SB race block cam tunnel machined wrong

I know there are some 59 degree race blocks that were incorrectly machined with a 50 mm cam tunnel. I am working on making a set of custom cam bearings to make this work. The trick has been getting a piece of 850 aluminum alloy to make them from. I had to have a foundry cast me a piece. I didn't know if anyone else out there has one of these blocks?
Dave

9.200 deck with 59 lifters

Why not have the tunnel machined and run 54,55 mm cam? Thats what I did.

Or plug the lifter bores and re-machine them to 48*

The push rod geometry on the 9.2" deck 59* isn't pleasant

....there is still a 9.20 deck 59 degree block in the parts system. It's in the Atlanta depot

Yep - got a new one on the shelf. Wallet has been trying to decide for about 10 years the best way to use it. I'll probably have more money fixing the cam and bearing issue than the rest of the motor. I can't really make the cubic inches I wanted to, either - I'll probably stay with a 3.79 stroke to keep a decent pin height and not pull the pistons out of the bottom of the block too far.

yes this I think would be best

Ryan has plugged the lifter bores before, and re machined for 48 degree bores. But he said that would be a lot more work than making a set of cam bearings. I just finished the bearings. They were easier to make than re machining to 48 degree. Although I would agree that improving the push-rod angle might be worth the extra effort.

ok, where do I get a 54/55 mm 59 degree cam from, other than a custom billet? If I am going to do a custom cam, then why not a 50 mm so I don't have to re-machine the tunnel? Right now I am told that it is a 6 month lead time to have one made. And I don't have 6 months. I think I would still move the lifter bores to 48 degree before I would do a custom cam, so then I get the benefit of the improved push-rod angle, for my effort.

Talk to Danny at predator cams. Good guy to deal with.

LSM 248-674-4967 I had one made for me in less then three weeks before the gators this year 54 mm. 9.200 59 degree buzz it pretty good with no issues.

the 50MM is not a problem for comp cams to do (they have the size listed in their catalog 1.968). I would call and ask about the 59 degree angle. If it's not to big they might be able to do it. they also list round cores.


Joe

hehehe.... remember going through my babbit cam he77 a couple years ago when NOBODY had them. The R3 world is an interesting one

Did you make the spacers? I also have one of these blocks. If I remeber right one of the spacers would only be like .008 thick. I thought about pouring some out of babbitt and machineing the whole bearing.

...

...

You get that cam from the same place you are going to get the 50mm, which will also be a non standard core custom grind. The larger core is always the best option from a cam standpoint. Larger equals stiffer. The last custom tool steel billet I had done, which was a couple months ago........took 3 weeks to get

Well, I know we could have gotten a custom cam made. We can argue about how long it would actually take. I am not building this motor, Ryan is. And he made the decision that he wants to be able to use an "off the shelf core" 59 degree cam, in this motor. So given that, here is what I did. I had a foundry cast me a piece of 850 aluminum alloy. In order to get the piece cast and shipped to me in the same week, I had to accept a raw piece like this with no core out the center or rough machining done prior.

Starting rough turning....

My three rough pieces.....

This is the number 5 bearing.....(ID not honed to final size yet, and oil hole not drilled yet)

Here is #1 - #4. We then honed the ID to final size on the rod hone, using stones for aluminum. This had not yet been done in this pic. Also the oil feed through hole had not been drilled yet.

Cute, very cute!

R.

So you are using the aluminum as the bearing with no other bearing right?

Bronze not a suitable material?

Kevin

How much press fit will you be using on those? I'm going to ask a possibly stupid question and ask if you took that into account when you finish honed the ID?

I believe Ryan has them set up for 0.002 press. Yes, Ryan took the crush into account when honing. I know he said the #5 came right on where he wanted it after installing it.

Yes, this id the final bearing surface the cam will ride on.

You might be able to use Bronze, I don't know. Ryan researched what other people have typically done in the past for something like this, and they have been 850 alloy aluminum. High tin content. The oil clearance he said is typically set up looser than babit. He was shooting for 0.002-0.003 oil clearance, for this setup.