i have a nice set of hooker steps with merge collectors came off a prostock car so i had to change the flanges from the drce bolt pattern.also have set of zoomies but after reading everybodys commets i think they are NOT the way to go. jeff

What if you ran a smaller zoomie like a 2" or 2 1/8"?

Or maybe even a stepped pipe,start with a 2 1/8" into a 2 1/4"?

This is for nofear69, There would be virtually no difference to the engine reguarding primary diameter with zoomies on a naturally aspirated engine. simply put zoomies are zoomies, diameter be damned. As for the tiny 2.125 primarys on a 582 racing engine with a step to any diameter would work ok on a 500 to maybe 600 horsepower hyd cam mild engine in a heavy street car. That small of pipe may not even clear the entire exhaust port on most racing heads now a days for a engine this large. The 582 will require a 2.25" primary in most any power level baring the previous example. The 4 in to one collector helps scavenge the spent gasses out to help aid in initiating the incoming air charge. zoomies do nothing for a naturally aspirated engine but make a cool sound according to some, or so I am learning. I hope this additional explanation helps my earlier entry make sense.

I was considering putting zoomies on my non blown alcohol injected sbc altered just for the sound but I probably won't. There isn't much info. out there for this application. I guess its all experimental but they should be left for the blower cars.

This guy just put these up forsale Ad #1452722.

i hope the steps i have are big enough for my 582 i'll be running 1/8 mostly but i wounder what a 2 1/2 primary with a 5 inch merge collector would act like i bet too big down low(in the 1/8)and great at the big end(in the 1/4)the motor seamed real responsive with a 2 1/4 header on it last year BUT never made it to a 1/4 track or had a chance to put the steps on it to see the difference. jeff

No matter what head you are using be it 12 degree pro stock or 24 degree brodix type stuff, your engine will never like 2.5" primarys at the head under any circumstances guarantied. The 2.25 primarys stepped to 2.375 may be nice for your set up and more forgiving than it would be with 2.373 on the head with 2.5 to collector and unless you shoot tons of smack in your engine, the 5" collector is way over sized as well. There are more detramental effects to over sizing your pipes than under sizing. Remember the step is intended to enhance the top end horsepower for higher rpm usage and will not increase the bottom end power numbers, in fact they are lower than what a single diameter primary will produce.
Stay with what you have been using, The larger headder will not assure you more performance on the top in all instances.

i'll be trying my steps they are 2.375 stepped to 2 1/2 with a 4 1/2 merge collector.do you think a straight 2 1/4 would work just as good? also how do the comp guys make zoomies work on the fed with 406,s and stack injection? just curious thanks jeff

The 2.25" single dimension primary will not behave similar to a step pipe of any size. Your previous entry noted that you were using a 2.25 primary with good results, and that was the basis on my recommending that you use that size pipe. In that same entry concerning the 2.25" pipe, you indicated that you might try a 2.5" primary which is too big for anything I have ever seen that was using carb's and nature to fill the engine. When you look at all the different combinations that people try to run and notice that you have a combination now and then that seems to defy physics by using an arrangement that should not work well, like the zoomies on the alcohol car using Nature to fill it, (No blower). There is more to the picture than you could see, or there were huge concessions made in the torque department and engine harmony for a theoretical perfect top end tune-up. Let me know if you ever figure out the answer to that one, I am sure it would be very interesting to hear the reasoning. I have had no success nor have I heard of any one having any luck with that configuration on a naturally aspirated engine.
This will be my last entry on this thread, I hope you find this information entertaining or helpful, good luck