The motor is a carbed 355, Q-jet, stock heads little work, compcam 262, headers, exhaust, edelbrock intake, msd 6al. msd wires, i heat range colder plugs.

The motor was runnin untill i took it to the track a few weeks ago. took 3 runs, no problem, on fourth run, it pull fine from the line, top out 1st gear at 5800, shift, pulling into second then at about 4 - 4500 rpm the car losses all of its power and starts to miss like crazy, next run, the same thing. that is the first problem

since this has happened the car now has a miss at cruise rpm's, the lower the rpm the worse it usually it is, along with a loss of power throughout the driving range.

Any ideas???

I was thinking fuel pump or filter, but changed to a nother stock pump i had and it did the same thing. (mechanical pump) i am not ruling out the pump yet

i thought it might be ignition, so i replace with complete other HEI that i had, no fix

please help, want to go to track on fri

thanks
Bradford

 

Take a good look at your valve train. Don't be too surprized to find a bent push rod, cracked rocker, pulled rocker stud, or broken spring.

I wish I had taken a photo, but I recently had a pretzeled push rod on a 'Vette from shifting at 5,400 RPM with a only slightly better than stock set of valve springs and decent cam. The PVS rockers started to let go, and it went south from there. Fortunately, there was no other significant damage. The driver mentioned that he "Thought there was a little miss..."

 

If it was in the valve train wouldnt it do the studder in all gears at the same rpm. It only had the major studder in second gear at wot.

The problem occured in two different motors, i had a 305 that did this and i though it was the motor so i changed it to a 350 and it didnt do it till about 1 week later. then it started again. that is why i think it is some thing related to the car and not the motor its self,
i have two different valve trains between the two motors so that is ruled out.

 

Is this a manual trans or an automatic?

Since you have a Q-jet, maybe take a look at your air valve, it may be to loose. That won't cause a misfire, but it will bog and lose power if its too loose.

Mine was to loose, but it was fine in first and second, but 3rd or higher it would bog really bad sometimes. I tightened it up a little, and now its great.

As for the misfire.. my 350 did that a bit untill I changed the plug wires. I think they were cross firing because they were all burnt, old and worn out. Take a look at your wires.. if they are old and burnt, then they probably need replacing and could be the cause of your misfire.