Exhaust Primary Tube Diameter

Just curious what diameter primary tube is common with either the screw blown funny cars, or the really high power outlaw guys? 2.500", or 2.625", or......?

If a person had been running 2.500" zoomies, and then switched to a large common collector deal, would it be wise to upsize the new primaries or not? Collector will be 5.000" open, no muffler.

I'm "assuming" that a merge style collector is of zero benefit in a blown appliction?

 

I think that a collector would benifit a blown engine ,it would help to not drop cyl. as i understand it, it helps scavange the cyl's that are not fireing, it would look odd but when you think outside the box every thing is odd. bet it would help top fuel cars & fuel funny most.

 

we switched from zoomies to downsweep borlas on my dragster (BBC, 8-71), and lost a couple of mph and about .05's in the 1.8th. Could be they weren't big enough, though

 

didnt rick santos try headers with a collector years ago on his blown alcohol dragster?

 

In this case I have to run a collector per side due to the body layout. I've got exactly one place to dump the exhaust per side, about 5.500" wide.

 

George(Rick's dad) and I talked about this at indy one year. He used 2.5 inch S/C headers and ran within .004 of the zoomies. Vibration would have taken its toll over several runs, so they let it go. If you know the temp coming out of the head, you can figure how long to go on the primaries, make equal length pipes, stagger them into your collector, do the twmp drop measurement on it and cut to length. You'll find out that the weight isn't worth the benefit. We make just as much HP and torque with 9 3/4 in. zoomies as with the longer pipes and they break apart less. Make 'em out of stainless U-tubes and flanges. only weigh 6 3/4 lbs per side.