exhaust to dual or not

[fred79]

the 77 blazer i was looking at needs an exhaust it has dual exhaust on it but if i need to replace it what should i run should i run duals again run a single and if I run a single how big should it be 2.5-3 inches. i have a free flow 2.5 inch cat i would like to use it but if its not right i'll sell it toward new parts.

 

[K5Johnny]

I have an 80 blazer with a 350ci holley 600cfm and street dominator intake I run 1 5/8 headers to 2 1/2 pipe to a single 3 1/2 exaust with a flowmaster 40 series all the way out the rear of my truck like stock it runs great and sounds really good

 

[trailblazer87]

You need a little back pressure to make the low end power.
If you go single 3" is okay, if you go duals I wouldn't go any bigger than 2 1/2".

 

[84_Chevy_K10]

3" duals won't lose you power but it probably won't gain you any either.

 

[sosamantx]

if the engine is stock or slightly modified, i wouldn't go more than 2 1/4 - 2 1/2" for dual exhaust, and probably not more than 3" for a single exhaust. dual exhaust is probably going to cost more since there is extra labor, muffler, parts, etc. a good 3" single exhaust should be just fine (that is what i have, but i had no choice), but i guess it's all just preference, some people like the look of a dual exhaust. anyway, anything more than 2 1/2 for duals, and you lose torque (low end), but you might pick up some hp?? anyway, once i can get my blazer lifted on a car lift, i'll snap some pictures of my exhaust and post them on my blazer webpage that i don't have yet. /forums/images/icons/wink.gif

 

[fred79]

my real question is should i keep them duals or should i move to a single exhaust dual are more expensive and all but if its worth it for free flow or power i would keep em but i always thought it would be easier to deal with scavaging with a single exhaust. i think they are currentlty 1.5 inch pipes they look pretty small. could i runa single 2.5 inch or would that be to small, and also within a few years i would be upgrading the engine as teh stock 140hp just woulln't cut it for me what size would i need for say a 383 putin out 350-370 horsies. /forums/images/icons/crazy.gif thats were i am thinking now and if i can buy pipes once all the better! /forums/images/icons/grin.gif

 

[Mr GearHead]

Duals or a single is a personal choice and properly done both will work fine. I like duals but that is just me. For duals I would use 2 1/2" and for a single I would use 3". As for the cat, 1977 Blazers did not have a cat unless it is a two wheel drive or a California truck. If you do not need a cat to pass an inspection I would not use one.

 

[Seventy4Blazer]

2.75 inch TRUE duals with cross over and no cats... or 3.25 inch single off your cat...

 

[reddog64]

My first blazer, a 78 had a strong 350 and i gave it dual 2.5 w 40 series.. i noticed increased low end and smoother high end...

My second one a 78 chev truck had a BBC 468 that i put on dual 3 inch with 40 series.. noticed less bottom end torque and couldnt rev as high...

SO...

ON the current blazer with a good sbc 400 i'm going with dual 2.5 series 40's /forums/images/icons/smile.gif Lowend torque is good...

Your motor uses backpressure to suck exhaust out... Backpressure is a good thing!

-Aaron /forums/images/icons/laugh.gif