I'm going to make my own cat-back with a dynomax bullet muffler, and have it come out 2 LT1 rectangular tips, and the tips are 2.5", so I wanted to know if it would be best to go with a 2.5" pipe the whole way, or try a 3 " then bring it down to 2.5" for the tips?

 

if u plan to stick w/ the 305,i recommend the 2.5,but if u plan to put in a 350 or bigger motor in the near future,then id go w/ the 3". the 3" on the 305 will prob loose some torque. but then again,GM had 3" on 305 TPI cars tho,so i dunno

any1 else have advice?

 

I plan on adding intake manifold, carb, open air cleaner, cam, and heads in a month or so also...

 

You might have some clearance problems with the 3 in. exhaust going over the rear axle. If you go with true duals and lt headers, you will have ground clearance problems unless you notch the frame.

 

3" I pipe into muffler, 2.5" outlets.

Dont waste your time or money on a 2.5" I pipe.

Dont worry about the clearance, it will fit with no problems.

 

you won't have a problem with the 3" setup going over the axle, it will be fine, a 3" will be alot better for the 305, the 3" setup on the 3.8 6 bangers in the 4th gen camaros and birds helps alot over the stock setup, so a 3" is definitely not over kill. If you were running duals a 2 1/4 dual setup or 3" cat back would do the trick pretty nicely.

 

Just be prepared to crim the 3 in when it goes over the axel.

 

My car will be lowered about 1.5" also. Its been around 10* all week, so I haven't been able to get under it and look at it.

 

And the reason you are not going with a commercially advailable one is?

 

Would it be an option to remove the cat. converter and put in place of it your new Bullet muffler? Weight savings right there is obvious and then from your bullet muffler bent slightly alongside the driveshaft and then turned down slightly and dumped BEFORE the axle... Again a weight savings and a money saver also since any performance oriented exhaust shop can fab a setup like that with your included muffler for under $100. I basically run something like that but with a 2 chamber flowmaster in place of the cat. converter and I even have a cutout installed just before the muffler. It works really well on my 305 and it should be good for a larger engine but my next plan is 4" oval tubing with the same setup and a larger 4" muffler to go with it. Should still be cheaper than some bulky cat back system with dual exits, a big crossflow muffler and nice looking tips. ya know?

Should be good for 15's with a mod or two more easily.

 

I can't remove the cat, because I still have to pas e-check. I think I could hit 15's now. My last run was 16.1, and was going down the whole night. Since then I have taken the back seats out, and found out it wasn't running right, because the ignition was starting to take a dump.