Small Block & Big Block Chevy Specific - Cam issue!

Well guys i wanted to see what yall guys think could make this happen and maybe why. My car was running like crap so i took it back to the shop and we find out that one of the lobes on the cam is rounded off. We found out because one of the valves was only lifting about .100 Just wanted to know what causes this and why. Its a hydraulic flat tappet cam just incase that helps. Could it just be a bad part or could something be wrong with any of the valvetrain? We already replaced the cam and is getting put back together as we speak. Thanks!

Yes to everything.

Could be a bad cam, bad lifter, but more common improper break in, wrong oil.
Also any valve train part binding up, coil bind, retainer to guide contact, valvetrain geometry off, etc, etc, etc.

When you break the cam in see if you can find some GM EOS to add to the oil, use 15w40 rotella t diesel oil, make sure it starts right up and can hold 2000 rpm for at least 15-20 minutes straight.
Did you do/check all this the first time?

Actually the shop that built the engine for me and installed it should have done that. It was a brand new engine when they wore it in. They said they did it on their dyno. The engine had a lil over 3000 miles when this happened and now that they put a new cam in it they said they were going to wear it in as well but i dont know how they do it.

Thats odd. Every cam I ever had wear a lobe off did it within the first 20 minutes.

Well i talked to the guys at the shop and they said that they use that rottela oil to break in the cam. And they break it in on their dyno. Once the cam is broken in and everything is fine what oil should i use from now on when i do oil changes. Mobil 1 synthetic would be good? Or i can just use regular mobil 1 or any other brand.

Anything once it's broken in properly.
I'd be looking for a reason why the lobe went flat. Otherwise 3000 miles later you might be doing the same thing.
Did they give you a reason? And what did they do to get all the metal out of the engine?

improper lash?

Anything once it's broken in properly.
I'd be looking for a reason why the lobe went flat. Otherwise 3000 miles later you might be doing the same thing.
Did they give you a reason? And what did they do to get all the metal out of the engine?

They really have no idea why it did it. They machine and build racing engines so im sure they know how to build one. And they said they've only seen that happen twice. And about the metal they are going to do a couple of oil changes to try to get most of it out.

generally worn cam lobes come from improper break in or too high of spring pressure,when running dual spring we take the center one out for break in and install a set of 1.3 ratio rocker arms.Comp cams breakin lube helps also.

generally worn cam lobes come from improper break in or too high of spring pressure,when running dual spring we take the center one out for break in and install a set of 1.3 ratio rocker arms.Comp cams breakin lube helps also.

I dont know about the spring pressure so ill have to ask.

What was the lift of your cam with 1.5 ratio rockers? What brand of cam did they use?

What was the lift of your cam with 1.5 ratio rockers? What brand of cam did they use?

the lift with 1.5 RR is int. .507 exh. .510 and it was a comp cam

the lift with 1.5 RR is int. .507 exh. .510 and it was a comp cam

The lift is less than I thought you were running but the same cam company as I suspected. If you had been useing say a .390 lobe (.390" x 1.5 = .585" lift), they have a tendency to have a very short life span due to how sharpe the angle is on the nose of the lobe. Over the "life" of the cam the bottom of the lifter eventually makes contact with the nose of the lobe, taking the hardness out of the cam. I would have to venture to say that in your case the cam wasn't properly treated in the nitriding process and ended up being a "soft cam". I was talking to a freind that was a diehard Comp Cam guy and was decussing failure's of flat tappet cams in bolth BBC's & SBC's, my thoughts on the subject are our conclusions of our discussion.

The lift is less than I thought you were running but the same cam company as I suspected. If you had been useing say a .390 lobe (.390" x 1.5 = .585" lift), they have a tendency to have a very short life span due to how sharpe the angle is on the nose of the lobe. Over the "life" of the cam the bottom of the lifter eventually makes contact with the nose of the lobe, taking the hardness out of the cam. I would have to venture to say that in your case the cam wasn't properly treated in the nitriding process and ended up being a "soft cam". I was talking to a freind that was a diehard Comp Cam guy and was decussing failure's of flat tappet cams in bolth BBC's & SBC's, my thoughts on the subject are our conclusions of our discussion.

Basically a bad part? Oh and im using a 1.6 rocker ratio just incase you didnt know.

As long as the lash wasn't to tight, then that is what I think your problem was. The lobe lift is a .338" lift on the int. and .340" on the exh., you shouldn't have had any problem's with those milder lobe profiles.

Well im going to pick up the car tomorrow guys. Hopefully everything is good from now on. Wish me luck guys!

good luck!! and i wanna hear it later ;-b

Ima try to post pics of the cam and lifter this weekend. Pretty crazy stuff!

m not sure if this could be a reason for your cam going bad, but ive heard of a lot of flatt tappets going bad because oil companies have taken the zinc out of all the oils now... it had to do something with the catalytic converter, but they didnt know it would screw up cams.

They don't care if it screws up flat tappet cams. It's been over 20 years since theres been a factory produced engine with a flat tappet cam, all went to roller cams.
Zinc and all the other additives used to help flat tappets live have been eliminated because they are harmful to the environment.
They've even removed it from the diesel oils within the past year.
The only option now is racing oil, designed for offroad use, most still have the additives for flat tappet cams.
They are really only needed when running high lifts and big spring pressures.