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Old 10-01-2022, 09:44 PM
transam81 transam81 is offline
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Default Camshaft won’t fit into new bearings

Hi, new here.

I am replacing both camshaft and cam bearings in my Pontiac 400. It has been previously rebuilt. The old
bearings were unidentifiable so I ordered
Clevite standard cam bearings which fit perfectly into my block when I installed them. Now neither the new or old camshaft will fit through the new bearings.
The inner diameter is too small but outer diameter is perfect.

Why won’t my new or old camshaft fit into a standard bearing? What bearings should I try instead? Oversize/Undersize?


Last edited by transam81; 10-01-2022 at 09:50 PM.
  #2  
Old 10-01-2022, 10:21 PM
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So you can not even get the heel of the cam into the front cam bearing?
The bearings must be installed perfectly straight, any even very small amount of cocking to the left / right or up or down and the cam will not load in because that cocking pinches in the bearing .

.003” of cock creates .003” of pinch and that’s all there was for the needed bearing to cam clearance.

Did you use a cone type installer, or the puller type?

What part number bearings did you get and was the box open when you got it?

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Old 10-01-2022, 10:43 PM
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I am unable to even get it started into the first bearing. I used a cone type installer. I set the bearings so they were perfectly inline with the oil holes, they appear straight. Part number on the new bearings is Clevite SH292S.

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Old 10-01-2022, 10:44 PM
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Quote:
Originally Posted by 25stevem View Post
So you can not even get the heel of the cam into the front cam bearing?
The bearings must be installed perfectly straight, any even very small amount of cocking to the left / right or up or down and the cam will not load in because that cocking pinches in the bearing .

.003” of cock creates .003” of pinch and that’s all there was for the needed bearing to cam clearance.

Did you use a cone type installer, or the puller type?

What part number bearings did you get and was the box open when you got it?

I am unable to even get it started into the first bearing. I used a cone type installer. I set the bearings so they were perfectly inline with the oil holes, they appear straight. Part number on the new bearings is Clevite SH292S - unopened

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Old 10-02-2022, 02:33 AM
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Probably a good time to mic the cam journals (or at least journal #5 that would go in first). Just for conversation sake take your old cam and see how it fits. If that isn't handy try the opposite end of the cam and see if it fits any better. Not unheard of that cam journals can be incorrectly machined a tad too large.

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Old 10-02-2022, 06:33 AM
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Note that having all the bearings perfectly lined up with the oil feed holes coming up from the main web does not guarantee that they are 100% perpendicular to the cam bore which they need to be .

Here’s some info that might help you if you have measuring tools.

The OD of the cam should be 1.8992” - 1.8997”

Bearing wall thickness .644”

Oil clearance .012”- .0037”

All 5 bearings are the same.

These spec’s are out of my Federal Mogul catalog for there part number 1220M bearing set .

For a SH292S TRW / Speed Pro bearing set there oil clearance range goes from .001” to .006” .

There max length of the bearing is .690”

Wall thickness is near the same at .643”

Do you have any of the old cam bearings?
If so do they load on to your new cam?

Once you get this resolved another point to keep in mind that folks mess up on is using too long of a Valley pan cover bolt.

These two holes go right down into the cam Tunnel and if these two bolts are too long you can badly pinch in these two cam bearings.

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Last edited by 25stevem; 10-02-2022 at 07:13 AM.
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Old 10-02-2022, 07:18 AM
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IF your cam bearings were original, i have been told that PMD use to finish hone some/all cam bearings to correct for machining tolerances/dimensional shift, that would not allow the cams to be installed wo this cam journal line hone.
I have had a couple builds that i could not put a cam in upon taking it out of the machine shop. One 455, One IA2 rebuild w teflon coated cam bearings, Each time Block went back, cam journals were line honed and NEW bearings installed, no further issues. Needs to be done perfectly so crush is maintained.
Since then i always bring the cam when i drop off the so they can prefit cam, to insure issue free build once i get it home. Time is money both ways.

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Old 10-02-2022, 08:55 AM
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Quote:
Originally Posted by lust4speed View Post
Probably a good time to mic the cam journals (or at least journal #5 that would go in first). Just for conversation sake take your old cam and see how it fits. If that isn't handy try the opposite end of the cam and see if it fits any better. Not unheard of that cam journals can be incorrectly machined a tad too large.
In opening post, he said old cam doesn’t fit either

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Old 10-02-2022, 09:14 AM
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Is why i install my own cam bearings, and (you could) buy/have 2-sets to attain 1-install.

remove 1 or 2 and trial-fit the cam before the next pressing. Oil-wet should help, not hurt.

Hone-efforts should only be done by someone who has a stake in the results.

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Old 10-02-2022, 09:24 AM
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Quote:
Originally Posted by mysticmissle View Post
IF your cam bearings were original, i have been told that PMD use to finish hone some/all cam bearings to correct for machining tolerances/dimensional shift, that would not allow the cams to be installed wo this cam journal line hone.
I have had a couple builds that i could not put a cam in upon taking it out of the machine shop. One 455, One IA2 rebuild w teflon coated cam bearings, Each time Block went back, cam journals were line honed and NEW bearings installed, no further issues. Needs to be done perfectly so crush is maintained.
Since then i always bring the cam when i drop off the so they can prefit cam, to insure issue free build once i get it home. Time is money both ways.
/\ Exactly.. cam bearings get finish hone..

