A quick, dumb, easy question...

[Fastjeff57]

If one suddenly LOWERS the exhaust restriction on a 2 stroke OB, will the jetting need to be changed? If so, will it need to go leaner or richer?

Thanks,

Jeff

[Fastjeff57]

I guess it's not that easy a question to answer after all!

I recall having to re-jet richer when I put open headers on my Pontiac, but that was four stroke.

Jeff

[champ20B]

It depends on how efficient the motor was to start with......but ultimately, I would say a bit richer. It will be more powerful than a closed restricted style exhaust, but more feul will be evacuated during the induction because of less restriction on the exhaust side, resulting in more needed fuel. It might become a slightly faster "gas guzzler". Stock race engines are kind of like that.

My Champion Hotrod came with the optional "open Stack" along with the stock cover plate. I tried my open stack, and besides having ringing ears I noticed that the exhaust was wet with residue oil/gas. It will go a bit faster as well. I turned my carburetor a little bit richer and it seemed not to mind at all when I did also.

[Fastjeff57]

Thanks!

Jeff