In putting new AFR 195s on my 70 Z28 today I figured it'd be a good idea to check on the health of my solid lifters & cam lobes. All lifters looked normal(12,000 miles on the motor) except the #2 exhaust. It has a polished portion that is slightly offset from the middle where it contacts the cam(exactly as much as the bore is offset to the cam lobe). It's obvious that it hasn't been rotating in the bore. The lifter rotates easily by hand, so it's not a problem with the bore being too tight. No damage yet but it's just a matter of time.

There's no detectable wear on that cam lobe but it's hard to be sure looking down through the bore. My engine builder(very experienced) thinks that that cam lobe doesn't have enough of an angle on it to cause the lifter to rotate.
He doesn't think there's a cure except to replace the cam & he's probably right.

So, I hate to toss this cam because I've been very happy with it. Has anybody heard of this happening where it wasn't the cam that caused it? If so, what else could account for lack of rotation? I just want to make sure I really have to yank that cam before I do it. I appreciate any and all thoughts.




[Modified by Les, 12:41 AM 3/22/2004]

 

Hard to diagnos without seeing it. If you agree it is not rotating in the bore the first thing I think of is the angle on the cam is gone, perhaps it can be reground :confused:

 

Contact the cam manufacturer and get their opinion. Is it the angle on the cam or the crowned lifter that causes it to rotate??

 

I tried to reach Harold Brookshire at Lunati today but couldn't catch up to him- it's an Ultradyne cam & he used to be the owner. So far all opinions are that it's likely to be the cam. The odds of a lifter being mismanufactured & not having a crown are slim to none. To answer your question, it's a combination of angle on the cam lobe & a crown on the lifter that causes the lifter to rotate.

On the bright side I found a cam that looks better than the one it would replace. Comp Cams XE282S- 282/290 advertised duration, 244/252 duration at .050, and lift is .520/.540....Comp says the ramps are more aggressive than the Ultradyne & AFR says it's a very good match for the 195s. Power range is 2400-6800 RPMs w/ a redline slightly north of 7000 RPMs. Idle is described as "rough"....I wouldn't have it any other way ;)
So, it looks like it's time to dig a bit deeper into my pockets & go for it. Thanks for the input guys. :cheers:

 

Les - I'm a solid lifter man. You said that you can't see down in the hole. What you need is a dial indicator and run it across the lobes faces and compare it to another "Good" lobe.

Maybe the lifter is lacking oil in it's bore...... With one of those distributor height checker/oil primers from Moroso you could spin the oil pump with that lifter pulled out and see if it's getting good flow through the nearly 1/4 inch oil passage. or with it all together if it's pumping the same amount on to the rockers.

I'm running the Crane Baby solid 238/248 mid 500 lift and 114 lc

 

Les - you may want to check out Crower. They've designed some lightweight solid lifters with a small metering hole on the face to lube the cam. Look in their catalog for the Coolface lifters. Nice cam selection too. :yesnod:
http://www.crower.com

 

71coupe,
Funny you should mention that- I used those when I swapped cam/heads on my Vette & I just ordered a set of them today for my Z28. I also ordered the Comp Cams cam mentioned above & the rest of what I'll need for the cam swap. I decided that it's not worth worrying about the lifter/cam problem recurring & taking the chance of an outright failure later. Besides, I should get a bit more performance in the process. Thanks for the help. :cheers: