[Stan65]

hurryinhoosier62,

I’m located in Central Illinois. I am a machinist of sorts. Mostly CNC, but I do have an old Monarch Lathe and a Bridgeport knee mill at home. I used to help out a local street rod shop that has since closed. He had a 4 axis CNC mill and a CNC lathe that I wrote a lot of code for. Made a lot of neat parts. I do a lot of design work in AutoCad today, but since losing my access to the CNC machines , I outsource my projects to a local machine shop.

[Stan65]

mgarblik,

I really appreciate it!

I sill want to try to center less grind the OD of a .010 over bearing. Would only have to remove .0023 +/- .0002 to get where I need to be. Part of the first set that will get screwed up. Lol.

I’m gonna install a set of standard P4’s in 1, 2 ,3 and 5. Then slip a cam in while putting #4 in while I’m installing it to make sure it’s straight.

If it’s not straight I guess line boring will be in order.

[mgarblik]

Heard back from David Butler already. He is in for 5 sets. So that is 21 sets now with your 3. Anyone else interested in getting a set or 2? 4 more sets and they go in line for production.

[Stan65]

mgarblik,

Depending on price point, I may buy more to make it happen.

[Formulas]

Originally Posted by hurryinhoosier62

Spray welding is used in turbine engine components, not recip engine components. Oversize cam bores and main saddles are weld then machined back to standard in aircraft recip engines.

I said aircraft and got you all excited didn't I... I have seen it used in places you have not described having spent 34 years in fighter and bomber aircraft production and flight test

a thin metallic layer applied to a pontiac cam bearing shell theoretically would tighten it up..

it seems as though there is a more mainstream resolution in work for the noted cam bearing

[Shiny]

Is a shim a viable approach? The bore sounds round, shims are precise (ie feeler gauge), and an anaerobic locker should be enough to prevent rotation.

[Stan65]

Formulas,

I may look into nickel plating with one of the teflon coated bearings. The teflon will protect the bearing surface from plating. The hydrogen embrittlement issue may be able to be felt with by heating them to 350 degrees for 4 hours after plating. Sounds like an interesting little science experiment.

Shiny,

I looked at speede sleeves, but the thinnest I found was .011 and I’m sure the ID/OD isn’t available. I thought about shim stock, but I don’t think I could get it to press in uniformly enough at .002 thickness without tearing or rolling.

[hurryinhoosier62]

Originally Posted by Formulas

I said aircraft and got you all excited didn't I... I have seen it used in places you have not described having spent 34 years in fighter and bomber aircraft production and flight test

a thin metallic layer applied to a pontiac cam bearing shell theoretically would tighten it up..

it seems as though there is a more mainstream resolution in work for the noted cam bearing

Spent nearly thirty years of my life in aircraft maintenance; old habits die hard. Theoretically isn’t reality. The babbitt surface on bearing is actually fairly fragile. If memory serves me, spray welding uses temps in excess of the melting point of antimony( the main component in babbitt). The steel shell of the bearing would be a better surface, but there is still no guarantees it would work. It does wonders on block decks, crevice seal areas, water pump housing surfaces, and most other low stress areas.

[hurryinhoosier62]

Originally Posted by Stan65

hurryinhoosier62,

I’m located in Central Illinois. I am a machinist of sorts. Mostly CNC, but I do have an old Monarch Lathe and a Bridgeport knee mill at home. I used to help out a local street rod shop that has since closed. He had a 4 axis CNC mill and a CNC lathe that I wrote a lot of code for. Made a lot of neat parts. I do a lot of design work in AutoCad today, but since losing my access to the CNC machines , I outsource my projects to a local machine shop.

Good machines to have. I learned manual machining on a Bridgeport and a Clausing lathe. We used to have an align bore fixture for the Bridgeport we had in our diesel production area. We align bored Triton cylinder heads for +.010 over bearings when cam bores were spun( VERY common problem in the Romeo/Windsor/Triton engine family). I’ll see if I can find one in your area.

[Formulas]

Originally Posted by hurryinhoosier62

Spent nearly thirty years of my life in aircraft maintenance; old habits die hard. Theoretically isn’t reality. The babbitt surface on bearing is actually fairly fragile. If memory serves me, spray welding uses temps in excess of the melting point of antimony( the main component in babbitt). The steel shell of the bearing would be a better surface, but there is still no guarantees it would work. It does wonders on block decks, crevice seal areas, water pump housing surfaces, and most other low stress areas.

Keep up with the times the link i posted said it can be done on a piece of chocolate but not recomended and it can be applied to wood as i and the article mentioned,

theory is the birthplace of reality.

