Matt Brannon - Midwest Bayless
Mad.Matt
Hey Folks,
Thought I'd share something today. Working on a customer's cylinder head for the last couple of days. They wanted a PBS cam installed into an existing head, and asked for the cam tower to be shaved to compensate for the difference in base circle. A pretty common requirement.
We milled the cam box -.040 (with -.005 off the head's cam-box mating surface) for -.045 total. Brought the shims down a smidge to the 3.7X range. Got the whole thing shimmed up, went to do the final check, and what do I find, but one of the buckets hung up on the cam itself near one of the bearing areas:
This is only the second time I have seen this happen. Unfortunately this was not caused by the cam having too much run-out in the base end of its mounting, that was the first thing I checked in hopes that it was a quick fix. Its clear from inspection that this was caused by the factory cam having not been cleaned up well enough when it was made. None of the other bearing areas have this much material in this spot, and all the other buckets clear just fine. If the cam had .010 less lift, the cam box had been milled .010 less, a slightly thicker gasket happened to have gotten grabbed, or the valve stem height was a few thou shorter, might not have been a problem. Murphey at his finest!
Thought I'd share this as a friendly reminder that when installing an aftermarket cam, you have to be sure that with the lobe straight up, you can spin both the shim inside the bucket, and the bucket itself freely before calling the job "complete".
-Matt
Thought I'd share something today. Working on a customer's cylinder head for the last couple of days. They wanted a PBS cam installed into an existing head, and asked for the cam tower to be shaved to compensate for the difference in base circle. A pretty common requirement.
We milled the cam box -.040 (with -.005 off the head's cam-box mating surface) for -.045 total. Brought the shims down a smidge to the 3.7X range. Got the whole thing shimmed up, went to do the final check, and what do I find, but one of the buckets hung up on the cam itself near one of the bearing areas:
This is only the second time I have seen this happen. Unfortunately this was not caused by the cam having too much run-out in the base end of its mounting, that was the first thing I checked in hopes that it was a quick fix. Its clear from inspection that this was caused by the factory cam having not been cleaned up well enough when it was made. None of the other bearing areas have this much material in this spot, and all the other buckets clear just fine. If the cam had .010 less lift, the cam box had been milled .010 less, a slightly thicker gasket happened to have gotten grabbed, or the valve stem height was a few thou shorter, might not have been a problem. Murphey at his finest!
Thought I'd share this as a friendly reminder that when installing an aftermarket cam, you have to be sure that with the lobe straight up, you can spin both the shim inside the bucket, and the bucket itself freely before calling the job "complete".
-Matt
