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New cam binding - Cam bores reamed back to STD
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tweakhx
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PostPosted: Mon Oct 12, 2020 7:12 am    Post subject: New cam binding - Cam bores reamed back to STD Reply with quote

Good morning everyone!

First off, Thank you for your replies or if you can direct me to a thread with more info! I've searched and haven't found much in the past few weeks.

I just recently had my AS41 case for my '71 bus sent off to Painter's Grinding in Denver to have the cam bores reamed back to standard (the old and new cam were freezing up when I torqued the case.

I got the case back and put in a new set of double thrust Mahle cam bearings and the new cam along with a little assembly lube. I already put the new cam in, hit it once fore and aft, and got the thrust surface sanded slightly for endplay.

I torque down the 6 nuts to 25ftlb and the new cam, again, freezes in the case. I let off the bottom middle nut slightly and it will free up. I put the old cam in with the new bearings and everything spins fine. The old cam is is decent shape with no pitting or wear on the lobes.

My question.. is there anything I can do to the new cam to stop it from binding? As far as I can tell the case isn't warped or cracked. Would using the old cam with the new bearings be OK?


-Scott
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UK Luke 72
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PostPosted: Mon Oct 12, 2020 7:36 am    Post subject: Re: New cam binding - Cam bores reamed back to STD Reply with quote

Remove the middle bearing and but a DTI on the centre bearing to see if the cam is bent.
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PostPosted: Mon Oct 12, 2020 7:41 am    Post subject: Re: New cam binding - Cam bores reamed back to STD Reply with quote

install and torque all of the case nuts. the case won't settle down until torqued.
mag cases move alot with age.
Apart, they are no where near flat.
Only consder full torque to be any sort of reference.

Measure the OD of the cam journals to see if the new one is bigger than the old one.

A slightly tight cam is not that big of a deal. It won't lock up or anything like that.
It will wear-in as it were.

Also, you should Never tap on a cam. They are cast and will break like glass.
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PostPosted: Mon Oct 12, 2020 7:42 am    Post subject: Re: New cam binding - Cam bores reamed back to STD Reply with quote

tweakhx wrote:
Good morning everyone!

First off, Thank you for your replies or if you can direct me to a thread with more info! I've searched and haven't found much in the past few weeks.

I just recently had my AS41 case for my '71 bus sent off to Painter's Grinding in Denver to have the cam bores reamed back to standard (the old and new cam were freezing up when I torqued the case.

I got the case back and put in a new set of double thrust Mahle cam bearings and the new cam along with a little assembly lube. I already put the new cam in, hit it once fore and aft, and got the thrust surface sanded slightly for endplay.

I torque down the 6 nuts to 25ftlb and the new cam, again, freezes in the case. I let off the bottom middle nut slightly and it will free up. I put the old cam in with the new bearings and everything spins fine. The old cam is is decent shape with no pitting or wear on the lobes.

My question.. is there anything I can do to the new cam to stop it from binding? As far as I can tell the case isn't warped or cracked. Would using the old cam with the new bearings be OK?


-Scott


Just to be clear.....you rap the cam fore and aft....after.....you torque the case. Torqueing the case misaligns the cam bearing shells at their contact edges as the case crushes them. Rapping it fore and aft re-sets this.
So....rapping it fore and aft BEFORE you have complete crush does not do it. Ray
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mark tucker
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PostPosted: Mon Oct 12, 2020 8:07 am    Post subject: Re: New cam binding - Cam bores reamed back to STD Reply with quote

all the above and polish the cam journels, most are too ruff... aswell as you need to deburr the lobes edges.
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PostPosted: Mon Oct 12, 2020 8:09 am    Post subject: Re: New cam binding - Cam bores reamed back to STD Reply with quote

tweakhx wrote:
Good morning everyone!

First off, Thank you for your replies or if you can direct me to a thread with more info! I've searched and haven't found much in the past few weeks.

I just recently had my AS41 case for my '71 bus sent off to Painter's Grinding in Denver to have the cam bores reamed back to standard (the old and new cam were freezing up when I torqued the case.

I got the case back and put in a new set of double thrust Mahle cam bearings and the new cam along with a little assembly lube. I already put the new cam in, hit it once fore and aft, and got the thrust surface sanded slightly for endplay.

