I have done the firing and exhaust graphs, they are representative as such, I wont say that the curves are a precise fit to the actual pressures etc.

The top set is for an 8 cylinder, top 4 being 1 bank and the lower being the other bank, the shaded areas are the exhaust phase and below that are the exhaust banks pressure curves, it appears if I am looking at this correctly that the V8 has more interference on each side as the firing is not as uniform as the 6 cylinder which shows below.

Not sure what this all means, but has been interesting research, my guess is that as the 6 Cyl is more equally matched on a dual exhaust then maybe that's why the V8 gains more from the H or crossover as it aids the interference from the negative pressure that follows at the end of the exhaust pulse, hmmn still pondering.

Just realized I cant attached the graphs here, email me at jon@builddesign.org.uk if you are interested I will email them to you.

Jon

The x scavenges as it joins like a Siamese twin so there is no resistance due to it's connection, where H balances the pressure waves, but will not scavenge like an X, in order to balance the pressure the resistance needs to be as low as possible.

(X) or (H) PIPE | Grumpys Performance Garage

a load of theory here and much more reading, everything seems to talk about V8's, but it looks like my straight 6 with dual exhaust would also benefit. I like the reduction in cabin noise benefits and the exhaust tone would suit me too, I will look more into the use with a straight 6
I hope you don't think I'm sticking my nose in.
I love what your doing with the car and a great thread too.

many thanks for sharing it all

Jon

Clyde,
I don't want to post this on your thread, as I don't want to look like I know what I'm talking about, but reading more about this theory, my very limited understanding as far as it goes after reading more on this subject is that the crossover on the H should not be less than the main pipe. That as far as I can understand is that the gases will follow the line of least resistance and the H has 2x 90deg bends to overcome so a smaller pipe will have more resistance, so the shorter and bigger the pipe the better.
have to do this in 2 messages as its too long !

Question for you when you get some time. Our 1960 MK2s have a unique feature for that model year only that I can tell, which is the inset sun visors. Do you still have a headliner in your car? I was wondering how they fit around the visor inserts, and could use some pictures, as my car came with no interior. Thanks, Chuck Bush (csbush)

Clyde, you sent me a message or email that accidently got deleted. If you'll resend I'll respond. Thanks. Doug Dooren