Upgrade Headers

[rustyrims]

Are you thinking of making your headers bigger than your exhaust valve?

[Hapnyny]

I’m in the market for a crate motor, the 347 striker pushing 500HP is a good fit but I’m concerned about the existing headers on the Cobra now. Thinking of getting 1 3/4 type header so I don’t choke the motor.

[G_Edmonds]

I went thru all this some years back when I changed motor platforms and went up considerably on power. A race builder did my headers. Actually my whole exhaust. If you go bigger on headers you need bigger collectors too. If you have the original CR side pipes, they are very restrictive. I got Classic Chambered cobra packs and love ‘em. Everybody is different but I chose the “packed ones”. They are not too loud to talk to a passenger at cruise but really sing when you wind them up.

[Hapnyny]

I think I have the same package.

[spdbrake]

If you do go to a 1 3/4" headers the flange area will be choked down to what you currently have due to the flange bolt spacing. There are a few head manufacturers that make alternate header flange bolts spacing, Trick-flow, Dart, Blueprint, and more.
But even if you change heads and flanges you're still stuck with the diameter on the side pipes. Same chokepoint, just further downstream.

Also it looks like your #1 cyl aft header bolt is loose in pic#2.

[Hapnyny]

Thanks SPD!

Great point! I’m almost thinking of just keeping it as a 289 MKII build and work on another project. The bolt was lose and it was fixed.