I torque down the 6 nuts to 25ftlb and the new cam, again, freezes in the case. I let off the bottom middle nut slightly and it will free up. I put the old cam in with the new bearings and everything spins fine. The old cam is is decent shape with no pitting or wear on the lobes.

My question.. is there anything I can do to the new cam to stop it from binding? As far as I can tell the case isn't warped or cracked. Would using the old cam with the new bearings be OK?


-Scott


What kind of cam and what kind of bearings? Unless it a SUPER HIGH performance build, I never use double thrust cam bearings. IF you do, you have to sand on the thrust flange. I'm not saying it isn't possible but I would give you a better chance of winning the lottery than the cam bore being too small on a new case.
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tweakhx
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PostPosted: Mon Oct 12, 2020 8:34 am    Post subject: Re: New cam binding - Cam bores reamed back to STD Reply with quote

UK Luke 72 wrote:
Remove the middle bearing and but a DTI on the centre bearing to see if the cam is bent.


Sorry, DTI?
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tweakhx
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PostPosted: Mon Oct 12, 2020 8:35 am    Post subject: Re: New cam binding - Cam bores reamed back to STD Reply with quote

Ohio Tom wrote:
install and torque all of the case nuts. the case won't settle down until torqued.

Also, you should Never tap on a cam. They are cast and will break like glass.


I did think of this, but haven't had a chance. I will try that tonight. Thanks!
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tweakhx
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PostPosted: Mon Oct 12, 2020 8:36 am    Post subject: Re: New cam binding - Cam bores reamed back to STD Reply with quote

raygreenwood wrote:


Just to be clear.....you rap the cam fore and aft....after.....you torque the case. Torqueing the case misaligns the cam bearing shells at their contact edges as the case crushes them. Rapping it fore and aft re-sets this.
So....rapping it fore and aft BEFORE you have complete crush does not do it. Ray


Thank you Ray for explaining why this is done. I will try this tonight.
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tweakhx
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PostPosted: Mon Oct 12, 2020 8:36 am    Post subject: Re: New cam binding - Cam bores reamed back to STD Reply with quote

mark tucker wrote:
all the above and polish the cam journels, most are too ruff... aswell as you need to deburr the lobes edges.


Will do, thanks!
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PostPosted: Mon Oct 12, 2020 8:38 am    Post subject: Re: New cam binding - Cam bores reamed back to STD Reply with quote

tweakhx wrote:
raygreenwood wrote:


Just to be clear.....you rap the cam fore and aft....after.....you torque the case. Torqueing the case misaligns the cam bearing shells at their contact edges as the case crushes them. Rapping it fore and aft re-sets this.
So....rapping it fore and aft BEFORE you have complete crush does not do it. Ray


Thank you Ray for explaining why this is done. I will try this tonight.


+1

also, if you do this usually you'll see the thrust surface is in spec, some people sand it before doing this and end up with too much fore/aft play.
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PostPosted: Mon Oct 12, 2020 8:42 am    Post subject: Re: New cam binding - Cam bores reamed back to STD Reply with quote

[email protected] wrote:


What kind of cam and what kind of bearings? Unless it a SUPER HIGH performance build, I never use double thrust cam bearings. IF you do, you have to sand on the thrust flange. I'm not saying it isn't possible but I would give you a better chance of winning the lottery than the cam bore being too small on a new case.


I should have stated in my original post that this is a 100% stock rebuild. The cam is new from Jbugs (I can't remember the brand name at the moment, it came in a red triangular box.) and the bearings are Mahle. I read using double thrust is just extra "insurance." Plus I had already tried two sets of Silverline bearings and neither worked (this was before getting the cam bores reamed, but they seemed to fit tighter anyway)

The thrust surfaces are sanded. I used fine wet sandpaper. I will try a few of the forementioned things and will update this thread.

Thanks!
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tweakhx
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PostPosted: Mon Oct 12, 2020 8:46 am    Post subject: Re: New cam binding - Cam bores reamed back to STD Reply with quote

Lingwendil wrote:


+1

also, if you do this usually you'll see the thrust surface is in spec, some people sand it before doing this and end up with too much fore/aft play.


