Change Cam Bearings

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Change Cam Bearings

Post  dbshelton on April 29th 2018, 1:17 pm

Is it possible to remove and replace the cam bearings in a 460 that has the crank, rods, and pistons already assembled in the block?
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Re: Change Cam Bearings

Post  Frank Merkl on April 29th 2018, 8:12 pm

you can but not the easiest!! the hardest part is lining up the oil gallery but can be done
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Re: Change Cam Bearings

Post  samiam on April 30th 2018, 12:56 am

dbshelton wrote:Is it possible to remove and replace the cam bearings in a 460 that has the crank, rods, and pistons already assembled in the block?

I have the tool set, Blue Point GA 285, im looking to sell, 130. shipped
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Re: Change Cam Bearings

Post  dfree383 on April 30th 2018, 7:25 am

Why would you want to? It's not hard to pull a rotating assemble and do it right.
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Re: Change Cam Bearings

Post  rmcomprandy on April 30th 2018, 10:23 am

Because of the timing chain resistance, the front usually wears more than the other 4.
Changing just the front is pretty easy.

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Re: Change Cam Bearings

Post  dbshelton on April 30th 2018, 10:16 pm

The reason I am asking is the cam is too tight. Not sure if a bearing may be in a touch crooked but the new cam won't go in all the way. It gets tighter as you go through each of the bearings.
The first mistake? ALWAYS install the cam first in case there are any problems! I know better, but I didn't have the cam when I put together the rest of the short block.
I took the old stock cam, cleaned it up and it goes in but has a slightly tight spot when you rotate it.
To make matters worse, I was getting frustrated and knocked the new cam off of the bench and seriously chipped a lobe so I had to order another cam.
Damn, I'm 60 years old, I should know better. This certainly ain't my first rodeo, but it sure looks like it!
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Re: Change Cam Bearings

Post  cletus66 on May 1st 2018, 8:58 am

The cam may be bent. I recently ordered a Howard's cam, and my machinist wanted to check it for straightness before I took it home. He put it in v blocks with a dial indicator and said, "Yep, it's bent. Don't look." Then I heard a big bang when he smacked it with a hammer and told me it was fine now. He said it is pretty common for them to be bent. I don't know if it is from shipping or what it is.
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Re: Change Cam Bearings

Post  DaveMcLain on May 1st 2018, 12:25 pm

cletus66 wrote:The cam may be bent.  I recently ordered a Howard's cam, and my machinist wanted to check it for straightness before I took it home.   He put it in v blocks with a dial indicator and said, "Yep, it's bent.  Don't look."   Then I heard a big bang when he smacked it with a hammer and told me it was fine now.  He said it is pretty common for them to be bent. I don't know if it is from shipping or what it is.  

Straightening the cam core is a big part of cam grinding because cams are ground on centers and run on journals. Having the base circle of the lobe run on the same centerline as the journal is very important. They are often checked, straightened(beat on), rough ground, checked, straightened(beat on) and then finish ground.

They are usually straight enough out of the box to not cause any problems BUT many times cam cores can come with journals that are a bit too big or right at the top of the spec so before you do anything check the sizing of the journals. If they are too big you can polish them to gain the needed clearance. This is very common on big Ford roller cores in particular.

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Re: Change Cam Bearings

Post  dbshelton on May 1st 2018, 9:44 pm

DaveMcLain wrote:
cletus66 wrote:The cam may be bent.  I recently ordered a Howard's cam, and my machinist wanted to check it for straightness before I took it home.   He put it in v blocks with a dial indicator and said, "Yep, it's bent.  Don't look."   Then I heard a big bang when he smacked it with a hammer and told me it was fine now.  He said it is pretty common for them to be bent. I don't know if it is from shipping or what it is.  

Straightening the cam core is a big part of cam grinding because cams are ground on centers and run on journals.  Having the base circle of the lobe run on the same centerline as the journal is very important.  They are often checked, straightened(beat on), rough ground, checked, straightened(beat on) and then finish ground.  

They are usually straight enough out of the box to not cause any problems BUT many times cam cores can come with journals that are a bit too big or right at the top of the spec so before you do anything check the sizing of the journals.  If they are too big you can polish them to gain the needed clearance.  This is very common on big Ford roller cores in particular.

I think this is exactly what the problem is. I removed the old stock cam, lightly polished the journals, cleaned and oiled the journals, re-installed it, and it now turns freely and smoothly. It looks to me like the bearings are OK so hopefully the new cam is OK, but if it isn't, I have a good direction to go. If I need to take a touch off and polish the journals, what grit should I use?
Thanks guys.


Last edited by dbshelton on May 1st 2018, 9:56 pm; edited 1 time in total (Reason for editing : more info)
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Re: Change Cam Bearings

Post  DaveMcLain on May 3rd 2018, 7:56 am

I'd try starting out using a new 320 belt to take off material and then use a worn out one to finish the journals.

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Re: Change Cam Bearings

Post  pmrphil on May 3rd 2018, 8:07 am

Just be CAREFUL - a new belt will take material off very quickly. Keep in mind it's supposed to stay round Cool

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Re: Change Cam Bearings

Post  dbshelton on May 5th 2018, 11:49 am

New cam won't fit either. Went ahead and removed pistons, rode, crank and changed out the cam bearings. Cam still won't go. I think I'll load up the block and cam on Monday and take it to Mark's Machine Shop and get him to fix it. Probably what I should have done in the beginning.
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Re: Change Cam Bearings

Post  pmrphil on May 5th 2018, 12:51 pm

Mike the journals of both cams and compare - if the old one fits it's very possible the journals are on the high side. I've had most Comp cams like that.

