Are high stalls more or less efficient than stock and do they affect dyno numbers?

 

You will dyno less, unless the converter is LOCKED UP, then it doesn't matter.

 

Yes

 

Yes they do affect dyno numbers.

You should concentrate on ET and mph. Dyno numbers are pointless. Especially peak numbers. It's how flat they are that really matters.

If you care about dyno numbers I hope you have an LSx.

 

Chassis dyno numbers are far from useless, even with a non-lockup race converter. But you can't use them to get an "absolute" measurement of engine power. Of course, this is true for any combo on a chassis dyno - auto or manual. What they are useful for is tuning and determining the effect of mods. They provide a reproducible number that can be used to judge the effect of mods. This is true regardless of the converter (as long as the same one is used, of course). An unlocked converter does introduce another variable into the testing. So, if you are looking for very small changes it might obscure them. But if the change is more than a couple of hp you will reliably see it on a chassis dyno. This is very useful compared to tuning at the track, for any number of reasons.

However, as one of the above posts implies, you do not race dynos (unless you have a Poopra), you race cars. Dyno results do not pick winners at the track. One gross example is how cars go quicker with a high stall converter but dyno less.

Rich