Dyno Results (Long)

Did a 4 hour dyno session today. The car is a '65 Belvedere with a 440, TF tanny with a 3800 stall converter, 4.1 Dana and weighs about 3600 without the driver. Last runs at the strip was 12.42/107.5 best and it has done a 12.16/111 best.

The rear wheel HP hit a max of 342 at about 5200 RPM. Dyno operator says that is equivalent of 425 at the flywheel. Doing some math, he either is using a flat 20% loss through the drivetrain or maybe he knows more.

I expected more, like 375 to 400 or so. Still, not bad numbers. Given my previous dyno reading on another brand of dyno was 357, it's OK.

The motor has two weak cylinders with 25% and 45% leakage. The rest were in the 5-10% range. The worst cylinder has some finger nail catching scores in it.

What did we change during our various runs today? The focus was on the jetting. Turns out the jetting on the AED Holley was four and a half jets too rich. Took the primary down from 79 to 75 and the secondary from 88 to 83. When we went in, the AFR was running in the 10-11 range and now running right around the ideal 12.4 AFR range.

Also, we found that new $200 Rev-N-Nator ECU with four runs down the strip was defective, apparently - need to discuss this with them and I'll get back to the group. Swapped that out for a Mopar Chrome box I'd just taken off and it was bad. Threw a Blue box on and it ran till about 5000-5200 which is consistent with what I'd Heard. Borrowed another Chrome box and that fixed it. These bad ECUs could explain some of the weaker runs I've had of recent including some high speed studders.

Another thing I learned. When you change the ECU, it may affect your timing. After swapping out to the good chrome box, we found the timing had changed from 35 degrees advance to 0 degrees. We changed nothing but the ECU and that was the result. Surprised it even ran at that value but it did hit 275 HP.

Some dyno issues to discuss FYI. Today's dyno was a Mustang 4WD unit. All my previous runs were on a DynoJet brand dyno. The operator today said that the Mustang will read lower than the DynoJet. The simplest conclusion is use the same dyno for any subsequent test if you want to judge the impact of changes to your combo.

Bad news for the day is unrelated to the dyno run. I had replaced a bad tube on my slicks and needed to get the wheel balanced. They determined that the wheel was bent. This is the same wheel that I have had on back order since the end of the May. There goes this weekend's race at Monster Mopars at Norwalk/Summit Raceway Park.

Akron Don Gallimore