Thanks guys for the info on the Jimmy header. I considered Smith's suggestion on the short stacks (<8") and I also considered dumping directly into the large collection box.

However, from all the engines I've had on the dyno (conventional engines...not this geek) I've seen large TQ gains below peak TQ, and usually a 1-1.5 percent increase in peak HP, with a 4 into 1 header. On one 406 SBC I verified a 96 lb.ft. increase in TQ @ 4500 RPM when I extended the collector to 18 inches.

I'm satisfied (???) with the HP & TQ (346 & 347) but the thing is a complets dog below about 3500 RPM.

I've decided to build an adjustable 4-1, 1 3/4 x 40" with a 3 or 3.5" collector. If that doesn't work I'll try something else.

Thanks, Ron