I am totally stumped. Here it goes:
Ever since I put the motor back in my car this spring, the motor totally falls on its face at 6400 RPMs. This motor easily revved over 7000 RPMs last year. The things I changed this winter were: Comp 987 valve springs(replaced the Edel. Sure Seat 5767's), Milodin 7 quart oil pan, and a heavily built GN 2004-R and a Vigilante 3200 stall. I really wanted to know what the problem was, so I took the car to the chassis dyno I ran on last year. To my surprise, the car easily revved to 7300 RPMs on the dyno.. The motor ran very strong and made 357 HP @ 6100 RPMs on the dyno with a beautiful fuel curve. After I left, I tried it on the road and it totally flattened out at 6400 again. My first thought was a possible dry fuel pickup problem with acceleration. I filled the tank to the brim and had the same problem. Second thought was a problem with venting in the tank. I vented the gas cap and same problem. Third thought was possibly too much oil in the pan. I took a couple quarts out to no avail..... Someone mentioned a possible transmission problem, but I dont understand how it could not do it on the dyno. In motion the car does it, stationary it doesnt... I'm stumped. Any thoughts would be greatly appreciated. Sorry for the long post.

 

Do you hear any kind of noises at 6400 RPM? Describe what happens a little more. Also, do you have carb, intake, heads, and cam specs you could share with us? Those are pretty impressive numbers.

 

At 6400, the motor sounds like its floating and breaking up really bad. It has E-Tec 200 heads, a Mighty Demon carb, and a bigxbig Comp roller cam.

 

How about the air cleaner? How did they run that on the dyno as compared to driving the car?

Spark plug wires arcing to the hood?

Check every single thing that's different between a dyno pull and a real drive. It isn't the transmission, since that doesn't change. Something is different about opening the hood, removing the breather, the air temp, etc.

 

Hmm, the air cleaner never left the motor because the last time I dyno'ed it, removing it made no power difference. The plug wires run under my headers. About the only difference on the dyno is that the hood is open, and the car is strapped down. Hmmm, uncovering the jets in a carb is just a launching problem right?