Manager Forum

protraxrptr17 wrote:Exact same symptoms as before the valve job. No better,no worse. We will see. I'm doing the job right now. These rockers are not like the old style. These have shoulder bolts. No adjustment. It's all done at the lifter.

I agree with you on the rocker adjustment for the 7.4L engine.

Am really curious if lifter replacement fixed this motor issue.

Fixed!!!!!! Praise God!!!

glad it's fixed. what solved it................

Lifters.

'scuse me for butting in, but I found this ordeal rather interesting to follow. The bottom line appears to be a lifter pumping up, but I'm still kind of curious about the scope trace that was posted earlier in the thread. That trace looked to me like it had a floating ground. Did you happen to capture a trace after the repair ?

your not butting in this is a community effort all comments or questions are welcome. and welcome to the forum glad to have you

No I didn't. It ran good so I shipped it. Never been so glad to see a vehicle gone from my shop. Please elaborate. I want to learn as much as I can about these secondary patterns.

i'm also wondering if a ground issue was resolved during the lifter replacement..............................

ok let me see if I can do this .....
close enough I guess. This is what I would have expected to see as a scope trace on ths vehicle. Schematic shows this as a distributor engine so this is how a normal parade trace would look. Notice the fifth cylinder trace. Low firing voltage,ragged burn time, no distinct cut off, no coil ring. Firing order 18436572 this would be cylinder #6. Keep in mind that at 600 RPM, this trace repeats five times a second. At 3000 Rpm, 25 times per second. sometimes you gotta look through several traces to find an intermittent misfire. The image that you uploaded showed either a bad ground reference on the scope *OR* a bad ground in the ignition. Needless to say, the image you uploaded was not a viable reference. Thats why I was curious to see the "after" shot. If in the course of replacing the lifters you inadvertently fixed a bad ground in the ignition, you still wind up with problem fixed, but was it really the lifters ???

I can say with absolute confidence that there was no ground issue before or after lifter replacement. I dont see how a bad ground could only affect one cylinder in a distributor ignition. Not saying you are wrong, just dont see how.

The screenshot you posted is much different than mine. I would be more concerned with number 6 than 5.