I have a 305 TPI IROC-Z and plan on upgradin the stock exhaust to some flowmsters. I am gettin the Edelbeock headers and might get them Jet coated. THose run into a single 3" pipe, which i was gonna add a Random Tech 3" cat, then into a Y-pipe that is 2.5" through each pipe into a 40 series flowmaster muffler on each side. Is this a good setup for my car that has a 212/218 dur comp cam and ported intake?

 

You'll have to run the Y-pipe after the headers then the cat into the straight pipe.

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"Putting any amount of money into a RICE BURNER is like wiping your a$$ with a turd. "
'86 IROC
T-TOPS, TINTED WINDOWS, BRAKE LIGHT BLACKOUTS
GM GOODWRENCH 350
EDELBROCK TES HEADERS
3" Hooker CatBack w/Aero Chamber muffler
EDELBROCK 600CFM CARB.
KN AIRFILTER
ACCEL HEI DISTRIBUTOR
160* Stat, just switched to 180* b/c of winter coming and going to college in the mts.
3:73 Posi
Rebuilt 700R4
B&M Megashifter, 5" Autometer Tach w/shift lite

 

well if i understand what ur saying. which is have headers, then a y-pipe after it, cat, then another y pipe to split it again. why not run true duals?

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- David
88' GTA 5.7L TPI MODS---> air foil, K&N, Shift Kit, 180* therm, TB bypass, Gutted CAT, Flowmaster 80 Series Muffler added to Unkown CatBack, Ported Intake

http://www.geocities.com/david_angel_16

 

Yep, 2.5 true duals flows better than a single 3", even 2.25 duals flow more than a single 3.

 

Yeah, but on a 305?

 

I'm putting true duals on my LB9 as soon as I get my studying done (college takes up a lot of time). I bought a lot of mandrel bends (out of summit) that I will be welding together. Good luck , right. Why am I even on this board? I ought to be studying right now if I ever want to drive my car again.

 

Two 2.25" pipes are only .5 sq. inches larger than one 3" pipe. That's not enough to justify going through the trouble of running duals.

Although two 2.5" pipes have 8.86"sq. of area. Only a 3.5" pipe will be larger. It's area is 8.95 sq. inches.

A 3.25" won't be larger. It falls short at 7.67 sq. inches.

So running two 2.5" pipes would be worth it. Although it is a little more expensive, and a little more weight added to the car. Then you gotta add a crossover "X" pipe, or and "H" pipe to gain the full effect of having duals. Then there's the ground clearance issue.

If it's a street car, driven every day, then there are some sacrifices that are gonna be made by having duals. I think they're great. Just not very suitable for our cars. That's all. But they sure do look good.

AJ