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Re: Change Cam Bearings

Post  dbshelton on May 5th 2018, 12:53 pm

What is the size of the cam journal supposed to be?
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Re: Change Cam Bearings

Post  pmrphil on May 5th 2018, 1:15 pm

2.1238 - 2.1248 is the spec, but normally I request them right on the minimum, and occasionally STILL have to polish off a couple tenths.
Check the DIFFERENCE in your 2 cams, as your old one fits as-is.

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Re: Change Cam Bearings

Post  dbshelton on May 5th 2018, 3:21 pm

I'm measuring 2.1249 on the new cam. The old cam measures 2.1242. (At least that's what my Chinese mics are reading)

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Re: Change Cam Bearings

Post  pmrphil on May 5th 2018, 7:19 pm

I'm not surprised, if I don't order it special, they usually measure right at the high side. Hard to believe how little (or no) clearance changes things.
Is it a big deal for you to send it back and have them grind another thou off it? That's really the best way around this. Polishing off a couple tenths is one thing, tough to keep it flat across the journals if you try any more than that.

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Re: Change Cam Bearings

Post  dbshelton on May 5th 2018, 9:44 pm

I really appreciate the help. Many times it helps me to type things out when I run across a problem. Both of the new cams ( the first one that I screwed up and the new one ) measure out exactly the same. I don't think I will ship this back.
Now this project has become a challenge. I had to order a couple of sanding belts to polish the journals down.
For some reason, the old cam is pretty hard to install with the new cam bearings, but once it is in place it turns freely. Seems kinda strange to me.
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Re: Change Cam Bearings

Post  DaveMcLain on May 5th 2018, 11:39 pm

dbshelton wrote:I really appreciate the help. Many times it helps me to type things out when I run across a problem. Both of the new cams ( the first one that I screwed up and the new one ) measure out exactly the same. I don't think I will ship this back.
Now this project has become a challenge. I had to order a couple of sanding belts to polish the journals down.
For some reason, the old cam is pretty hard to install with the new cam bearings, but once it is in place it turns freely. Seems kinda strange to me.

That's pretty normal to see after installing a fresh set of bearings and no big deal. Cam bearings are very forgiving and it should work just fine once you take a little off of the journals. Most of the time cam grinders don't do anything to the journals of the core at all they only grind the lobes on a core from Engine Power.

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Re: Change Cam Bearings

Post  dbshelton on May 6th 2018, 9:54 am

Thanks guys, I'll post the results.
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Re: Change Cam Bearings

Post  pmrphil on May 6th 2018, 10:51 am

I've sent better than a half dozen back to Comp to have the journals "touched up" when they miked at (or above) the high side. Never a charge, I just pay for shipping. Usually turned around in a day. Even when it's on the order to check size and grind to the minimum, it gets overlooked.

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Re: Change Cam Bearings

Post  dbshelton on May 7th 2018, 9:36 pm

That wasn't bad at all! Ordered a few 1" x 30" 320 grit and 600 grit belts from Amazon so they came in the mail today. Chucked up my cam in my lathe, held the belts by hand as evenly and as smoothly as possible and kept them off of the journals, cut a little, cleaned the cam and checked it in the block. Did this 3 times (I didn't want to take any more off than I had to). Polished with a 600 grit belt afterwards. Ended up at about 2.1240" It took me all of about 45 minutes to do all of this, then lubed up the cam real good and stuck her in. Turns very evenly and smoothly, just as it should. Now I know what to do if it ever happens again. Tomorrow night I'll start putting the crank, rods and pistons back in. Thanks for all of the great advice!!!!!!
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Re: Change Cam Bearings

Post  cletus66 on May 7th 2018, 10:29 pm

Excellent... Cool
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Re: Change Cam Bearings

Post  Lem Evans on May 7th 2018, 10:40 pm

dbshelton wrote:That wasn't bad at all! Ordered a few 1" x 30" 320 grit and 600 grit belts from Amazon so they came in the mail today. Chucked up my cam in my lathe, held the belts by hand as evenly and as smoothly as possible and kept them off of the journals, cut a little, cleaned the cam and checked it in the block. Did this 3 times (I didn't want to take any more off than I had to). Polished with a 600 grit belt afterwards. Ended up at about 2.1240"  It took me all of about 45 minutes to do all of this, then lubed up the cam real good and stuck her in. Turns very evenly and smoothly, just as it should. Now I know what to do if it ever happens again. Tomorrow night I'll start putting the crank, rods and pistons back in. Thanks for all of the great advice!!!!!!

Thank you.....that's the way it usually works. I would not be susprised if the run out at the journals was less now.

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Re: Change Cam Bearings

Post  pmrphil on May 8th 2018, 8:06 am

dbshelton wrote:That wasn't bad at all! Ordered a few 1" x 30" 320 grit and 600 grit belts from Amazon so they came in the mail today. Chucked up my cam in my lathe, held the belts by hand as evenly and as smoothly as possible and kept them off of the journals, cut a little, cleaned the cam and checked it in the block. Did this 3 times (I didn't want to take any more off than I had to). Polished with a 600 grit belt afterwards. Ended up at about 2.1240"  It took me all of about 45 minutes to do all of this, then lubed up the cam real good and stuck her in. Turns very evenly and smoothly, just as it should. Now I know what to do if it ever happens again. Tomorrow night I'll start putting the crank, rods and pistons back in. Thanks for all of the great advice!!!!!!
Hot Sh*t !! Great to hear.

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