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cam bearings too tight

Posted By: mickm

cam bearings too tight - 09/28/11 12:50 AM

got the block back from the machine shop, and the cam wouldn't go in. took it back, and we started playing with it. out of the block, bearings fit nicely on the cam. in the block, 3 out of the 5 were too tight. we did a lot of playing around, but finally i had to leave.

this is a mopar hemi (not world) mega block.

in the end, he found that all the holes were .0005 to .001 too small, and so were crushing the bearings when they were inserted in the block.

i brought him an old cam, and he grooved the journals on the lathe, and then inserted the cam and made 1 turn and removed it. buffed the bearings with scotchbrite, and now the cam fits like a dream!

how common is this on these blocks? i've heard of issues with these before, but all of the holes to be too small?

also the hole to the driver side head from the #4 bearing did not match perfectly, so i had him enlarge the hole in the bearing so it is completely open.

anything else i should be aware of here??
Posted By: therocks

Re: cam bearings too tight - 09/28/11 12:53 AM

Ive heard quite a few that were tight.A good machinist shop should check them.Thats why they really need the cam if they install the bearings.The oil holes are the same.Some line up great some not so good.Rocky
Posted By: mickm

Re: cam bearings too tight - 09/28/11 12:57 AM

Quote:

Ive heard quite a few that were tight.A good machinist shop should check them.Thats why they really need the cam if they install the bearings.The oil holes are the same.Some line up great some not so good.Rocky



i didn't bring him the cam initially. i should have brought it, he should have asked

but he took care of me...
Posted By: MR_P_BODY

Re: cam bearings too tight - 09/28/11 12:58 AM

Quote:

got the block back from the machine shop, and the cam wouldn't go in. took it back, and we started playing with it. out of the block, bearings fit nicely on the cam. in the block, 3 out of the 5 were too tight. we did a lot of playing around, but finally i had to leave.

this is a mopar hemi (not world) mega block.

in the end, he found that all the holes were .0005 to .001 too small, and so were crushing the bearings when they were inserted in the block.

i brought him an old cam, and he grooved the journals on the lathe, and then inserted the cam and made 1 turn and removed it. buffed the bearings with scotchbrite, and now the cam fits like a dream!

how common is this on these blocks? i've heard of issues with these before, but all of the holes to be too small?

also the hole to the driver side head from the #4 bearing did not match perfectly, so i had him enlarge the hole in the bearing so it is completely open.

anything else i should be aware of here??



Thats quite common to have to size the bearings...
I have a cam for that purpose laying around here
Posted By: mickm

Re: cam bearings too tight - 09/28/11 01:00 AM

Quote:


Thats quite common to have to size the bearings...
I have a cam for that purpose laying around here




well at least i have one now too!
Posted By: Hot 340

Re: cam bearings too tight - 09/28/11 01:34 AM

Quote:

Quote:


Thats quite common to have to size the bearings...
I have a cam for that purpose laying around here




well at least i have one now too!

Can you post a pic of the cam? Im trying to see what you did incase I run into this...
Posted By: 383man

Re: cam bearings too tight - 09/28/11 03:34 AM

Had a problem with my 440 block when I built my 493. I put the # 1 and 5 cam bearings in and the cam turned fine so I installed the bearings one at a time. I found # 3 bearing had a scratch mark on the back of it as it had a small piece of metal rolled into the cam bearing bore making the bearing high at that spot. I looked where the bearing scratch was and found the protruding metal and removed it. Fixed it right up. Ron
Posted By: Mike Swann

Re: cam bearings too tight - 09/28/11 03:46 AM

#80 grit wet/dry is your friend.
Posted By: mickm

Re: cam bearings too tight - 09/28/11 03:47 AM

Quote:

Can you post a pic of the cam? Im trying to see what you did incase I run into this...



i will get the block and cams back in the next day or so. i'll post some pics when i get my hands on it.
Posted By: WheelsUp73

Re: cam bearings too tight - 09/28/11 08:18 PM

I use red scotch brite and WD 40 to massage the bearings. Also check the cam on V blocks and a dial indicator to make sure its not bent
Posted By: Clanton

Re: cam bearings too tight - 09/28/11 10:24 PM

if you have more than 1 core to use maybe cut each cam bearing serface of like a puck so you can check them indevidualy also.
Posted By: Crizila

Re: cam bearings too tight - 09/28/11 11:51 PM

Quote:

Quote:

Quote:


Thats quite common to have to size the bearings...
I have a cam for that purpose laying around here




well at least i have one now too!

Can you post a pic of the cam? Im trying to see what you did incase I run into this...

One I just did for a sm blk. Cut the grooves in each journal on an angle and slanted towards the leading edge ( as you would rotate the cam bolt - clockwise ). Chamfered the trailing edge of each groove and stoned the leading ( cutting )edge.

Attached picture 6846782-cambrgtool.jpg
Posted By: Hot 340

Re: cam bearings too tight - 09/29/11 01:36 AM

Quote:

Quote:

Quote:

Quote:


Thats quite common to have to size the bearings...
I have a cam for that purpose laying around here




well at least i have one now too!

Can you post a pic of the cam? Im trying to see what you did incase I run into this...

One I just did for a sm blk. Cut the grooves in each journal on an angle and slanted towards the leading edge ( as you would rotate the cam bolt - clockwise ). Chamfered the trailing edge of each groove and stoned the leading ( cutting )edge.

I get it now. How much stock on the bearing can you safely take out?
Posted By: mickm

Re: cam bearings too tight - 09/29/11 03:58 PM

this is what he did. took some material off to one side of the groove to accumulate the removed bearing material. this works, although i like crizilla's better.

he put it in and gave it 1 turn, and that was enough to clearnace them properly, although i think he did a few more to be sure. then scothbrite and away we go!

Attached picture 6847742-IMG_0965.jpg
Posted By: gbolten480

Re: cam bearings too tight - 09/29/11 07:13 PM

I personally like the ingenuity that is shown on this topic & have experienced this on a second gen hemi block manufactured in 2005. At the following site - Mike Ware sheds a little light on the topic. Hope it helps. Right side column - down a bit.

http://www.musclemotorsracing.com/muscle-mike-blog.html
Posted By: John_Kunkel

Re: cam bearings too tight - 09/29/11 08:44 PM


OK, the bearing bores in the block are undersized from the factory so that begs the question "what did the factory do?" The answer is they either scraped them or bored them.

I don't like the idea of using any abrasive material like Scotchbrite, sandpaper, hone, etc. due to the possibility of impregnating the soft babbit with grit.
Posted By: mickm

Re: cam bearings too tight - 09/29/11 09:27 PM

Quote:


OK, the bearing bores in the block are undersized from the factory so that begs the question "what did the factory do?" The answer is they either scraped them or bored them.




that also begs more modern questions. like if this is a known issue, why can't the factory just get it right on these newer blocks? it is obviously a simple machine setting issue, because the bores are not too big, or all over the place, they are always too small, and almost always by the same amount.

Quote:


I don't like the idea of using any abrasive material like Scotchbrite, sandpaper, hone, etc. due to the possibility of impregnating the soft babbit with grit.



makes sense. i would think that just going over them lightly as a final cleanup wouldn't do any harm though. one would hope...
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