[Augusto]

for a street '67 mustang with a mild 351W should I fabricate headers with 1-1/2 or 1-3/4 primary pipes? how long should they be?

I own a muffler shop and I can fabricate headers but never done any project like this so I have no clues, there is no 1-5/8 pipe available here so I'm limited to 1-1/2 and 1-3/4 diameters.

what would be a good collector size?

the down pipes will be 2-1/2 with an X crossover and 2 glasspacks.

Importing stuff from the USA is very expensive over here, this is why I won't be buying already made headers, besides it's more fun DIY.

thanks

[JeffB]

Since you have 1 1/2" & 1 3/4" I would fabricate the Tri-Y headers like in this Pic,these fit 65-69 Mustangs 289-351, collectors are 2 1/2" these produce strong low and mid-range power.

[Augusto]

very cool, is the pipe arrangement compatible with the 351's firing order?

are those pipes 1-1/2 or 1-3/4 ?

thanks

[ericnova72]

You could also fab a step header, come off the head port with 8-10" or so of 1-1/2", then continue on with 1-3/4" down to the collector. Step headers have become very popular here in the States, helps to broaden the powerband by increasing low end torque.

Primary pipes 32-36" long, with 3" collectors 18" long.

[Augusto]

that's a good idea also, I use step headers on the motorcycle engines that I use to power the single seater off-road buggies that I build, they perform great and sound very well, I have also made them in 3 steps, 1" to 1-1/4 to 1-1/2 or 1-1/2 to 1-3/4 and to 2", depending on the engine used.

[JeffB]

The primary "Y" shaped tubes that come off the flanges are 1 1/2" and connect into the two 1 3/4" that flow into the 2 1/2" collector.No problem with the firing order.If you Google "Mustang Tri-Y headers" you will find a lot of info and pictures online you can use to help fabricate them.

[Augusto]

thanks a lot, I'll spend a few hours on google, thanks God for the internet