rcdblink716

I just built a 342 for my coupe and have been running into some tuning issues. It's got a mighty demon 650 and it's wanting stumble when you get on it. If you are riding in first at like 2k and just step on it, it wants to stall and occasionally pops through the carb. I've spent some time tuning the carb and don't think it's that. Also, when it does actually go when you get on it it will get real bad valve float. Like it hits a rev limiter. Do ya'll think I just need to re adjust the valves or could it be something more? Also, how far past zero lash do ya'll recommend going?

67mustang302

Prolly needs a serious valve adjustment. As far as adjustment, do it the way the rocker arm manufacturer says. Once you know valves are set right, then try tuning it

rcdblink716

The first three times I adjusted the valves I did it exactly as comp said to do. All 3 times I had no compression. So I adjusted them the way I know how. Find where both valves are closed on that cylinder, find zero lash and then go 1/4 to 1 full turn past zero lash

67mustang302

Pedestal or stud mount? And did you have compression afterwards?

rcdblink716

Stud mount. It appears to have compression now.

67mustang302

Appears? Have you done a compression check? Make sure you have compression, then make sure the timing is right(or reasonably close) then start messing with the carb. What's in it btw? Heads, cam, intake etc etc

rcdblink716

Excuse me, it has compression. the timing was set long ago. the carb is tuned to a factory barry grant tune. It's a sportsman block, eagle crank and rods, forged probe pistons, trickflow stage 2 cam, trickflow track heat heads, comp cams gold race roller rockers, parker funnelweb intake, mighty demon 650 carb. lots more parts but that's the basics

67mustang302

Vacuum 2nd or mech 2nd, and have you pulled the plugs to see what they look like?

rcdblink716

mechanical second, pulled the plugs about a hundred miles ago and theywere black. Did a little tuning, and the weird thing is that it was running lean. I dunno. I'm going to adjust the valves tommorow I think and see if it clears it up.

67mustang302

Black ain't lean, it's carbon build up from running too rich, you could have jetting that's off(factory tuning is only so accurate) or it could be an accelerator pump for the 2ndary