Hey all,

When I bought my 67 Chevelle, the previous owner had put 2 inch dual exhaust on. Would it make more HP if I go with 2 1/2!! I have a 350 Bored to a 355 with Dart heads KB pistons, Edelbrock Carb (600) and a Edelbrock manifold. Also any idea what kind of HP i would pushing with the set up i have right now? Please bare with me I am new graemlins/clonk.gif Thanks for your help in advance :D

Brett

2" is plenty for the 355CI set up the way you have it. For the money you would dump on a larger exhaust, you could change the rear gears for a huge performance gain.

I would go for a 2.5" exhaust for sure..especially since you have some decent heads,and I'm assuming you have some compression too.
2" systems are for total stockers and 307's :D
Jegs offers a 2.5" mandrel bent exhaust w/mufflers for less than $180 FYI or you can get the Flowmaster 2.5" system that has an H pipe,but comes w/o mufflers for $200

My RV camed 350 really responded to 2.25" pipes from the 1-7/8" that were on it. The biggest power boost of any mod. This is with manifolds. Although going from stock type blown mufflers to Dynomax Super Turbos might have accounted for a large part of the increase. If your 2" system is in good shape and the mufflers are not a restriction, you may not gain much. But if the system need replacing, go for it. Have an "H" or "X" pipe installed, too. They allow the exh gas to take the path of least resistance. 2.25" pipes might be better since it will keep velocity up better than a 2.5" system. The larger pipes really help when the RPM goes up. At lower rpm the smaller pipe is better.

Thanks guy's!

My current exhaust is brand new, however it is way to quiet I want my car to soung like a muscle car not a stock car! I think for now I will leave the 2" pipes and put some better sounding mufflers, and then down the road I will put all new 2 1/2 :D Can I have 2 1/2 mufflers installed so when I am ready to install 2 1/2 exhaust, I don't have to buy mufflers again?

Soon as I can figure out how to get a pictire of my car on here, I will show you all my new baby graemlins/hurray.gif Once again I thank you guy's for your help graemlins/beers.gif

Brett

Brett,

I responded in a haste earlier, I should have asked 2 questions first. What kind of cam is in the car? Headers or stock manifolds? I offered my experience based on your running a 600 CFM carb. Even with the Dart Heads, if you are not running the motor hard enough, the CFM requirement will be quite conservative. Now, if you are spinnnig the 355 to 6500+, a larger exhaust will work. But if this is a typical 5500 - 5700 rpm hydraulic cam motor, what you have is adequate.
As is typical, without all of the facts, the answers will vary.

My 2.25" system has 2.5" muffs. Works great.

Howdy all

These are the specs on my cam

.050 Dur 204 214
SAE 278 288
CAM LIFT 0280 .295
Valve Lift .420 .443
Lobe CTRS 107 117
Lash HYD

I'm not sure what these mean graemlins/clonk.gif I know the engine has been ballanced. I do have headers and an after market Performer RPM.

Thanks

Brett

Same cam I have. 2.5" will be too big. 2.25" is perfect. BTW, throw some 1.6 rocker on. That cam really responds to them.

That should be the great old "Performer" cam and remember a stock, '67 Camaro SS with the 295hp/350 motor came with 2.25" duals on it..

pdq67

I vote for a 2.5 inch system. If you decide to step up later you won't have to redo the exhaust system. My 70 is pretty quiet and has a 2.5 inch system on it. A 2.5 inch system to the back with an x-pipe and a nice sounding muffler is how I would start.

Thanks for all the feedback :D If I were to E-mail one of you pictures of my car, is thier any way you could put the pics on the forum? I have a digital camcorder that takes still shots, however my pc does not have the correct hook ups? The guy who sold me the camcorder said it would not be a problem to hook up to my pc :mad: that's a whole nother story.

Thanks

Brett

2.5" certainly won't hurt. I ran 2.25" on a 350 in a '70 Nova with that cam and 1 5/8 headers, and I switched to 2.5" when the exhaust needed replacing (in anticipation of a bigger and better motor down the road). While I cannot say the 2.5" helped, I can tell you it did not seem to hurt.

Ditto what Pat said about 1.6 rockers.

Hey all,

I do have Roller Rockers, however I'm sure if they are 1.6 are not, How do I tell?.

What mufflers would give me the best muscle car sound?

Also is thier a big advantage to installing a K&N Air filter, verses a fram? Pat Kelly, what do you have for a car?

I don't know if you guy's are close to South Dakota or if you will be in the area, but the last weekend in August in Deadwood, Is cool Deadwood nights ( Big Car Show And swap meet) graemlins/hurray.gif

Thanks again

Brett

All the 1.6 rockers I've seen, not that many sets, say 1.6 on them.

I think the K&N, or another of the same type, is worthwhile. They are rather expensive but you'll never need to buy another filter.

I have a 66 and 67 El Camino. You can check them out by clicking on the link in my sig (go to the bottom of the page). The 66 has an engine much like yours.

Muffler sound is a personal choice. Flowmasters are popular but you'll sound like a Mustang smile.gif (at least to my ear). I like the Dynomax SuperTurbos on my 66 for a driver. The Dynomax Welded UltraFlows sound great with a very deep rumble. They may be a bit on the loud side for a driver but should be OK for a weekend car.

Hey Pat Kelly,

Very cool Elkys graemlins/beers.gif graemlins/thumbsup.gif Thanks for the info

Brett

Thanks, I need to update the pictures for the 67. It now lifts the left front tire a couple inches.