At a crossroads - AGAIN.. Cam Bearings
 

After close to 200 runs into the season (which had been going extremely well), the front cam bearing left the chat in my MR1A block. Come to find out every cam journal measures greater than 2.032" (one was as wide as 2.0327, over .002 out of tolerance).

Has anyone had direct experience with finding a solution to this, or is this a case where it will need to get bored/resized for either an oversized bearing or just scrap all this $#!+ and push a 50mm roller bearing in it and be done (then new cam, push rods, etc)? The cha-chingas are adding up fast and making my head spin.

The other option sounds much less entertaining - ordering dozens of bearings looking for a few 2-3-4 sets (in hopes) that they would give the proper crush (0.004-0.005)? This sucks!

As you mentioned, you have a bunch of options, none are super easy. First and most important, do you have a machine shop that has a line hone mandrel small enough for your cam tunnel? If they do, that opens up more options. If they can line hone the cam tunnel to any size, get into the DuraBond catalog and go through one by one the progressive cam bearing sizes available both ID and OD. There may be an existing cam bearing with the stock Pontiac ID and an OD to some size they can hone the tunnel to. That's the easiest because you won't have to buy a new camshaft. If they have line boring capability, like a Rottler F65, you can bore the tunnel for 50 MM bearings but will need a new cam.

I bought an IA II block that had the cam tunnel all messed up. You could push the can bearings in with your fingers. It was supposed to be bored for 50 mm bearings. I found some tractor cam bearings in the Dura Bond catalog and honed the tunnel to fit. You do have some options.

Well that's a bummer!

Can the cam bearing ODs be tin-plated to build up the OD?

.010 bearings are readily available. Can your guy turn down the OD and get the proper press fit?

There is one bearing really close, but would leave the cam clearance too wide I believe. 2.0327 bore, with .0611 wall would leave real close to .010 - too much.

A shop down the road from my machinist wanted $1250 to bore/install 50mm bearings, then add-in the cost (and wait time, barf) of a new cam, probably new push rods (my manton ones are badass and I just bought them). Looking at $2500+ and probably 8-10 weeks, but that comes with re-assurance and probably some added HP, because who can order a cam and not want to improve lol... However, I can't justify that cost when everything is still in good enough shape to reuse.

I think the best bet is to just open the bore up another .003ish and settle in with the 0.010 oversized and hope them not being coated doesn't cause any further issues. I'm hoping this option will save me a couple G's and several weeks because I need my car on the track. Have an 11 round lead in points at 1 track 4 races into the season....

What sucks the most is paying a boatload of cash for a block that wasn't right from the beginning.

You might check the classifieds as member MysticMissle just listed a 55mm cam and lifters.

If +.010 cam bearings are available and that will do the job for you, that's exactly what I would do. Lowest cost and least hassle to get you back on track. I have owned a bunch of aftermarket Pontiac blocks with all kinds of defects. Oil gallery drilled into water, clutch crosshaft ball drilled into water, block with no lifter oil feed holes, block cracked at screw in oil plug in the back, cam tunnel problems, rear main seal groove machined wrong. This is to name just a few. Choose the path of least resistance to get it fixed and go racing. Otherwise, it just drives you crazy. All the low production, aftermarket blocks have similar issues, The Rocket Olds block, 4 different versions of the Ford FE blocks, some SBF blocks and many others.

Hey Paul!

I spoke with him Friday and he was able to find a 2 inch mandrel and ordered two sets of oversized bearings today to go this route. I appreciate him (and you) for trying to save me the cost of eventually having to line bore the cam tunnel more than once if I ever go the 50mm route.

I seem to have misplaced my cam thrust bearing (maybe once I clean up my damn shop it'll turn up - or probably after I order a new set lol). I do see that the Rollmaster Red series says on the box "Machined for Torrington roller bearing" but I can't find any information on what that part number would even be. Not sure if you would know what that part number is? Rollmasters website is archaic and little to no information is on their site for the Pontiac set with the IWIS chain.

Thanks again gents.

Great!

Go with the Cloyes and don't look back.

IDK about the Torrington set up from Rollmaster. BOP stocks the Sims set up.

I am glad to hear your machine shop has that 2" long mandrel. They are hard to find and Sunnen gets over 5K for a new one now. I have had one on our wish list for years at my school. Hasn't made it to the top of the list yet. Should come out better than new.