What's the best size exhaust?

[doug720]

I see lots of different size exhaust, 2", 2 1/4, 2 1/2", 3", etc, etc... ?
I have a stock 2F, that I am getting ready to finish desmoging along with having the dist and carb tweaked by Jim C.

But I'm not sure what size pipe to use, and what muffler. I was leaning towards a flowmaster...But? Please not too loud and NO DRONE!

Mine has to be custom to clear my Aux fuel tank next to the driveshaft. Where have you exited the tail pipe? Stock rear, behind rear tire???????

I also saw a relpy to a old post that had a picture of a non-US exhaust and intake manifold. I searched for an hour and could not find it again. Anyone have any experience with this set up?

I have to do a new exhaust, so lets hear what you have done and why.

Thanks

Doug

 

[freds40]

2 1/2. It opens up the stock system enough to get a tad more power but not so much that it will kill the bottom end.

 

[GLTHFJ60]

2.5. Awesome top end power with headers as well as lots of low end torque.

 

[agent orange]

I like the 2.5 i have on my truck. Nice rumble at idle but its not too loud, the cat takes a lot of the sound out. Ive got a magnaflow cat and a thrush welded muffler, like 80-90 bucks for both from summit. I have the exit right behind front drivers side spring hanger, it would be a lot quieter with a longer tailpipe and if it was turned down instead of out the side.

 

[fliphkd778]

Headers have been good to me so far, except my gas mileage got killed. I opted to not go with a heat riser for the intake when i desmogged mine w/ headers; 13 mpg to 6.5. I'm going to order a riser this week, and hopefully my dizzy will come back from Jim C. I can't seem to get a hold of him, I sent the dizzy to him a little over two months ago...

Jim where art thou?

 

[brian]

2 1/2. It opens up the stock system enough to get a tad more power but not so much that it will kill the bottom end.

these are four strokes not two strokes. back pressure is not needed.

 

[Nemesis Gnat]

these are four strokes not two strokes. back pressure is not needed.

can of worms...

 

[rover67]

can of worms...

yeah, don't go to big..

it will hurt bottom end.

I ran a flowmaster (i think it was a 40 series) on my 2f with a cat (aftermarket) 2.5" and it sounded and ran great.

 

[FL cruiser]

The header/flowmaster40/2.5" pipe sounds great, and I drove mine that way a long time until I went on a 12hr road trip. It got kind of tiring in an open air vehicle. Came home swapped the flowmaster for a Dynomax Super Turbo. Doesn't sound quite as cool, but easier on the ears on a long trip.

these are four strokes not two strokes. back pressure is not needed.

Pretty much agree.
Maybe not the perfect test to compare to a Land cruiser.
Someone did a fact/myth type dyno tests on a stock Chevy 350, mild street performance cam with headers and exhaust system. I'll try to find the article. It was either Super Chevy or Hot Rod.
They removed pieces of the exhaust system one at a time, and re dynoed each time. Only when they got down to open headers did torque numbers start going down in lower RPM's. I think they determined headers with 30" of open pipe was optimal for low end.

 

[FL cruiser]

This isn't the article I was looking for, but some good reading.

Exhaust

 

[PabloCruise]

See what Jim C has to say about the topic...

 

[lehiguy]

The header/flowmaster40/2.5" pipe sounds great, and I drove mine that way a long time until I went on a 12hr road trip. It got kind of tiring in an open air vehicle. Came home swapped the flowmaster for a Dynomax Super Turbo. Doesn't sound quite as cool, but easier on the ears on a long trip.



Pretty much agree.
Maybe not the perfect test to compare to a Land cruiser.
Someone did a fact/myth type dyno tests on a stock Chevy 350, mild street performance cam with headers and exhaust system. I'll try to find the article. It was either Super Chevy or Hot Rod.
They removed pieces of the exhaust system one at a time, and re dynoed each time. Only when they got down to open headers did torque numbers start going down in lower RPM's. I think they determined headers with 30" of open pipe was optimal for low end.

That engine would have had 1.5 to 2 times the volumetric efficiency of a 2F. Try running the 2f without any exhaust at all and you find that it is gutless beyond words. I have driven them with open headers and they suck. From my observations of three decades of engine tinkering, the lower the volumetric efficiency, the greater the need for back pressure. But I will throw my hat in with the rest of them and say that a header with 2.5" or even 2.25" pipes works well.

 

[tonkota]

I'm loving my 2.5" single exhaust. Sounds good with a quiet type muffler. I've been meaning to get a sound clip of it.

 

[Tofudebeest]

these are four strokes not two strokes. back pressure is not needed.

Unless you're running a diesel....eh?

 

[ntsqd]

Any spark ignition engine tuned to run with some amount of back pressure will loose power when run without it. Some are just more sensitive to changes in the tune than others are.

 

[Red04VXE]

What about for a 2H with extractors?????: