One engine is making 5psi, the other 7psi. Which Is right where it should be when comparing 3% over to 6% over. He doesn't have a blower problem, he has mismatched pulleys.

How do you know it didnt take that to make the same power on the dyno? your only looking at max boost also...

If you need to run two more psi to even the power up between a matched set of engines, you did something seriously wrong. Going from 5psi to 7psi on a setup like that can easily be 50-60hp.

What does "max" boost have to do with it? If the blowers have different drive ratios, your boost at cruise will also be different. Which according to rob , that is the case.

How do you know these engines were even dynoed???

Pretty sure Rob said they were dynoed last time they were refreshed. He did say Chief built them at one time also. If You have wear in your teflon strip or repaired rotors it can be low on boost and need a larger pulley for mid range to equal out - thus having a weaker blower. At max boost your spinning the rotors a lot faster where the problem is overcome by rotor speed and that’s why the boost crawls up. You need to look at the boost curve.

I wouldn't want to band aid a worn out blower by putting a smaller pulley on it. If it was down on boost, then I'd have it repaired. Either way, a good starting point is to have two identical blowers, two identical engines, and two identical drive ratio's on the blowers. If one is down on boost, i'd be wanting to send it out.

I was gonna suggest possibly a prop being off also. Ive seen it a lot with the old SSM cleavers. Sometimes can be off in pitch a full inch. Someone might try driving the one blower harder to make up for the additional pitch, in effort to keep the RPM in synch.

The prop deal makes perfect sense also! Just as someone would put a pulley on to fix a prop; it doesn’t always make sense to spend $1,500 on a blower when a $50 pulley fixes everything!