreciated.
Posted By: 1Bad440

Re: Fitting cam bearings? - 12/20/09 08:50 PM

I had it happen before after the short block was assembled. I always take the cam now
Posted By: Al_Alguire

Re: Fitting cam bearings? - 12/20/09 08:50 PM

Pretty common on a BB Mopar...
Posted By: goldmember

Re: Fitting cam bearings? - 12/20/09 08:58 PM

I've had a few SB cam bearing troubles. My new machinist does it a little different than most. He measures the cam bearing bores and claims he finds them often on the small side. He hones any that need attention before installing the bearings. I have had no issues since I started having him do his thing. LOL
Posted By: Mopar_Rich

Re: Fitting cam bearings? - 12/20/09 09:37 PM

Many people have never heard of a "bearing knife", or seen one used - but this is very common with a mopar. Sounds like you're in good hands.
Posted By: SSDAcuda

Re: Fitting cam bearings? - 12/20/09 10:27 PM

I like to do my own cam bearings and am very careful. You need to lube them up and stay on top of the tool to keep it as close as you can to alignment. Haven't needed to scrape since I've been doing it myself.

And checking the bearings before is inaccurate since the bearings are an interference fit in the block.

The problem is usually mis alignment which can only be fixed by scraping or replacing.
Posted By: MR_P_BODY

Re: Fitting cam bearings? - 12/20/09 10:52 PM

Quote:

My favorite machinist has retired. I tried a new guy I had good luck with in the past, on chevy engines, but left feeling a little uneasy. He had to "fit" my cam bearings. The cam was too tight and would not install and turn. I had to take the block back along with a cam for him to "fit" the bearings? I have never had this issue before so is this just an issue with some blocks or do I need to take my next block down the road? your appreciated.



Alot of shops have a old cam with a slot cut it in
the bearing journals as a cutter blade.... makes
a perfect sizer, put it in and give it a few spins...
I have one myself and spin it with my impact....
perfect
Posted By: SSDAcuda

Re: Fitting cam bearings? - 12/20/09 10:57 PM

It is cutting material from the bearing which shouldn't have to be cut.
Posted By: goldmember

Re: Fitting cam bearings? - 12/20/09 11:06 PM

I've scraped cam bearings over the years and yes,I feel the modified camshaft trick may work fine. In the future I won't have to worry with those tricks,I hope.
Posted By: John_Kunkel

Re: Fitting cam bearings? - 12/20/09 11:14 PM


I've used the old cam with slotted journals for years, works every time.

Attached picture 5679954-Cambrgream.jpg
Posted By: SSDAcuda

Re: Fitting cam bearings? - 12/20/09 11:54 PM

Not saying it wont work, just saying it is a bandaid for misalignment by the installer

Would you scrape your rod or mains for extra clearance??
Posted By: maundmotorworks

Re: Fitting cam bearings? - 12/20/09 11:59 PM

Quote:

Not saying it wont work, just saying it is a bandaid for misalignment by the installer

Would you scrape your rod or mains for extra clearance??



What do you think they did in the old motors with poured babbitt bearings? Cut to fit!
Posted By: Sport440

Re: Fitting cam bearings? - 12/21/09 12:07 AM

Quote:

Not saying it wont work, just saying it is a bandaid for misalignment by the installer

Would you scrape your rod or mains for extra clearance??



Its not a alignment issue IMO, The bearing itself is so wide that once pressed in it would be self aligning. Its a thickness issue thats resolved by honeing/bearing knife or the Kunkle cam fix.


I use the slotted cam fix, works great. This cam bearing problem is common with BB I guess its better to make the bearings a little thick vs a little thin. You can take clearence out but you cant put it back in. mike
Posted By: maundmotorworks

Re: Fitting cam bearings? - 12/21/09 12:09 AM

Quote:

Quote:

Not saying it wont work, just saying it is a bandaid for misalignment by the installer

Would you scrape your rod or mains for extra clearance??



Its not a alignment issue IMO, The bearing itself is so wide that once pressed in it would be self aligning. Its a thickness issue thats resolved by honeing/bearing knife or the Kunkle cam fix.


I use the slotted cam fix, works great. This cam bearing problem is common with BB I guess its better to make the bearings a little thick vs a little thin. You can take clearence out but you cant put it back in. mike



Exactly! I made my own cutter cams too and it does the trick!
Posted By: SSDAcuda

Re: Fitting cam bearings? - 12/21/09 12:23 AM

Quote:

This cam bearing problem is common with BB I guess its better to make the bearings a little thick vs a little thin.



I guess my street hemis must use the thin bearings
Posted By: Sport440

Re: Fitting cam bearings? - 12/21/09 12:54 AM

Quote:

Quote:

This cam bearing problem is common with BB I guess its better to make the bearings a little thick vs a little thin.



I guess my street hemis must use the thin bearings




Wait a minute, are you onto something? Do they sell thin and thick Cam bearings. Fill us in , mike
Posted By: turbobitt

Re: Fitting cam bearings? - 12/21/09 04:24 AM

FWIW , my mopar mega block had cam bearing journals #2 and #3 .0015" undersized and wouldn't allow the cam to spin because of tight fit. My machinest and I made special mandrels to fit in the nearest bearing bores and align bored the undersized bores to the correct dimensions.
Allan G.
Posted By: 47hudson

Re: Fitting cam bearings? - 12/21/09 04:18 PM

Thanks guys that's what I was hoping to hear. He mentioned the grooved cam trick but said he could no longer locate his for a Mopar. I feel better now.
Posted By: MuscleMike

Re: Fitting cam bearings? - 12/21/09 05:15 PM

Cure the problem not the symptom!

On my web site I wrote a quick few paragraphs in "Mikes Blog" about "the real real reason why your cam won't turn."

It is a block issue not a bearing issue. Click below to goto my web site.

Mike @MM
Posted By: John_Kunkel

Re: Fitting cam bearings? - 12/21/09 07:28 PM


If it's a block problem what did the factory engine plant do to size the bearings?
Posted By: goldmember

Re: Fitting cam bearings? - 12/21/09 09:04 PM

Just a guess based on the poor job with other machining operations on many factory blocks,they used a old cam core with grooves cut in it to make it usable. The problem would be that every set of cam bearings installed in that block will need "work" if the bores are not correct. I prefer Mikes plan but other methods obviously are doable.
Posted By: Sport440

Re: Fitting cam bearings? - 12/21/09 09:55 PM

Quote:


If it's a block problem what did the factory engine plant do to size the bearings?




This is what I would like to know too.

If 10 out of 10 blocks were out of spec that you checked, this would indicate that a Major majority of the blocks were out of spec.

What a Major Unproductive PITA that would be to have to clearence that many blocks. mike
Posted By: RyanJ

Re: Fitting cam bearings? - 12/21/09 10:19 PM

We also hone the cam tunnel like MM for proper babbit cam bearing fitment.... just did 2 R3's today.

Have never had a cam go in "tight" & bearings need scraped, when the tunnel was properly sized before bearing installation.
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