Dual Exhaust with stock exhaust manifolds:

[vandelay industries]

Do you feel dual exhaust really makes a difference (power and/or mpg) if you are using the stock exhaust manifolds?


a) in general?

b) if the engine is only 262 CID AND is only used for transportation AND will rarely be turned over 3500 rpm?

 

[jkroberts]

Best thing to do is remove the category and do a high flow Y pipe. But based on the info you gave if it's not broke don't fix it

 

[vandelay industries]

i guess i should give more detail. Also, i may be jumping the gun here:

Basically, as you may or may not know i have transplanted a 4.3 v-6 where a v-8 was (truck has always had 305 and 350's all along. And yes, the move to v-6 is weird i know, but i like this engine and it was available just sitting in my garage when this last 305 blew.....)

The truck has dual exhaust which ran from the stock v-8 manifolds. It has worked well.

The v-6 manifolds don't quite match up with the v-8 manifolds (close, but not exact. And not close enough to bolt up. You would think they would/should, but they don't.....) thus the downpipes don't match and can't bolt up.

So, i'm thinking, in order to get the truck running asap, as i kinda need it for daily transportation, is to just get a stock y-pipe and run a temporary flex pipe to one muffler; This way i can drive it. And drive it to the exhaust shop and not have to worry about finding a tow to and from the shop.




The shop may then suggest to just keep the y-pipe and weld pipe off of it to complete the exhaust system OR slighly modify the v-8's dual setup to fit the v-6 manifolds.

So yeah, i am probably jumping the gun here. Also, i should add that the v-6 is stock and will remain so and only makes about 155HP at like 4000 rpm , but i don't plan on revving it that high. 230lbs of torque at 2400 rpm.


NOTE: very hungry and tired. Will provide more detail shortly after a meal.

 

[jkroberts]

It's not a performance motor so just modify what exhaust you have to fit uo. No need read inventing it

 

[Blue85]

Just wanted to mention that I have driven from my house to an exhaust shop with open headers. Keeping the throttle pretty much completely shut all the time is a real challenge, but if you get pulled over, what more can they ask, since you are currently on the way to fix it.

Plus it's fun to tell the guys at the exhaust shop "I think I might have a leak" and get them to look under there while you start it....

 

[vandelay industries]

Just wanted to mention that I have driven from my house to an exhaust shop with open headers. Keeping the throttle pretty much completely shut all the time is a real challenge, but if you get pulled over, what more can they ask, since you are currently on the way to fix it.

Plus it's fun to tell the guys at the exhaust shop "I think I might have a leak" and get them to look under there while you start it....

i've considered this. Here, if you get pulled over it won't be a fine, but they will most likely require an inspection after getting the problem fixed.

My main worry about doing this is the fumes/residue will get all over the place and possibly inside the cab.

i may have to drive a considerable distance to get to a decent shop.

i think what my plan is now is to get a stock y-pipe for the 4.3 and run flex tubing to one muffler.

 

[jkroberts]

I ran my ls swap open headers 6 miles to the exhaust place after my swap. Second best time I've had with my k5. No fumes, no residue. Your results may vary

 

[dyeager535]

I *personally* think that the manifolds are so restrictive in most forms, duals (edit: with manifolds) on a low RPM motor are not going to help enough to be worth any hassle. They might free up something, but independent dyno tests have shown 25HP with just headers and a re-tune on a carbed, stock V8 SBC time and again (which if I'm not mistaken, most 4.3L manifolds somewhat mirror in design), that indicates the manifolds are a serious restriction. If the manifolds are the problem, nothing you do downstream is going to make anywhere near the difference of addressing the manifolds will.

I really don't know if there is a large difference between dumping manifolds with no exhaust and running exhaust with no mufflers, but as long as I'm not into mine (with no mufflers) it's no more obnoxious than others who have mildly throaty aftermarket mufflers. If you step on it, people know you are there.

Unless it's running horrid, the exhaust at speed isn't going to be much, if any, of an issue. How long of a drive are you talking?

 

[diesel4me]

If your going to use flex pipe,you may as well use it to temporarily hook up the existing duals..(and it most likely wont pass inspection,here in MA flex pipe is "illegal",but many shops overlook it )..a new y-pipe will cost 50 bucks probably..could make what you have hook up for that or less..
I'd just chop off the front pipes and get whatever elbows you need at a parts store and graft them into the existing duals..

Duals are not a must on a smaller engine,but they do help some,and sound better..your V-6 has about the same HP and torque as my 6.2 diesel...