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Old 10-02-2022, 10:55 AM
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Quote:
Originally Posted by transam81 View Post
I am unable to even get it started into the first bearing. I used a cone type installer. I set the bearings so they were perfectly inline with the oil holes, they appear straight. Part number on the new bearings is Clevite SH292S - unopened
But did you install the cam bearings in the proper sequence?

Example Cone Installer, 1st bearing installed would be the #4 Cam Bearing.
Cone centered tightly in the #1 cam journal position.

Second bearing installed would be #2 bearing with the Cone installed in the
#5 Cam Bearing location.

Then install #3 with the cone in either the front or rear of the block, #1 or #5 position.

Next install #5 (from the Inside of the block) and cone on #1 position.

Last install #1 (from the Inside of the block) and cone on #5 position.

Never going to be true for the cam without a similar sequence.

Tom V.

Bearings should have been checked against cam journals before starting installation to make sure bearing were correct diameter
for the camshaft journals with the parts OUTSIDE the BLOCK.

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Old 10-02-2022, 10:59 AM
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I had a similar problem with my signature engine. I wasted a couple sets of cam bearings in the process.
What I did was use a brake one and WD-40 to see what the problem was with the journals in question. In doing so I saw that the outside of the journals were just a bit smaller than the inside. I honed them until the ends of the journals were the same size as the middle . I installed new bearings and the cam went in. I'll probably get some flak for doing this. but it worked.

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Old 10-02-2022, 02:54 PM
transam81 transam81 is offline
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Quote:
Originally Posted by 25stevem View Post
Note that having all the bearings perfectly lined up with the oil feed holes coming up from the main web does not guarantee that they are 100% perpendicular to the cam bore which they need to be .

Here’s some info that might help you if you have measuring tools.

The OD of the cam should be 1.8992” - 1.8997”

Bearing wall thickness .644”

Oil clearance .012”- .0037”

All 5 bearings are the same.

These spec’s are out of my Federal Mogul catalog for there part number 1220M bearing set .

For a SH292S TRW / Speed Pro bearing set there oil clearance range goes from .001” to .006” .

There max length of the bearing is .690”

Wall thickness is near the same at .643”

Do you have any of the old cam bearings?
If so do they load on to your new cam?

Once you get this resolved another point to keep in mind that folks mess up on is using too long of a Valley pan cover bolt.

These two holes go right down into the cam Tunnel and if these two bolts are too long you can badly pinch in these two cam bearings.

I removed one of the new bearings and it measures about 1.895 on the inside diameter. I measured the old bearings (not factory ones) and they are about 1.9030ish. Outside diameter is the same (2.0270ish)

The old bearings slide perfectly onto both old and new camshaft. I just don’t understand why a new bearing wouldn’t fit onto a new camshaft if the diameter is correct.

I need a bearing with a larger inside diameter than “stock” to fit through my camshafts

  #14  
Old 10-02-2022, 03:02 PM
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On my 421 build the cam went into the first 4 bearings but wouldn’t go in any further so we used a homemade reamer:

https://forums.maxperformanceinc.com...9&postcount=27

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Old 10-02-2022, 03:20 PM
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Well for future reference for others who might read this, I to once had a issue with cam bearings out of the many times I had installed new ones.

From that day on when I open up a box of bearings to install I first make sure that everyone of them can slide onto the new cam as they should.

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Old 10-02-2022, 03:47 PM
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[QUOTE=25stevem;6376712]Well for future reference for others who might read this, I to once had a issue with cam bearings out of the many times I had installed new ones.

From that day on when I open up a box of bearings to install I first make sure that everyone of them can slide onto the new cam as they should.[/

"Assume" will always get you in trouble. Pre-Checking parts takes little time and saves a lot of redo or rework.

Tom V.

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Old 10-02-2022, 03:56 PM
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Quote:
Originally Posted by transam81 View Post
I removed one of the new bearings and it measures about 1.895 on the inside diameter. I measured the old bearings (not factory ones) and they are about 1.9030ish. Outside diameter is the same (2.0270ish)

The old bearings slide perfectly onto both old and new camshaft. I just don’t understand why a new bearing wouldn’t fit onto a new camshaft if the diameter is correct.

I need a bearing with a larger inside diameter than “stock” to fit through my camshafts
If your ID measurement is accurate, your bearings are out of spec or were mislabeled.

The bearing is spec'd to work with cam journal diameters from 1.8992 to 1.8997:

https://web.tecalliance.net/mahle-ca...:0;groups:8293

Your 1.895 measurement is clearly too small to be "in spec" and explains your issue, but why seems a mystery....

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Old 10-02-2022, 04:33 PM
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Upon testing the second bearing, it is the perfect inner diameter, just the first one is far too small.

I was able to take 1000-3000 grit sandpaper on the new bearing until it made an inner diameter that will fit snugly over the old camshaft for testing. Since the new bearing got a bit damaged while removing I will order another set and do the same to shave it down to the proper inner diameter that will fit on the new cam. Hopefully this isn’t too sketchy and it works out.

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Old 10-02-2022, 04:53 PM
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Check the fit of all the new bearings you get on the new cam first .
That way if you find you have another misfit bearing deeper in the block you know you have another good fitting bearing there.

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Old 10-02-2022, 09:03 PM
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Quote:
Originally Posted by 25stevem View Post
Check the fit of all the new bearings you get on the new cam first .
That way if you find you have another misfit bearing deeper in the block you know you have another good fitting bearing there.
X10 "XXXXXXXXXX" Some very good advice there.

Tom V.

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