CK5
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Exhaust
- Thread starter 79jenny
- Start date
Twice as much to buy, twice as much to go wrong, and not necessary compared to a single 3" on any sort of 350 you are running manifolds on.
Do what you like, it's your rig of course, for me, having to fight all the dual exhaust components when I'm working on the truck made going back to single a wise choice IMO.
FWIW I've found single 3" with free flowing components (including a catalytic converter) to sound pretty good on a 350. Not too obnoxious, but not quiet either.
Now if you just like the look of duals, no choice really.
had true dual's years ago . i much prefer the overall sound of a good 2.5" pipe set in to a builder Y-fitting and out the 3" single . add your fav muffler in there and be good . less cludder under the bottom and as said less stuff to go wrong .
the truck i had 2.5" duals on when the mufflers went bad from rust i swapped out the pair for the same muffler but 2 inlet and single 3" out and WOW so much less incab droan on the ears . and outside had a more solid sound over the kind of semi choppy pair of mufflers if you want to call it that .
the truck i had 2.5" duals on when the mufflers went bad from rust i swapped out the pair for the same muffler but 2 inlet and single 3" out and WOW so much less incab droan on the ears . and outside had a more solid sound over the kind of semi choppy pair of mufflers if you want to call it that .
My 76 C20 had 2" duals with glasspacks and a H pipe crossover. Gave me a bit more top end but ended up with cracks at the H pipe due to me towing some very heavy loads and the frame flexing while taking off in granny low. Took out the H pipe and gained my bottom end a bit and no problems after that. Had that truck for 15 years with the same exhaust.
85 C20 had 2" duals with glasspacks and no problems until it got T boned by a Mustang doing about 50mph.
77 GMC Jimmy has had 2" duals with glasspacks for the past 20 years and no problems.
These all had the stock manifolds and all 3 went offroad, some when they werent supposed to. Tighten the donut gaskets, run a week or so, retighten and add a locknut and you shouldn't have any more problems.
I live in Northern California where we don't salt our roads so that may have something to do with the longevity of things too. Never had a muffler or glasspack rust out.
Very good episode. I was surprised that the quality of the Y or crossover made a difference. I didnt think it would make a difference at all.
i learned a LOT from that episode for sure . but i had a felling it was going to be a BIG prove it wrong and right episode on all the years of this works and that dont .
I still think they need to do an episode of how to make torque down low for all us 4wd guys. Cam, intake, heads, exhaust, all of it.
dont need to its simple ........ BIG BLOCK SWAP 
I agree, but not everyone can do that with smog laws and what not. I've got a 400 but would still like to know more ways to create more torque or more HP. Especially for cheap and still comply with smog. I've done pretty good so far, but I still want more. Yes, I could move to Nevada and not have to worry about it, but beating them at their own game is kinda like me flipping them the bird. I just have to put a bit more thought into it.dont need to its simple ........ BIG BLOCK SWAP
Fan of the 50 series
K5 has 2.5” Y into 3” single 50 series
‘68 C10 ran dual 2.5”, H pipe, dual 50 series. That 5.3 LS sounded so damn good, just pure exotic sex on the highway. Best exhaust note I’ve ever heard.
K5 has 2.5” Y into 3” single 50 series
‘68 C10 ran dual 2.5”, H pipe, dual 50 series. That 5.3 LS sounded so damn good, just pure exotic sex on the highway. Best exhaust note I’ve ever heard.
Not quite, but close.
3" pipe has a surface area of about 7 square inches.
2.25" pipe has a surface area of just under 4 square inches, so duals would be 8 square inches so a little more "area" than a single 3".
However, dual 2.25" pipes have a lot more surface area which basically causes friction and reduces the total air flow.
Down low, it's displacement or diesel. Anything you do to the motor shifts the powerband up, short of maybe appropriately sized exhaust with headers. You make more power, but it's not on the low end. As small as all the GM truck cams were, and as bad as most of the truck heads flow, I doubt there are any gains to be had on JUST the low end.
nitro_rat
1/2 ton status
You can make more power on just the low end. A good flowing set of small cc runner heads (World SR Torker for example), aggressive ramps on a low lift cam (one of the smaller cams in any manufacturer's "4x4" line), and a unconventional intake manifold (Offenhauser dual port) paired with a Q-Jet or Thermoquad.
The odd Offy intake is the ONLY aftermarket intake with a lower BSFC (brake specific fuel consumption) than a factory intake. One of the unique properties of that intake is that it can be lugged at WOT without causing engine and exhaust gas temps to rise. Perfect for dragging a mobile home up a hill with a small block.
That combo probably won't make much more peak power than stock but will have a lot more area "under the curve."
Carefully ported 305 heads would work well on a 350, the aftermarket heads would probably be better on a 383 or 400. Small chambers, zero deck, and dish pistons (like the big dish Kieth Black hypereutectic slugs) would work to keep compression and efficiency where they need to be.
Yes, surface area can be misleading, even flow numbers can be malarkey depending on how the test was ran
Here’s a rabbit hole for those of you that want
How To Calculate Muffler Size and Exhaust Pipe Diameter | Exhaust Videos
If you're a math wiz and/or an engineer, you're probably going to like this article and the resources we've linked to. However, if you find yourself getting stuck (or bored) with the info below, here are the key take-aways: 1. The factory exhaust pipe diameter is usually a good choice for most...
www.exhaustvideos.com
When I replaced the stock exhaust on my old ‘88 k5, and bought walker stock replacement pipes, everything was 3”. Was surprised it was 3” stock. That was 15yrs ago, but I’d think that would be an easy cheap way to upgrade to single 3” on the older k5’s (assuming non tbi squares).
was there a factory dual exhaust out each side at some point? I know diesels had it, but what about the gas squares?
was there a factory dual exhaust out each side at some point? I know diesels had it, but what about the gas squares?
I know the gas 80's k5's had a single in, dual out muffler and both pipes exited on the same side. My 84 k10 was the same way.
Nothing that got a catalytic converter got "real" dual exhaust. IIRC it was an option on some or all of the trucks that didn't get converters.
nitro_rat
1/2 ton status
Most of the pre-TBI 80's trucks/subs/blazers were set up that way originally. The 3" single system was a common replacement as it was cheaper/easier.
When I was putting my engine together, I did not research the Offenhauser manifold, didn't know anything about it really. My original heads were so small they belonged on a lawn mower. Went with 2.02 World Products Torquer heads, Comp Cams 4x4 cam, full roller rockers for longevity, +3 qt Moroso pan with crank scraper and windage tray for additional cooling and maybe a bit of HP on the top end, true dual exhaust, rebuild Quadrajet and Jegs dual plane intake. So not far what you prescribe. Stock pistons with trued up con rods and a reconditioned crank. Con rods were a bit egg shaped so I had them trued up for 80$. Hopefully I can have my Corvette manifolds on and exhaust done before the end of Jan. Thats about my last upgrade unless I go full roller cam, but that's a chunk of change to convert over.
Always looking for other performance upgrades and ideas.
