Another undercar exhaust question

[DanEC]

I'm planning on a street Cobra build and was reading the Chuck Brandt build site and his experiences with the undercar exhaust system. Apparently the ERA system consists of 2 inch headpipes, mufflers and tailpipes which just sounds very restrictive, even for a mild FE motor. Apparently he thought so too. Has anyone had experience with fitting a larger diameter system under car with full tailpipes to the rear? I definately want 2-1/2 inch head pipes and 2-1/2 inch in/out mufflers. After that I could live with going down to 2-1/4 inch tailpipes if necessary, since I'm figuring on a fairly mild FE motor - probably 450 flywheel HP or less. I would rather avoid exhaust outlets in front of the rear wheels. I'm planning on no more than 275/50 - 15 tires in the rear which should free up a little space in the wheel wells. I would be interested in experiences from other street car builders.

thanks

Dan

[Karl Bebout]

You might want to look into rectangular tubing. You could get better exhaust flow and still have some clearance.

[JBo]

you might want to try the "chambered mufflers "; round; that have been explored on this site. Wheel houses on csx3000 replicas; dimensionally correct; may not accept mufflers, AK's barley did and they had an extra 2" of clearance per side.Original 427's had under car mufflers or in the case of my ex had GT350 R model systems that exited in front of rear wheels as you state.

[Maricopa]

Dr Gas has some nice ovalized tubing and very low profile SpinTech muffs.



These are 3" (reduced to 2.25" tall). Mine don't run out the back, but they could be made to.

[428street]

Dan:

I have an ERA street car with the ERA exhaust system and I can't be any happier with it. Now, understand I am not a gear head, racer or have any visions of tracking the car (not that any of those things are bad - just not for me). I have a dyno'd 400 HP FE PI engine...my car has extremely quick response and is very smooth...not sure what I am missing but I can't imagine anything restricting my speed or acceleration because of the ERA system...

[FrankJohnson69]

Dan, PM me with e-mail address and phone number and I'd be happy to call you and discuss this at great length with you and what I've gone through with my under car exhaust. You won't get 2 1/2 inch that I can tell you right now.

Frank
ERA-722

[mickmate]

The trouble with these cars is they are 10 lbs of $h!t in a 5 lb bag. Nothing fits, you'll have trouble fitting an undercar exhaust of any great size and according to my muffler supplier the 2 1/2" will flow an easy 450 HP 2" ain't gonna hurt that thing a bit.http://www.classicchambered.com/clas...cts.html#cobra

[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

[strictlypersonl]

When the suspension is at full droop, the lower control arms hang substantially below the plane of the chassis outside the main frame rails. Consequently, the only possible path for the pipes is under the main frame rails. With a normal ground clearance there of 5.5", you'd end up with around 3.5" ground clearance, even with oval pipes.

[DanEC]

OK - thanks. Good information. More thinking to do.

Dan

[RICK LAKE]

DanEC what rearend is in your car? 9" or Jag IRS? Rick

[DanEC]

Originally Posted by RICK LAKE

DanEC what rearend is in your car? 9" or Jag IRS? Rick

Hi Rick. I'm planning on the standard Jag rear end since I understand the ERA rear interfers with undercar exhaust. I appreciated the advice over the phone the other night on ERA kits. Take care.

Dan