BBC eating lobes off of Camshaft(s)

[strangler]

My 396 has destroyed 3 cams in >5000 miles. I dont know why. Buildup:

69 396 block and crank
12:1 (with 106cc) forged pistons
Dimple rods
781 heads with new seals, seats, 3 angle etc.
120lb seat pressure springs
diamond racing pushrods
harland sharp roller rockers
manley rocker studs and guideplates
holley dual plane
edelbrock 750
MSD ready-to-run

cams have been:

Mild hyd flat tappet .500 lift - first lobe to dissapear, and lifters worn through. Stock rockers were used at the time, so I thought they were binding and replaced them with the roller rockers.

Then I installed another mild hydraulic (roughly .510)- along with new lifters and the new rockers it was installed after flushing out the motor. It lasted about 10 minutes before the stock replacement pushrods turned into wet noodles, and broke the pressed in ends off of them. The cam was also scratched so it was replaced with the next one

Installled a solid L-88 replacement (.560/.580)- Installed this cam with new solid lifters, roller rockers, and the new diamond racing pushrods. Cam worked fine with no damage to any of the parts, but the cam made no power with my combination, so it came out last week to be replaced again- starting to understand my frustration?

OK, last week I installed a Comp Cams .595/ 294s cam and new lifters. Inside of engine was still clean and lifters slid right into bores with no problems. Comp asked for .022 hot for a lash, so I lashed the rockers cold at .024, started it up with fresh oil, and ran it at 2500-3200 for 15 minutes or so- having good oil pressure. Yesterday I started it up again and drove it around the block to warm it up, came home and drained the oil, and removed the valve covers to re-lash the now-hot rockers. They were all about .001 loose, so I went through and re-set them all to the .022 that Comp asked for.... nothing funny, they were all within .002 So I decided to drive it to my Dads house 40 miles away to further break it in, and ask his advice on some carb issues Id been having. By the time I got off the highway (after running about 2900rpm) the motor was feeling fairly dead, like it was running really rich, yet without the smoke, and now it was popping through the intake. Removed valve comes again and foung #6 intake to be dead, not so much as a 1/8" of movement. Any ideas before I scrap this whole POS and build a different engine? My Dads convinced the valve springs are too stiff, but I selected this last cam with those springs in mind, being exactly what Comp would reccomend. Thanks for any advice.

454 short block wanted......

[astroracer]

Did you check the springs? I would have them all checked to verify they are what you think they are... If it's not the springs then you have some geometry issues and you need to verify pushrod lengths. Especially if the deck and/or heads have been milled a bit. If the rods are to long they will cause the problem you are experiencing.

[yody]

couple of red flags. First I believe a 292H is a hydraulic cam, which would not require any sort of lash. Just preload, if you had a misprint and it is a a 292S which isn't in existance, its really a 294S and the Hot lash is supposed to be .22 then the cold lash should be .18 not .24.

First off, you need to check your valve springs, and second if they are dual valve springs you MUST pull the inner springs for break-in. For an example, on my first fire up with the old solid flat tappet, I somehow messed up and only pulled the inner valve springs out of one head!!! well the cam went flat and it turned out that every lobe on teh bank where both valve springs were left in was flat. SO that tells me on BBC with the spring pressures and such that the inner spring needs to be pulled until cam is fully broken in.

Second you need to make sure all hte lifters/pushrods are spinning when the engine is running, if they aren't spinning the cam will go flat.

Third go to GM and get a bottle of EOS and pour that in before cam break in, that has some good adidtives that help the metal wear etc.

Fourth, how long are you cranking on it before it fires? Ideally you want it to fire off immediatly, the more dry cranking the more wear on teh cam.

[strangler]

It is (read: was) in fact the 294s, and it fired right away, but I did not seperate the valve springs. Already found a 70 454 short block with a spun rod that Im picking up tonight. Its my new project, and I think Its gonna be a full roller.... Im sick of breaking this stuff.

[Zee]

http://www.lazercams.com/

[my72vette454]

Hey strangler here are some things I have learned about big block chevys. First off the automotive oils produced today are missing some components such as zinc that helps with scuff protection. Since the oem's are almost all roller cams anymore and for enviromental concerns they have dropped some additives out of some oils. For breaking in a new cam there are several things I know of to help, first off I think its comp cams that makes a cutter that goes in the lifter bores that cuts a small groove from the oil galley down to the bottom of the lifter bore to feed more oil on the cam just in front of the lifter. Also use a quality diesel spec oil for breakin such as rotella or dello as it still has zinc in it. The bottle of EOS from your local gm dealer will help too and I think several cam mfgs have a zinc suppliment that you can add to the oil for breakin. I have learned all this the hard way and I know how frustrating it is. Hope this helps,

Mike

[LS1Bandit]

I have a 454 i'll sell ya, runs AWESOME!!