Oh ****. I see it now and I do NOT have .354 to spare for sure. Damn and I was moving right along. Hammer? Apply heat? Not sure how the coating will take the hammer with or without heat. I don't see another way around it does anyone else?

have the 2 header flanges angle milled

I don't think so. The tubes were staggered between one another already...

Interesting @johnmiffco. There are actually 1/4 inch flanges that bolt to the headers with studs. The header flanges bolt to these flanges. I could possibly take a little material off of each. Big question is trying to figure out what to take off and where to get them back to normal location. I'll have to do some research to better understand what specifically happens when AFR moves the exhaust ports up 1/4" with all the angles involved.

Have you ever done something like this? So far, I like this option the best. Between the flanges on the heads and the header flanges, I bet I have enough. It also seems possible to just cut the flange off the header all together and re-weld it. I might leave that one up to the manufacturer if they will do it (Lightning).

Thanks for all the input.

Tom

Two flanges, the header flange does not bolt directly to the head..??

EDIT: I can see the flange on the head, the one without the header installed, why are these set up like that ?? no wonder you're having clearance issues, this moves the header tubes 1/2 inch closer to each other, or my eyes deceiving me.

the adaptor bolted to the head is old school stuff we did many yrs ago
to use big tube headers on a sb,,,,,as big tube header flange had a different 3 bolt pattern for the 2 center ports as the sb 2 head bolts were so close together
could not go to a bigger tube in between bolt pattern would cover some of the bolt,,,,
when bought the new heads could have had them built ,,,drilled/tapped for the different header flanges and done away with the adaptors which would gain u .500 more clearance alone,,
still can be done but would have to take off heads and have re tapped,,,and other holes filled
u have an easy fix still as is ,,,,,,,
with 1 header bolted to a motor
set a board on the stringer like a 1x6 or so and get it to stay there and be "level"
use some kind of square to set on board to go against header where they are touching and mark the level board on stringer
take off header and put header on other motor and repeat,,,,,
the distance between the lines on board is the amount u need to remove by 1/2 each
this gives u the amount needed for clearance,,,,,,if under .100 pr side can just flat mill off some of head adaptor and header flange and still have plenty strength on flanges
if over u can angle mill,,,,,,as angle mill at head for instance,.050 will give u over .100 + 1'+ up the tubes as further away from the angle pivot gives more clearance up higher
hope understand this,,,,,
im a builder/fabricator and have had to fabricate things to match or clear forever
but need 1rst to find out the amount of distance the pipes are hitting then decide amount and how to clear
making clearance on the 2 flanges is simple and way better than denting up ur pipes
good luck
john

Well in this case old school and big tubes dont fit,,,,,Im sure the OP will get it figured out

Great info and I like the idea about the board and square to figure out exactly what I need to remove. According to earlier post, math suggests under .400 total so .200 each side. I could do .100 from plate on head and .100 on header flange and possibly have what I need.

More work to do.

And, you are right about the purpose of the flange on the head. No way to get headers like these with water jackets on a small block head without this trick. These are not really old school as they were just built custom for the application by Lightning. The issue is with the guy that did the measurements. I measured everything they needed with stock heads and these .25 raised exhaust ports were not considered. My bad completely.