The Stovebolt Site Forums The Shop Area Engine Shop dual exhaust

Has anyone put dual exhaust on there six and did you see any improvement in performance/gas milage?
If you were to put dual exhaust on do you have to do any changes to the carboration?

Yes a bunch of people have added dual exhaust and there has been extensive discussion of it. Run a search. You'll find some very good info.

oldtruck,

My advice is to split your stock cast iron exhaust for duals now, then if you want to add a Offy 2x1 carb intake later, you would not have to grind the offy to fit. Its a pain in the F*** and many grind too much and ruin the intake. If you go with the Fenton castiron exhaust now you will have to grind the Offy to fit. The Cast iron intake will fit with the Fentons if you go that way. Make any sense?

I just added Fentons and they don't exactly fit from the get go. You would still have to do a lot of detailed grinding onthe fentons not to mention having to fabricate a heating system for your intake. Knowing what I know now, I would probably have the stock manifold split like 52pu says. It already has a heatriser spring and butterfly valve that diverts exhaust heat to the intake which works better than heating with tubes from fentons or water lines no matter how you hook them up. I chose the latter and I have to take it all apart again because my intake is leaking a little from the heat plate that had to be fabricated. A lot of work. Whatever you do, dual pipes on these sixes just sound so cool! And by the way, If you split your manifold and use you stock intake, you wouldn't have to do anything to the carb. With fentons, you have to re-bend the linkage to make it work - another pain in the A@#.

There's a thread on this in the Hi-Po Shop. I just explained why I preferred the headers on my 292. I don't regret putting them on a bit, even if they needed a little work (along with the Offy intake) to get 'em to fit. It took less than 2 hours.

Old Truck,

I split the manifold on my 46 - 216 and run duals with glass packs. Don't know about any change in mileage per-say, but the performance seems to be better, and sure can't beat the sound of the split manifold and duals.

Regards,

i first put on the offenhauser dual manifold and had it for a couple of years and saw an improvement. last year i added fenton headers and saw a distinct improvement in performance. as far as fuel ecomomy i never checked before and have nothing to compare to. but i do like the improvement in performance noticeable enough i am not going to change my 2.73 nova gear ratio. if i want to stop light race i use my PT cruiser turbo, ( will FLY ) just got back from sons in indy had a lot of fun with the PT would like to have driven the truck, 95 degrees no ac in truck, wimpy RON

I just got my truck back from the exhaust shop. I don't know what the split manifold would sound like but I can tell you the fentons with Patricks' stainless bazani dual muffler sounds outrageous! Nice and mellow at idle and a great rappy growl on acceleration. The increased performance is very noticeable. I used to get about 14 - 17mpg around town and I have a lead foot. It's going to be hard to stay off the gas with my new pipes, but I will chime in in a couple weeks with a gas mileage report. ChevyAsylum - less than 2 hours? Does that include fabricating the heat system for the intake, parts fetching time, and assembly? You must be very good or I'm a lot worse than I thought. I'm actually happy that I went the header route - I just want to make sure he knows what he's in for.

Doctasuds;
My exhaust system is in shipment from Patrick's. How did you find the fit and installation or did the shop do it? Just curious.

I just bought the headers and muffler. I did all the fitting and grinding for the headers on a mock-up head on a bench. I can't imagine how hard and frustrating it would have been trying to do it on the motor in the truck. I had the fentons ceramic coated (before I had to grind them to fit as I'm unexperienced and assumed they would). Media-blasted and painted the stock intake myself. I finished the intake heating system and a few other things (New and painted master cylinder, water pump, thermostat housing, generator, fan, pulleys, brackets, fabricated oil lines, etc...) Once I got it running, I drove it a few miles to the exhaust shop. You should have seen heads turn while I was driving to the exhaust shop before the pipes and muffler were installed. You couldn't have knocked the smile off my face with a baseball bat! Hope this helps, Good luck!

Splitting your manifold is pretty easy and not to expensive.The fentons are ok but for the same money you can have a set of tuned tube headers.the only problem with them is lack of heat for the intake.

I agree. While the Fentons are good for a cast iron solution, they will not make the torque that a set of full-length tuned headers would make.

Does anyone make a pair of full length tuned headers for the 235??? Or do they have to be custom-built?

I would imagine the Fentons would out-power a split stock exhaust manifold, but the split exhaust would outpower a stock single exhaust. Still, any improvement is good, whatever level you go to.

I wish there were better options for induction though. Even Clifford's intake isn't ideal from a performance standpoint.

Tuned length headers shouldn't give noticable improvement over a split manifold on a 235 with siamesed ports, no real way to get a tuned length.

Okay, that makes sense. Except for the fact that a log manifold has to have the exhaust gasses forced out of it. Maybe at lower rpm's that's not even an issue, which is where these motors operate at.

I had a 62 Bel-Air with 235 it had tuned equal length tube headers i believe they were Hooker had a fenton 2 carb manifold with 2 Mono jets that thing would pull so hard it hurt your neck.had the original 3 spd tranny and 3:55 gears