Exhaust installation

[Mrturner1]

Hey guys I have a 1970 C10 LWB and I'm getting ready to do 3" exhaust all the way back to the bumper. Should I wait until after I lower the truck so I don't run into clearance issues or will it be fine. Also is the some specific route the exhaust guys should be running the pipe? I'm going to do a 2/4 drop I think, nothing crazy.

[demian5]

I am about to lower a 70 C10 i just picked up and from what I see, I'm gonna have to hack mine off at the mufflers. It already shows a witness mark of hitting on the passenger side at stock height. And it would hit solid at a 3" drop. I would wait.

[BILT4ME]

I would wait and do it after the suspension mods. There will be unforeseen clearance issues with shock angles or brake lines or air lines.

[Mike C]

Wait. And I would seriously reconsider the 3". Loud. Not worth much power. Hard to route over rear axle. Expensive.

[Mrturner1]

Is it easy to cut holes for the exhaust to run through the rear crossmember or whatever that peice is that the driveline goes through?

[biketopia]

Hard or easy is relative to your skill set. If you're already lowering it why not look into something like this https://www.brotherstrucks.com/63-72...tinfo/TAC72HD/ ?? What are you using to lower your truck and how far? But like the others have said, definitely wait to run the exhaust tell your suspension and ride height are figured out and installed.

[Mrturner1]

Originally Posted by biketopia

Hard or easy is relative to your skill set. If you're already lowering it why not look into something like this https://www.brotherstrucks.com/63-72...tinfo/TAC72HD/ ?? What are you using to lower your truck and how far? But like the others have said, definitely wait to run the exhaust tell your suspension and ride height are figured out and installed.

Thanks for the link, that looks like exactly what I need!

[Mrturner1]

Originally Posted by Mike C

Wait. And I would seriously reconsider the 3". Loud. Not worth much power. Hard to route over rear axle. Expensive.

I'm not to worried about loud, I only drive it once or twice a week for fun.

[biketopia]

Happy to help!!

[Mike C]

Originally Posted by Mrturner1

I'm not to worried about loud, I only drive it once or twice a week for fun.

Then why pay extra for the 3" exhaust? You pay for installation because it's more difficult to fit, you pay for material, pay for mufflers, etc. Not knowing your age or how much you may wind up driving it you probably regret that. WAY more expensive to boot.

Engine masters did a YouTube on a 2 1/2" vs 3" exhaust on a 650 hp 454. Even on that relatively high output built motor the gain was only 20 hp and that was at the highest rpm range. That test talked me out of 3" for my Camaro.

[midniteblues]

I set my 67 up for 3" but came across a 2 1/2" "kit" dirt cheap
So to save a buck i used it.
Its much louder than i thought it ever would be.
Im glad its 2 1/2 cause going over the rear with 3" and a 7" drop wouldve been a huge pita even for a shop too do.

I have 3" from headers too the mufflers on my car and 2 1/2 tail pipes and it sounds and flows good. I cant tell ya if it makes any differnce though.
But its what fit well.
I planned 3" for that too till the shop showed me the bends they would have too make and they came up with the smaller tailpipes idea.

My suggestion is too keep it up in the frame though your plans may change on the amount of drop your considering.
the last thing you want is knocking off a pipe or huge dents in it.

Besides the way your going ya might as well wait till you back halve that truck then get it done🙊

[Ekliptix]

Originally Posted by Mike C

Then why pay extra for the 3" exhaust? You pay for installation because it's more difficult to fit, you pay for material, pay for mufflers, etc. Not knowing your age or how much you may wind up driving it you probably regret that. WAY more expensive to boot.

Engine masters did a YouTube on a 2 1/2" vs 3" exhaust on a 650 hp 454. Even on that relatively high output built motor the gain was only 20 hp and that was at the highest rpm range. That test talked me out of 3" for my Camaro.

That test and video convinced me to go WITH 3". It dispelled the idea that more flow (3") reduces power and 2.5" would add 'needed' back pressure to improve power. There were gains through the entire RPM range with 3" over the 2.5". https://www.youtube.com/watch?v=_PVXvHkr-Vs. I admit my engine is not making as much power as theirs, but I do not believe I am losing any power with 3".

My setup is a 402BB making 430hp/460tq and I went with 3" for the potential power gains plus the bigger sound I'm hoping for. I even bought the CCP (CPP?) cross member to route the 3" exhaust through. However, in my case the Hooker headers came out too low, so the exhaust is running under both crossmembers now.

However, there was a clearance issue. The exhaust shop had me come in for them to explain. My truck is has a 6" lowering coil in the rear (ECE). Specifically they could not get the 3" exhaust over the axle and around the Super Track Bar easily. They said the only way was with a ton of exhaust cuts + welds that would cost a lot more. So, they did 3" all the way back into the mufflers (with an x-pipe) then 2.5" from the mufflers back. It's all done but I have not had time to head to my mechanic's place to hear it running.

[Mike C]

Everyone has a different goal and mine is relatively big power very quietly. I have a loud car to drive and the truck I want quiet. And 3% power gain for all of the negatives I mentioned above just don't make sense on a street car. 12 hp on a 430 horse motor.

I'm building a .030 '69 427 oval port motor. 10:1 compression, smallest nitrous hydraulic roller (extra exhaust duration for better exhaust flow, wider LSA), GM performance parts dual plane, 750 double pumper. The goal is for this install to look and sound like a crate motor install done back in the day. GM steel fuel lines and deep groove pulleys will be used. Aluminum water pump and GM intake will be painted orange.

I'm going to attempt angle milling reproduction big block 'vette manifolds to fit truck chassis, run 2 1/2" exhaust through Walker Hemi Turbo mufflers (extra long case). I cut 4" rings into my crossmember to run pipes between frame rails and above the trans crossmember for max clearance. And running mufflers/pipes on my leaf spring truck will be simpler than a coil truck.

Great thing about message boards is being able to take advantage of other people's experience and plans. Hopefully OP gets some good bullet points for either way. But as noted, my money is for 2 1/2" under 500 hp.

I have a tall dark 498" motor (.070 over tall deck 427, 4.5" crank) that will find a home in the Camaro and the jury is still out on 2 1/2" vs 3". Put I'm leaning 2 1/2" mandrel bent with x pipe as the best of both.