86iroc504

Hey guys. I'm at the point of an ls swap where I need my exhaust done.

Car is an 86 Camaro ls swapped with stock 4.8/4l60e combo, ls1 stock converter, 1 7/8 speed engineering long tubes, 3:73 4th gen rear upgrade.

I plan on building a n/a cammed , ported heads 6.0 that will be at least 400 at the wheels.

So I need something that will be a good fit for the engine that I plan to swap into the car at a later date.

What would you guys recommend?

2 1/2 inch custom y coming of the headers transitioning to 3 inch going into magnaflow catback then out catback as dual exhaust

Or

True duals 2 1/2 inch

skinny z

I've read that the Speed Engineering headers are a close fit to Holley's Hooker BlackHeart headers (although I can't confirm). If that's the case, and seeing that a single 3" isn't really going to cut it for 400 RWHP, I'd go for Holley's matching full dual exhaust system.

https://www.holley.com/products/ls_p.../70501439-RHKR

https://www.holley.com/products/ls_p.../70501326-RHKR

It would require a transmission crossmember modification or replacement to bolt in though.

86iroc504

I see. That is a bit pricey, especially not knowing if it's going to fit.

How many hp is the 3 inch catback single pipe good for?

skinny z

Regarding price, getting a y-pipe built out of stainless is pricey too. At least a well built one is. I've been there.

As for fitment, the Speed Engineering vs BlackHeart could probably be searched out here. But as you state, yes there could be a fitment issue.

On the performance side, that would have a lot to do with the single muffler.
A rule of thumb is that 2.2 CFM per CHP is required of an exhaust system before output starts to become limited. Lets say your 400 RWHP translates to 470 CHP. That's in excess of 1000 CFM needed and in a single muffler, that equals really loud.
Before I get set on fire here, yes, you can certainly get away with less. Many have. But I think it would be fair to say they're limiting the full potential.
There are also formulas that can be used to determine the CFM of the pipes themselves but a simple comparison shows that there's 9.8 sq.in. in the duals as compared to 7 sq.in. with the single 3". That's a 40% bump in capacity.
I believe Toddoky (a member here) from Holley has stated the dual BlackHeart (2 x 2-1/2") is good to about 450 HP. Taking that bit of engineering knowledge (Tod is an engineer at Holley), you can see how the 3" would be rated considerably less.

https://www.thirdgen.org/forums/exha...t-exhaust.html

skinny z

Here's another thread.

https://www.thirdgen.org/forums/ltx-...roduce-lt.html

86iroc504

Thanks. I read through them both. I am exhausted once again with this project

skinny z

Hey man. I feel your pain. One thing led to another on my rebuild and now I'm at a point where I can't pull the trigger on the next step.

Good thing it's a hobby.

zoidberg355

Google: engine masters single vs dual exhaust or watch it on motortrend on demand

86iroc504

I decided to pull the trigger on the Holley true dual system for 4l60e. It's on back order until next week, so hopefully it'll ship out next week.. I'm also fabricating a transmission crossmember.

skinny z

It'll be interesting to see how close the Speed Engineering headers are.
As for the crossmember, the Hooker/Holley part is probably are good template to work from.
I'll be waiting for your progress.
Good luck.

86iroc504

Yea, mine will be more angle/flat then round, but I got a hold of a good welding machine I'll post some pictures after its done.

As far as the speed engineering headers fitment of the holley true dual system, I came across this thread linked below so I decided to get it. Worse case hopefully it's not too much off


https://www.thirdgen.org/forums/ltx-...ooker.html.com

skinny z

Way back, when putting together an 80's Monte Carlo, I used 4" steel pipe that was cut in half so as to make an arch. This made a convenient bridge between the sections of the original crossmember for the exhaust to pass under. Like a pair of eyebrows. Pictures weren't as easy to come by then as they are now but there's undoubtedly something floating around the interweb as an example. Maybe I can dig up something.

86iroc504

Yea, I seem them. I have some heavy 3.5" pipe I was gonna use and may still but I think this way below maybe easier for me.. I'll finish it more tomorrow and see...

QwkTrip

iTrader: (22)

A 3" over the axle can be pretty decent if the system has a really good Y-pipe merge and a straight through muffler. I've heard Flowmaster sells a really good merge. There are one or two places that sell a 3.5" over the axle. And there is also the 4" over the axle but gosh they are loud.

I had a 6.0L 2000 Camaro with cheap Pacesetter long tube headers, patched into the teeny tiny stock exhaust, and an obnoxious Hooker muffler at the back. I'm mean we're talking cheap *** exhaust and it went 118 mph in the 1/4.

skinny z

Is this to say it only went 118 or it surprisingly went 118?

soloc4

something like this?

skinny z

To quote Christoph Waltz as Hans Landa, "That's a bingo!"
(Although the Monte Carlo crossmember is somewhat longer and thicker so the effect isn't so dramatic)
Nicely done by the way.

QwkTrip

iTrader: (22)

I was leaning toward the 'surprisingly'

86iroc504

Yea, that one too

86iroc504

Well, I did pull the trigger but it was backordered further, and I just decided to get a refund. Plus, the prices increased on both 409ss and 304ss. The 304 are in stock, I was gonna possibly look into getting those, but the prices increased...

I will have to look in another direction for now

skinny z

So, where do you stand at the moment? Did you get the headers?
I've come across a 4th gen dual exhaust kit (don't recall whose and my files are in my PC). I've been told from the cats back (or thereabouts, with or without cats) it's identical to a 3rd but there again, such as is the possibility with the Speed Engineering headers, there will be some fab work to get from the collectors to whatever part of the exhaust is next.
I'll see if I can find that file and any information on how well it fits.

86iroc504

I was talking about the 2.5" true dual exhaust system. I already have the speed engineering 1 7/8 headers.

I seen that dual exhaust for 4th gen cars , but its 3"..

86iroc504

Well Holley switched the prices back to where they were, so I pulled the trigger and got the 304 version which is like $1137.. A pretty penny but I was able to sell some stuff to come out of pocket less...

They shipped today. Apparently, they were the last pair in stock because now they aren't available till 1/31/21 and I believe the 409 version aren't available until 11/30/20

skinny z

It'll be interesting to see how it all comes together. For you more than me but interested none the less.