Hot Rods The cam ain't flat!

My 32 Cdan has a basically stock 73 350 that I had thought had a flat cam. Symptoms were rough idle when warm, vibration like not all cylinders doing their thing on the highway and bad valve ticking once it warmed up. I had tried every valve adjustment procedure I could find with no success. The only one I didn't do that might have told me something was adjusting them with the engine running. I had a cut out valve cover but it was still too much of a mess and too hard to get on the rocker nut so I gave up. I finally did a dial indicate check on each rocker and saw a few that were no where near the lift they should be so declared a flat cam and ordered a Comp 268H. Pulled the old one out today and was totally surprised that I didn't see any obvious rounded lobes. The lifters also looked OK but I'm not an expert at these things so took the cam to one of my local engine wizards/machinist and he said it looks fine. He declared this with a visual inspection but the guy has really impressed me with his knowledge in other situations so I tend to believe him. He suspects lifters were not doing their thing.

The engine has about 6K on it and it's a Heco n Mehico version so probably a Target motor. It was in the car when I got it with 4K on it.

Anyone else encounter this kind of problem? I know I've seen a report somewhere about a major lifter manufacturer going belly up a while back that forced a bunch of off shore stuff into the system that was suspect. I'm curious about the failure mode that would cause this problem. Is it the spring in the lifter, is it something I can see?

 

I always do a valve adjustment with the engine running. It's messy, but thorough. You gotta work fast, to minimize the mess. I sometimes place a cookie sheet over the area above headers to keep a lot of the oil off them.

 

Yea that's the only way I did them back in the day. Had some clips that would go on the rockers to plug up the oil hole. My clips are long gone although I think they are still available.

 

You can get those clips at O'Reilly's, but you have to order them in store. They get them from their local warehouse the same day. Usually. Tell the kid with the zits to look in their catalogs. Advise him he'll need to actually reach for the catalog.

 

Al least one local NAPA here in PA has the clips on the shelf. Just grab them and head to the counter.

 

old valve cover and a hole saw was my best freind for this , many people borrowed them from me . I haven't used them in such along time I forgot who still has them .. as for Gm hyd lifters , they had good and bad years , and still do , the hydraulic roller ones in the big blocks ( post 96) were known to collapse or fail to pump oil to the rocker arms , it was hit or miss on them .