duel exhaust conversion
 

I have recently purchased a 66 cooupe and would like to know what size mufflers and inlet outlets should i get to convert to duel exhaust. Do the inlets and outlets have to be off set??

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66 coupe

If your 289 is relatively stock, I would go with 2 1/4 inch exhaust all the way back. If you have modified it quite a bit, 2 1/2. It it were me I would go with tri Y or long tube headers, and put in the cross over (H Pipe). This would give you a healthy exhaust, support preformance improvements, increace power and milage. So muffler sizes would be determined by exhaust size. You can go straight through mufflers, I believe offsets are a bit quieter. Don't use glass packs. Muffler technology has come a long way.

I agree on the 2 1/2 on the way back. Use a crossover pipe. I prefer the 3 chamber Flowmaster with offset inlet [gets you around the driveshaft] and a center exit. Try and get mandral bent tail pipe where they go over the rear axle housing. Also, long headers, again I prefer Hooker's, they fit.