Ok so, we are really close to gettn my 65' nova running aftr a 4yr build. Looking for opinions on the exhaust size. 3" vs. 3.5".
3.5" mite be to tough to package. Im worried 3" is to small. Its a 700+ fwhp 427ci on pumpgas. I intend on running dual mufflers and an xpipe. Current headers are 1 7/8"x 3" long tubes by Stainless Works. We can easily cut merge collector back some making it into 3.5" if we can get the exhaust to fit 3.5" elsewhere. Nothing fancy, kikn it out infront of rear tires. Up n over rear is NOT an option for any size. So needless to say, my exhaust will be a short straight shot with very few bends. Any advice is helpful.

 

DUAL 3" should be plenty.

 

Here’s a link to a easy to use chart. You prolly fine with 3” duals and an X. I feel mufflers make a big restriction difference here as well.

https://www.exhaustvideos.com/faq/ho...pipe-diameter/

 

I spent so much money trying to make good hp, id hate to leave any on the table so to speak. We are gunna try the 3.5 first, but damn its tite under there...

 

Why?? You were just advised that 3" will do the job. Just make sure you use good mufflers.

 

Dual 3" is good to over 800HP NA.

Are you asking about single 3" vs 3.5" because even a single 3.5" won't be enough. Neither will a single 4" for NA...

 

No, its defly gunna be dual with an Xpipe. But the problem is some info on the internet is conflicting and it defly appears that the 3" is border line and does not account for mufflers. In a perfect world, i would like to use 3.5" n not worry one bit. Room to grow also comes to mind. Im quite sure we re gunna end up with dual 3". Im simply gathering some info/opinions b4 we struggle for no reason. I havnt cut many corners on this build, just trying to be thorough. Right off the bat im getting different opinions from my engine builder n my fab guy. One guy builds 8sec motors routinely, other guy has an 8sec car with time slips...i hate when they disagree,lol.

 

You have a 3” collector...even cutting it back I’m not sure jumping to 3.5” pipe would do any good. The 1 7/8 primaries are likely a restriction more so than the short 3” duals would be. I’ve seen hefty improvements going to 2” primaries at this level. There’s a guy on CF with a 454 build who went from 1 7/8 to 2” primaries and picked up all across the board. 3”exhaust. He then went to 2 1/8” primaries into 3.5” collectors along with 3.5” duals and picked up a good bit more. Jumped like 20-25 hp each step. He’s got hundreds of dyno pulls to experiment with exhaust and intakes.

 

Using "good" mufflers is my next hurdle. I gotta find something that fits and performs.

 

I have no doubts there...problem with my car is everything is aftermarket...we got prices on custom headers awhile back. I was blown away, n im not a cheap skate niether...i prolly just stick with 3" duals n see what the dyno says about it.

 

Give it a spin. No sense taking new headers off and hanging them on the wall before you ever even run them. You can always change them out if later. Who built your headers?

 

Mine are Stainless Works IIRC, sold by CBR exclusively for 1st gen novas with lsx swap, pro touring TCI front clip, and a 4l80e trans set up. They are the biggest/only i could find without going full custom. Which i would have done, but couldnt justify thier prices. 2 local guys who id trust, wanted alot more than double what my $1100 LTs ended up costing me

https://www.churchboysracing.com/col...the-62-67-nova

 

Thanx for the help to all. I think im gunna go with the dual 3" set up n try n find a good set of mufflers and xpipe/exhaust design. It ll save time and money on both labor n materials.

 

Burns x-pipe and mufflers are the best you can get... also stupid expensive.

 

Looking them up now.
Just out of curioscity, what makes Burns the best? Is it design/performance?

 

Make sure you get true mandrel bends when going over the axle and not the old muffler ship here is a 3 inch pipe and when we put it in our bender it kinks down to 2 1/4 to 2 1/2 halfway through the 180 degree bend.

 

^^^ There will be no going over the rear axle. It is impossible in my build.
Spent last couple hrs reading up n trying to educate myself, this link is pretty good sofar...
https://www.google.com/amp/s/www.hot...ader-tech/amp/

 

Here are some pics of what we are up against. Fuel lines and trans cooler lines will be getting rerouted. These were originally set up like this because of the original turbo set up this car started out as...

 

How bout a set of quality dual electric cutouts?

 

This would be a lot easier if you have just left the F70s on the car. Those are big look like 345s. Looks bad even with the suspension hanging down must be worse when tucked up there for clearance. You may want to look into the NASCAR squash pipe stuff. You could run it under the rear above the sway bar to at least dump behind axle not sure how it would look or what you would see from the back. Anything under car will probably drone. You could run a smaller pipe and use the electric cut outs or the stuff that they use on the C6 corvette where it poops along and then when it loose vacuum/give it gas it opens up the other flaps. Very good at keep drone down to a minimum.