Does anyone make custom headers for a 69 mustang out of stainless? I would like at least a 2" header. Right now I have Hooker 6114 that are Swain Tech coated. I think I am leaving power on the table with 1 3/4 headers. Ground clearance is a consideration. My 464 is making about 625 flywheel hp.
From a stop, can you spin your rear tires with a full throttle launch?
Sometimes
https://www.youtube.com/watch?v=J2hCd3FOcrU
Well, I was going to say if so, then your traction is leaving power on the table, and the small amount you would pick up with bigger headers would only add to the problem. However, at 11.87, I don't think you are making anywhere near 625 horsepower. Was this number off a dyno with no front dress? What kind of headers on the dyno?
Engine Masters had an episode where they bashed the primary tubes on a dyno motor, and the decrease in diameter had little effect on power. I'm a little surprised that none of our builders here have piped up with an A<-->B comparison, 6114's against 6375's (BTW, I can't believe how much the cost of those has gone up. We are getting hosed here big time).
If you are looking to lower ET, See if you can put that puppy on a chassis dyno, because that's a better tell than an engine dyno.