I posted this in the V12 engine forum but didn’t see much activity. I don’t like cross posting either.
To summarize. I pulled off my exhaust manifolds. Of the 4, 3 had cracked at some point. The repairs on 2 were holding up well. The repair on the 3rd one has failed.
I know that I can get them from SNG Barrett but I was also looking at headers as an option.
This is still a few months out, but as I’ve mentioned many times, I like to mull things around before making any decisions.
John, In general, headers improve peak horsepower at high RPM’s, but can reduce low end torque. Think about how you drive to decide if there is a benefit. Tom
I put headers on my 4.2 and later took them off. They threw off the mixture at higher rpm and responsiveness was reduced. No substituting of different SU needles worked.
Dennis
Really ? must have been the design of your headers then , or something else you altered at the same time, a UO needle will give more than you need on a standard engine, this post is about the V12 though, so can’t comment on that except to say a friend used to put replica Cobras together with the Jag V12, six twin choke Webers, and beautifully siamesed stainless headers, I always thought standard manufacturers manifolds to be a compromise between cost and how to tuck the things out of the way, all performance engines will show a power increase somewhere in the rev range, all else being correct…