Underbody Exhaust Help...ERA 427 Street

[DanEC]

Originally Posted by lippy

So does this preclude using a 2.5" or 3" system?

It depends on what you are using for headers and for an outlet. ERA's undercar fabricated header collectors are 2-1/2 inch with neck down just before the mufflers to 2 inch. So there is no problem cutting the neck down off, welding a short piece of 2-1/2 inch pipe to fill the gap to the muffler and then fit a 2-1/2 inch muffler that fits within the two outriggers and between the main chassis rail and the rocker panel - such as the low profile Spintech muffler I'm using. If you want to go to a 3 inch collector and head pipe, you will have to have them fabricated to fit to the individual header pipes off the engine that ERA has bent up and welded. If there is a 3 inch in/out muffler that will fit in the allotted space I don't know. But, I'm pretty certain there is no way to run a 3 inch tail pipe to the rear - requiring a side exit in front of the rear tire.

A side problem however, is that the undercar exhaust hangs pretty low. I'm sucking mine up just about as close to the floor pan as I can, but it will still be hanging a little below the main chassis rail and most of the muffler and head pipes are going to be clearly visible from the side of the car. My Spintech mufflers are only 3 inches thick which helps considerably as most are 4 inches thick. The additional dimension of a 1/2 inch larger pipe and 1 inch thicker muffler is all going to be hanging down lower from where I'm at - and that is not going to be practical or attractive looking. At that point you need to be looking at oval pipe and 3 inch Spintech or Dr. Gas mufflers to maintain ground clearance.

My 2 cents are that 2-1/2 inch is probably the largest practical size for undercar use - unless you go to oval.

[427 Street]

Thanks for the replies.

I spoke with Doug today. Pete said he could answer all of my exhaust tech questions. When I have a chance later, I will get my notes together and post what he said.

Thanks,
Nick