Hey gang..just the other day i purchased a pair of alum.waterjacketed headers that are like or are (imco thumpers)..this is something im going to reg up on my bbc / jet..i have ?? on the headers..(1) do they work on jet applilications..(2) how much water pressure do i need from the manifold/t valve..(3) since they are water jacketed.means water is not supposed to leak from ports..just asking..new to these types of headers..let me know if u have better knowledge of these.. thx  NO MAD

Those are a good choice and a good find ,no you dont run a T valve , your exit water simply passes thru the manifold ,riser and out into the lake (call if you need plumbing help) We sell alot or these (competitors) and have good sucess they are good alternative ($) to jacketed headers , Your current risers will limit you cam choices (duration @ 500 to some degree) the photo  attached is my V-drive cruiser the EMI's are rated (tested) for 750+ hp Tom

btw there are Tail pipe /riser options available ,if neccesary RE system cost new ,you might be suprised I'm very happy with mine and have had ZERO problems and the run "cool" (I'm al little testy right now nursing a 3rd degree bicept header burn)

Pretty sure you're gonna want to keep the gate valve to limit pressure coming into the block.

Hey Tom, the bends in the exhaust.... Any significant power loss seen with them? My friend has the IMCO's on his 502 but he's got nearly 90deg bends in the tubing exiting them. Seems to me it would cause some unnecessary turbulence, etc and ultimately a power loss? I'm going to his house tonight probably, I'll see if I can snag some pictures.

hey.thx for the input..will have trial run by the 1st weekend of march, will contact you for more info..damon..