Sidebar question on cloning the KB/ATR design.. How much vertical space do you need at a minimum on the passengers side? The frame on my Riviera has a huge crossmember that goes under roughly the #1 cylinder and I want to get the engine as low as I can in the chassis. Right now the Poston headers I have are barely 1/2in off of the crossmember and the vacuum block is in the hood insulation. Thanks,
It would depend on what size primary you use and what centerline radius you can get the tube in. I used 1.5" with a 2.5clr.
The number 2 primary uses a full 180 bend so it takes up 5" from the center of the port, to the center of the hole in the collector. To get to the bottom of the collector you need half the tube od plus one other full od (the collector is turned such that one tube is directly under the other). So 5+.75+1.5= 7.25 from the center of the port to the bottom of the collector.
Fyi, If I were to build another set, they would be log style like TA headers. They are a lot more work, but I think they fit better and allow better crossover and downpipe routing. You can see another thread here in this section where I built a log header for a stage 2 head motor.
Thought this was worth a bump. I came across this thread while doing a google photo search for headers outside of this forum. In fact out of all of the photos that caught my eye two of them were linked back to Mike's header projects (this one and the stage 2 header build). On the web you see so many so called professionals/fabricators posting up stuff that doesn't even come close to Mike's work. He is definitely has a gift in the fabrication.
They are nicer than my real ATR headers. On the ATR's it looks like the primary tubes are welded to the outside of the head flanges and I guess the reason would have been to avoid choking the exhaust port. Are the RJC flanges a little over sized so that they can be welded in the id of the tube or did you port them to match your heads after all of the welding was done ? Also did the tube come from Cone as well ?
I'm not sure what size tube rjc intended to be used with his flanges, but 1 1/2" fit down inside with no work to the flanges. Any bigger would have required opening them up. I did not do any port work after welding other than clean up the welds with a cartridge roll.
I use 304 stainless bends from columbia river mandrel bending, they sell the cone collectors also.