i have a 1972 gmc pick-up with a 350. I had driven the truck for atleast 500 miles with no prblems, then i started hearing a slight ticking sound, and at first thought it was just a hedder leak, so i checked the header gaskets and there was no problems. i continued to drive the truck for another day, and then it sat for about 2 weeks and i started the truck up to move it and it had a severe ticking coming from under the valve cover, which seemed like around number 5 cylinder and you could hear it clearly in the exhaust too. so i pulled the valve cover and i found that the intake rocker arm on cylinder 5 was way loose, i checked the rocker nut and it was tight, i checked the stud to make sure it hadnt pulled out, and i also checked the pushrod to see if it was bent and it wasnt. the pushrod does have i higher wear line on the lifter end than the exhaust rushrod on that cylinder. so i was wondering if this sounds like a collapsed lifter or maybe a bad cam, or just something more simple.
08-07-2010 05:58 AM
did you install a new cam? what brand... but more than likely lost a cam lob. lifter may have worn down to the point it has a hole in the bottom of it and is bleeding oil out.. i would say pull the intake...
08-07-2010 11:49 PM
no i ddint put a new cam in and i checked and seen that the lifter was still coming up when i crank the engine over, so its not a bad cam. and im pulling the engine out and gonna chevk it out
08-08-2010 01:56 AM
Maybe a broken valve spring.
08-08-2010 08:14 AM
The new cam and lifters will quickly pay for themselves in fuel savings and fix the problem, unless Monster is right and you missed a valve spring. When you pull the cam out, try a dial caliper both ways, on each lobe. Subtract the minimum reading from the maximum, multiply by 1.5 to the get approximate lift. I don't expect two of the holes to be exactly the same. A old smallblock cam is like having eight different cams in one; with each cylinder programmed and directed to do something a bit different from the rest.
Side note.. 7 years ago we tore down a 283 that everyone in town thought was a strong 327. Not only was it a 283 but had never been opened up and worn completely out in every way. The cam was the worst I'd ever seen come out of anything that wasn't skipping. most lobes rounded off but all still lifting at least some. No telling what kind of timing or had or lift, but it was an outrageous tire spinner. A 67 short bed 3 speed and was geared very low. Doesn't take a lot of lift to achieve bottom end torque but I'll never forget how bad that cam looked and how impressive a burnout it did the day before we took it down. Strange thing, but results not typical. I like a new cam :D