[hurryinhoosier62]

Originally Posted by Formulas

Keep up with the times the link i posted said it can be done on a piece of chocolate but not recomended and it can be applied to wood as i and the article mentioned,

theory is the birthplace of reality.

Sometimes…other times it is the graveyard. I’m going on my experience with spray welding.

[VCho455]

We tore down a 455 years ago that had a repaired #1 cam bearing. The cam bore had been overbored about a quarter inch and a aluminum spacer was installed. The spacer was staked in place with two Allen head set screws that were drilled and tapped so half the set screw was in the block and half in the spacer. Similar to the pulley in the photo.

We had no idea how long the the engine had been run with the repair as it looked like every other 75k mile plus engine from the outside. I used to have a photo of it but I can't locate it now.

Just food for thought.

[Shiny]

Possible to modify a non-Pontiac bearing that might have a stock diameter larger than Pontiac? Big block chevy?

[Stan65]

VCho455,

I have considered making a sleeve, it definitely wouldn’t be easy to bore just #4 and keep it all within tolerances for alignment to the other bores, but would allow the use of standard bearings.

Shiny,

I looked through the Dura-Bond catalog. They have a list in order by OD. Nothing close enough to make work.

I have a single .010 bearing on the way. Thanks PAUL K!

I have to make a mandrel to grind the OD to fit my bore vs boring my block for the .010 bearing. Since I have make the mandrel anyway, I’m gonna try to knurl the OD of a standard bearing just out of curiosity.

Thanks all!

[hurryinhoosier62]

Originally Posted by Shiny

Possible to modify a non-Pontiac bearing that might have a stock diameter larger than Pontiac? Big block chevy?

Good question! We used to do this with spun cam bores in 134ci Willys engines (you’d be surprised how many are still out there!). We used the # 4 bearing from 292/312 Y block Fords, then align bored the cam bore to .0015-.002 under the OD of the Y block cam bearing. I’ll get my Clevite cam bearing catalog out to see what cam bearings have the same ID as a Pontiac but a larger OD.

[hurryinhoosier62]

Originally Posted by Stan65

VCho455,

I have considered making a sleeve, it definitely wouldn’t be easy to bore just #4 and keep it all within tolerances for alignment to the other bores, but would allow the use of standard bearings.

Shiny,

I looked through the Dura-Bond catalog. They have a list in order by OD. Nothing close enough to make work.

I have a single .010 bearing on the way. Thanks PAUL K!

I have to make a mandrel to grind the OD to fit my bore vs boring my block for the .010 bearing. Since I have make the mandrel anyway, I’m gonna try to knurl the OD of a standard bearing just out of curiosity.

Thanks all!

Stan, as long as you have a cutter collar it is a fairly straight forward process. Does the machine shop you use align bore blocks? If so, find out what equipment they have.

[Stan65]

Whipped up a mandrel. Made a do-dad to hold a dremel. Need to get some new stones for the dremel and the oversize bearing and I’ll be on the way.

I didn’t have time to see if I could knurl the shell on one of the bearings. I will try that soon.

Thanks everyone!

[Stan65]

hurryinhoosier62,

Yea the shop can align bore. I’ll have to ask about what they say about boring the cam tunnel.

I hope to just fix the one bearing. And not have to bore the whole tunnel. The cam spins free with new bearing in 1, 2, 3, and 5. I just slid the #4 in as I was slide the cam in.

Stan.

[Stan65]

Just wanted to give an update.

Received the bearing from PAUL K today. Thanks again Paul! Did all the measurements and calculations, ground .0065 off the OD. Pressed it in and done!

Clearances on the bore of all bearings are within tolerance and can spins free.

Thanks all who helped with this.

Stan.

PS, I will still be in for one or two sets of oversized bearings if they become available again.

[mgarblik]

I am glad to hear the entire repair came out great. Are you still planning to pin that bearing? I would think it unnecessary and may distort it slightly. Also assume no bearing mount compound was used or necessary.
I have to wonder just what caused the issue with that one cam bore with no sign of the bearing spinning? If I just had to guess, possibly a cutter was chipped or found to have a problem in production on a given number of engines. Rather than scrapping possibly a few hundred blocks, they decided to have a short run of OS bearings produced to fix these blocks and nothing was clearly documented about it? Chrysler was famous for all kinds of assembly line machining fixes rather than scrapping engines. I have run into numerous Chrysler V-8's with 2-3 different diameter lifters in the same engine. That can be a real pain when rebuilding 50+ years later. Never run into a weird cam bore issue like yours though. Your machining skills and careful measurements saved the day.