I read about this. I guess where I failed is where Ray stated the case has to be torqued first. I hope I haven't sanded too much off!
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PostPosted: Mon Oct 12, 2020 8:51 am    Post subject: Re: New cam binding - Cam bores reamed back to STD Reply with quote

tweakhx wrote:
[email protected] wrote:


What kind of cam and what kind of bearings? Unless it a SUPER HIGH performance build, I never use double thrust cam bearings. IF you do, you have to sand on the thrust flange. I'm not saying it isn't possible but I would give you a better chance of winning the lottery than the cam bore being too small on a new case.


I should have stated in my original post that this is a 100% stock rebuild. The cam is new from Jbugs (I can't remember the brand name at the moment, it came in a red triangular box.) and the bearings are Mahle. I read using double thrust is just extra "insurance." Plus I had already tried two sets of Silverline bearings and neither worked (this was before getting the cam bores reamed, but they seemed to fit tighter anyway)

The thrust surfaces are sanded. I used fine wet sandpaper. I will try a few of the forementioned things and will update this thread.

Thanks!


Well, not to rain on your parade BUT I don't like and refuse to use those cams or cam bearings in my builds. I use only silverline cam bearings and stock German reground cams. I just don't like the quality of the new Chinese or Brazil cams compared to a reground German. You may have to debur on the thrust surface of the cam blank itself. Take note, however, that the German reground cams I use have only been ground one time and still have a very large base circle. I don't use cams that have a base circle that is the same diameter as the cam itself.
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PostPosted: Mon Oct 12, 2020 9:23 am    Post subject: Re: New cam binding - Cam bores reamed back to STD Reply with quote

Let me know if you need any help with this. I am in Rapid City and I have bearings and a cam bore tool. Never had one I couldn't get sorted out.

Brian
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PostPosted: Mon Oct 12, 2020 9:31 am    Post subject: Re: New cam binding - Cam bores reamed back to STD Reply with quote

Brian_e wrote:
Let me know if you need any help with this. I am in Rapid City and I have bearings and a cam bore tool. Never had one I couldn't get sorted out.

Brian


Thank you very much Brian! I will let you know what I find out tonight.
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PostPosted: Mon Oct 12, 2020 10:28 am    Post subject: Re: New cam binding - Cam bores reamed back to STD Reply with quote

[email protected] wrote:


What kind of cam and what kind of bearings? Unless it a SUPER HIGH performance build, I never use double thrust cam bearings.

Kinda funny to see how things are done different here and there. I hardly ever use anything else than double trust bearings
[email protected] wrote:

IF you do, you have to sand on the thrust flange.
ABSOLUTELY NOT! The first thing to do is give the cam a rap front and rear sort of to set the bearing. If that isnt enough you can do it once more. If that still doesnt give you the clearance you need, THEN you can sand the bearings slightly, but only then. Done this way the tolerance stays instead of wander off immesiately after the engine is started and boken in.
[email protected] wrote:

I'm not saying it isn't possible but I would give you a better chance of winning the lottery than the cam bore being too small on a new case.

I do not know with those repro stock cams. I have never used one.
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PostPosted: Mon Oct 12, 2020 10:56 am    Post subject: Re: New cam binding - Cam bores reamed back to STD Reply with quote

I use doubles here too, it's silly not too. It's an upgrade with no down side too it. 1st I'd be fitting the crank and checking if that spins on a closed case. If the crank won't spin either, the case has warped. For a quick test put an engineers straight edge across the main 6 case mating surfaces and look for day light on the centre main saddle pad.
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PostPosted: Mon Oct 12, 2020 11:06 am    Post subject: Re: New cam binding - Cam bores reamed back to STD Reply with quote

GARRICK.CLARK wrote:
I use doubles here too, it's silly not too. It's an upgrade with no down side too it. 1st I'd be fitting the crank and checking if that spins on a closed case. If the crank won't spin either, the case has warped. For a quick test put an engineers straight edge across the main 6 case mating surfaces and look for day light on the centre main saddle pad.


The crank spins nice and smooth. I'll have to pick up a nice straight edge to check that. Thanks!
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PostPosted: Mon Oct 12, 2020 11:14 am    Post subject: Re: New cam binding - Cam bores reamed back to STD Reply with quote

Has a fresh align bore job been done or at least checked by a vw machine shop. How's the end float.
All bearings need a slight crush fit and the flywheel bearing should not move back and forth in its fully fitted position. With dowel fitted
There's a lot of check n prep work on a case, and a lot that can go wrong.
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