I have a 69 Camaro (I believe SS) with a 350 engin and 350 automatic. The Engin is out of a 69 vette and it was rated at 350 hp. I am planning on rebuilding it and hope to get in the (300 to 375) hp range at the rear wheels ( I am taking about 18% off of the end of the engin HP). I am probably going to achive this by using a Holly performace package.

What I need to know is what size to make my exaust. I know I need some back pressure so I don't want to go to large. I am going to use headers and like the looks of the Flow Tech Afterburn Headers (from Jegs). Has anyone used these? I am planning on going with a dual exaust set up with flow master muffers. Are Flow Masters really that much better the a "Super Turbo Muffer"? Also is there any advantage in going with a chambered dual exaust set up.

My car is a street performer and will not see the track. I am looking to have good power and good low end torque. Any help is greatly apprechated.

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Just my .02 since your asking. I'd stay with Hooker or Doug Thorley headers. I don't have any experience with the afterburners, but the hookers & thorleys have proven themselves over time. They fit good, they're made out of quality materials and they've proven good HP increases.

After your headers, run some expansion chambers. This will help in producing low rpm torque. Another benefit would be a crossover pipe.

I'd keep the exhaust system around 2-1/8" to 2-1/4". That will be plenty and it won't be too loud.

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67 Camaro LS6 454/TH400/12bolt 3.73
1989 TransAm 5.7L WS6 W/all the options

With a daily driver I would stay with 2 1/4" duals with crossover pipe.
I would not recommend going over 2 1/2"

A good way to kill horsepower is a poor exhaust system. I have seen it many times where someone spends mucho dollars on their engine and headers and then backs it up with two kinked up little straws. The hooker headers mentioned above are a good idea. I would suggest 1 5/8 primaries. Do not get
1 7/8 for your particular engine combo. you will loose a substansial amount of torque. After the headers run a 2 1/2 manderal bent exhaust. Yes, 2 1/2. You will not loose torque doing so. Make sure you run a crossover pipe. If you like more "noise" run flowmasters or if you like it more quiet run the dynomax. Either one flows perfectly fine - just make sure you have 2 1/2 inch mufflers. As for tail pipes make sure you get mandrel bent tailpipes again in 2 1/2 inch diameter. 2 1/2 inch tail pipes will fit without a problem. There are several manufactures such as flowmaster that sell complete exhaust kits. These are great since they take all of the guess work out of finding pieces that fit together.
If you are having second thoughts about 2 1/2 inch diameter pipes, remember every one of those 5.slows come stock with 2 1/4 inch pipes. The first thing any musturd owner does is change the exhaust over to
2 1/2 inch mandrel bent pipes and believe me it makes a Big difference, and this is with that 225hp 302 motor. You have a much larger engine making a lot more horsepower.

cardude, Good Advice. I put the afterburner headers on my 67 and they do NOT fit without some hammer blows. My car has factory A/C and power steering. The afterburners hit both the A/C box and the steering box. I have to say that after all the trouble installing they do work well and have excellent ground clearance.
Hope this helps.

Thank you for the inforation. What exactly does a cross over pipe do for performace? How far back after the headers should one be installed.

Go with a full 2.5" mandrel bent system w/ 1 5/8" headers. An H-pipe style crossover tube does absolutely nothing. ET's the same, sounds the same.

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67 Camaro 410sb 11.63 @117.6
67 Camaro 388 ET-???
website (http://www.geocities.com/lonnie67_1966)

I used 1 5/8" Hooker comp headers on my 327-4 speed '68. Perfect fit. Get em coated. For exhuast, I used the Flowmaster #17129 system. This exhaust is pure art. 2 1/2" mandrel bent pipe, series 30 delta mufflers, polished stainless tailpipes. (and an H pipe if you care) fits, looks, and sounds just wonderful, for $320 from Summit!!

Everything I am reading is saying under 400 Hp go with 2 1/4" Pipes. Over 400 go with 2 1/2" pipes. I would love to get over 400, but will hopefully be in the high 300's. What effect do you think going with the larger pipes will have on my performace? Do Cross over pipes really help? There seams to be some disagreement within this post.

Going with too large of an exhaust system can hurt the low end tourqe. Also going larger will probably make it louder. The cross over may help with low end torque. I had one installed on my exhaust to help with the racket from the flowmasters. It did help to make it a little quieter.

Kent
67 SS 427

I think I am going to go with the dynomax muffers. I had glass packs orginal and my ears are still ringing.

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69 SS