Recently, our club in St. Louis came across a dyno tuner in Chesterfield, MO at Lynch Hummer. A couple of club cars (one being mine) went in for a tune. There were many lessons learned and things found that I would like to share to hopefully prevent someone from messing up their engine.
1) BG Carbs - Both cars taken in had BG Carbs, one a Mighty Demon, one a Speed Demon. It was found on both that there were many manufacturing flaws in the carb. The Mighty Demon had warped metering blocks and fuel bowls as well as out of round venturi's and throttle body. The Speed Demon was found to have an accelerator pump housing that was "warped" causing leakage at the accelerator pump diaphragm. Shavings were blown out of the metering blocks and fuel bowls in both.
2) Both carbs were found to be out of adjustment - partially due to their owner's
One running way too rich, the other too lean. We all know the issues either can cause. How were the cars running you ask? Well, both were running ok, satisfactory we'll say, but not great like we wanted, which is why we ended up taking our cars to the tuner.
3) On my car, the timing was off due to a faulty vacuum advance on the distributor that affected total timing and advanced the timing under acceleration.
4) Also, on my car, the spark plugs were replaced. The old one's had served their life, but were still in ok shape.
On to the good stuff. My car, as is baseline dyno is below, the blue line represents the dyno as the car came in, with nothing done to it. The Green line represents the dyno after the carb was rebuilt and new plugs were installed:
After finding the bad advance on the distributor, we determined a new mechanical advance distributor would be best. After that was installed, a final dyno pull and tune on the distributor was performed to achieve the final numbers below in blue. Red numbers show the initial baseline dyno:
The car has a crisper throttle response, cruises and starts much, much better. How did it get this bad? Probably my lack of complete knowledge on the carb and lack of proper tools to tune it. The other club member had amazing dyno numbers:
The whole point is, unless you have the software, the dyno, and the necessary tools at home to tune your car, please, please make an appointment with a professional. It will save you tons down the road. It saved our club two engine rebuilds I'm sure. Any questions, let me know, didn't want this to get too long....
460 Dyno and Carb Tune
Linear Mode
