Carbed LS engine stumble problem at 5500RPM!

[Rod P]

Carbed LS engine stumble problem at 5500RPM! any Ideas? driven and raced the car for 3 years and it just started about 4 weeks ago, I went to practice and right off the line the car hit 5500rpm and stumbled like a rev limiter,,,,here's what I have changed, and after each change a quick test run and the issue is the same

I thought maybe the MSD box, now new
bad Map sensor, now new
bad ground or power?, ran new wiring
bad coils?, 8 new ones
bad plug wires, now new
cam sensor faulty, new now
bad edelbrock carb, switched to a new holley
plugged fuel filters? I have 3 a post a pre and a carb filter, all 3 new now

ran out of ideas at that point, called MSD and they said alternator isn't charging? OK I'm game

now has a new alternator and an extra ground and a new charging wire and I have the same problem, just looking for any Ideas!!



any Ideas????

[67zo6Camaro]

I had a similar problem but with fuel injection. Eventually got worse. I finally found some issues. 1st vacuum leak (mine was at the back of the intake and a major one in the valley at knock sensor. 2nd spark plugs were older but looked good, however, they actually had a slight coat of burnt oil vapor because of the blow through on the PVC system. In addition the gap was worn because of the high revving abuse. and 3rd... bad lifter roller and valve spring. It could not keep up with the RPMs and started to float above 5500 RPMs. The way we drive with redline most all the time, the valve springs do get softer with age.

PS, my diagnostic codes showed multiple miss fires, and occasionally a knock sensor code, and occasionally a cam sensor code. I did leak down test, compression test and spark test before I actually found the vacuum leak.

My 2 cents. good luck.

[Sieg]

Rolling down the highway with GW.....bad/broken valve spring. Careful inspection required!

[Rod P]

Originally Posted by Sieg

Rolling down the highway with GW.....bad/broken valve spring. Careful inspection required!

Originally Posted by 67zo6Camaro

I had a similar problem but with fuel injection. Eventually got worse. I finally found some issues. 1st vacuum leak (mine was at the back of the intake and a major one in the valley at knock sensor. 2nd spark plugs were older but looked good, however, they actually had a slight coat of burnt oil vapor because of the blow through on the PVC system. In addition the gap was worn because of the high revving abuse. and 3rd... bad lifter roller and valve spring. It could not keep up with the RPMs and started to float above 5500 RPMs. The way we drive with redline most all the time, the valve springs do get softer with age.

PS, my diagnostic codes showed multiple miss fires, and occasionally a knock sensor code, and occasionally a cam sensor code. I did leak down test, compression test and spark test before I actually found the vacuum leak.

My 2 cents. good luck.

ARRRGGGG!!! I guess the valve train comes apart, I was told valves springs by some others also! I was just hoping there was an easy button, but I should have known better