How come the ports on the racing beat manifold are lower than the ones on the nikki. Is this for a earlier 12a or is this how it is supposed to be. I've been having trouble tuning the Carter that is mounted on it and was thinking this was my problem. The picture is of the racing beat ports on top of the nikki manifold.

 

Maybe their manifolds allow for some porting...

At any rate, I don't think that the port mismatch is your problem.

 

Compare the Racing Beat to the engine I'd say. The stock manifold may NOT match up to the 12a as well as the Racing Beat manifold does.

 

The ports on the stock manifold don't match the engine's ports either. The most amazing thing is that port matching the manifold to the engine actually *decreases* airflow.

You're probably thinking "wtf?".... Yup... that's what I thought. '

See here:
http://www.yawpower.com/Flow%20Testing.html

Example #1 in bold partway down.

Jon

 

I have compared it to the engine and nikki ports look like they line up perfectly. The racing beat looks like it sits to low. The secondary ports on the rb are almost 3/16 lower than the ones on the block. My problem was that whenever I would open the secondaries it would act like it was hitting a rev lmiter. I was thinking that some of the air was hitting that 3/16 on the block and creating all kinds of turbulence. Also my mikuni sits low like the rb does.

 

Should I try to make the racing beat manifold like the nikki one?

 

maybe they are jus bigger...

 

It's better if the manifold's ports are slightly smaller than the engine's. It's all about trying to diminish the reversion wave.

 

^^Yea thats what I was thinking, so why did they move the ports lower?