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Post  ChrisH on April 14th 2019, 1:59 pm

i decided to try roller cam bearing. I didn't need them, but figured for the heck of it I would try them. these are in a motorsport block by the way.

I installed them the first time after getting the block back form he machine shop and they were too tight. re-machined the block and now when the cam is in if you give it a flick at the snout it will spin 2 revolutions. I can also slide 0.001 feeler between the journal and the roller bearings all the way around.

here is the problems.
1. when sliding the cam in, the first three journals go in fine. when the fourth journal is fully inserted it gets tight going through the bores. Same thing when I am sliding the final journal in. when the cam is about 5/8" from being all the way in it gets tight again. once it reaches full insertion it is fine again. The journals are 0.0002 - 0.0003 under high side spec. so while they are on the bigger side they are within spec.

2. when the cam is fully in the bores and turned it walks back 1/8" . once I put the gear on the front this stops the walking, but you can feel it load and unload a little against the bronze cam retainer.

my first thought was the cam was bent slightly. however, it's run-out was 0.0005. that seems ok.


I know the cam bores were cut and honed on a proper mandrel but my question is does this sound like a bore is cut crooked? or basically the five bores are not perfectly aligned?

I also tried this:
1. removed bearing three, inserted the cam. Everything was "fine" (the tightness upon insertion was gone)
2. put three back in, removed four, inserted the cam. everything was "fine" (the tightness upon insertion was gone).

so my questions are:
1. if this is not correct, what is crooked and what is the best way to check it?
2. since it turns free and has proper clearance can this be ran like this? my real concern is the desire to walk backwards . BTW, this is a roller cam. forgot to mention this.

like I said in the beginning, I brought his on myself by wanting to try roller bearings. my biggest problem is trouble shooting information is limited on roller bearings like these so if someone has some insight it would be appreciated.

thank you
chris


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Post  litshoot on April 14th 2019, 10:58 pm

What happens if you put bearing 3 or 4 in the first or 2 journal

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Post  ChrisH on April 15th 2019, 12:09 am

no change. I also had another set of bearings, no change.

I got a 7/16 fine thread bolt to properly bolt the cam gear on and off course that stopped all walking. it also feels even on the turning pressure. I don't have a proper torque wrench to measure and watch inch lbs variation. if I didn't know about the two spots of assemble tightness I would look at the feeler gauge clearance and how well it spins and think there are no problems.

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Post  c.evans on April 15th 2019, 1:56 am

Are you pulling the roller cam bearings in, or driving them in? I would not be taking the bearings in and out this many times, you will lose crush on the shell. I made my own mandrels and I pull them in very gently. The cam bearing has a side with lettering and numbers, it is thicker and stronger than the other side. Only drive or pull on the side of the bearing with the numbers. I suspect the bearing holes in the block are not truly lined up or on center with each other.
Hope this helps, Charlie

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Post  Lem Evans on April 15th 2019, 10:22 am

.0005" run out is as good as it's going to get.

The journals being under the high side dia. so, you should be good there too.

Sounds weird but, does it act the same if you install the cam from the rear of the engine?


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Post  ChrisH on April 15th 2019, 8:11 pm

Charlie,
thanks for the heads up. I do drive them in. I had thought about pulling them in, but hadn't spent the time to build the jig yet. And yes, if I get this solved I will install a fresh set of bearings for reasons you mentioned.

Lem,
I had not thought of that. there is certainly something to be learned in that exercise. you get so brain locked on doing something a certain way (like cams load from the front) that occasionally you miss something.

ultimately I know this is in the block. its just a matter of which journals and exactly what is wrong (misalignment or the bore hole being "cocked"). then there is the little matter of fixing it.

thanks for the ideas.

chris Harrington

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Post  ChrisH on April 15th 2019, 8:13 pm

still waiting for someone to tell this is no big deal. it'll run for ever like this. Wink

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Post  JBR-3 on April 15th 2019, 10:32 pm

If the journals in the block are not co-linear, how large can you then bore them
before the cam bearings don't press fit anymore ?

Furthermore, how could they possibly not be co-linear after boring unless
the block casting somehow settled/shifted ?

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Post  10.0 on April 16th 2019, 3:23 am

If the bearings still have a press fit and cam spins nice, then I wouldn't worry.
I used needle cams bearings over a few times, just mark which hole they came out of.
Always drive them in from the lettering side[It's thicker]
I had a solid collet made for my cam bearing installer, easiest part of the whole shortblock was the needle cam bearings.

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Post  litshoot on April 16th 2019, 9:01 am

was it honed with deck plates, and you have heads off or vice versa. it shifts with the heads on?

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Post  ChrisH on April 16th 2019, 9:31 am

i think i found the culprit, bore three.

my bore gauge isnt long enough to properly measure this bore so i had to use snap gauges. installing the cam from the rear like lem mentioned shed a little light light on things. went back and measured bore three again and believe i found the issue. i need to find a longer bore gauge or an extension for mine to confirm. but it looks like that bore could still be a little tight. i wont be able to say for sure until i get a proper bore gauge length.

thank you for the help everyone.

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Post  Lem Evans on April 16th 2019, 9:10 pm

You may be better off replacing the bearings that have been 'crushed' more than once.


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Post  ChrisH on April 16th 2019, 9:50 pm

yeh, when I have it resolved I will install new bearings. $50 worth of bearings aren't worth a motor.

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Post  ChrisH on April 21st 2019, 11:06 pm

for anyone that is having trouble with cam fitment and has bore gauge limitations or roller bearing don't allow the use of one.

it hit me to just cut the end off an old cam, one journal and a couple lobes for a handle. this lets you feel, fit, test one bearing at a time.

its a free test and can give an idea about fit for individual journals. if they feel good then you know its a bent cam, or an alignment problem between bores.

by the way, even oem cams are fairly hard.

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Post  Lem Evans on April 22nd 2019, 10:46 am

Good thinking.

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Post  Mark Miller on April 22nd 2019, 11:08 pm

Lem Evans wrote:Good thinking.

X2!! Smile

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