vrtc350

iTrader: (1)

My friend is having a problem with his small block chevy. It seem that the exhaust lifter on # 6 has been beat up pretty good. There is most likely lobe damage to the cam shaft as well. The lifter(hydraulic) appears to have been gettin oil. He has said that this is a common occurance in sbc and that there is a fix of somesort to prevent this kind of failure. As I was talking to him and my Dad they recalled seeing an article somewhere about this. They just can't remember.

In comes me. Since I am the only one with high speed I''ve been recruited to find out this info. The only problem is after about an hour of looking I have yet to find the answer. Does anyone have any knowledge or experience in dealing with this problem. If anyone knows of any articles please link me.
Thanks for the help.

RB83L69

If the lifter is no longer perfect, the cam is wasted. Period.

Remember: lifter not perfect = cam wasted. There is no "look and see", no "maybe", no "probably", no "likely", no "it's only a little bit damaged", none of that. If the lifter is no longer perfect, the cam is wasted; no alternatives. There is no further question of it.

Your buddy will be replacing the cam and lifters at a minimum, that much is for sure. Or he'll be right back again soon to where he is now. And if he doesn't find and fix whatever killed the cam that's there now, he'll be right back where he is now, whether he replaces it all or not.

Now that we've got that over with: First thing to do, is figure out why the cam lobe went down. There are a number of possible causes. The most immediate suspect, is inadequate valve springs or improper installed height; check the installed height with a sprng mic especially on the damaged valve, and verify that the springs are at least .050" out of coil bind on a lobe of the same kind (exh in this case) that's still good. Next, is too much cam for the head setup; things like retainers smashing into the tops of guides (inspect the bottom of the retainers and the top of the guides CAREFULLY for signs of this).

If all of that is in order, you probably have a block issue; where the lifter bore doesn't point at the cam properly. If you have that, you might be able to fix it by switching to a roller; otherwise, you'll need to have the lifter bores bored out to a larger size (Chrysler and AMC are the 2 sizes commonly used) and use the lifters to match.

Good luck!!

vrtc350

iTrader: (1)

This setup has been together for a while. Somewhere around 5 to 6 years with no problems. The car is not a daily driver and never has been. So all of those things would have been checked prior to assembly. My dad says he has seen this in the same spot with many other chevys, good or bad. I will forward your reply to him. Any suggestion is better none. Thanks for the help.

RB83L69

The block thing was actually fairly common in 70s blocks. I've had more than one myself that did it. And my experience agrees with your dad's; seems like it's usually #6 or #8 exhaust that shows it up first. It's almost always a back cylinder, and more often on the right than on the left, and of course the whole exhaust side valve train is more stressed than the intake side, so it always toasts first from otherwiseequal conditions.

But I wouldn't just jump to that conclusion, without checking everything; even if it's been together for a while, it can take several thousand miles to turf a cam lobe to the point that you'd notice it and start look for why the engine won't run right. Valve train interference is particularly prone to do that, especially if the push rods or rockers are weak (stock "rubber" rockers); because they'll bend under the load, and act like the "fuse" in the system, and protect the cam from the full impact. So if it doesn't have something like Comp 7400 series push rods and 1300 series rockers, it could easily still be caused by something in the valve train crashing into something else.

vrtc350

iTrader: (1)

Thanks for the help again. I've sent your replies to him. You have provided some answers/suggestions that he can use. Of course ultimatley, the cam and lifter has to be replaced. I think he is looking for a way of prevention. Thanks again!

vrtc350

iTrader: (1)

Well my buddy has bought his new cam and most likely has it installed by now.

I was talking to my Dad the other day and we were discussing why the lifters in this pariticular area seem to get destroyed. It was a talk with a very knowledgable guy at a parts counter that he remember what was in the article pertaining to this issue. It seems that the problem with excesive wear in this area began when the zinc was removed from the oil. I guess it's adhearing properties and viscosity breakdown suffered somewhat. So what was the answer to this?

Diesel oil!

Think about it. You can get diesel grade oil in the same weight that you are currently using. Diesel oil is made to withstand an extremely harsh enviroment, high compression, high heat, etc. This kind of enviroment, while not as exteme as a diesel, is present in out own high performance engines. The diesel oil itself is a lot less prone to failure.

Vader

If you believe it is a lubrication failure, the Delvac oil is not a bad choice, but since it is not a daily driver, why not just go directly to Mobil 1? Do not pass GO! Do not collect semi-synthetics.