Cam bearing problems with very high spring pressure

[Guest]

Will traditional babbit-type cam bearings be reliable with 950-1000 lbs. of valve spring pressure? I have a block with 50 mm roller bearings in it now, but I'm thinking about putting 55 mm babbit-type bearings in that would not require me to bore the cam tunnel any more. If you had to choose between 50 mm roller bearings or 55 mm conventional bearings, which would be more beneficial? The cam will have about a .480 lobe if that playes a role in the decision. Thanks for the help.

[CNC BLOCKS]

Will traditional babbit-type cam bearings be reliable with 950-1000 lbs. of valve spring pressure? I have a block with 50 mm roller bearings in it now, but I'm thinking about putting 55 mm babbit-type bearings in that would not require me to bore the cam tunnel any more. If you had to choose between 50 mm roller bearings or 55 mm conventional bearings, which would be more beneficial? The cam will have about a .480 lobe if that playes a role in the decision. Thanks for the help.

We have 2 aluminum SBC with the big block cam tunnels these are blower rngines and we are around 1200 over the nose and they have worked fine for years. going to the 55MM core you can get a more aggressive grind and much stronger core but hold onto your wallet as they are very costly as they are gun drilled. Durabond bearing P/N GM 55T is what you want and it should work fine.

[ChrisU]

I normally try to use a roller bearing in a 1000-1200 pound spring app., but there are circumstances that prevent that at times.

The best babbit type bearing I have found is the Dart cam bearings. Don't know who they are using to supply them, but they have 3 oiling points, and a groove along the backside of the bearings, and they are coated.

Anyhow, after a full season on these bearings and a couple sets of 1100 pound springs, there wasn't any apparent wear on the coating. They look out of the box.

Again, I'd normally prefer to install roller bearings but I have not seen any power from them, and in this instance, didn't see any increased wear with the babbit... but I strongly feel one has to be carefull on which bearing they choose, and how it's oiling.

[airflowdevelop]

My exprience is to stay away from the roller bearings in a situation where you are looking for longevity. They don't deal well with changes in their atmosphere...Plus the quality of the bearing is crucial to its livelyhood.

I have run durabonds religiously on 1000+ over the nose, with no problem at all. I just pulled a BBC street motor apart with 2500 miles on it.. 1100 over the nose, durabonds look brand new!

Nothing wrong with dart coatings either...if you don't mind spending crazy moneys...


Dennis

[hornet340]

like Chris, i have seen good success with the Dart coated plain bearing, the 360* oil well machined in the rear of the shell certainly must be attributed to its life.
How ever has anyone had trouble with 460's spining cam bearings, i have had 2 different cam bearings spin in 2 seperate blocks now??????
i have heard they are common for it....
any insight??

dont mean to hi jack...

thanks
Tony

[Guest]

Thanks for all your help. Would anyone care to make a suggestion about the best route to take in my situation? Should I leave the 50 mm rollers in it or go to the non-roller 55 mm? What do you think is the better move?

[ChrisU]

Personally I'd rather have the big cam core over the roller bearings if I had to decide between the two.

I'd say go 55mm babbit.