single exhaust for 318...what size??

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74valiant

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im thinking i want to do a single 3 inch or something along those lines for my 318. it has headers, intake, and 600cfm holley.it will have a cam soon. this will be a mild street car. would a 3 inch work??
 
3' or 3 1/2'' would be good for a mild teen. Don't forget to check out all the
neat dual systems available now and they're reasonably priced. I'm sure they would outperform any single system that you could build. toolmanmike
 
You must want the stealth/sleeper look. Whats the HP level est.?

IMO, unless your looking for the sleeper look, you would be alot better off with a simple system ethier like a Jegs/Summit racing dual exhaust kit or a Pypes exhaust. A fella here just posted a Pypes set up on his Demon. Looks good.

http://www.forabodiesonly.com/mopar/showthread.php?t=52929
 
im not so much going for sleeper, as im going for different. the h.p. numbers wont be impressive. just a stock 318 with intake, exhaust, headers, cam and carb.
 
dont understand why youd go single...go dual- those kits from summit and jegs are a wicked deal and a few members here have used them with some pretty good results from what i can recall- not perfect, but they work
 
Single would male more sense on an early A, but it's certainly doable. The cross sectional area of a 3" pipe is about the same as a pair of 2 1/4" pipes, but it will flow slightly better due to less surface area.

Flowmaster makes some good 2 into 1 transitions, but they are a tad spendy. Then again, you'll only be buying one muffler. I'd talk to a good muffler shop and compare prices with one of the pre-bent dual systems..

I run a 3" single on my truck with a mild 350 (Buick 350 GS Stage 1), and it is perfectly adequate and reasonably quiet. Should be fine for your mild 318.
 
Dakota R/Ts came with a 3 inch system from the back of the cat back! They have a Walker Dyna Max muffler and the system works great. Guys have put duals on them from the cat back and gained only 1 or 2 hp, so the single 3 inch is just fine.
 
C130 Chief said:
Single would male more sense on an early A, but it's certainly doable. The cross sectional area of a 3" pipe is about the same as a pair of 2 1/4" pipes, but it will flow slightly better due to less surface area.
Click to expand...
Thats what I was thinking, but not the surface area issue.

Flowmaster makes some good 2 into 1 transitions, but they are a tad spendy. Then again, you'll only be buying one muffler. I'd talk to a good muffler shop and compare prices with one of the pre-bent dual systems..
Click to expand...
That is what I was thinking.

I run a 3" single on my truck with a mild 350 (Buick 350 GS Stage 1), and it is perfectly adequate and reasonably quiet. Should be fine for your mild 318.
Click to expand...
Buick makes a truck? >JK!<
 
I ran 2 1/2" single exhaust with a hi-flow muffler on a 1987 Gran Fury squad car, it had a stock 318 4bbl, (all 4 cats removed!), sounded baddass and improved power.
 
Rumblefish... Buick never made a truck, but Jeep used the Buick 350 in Wagoneers and Gladiators from 68 to 71 (before the AMC downgrade).

PC170074.jpg
 
The single exhaust is a good thing when done right.

If you want to do a little custom work, try this:

Run your header collectors down to 3" pipes and into a 3" merge collector.
Run the 3" pipe to a 3" Flowmaster and then out to the left. It will sound good and perform well. Very simple system. The bigger the muffler the quieter it will most likely be.
 
WOW! Learned something today. Nice truck, very nice truck.
 
a single 3 inch system flows as well as a dual 2 1/4, just make sure the Y pipe
is a good design decent sized pipes off the manifolds
 
Our Race Car is the record holding NHRA E/SA 1974 Dart Sport and we actaully use a single exhaust outlet on it. Its a great idea to use a single pipe, creates more scavenging. Doing the math I personally would use dual 2 1/8" pipes coming off the manifolds into a 3" pipe to the back. This would easily support much more HP than youll ever make. Make sure you use a nice merge collector from the dual 2 1/8" pipes to the 3", this is important for scavenging.

Mark Lelchook
Performance Welding
Racing Headers
 
thanks for the tip mark!! one thing though... i have long tubes with something like 3 inch exhaust flanges. should i go down to 2.25 from that then back to 3in. at the merge??
 
Thats tough, everything we do is mathmaticly correct, to keep the exhaust speed high. Really what needs to be done is the collector needs to be cut off and then go from your 4 primary tubes straight to a 2 1/8" or 2 1/4" pipe using a merge collector. Those two pipes need to be merged into a 2 into 1 collector, then with your 3" outlet. If you truly have a 3" collector on the headers now you have to try and transition it slowly, like in a 3 degree increment to the 2 1/4" or 2 1/8" pipes, then to the 2 into 1 collector. The key is not to lose exhaust speed in the system.

Mark Lelchook
Performance Welding
Racing Headers
 
are you building the system or taking it to a muffler shop? for what it is, you arent going to be setting records, go with 2 1/2 or 3" off the headers, you can do the 2 1/2-3" flowmaster Y not sure if they offer a 3-3, maybe magnaflow does. run 3" right out the back. no need for 3 1/2" on that car. id run the longest dynomax super turbo, a hemi model if you can get creative and fit it. or go with a std 14" long and run a short glasspack for a resonator next to the gas tank to keep it quiet. if you want to.
 
i found some hedman collectors pretty cheap that go from 3 inch down to 2.5, so i think im gonna do dual 2.5in. to a y pipe that goes to single 3in. out the back with a single 3in. flowmaster.
 
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