Another undercar exhaust question

[DanEC]

How well the ERA system flows could depend on the mufflers they use. I fear a 2 inch inlet/outlet muffler may have less than 2 inch tubes inside which would really be a constriction. I own a mid-year Corvette with sidepipes and for years I've heard about how restrictive the original GM versions are with 1-7/8 inch inner baffled cores - even on stock small block cars. Everyone pretty much understands these days with 3-inch systems that you need at least 2-1/2 inch headpipes and mufflers to support a big block motor or high winding small block. I guess a compromise might be to use a compact muffler with 2-1/2 inch nipples, 2-1/2 head pipes to the mufflers, and then neck down after the mufflers to the 2 inch tailpipes. I expect a cross over is out of the question with the main chassis rails.

Dan

[Gilby]

This thread is timely as I am currently having an undercar exhaust system built for my ERA. I could never stop the leaks on the original 4 into 1 collector so I went to restrictive exhaust manifolds about 3 years ago. Combined with the two inch pipes and DynoMax mufflers I'm sure it was restricted even with a mild 428. I have been thinking this over for a couple years. With the ERA there is very little room for a muffler so choices are limited if you want 2.5 inch in and out. Its the width of the muffler that gets you. If you want it to look close to original then you really need offset inlet on the drivers side in order to move the muffler forward to approximate the position of the original. A Hushpower will fit but it needs to be moved rearward and have an S bend in the inlet pipe. I went with a muffler from Stailess Specialities with offet 2.5 in and center 2.5 out. This muffler is very narrow and seemed the best fit. They also do custom sizes. I will try to use 2.5 inch pipes out the rear over the axle and angled up like an original with chrome tips. I may need to neck it down at some point in the rear. I don't know yet. I spoke with my fabricator today and he is almost done with the headers. I have not even seen them yet. What do you guys think looks best 2 inch or 2.5 inch tailpipes? Will 2.5 inch tips look out of place on an original looking street car?

Thx

[DanEC]

I would go with 2-1/4 or 2-1/2 inch tips at the rear. Most people are use to bigger tail pipes these days - whether muscle cars with upgraded 2-1/2 or 3 inch exhaust pipes or imports with big fart can mufflers. A 2 inch tip will probably look smallish and less original than a slightly larger one to most people on the street.

Dan

[DanEC]

A related question - has anyone tried to run oval exhaust tubing "under" the differential and IRS carrier, around the fuel tank and out the back - rather than in the wheel wells? How much clearance is under the IRS carrier to ground to work with, with a car at normal heigth? Old Corvette's use to run it this way but typically with a good spring on a Corvette, the differential sits a little above the wheel certerline and the half shafts angle slightly down towards the wheels which might give a little more clearance compared to an ERA.

Thanks

Dan