[prostreet6t9]

They look real nice.Hows 12.99 @ 112 mph on street tires sound ?? That was with the cutouts open,and it spun the tires through 1st,2nd & 3rd before it hooked up in 4th,then went through the lights.This is a Doug Nash 4 + 1 5 speed equipped car,and 3.00:1 rear gears,(3.28:1 1st).
Guy

Ain't nothing wrong with that! :thumbup:

 

[red65mustang]

prostreet,
basic strip calculator says:

3300lbs/9.61=725HP

by the basic Walker chart (attached) the 3" pipes were to small,,,3.5 recommended....

no surprise it did better with 4"

 

[wmhjr]

If your running the 2 1/4 tail pipes it woulnd't help much having the 3" before the tail pipes. A good exhaust guy can run 3" out the back. I think the 3" set up sounds way better also. I've alway's ended up with a deeper smoother sound.

I think he said he's running cutouts. Considering that the exhaust gases cool quite a bit, it's possible that 3" in front of the tailpipes may well still be an improvement with 2 1/4" tailpipes. When the cutouts are open, it would certainly be different, right?

 

[prostreet6t9]

I think he said he's running cutouts. Considering that the exhaust gases cool quite a bit, it's possible that 3" in front of the tailpipes may well still be an improvement with 2 1/4" tailpipes. When the cutouts are open, it would certainly be different, right?

I've never done any testing with different size tube like that. That would be interesting to see if that combo would improve anything.When the cut out's are open,it's a new ball game.

 

[prostreet6t9]

prostreet,
basic strip calculator says:

3300lbs/9.61=725HP

by the basic Walker chart (attached) the 3" pipes were to small,,,3.5 recommended....

no surprise it did better with 4"

Very true! As stated in my previous post my car and engine is a little out of the norm,but I have had similar results with other cars that had MUCH milder engine's. Some gained more than other's.

 

[RustoRod]

I agree with a good exhaust guy is hard to find and the pricing reflects that. I agree with the chart that 65 mustang posted. I think that project cars need good planning on the exhaust as well. The guy with the 500 -600 horse pontiac needs to think if that is going to be enough motor or is he going to use nitrous someday. The reason I say that is a well done 3.5" dual exhaust and mufflers is going to be expensive. It would be ashame if a few years later he wishes to step it up and now his exhaust is too small. From what I have seen and what is being posted a larger than required exhaust will not hurt performance. Now primary tube sizing on the headers is a different story.

 

[red65mustang]

Rustorod,
the Pontiac guy has correct size for the 350HP due to the 2.5" mufflers flow....
(LOL,,to run 12's with a 500HP Poncho would be a 5000lb tempest wagon)
(he has a 3" X pipe so all he would need to change is the mufflers to 3" to use a shot of NOS...)


prostreet's pipes were to small and the rules for a 725HP motor don't apply to a street car...
(heck, he needs to run open headers to see if he needs even bigger,,,not likely but?)

I don't see an answer to your question,,,all I see is "correct" size means no HP loss...

 

[RustoRod]

Actually, he did say it would cost me power. He brought up what he believed were personal examples of where a larger exhaust resulted in poor performance - and he only deals with after the collectors. In my case, I'm building a combo that's a 4.25" stroke, .035 over Poncho 400 bore, new KRE aluminum heads ported by SD to about 320cfm, around 10.8 compression, should run high 500's in hp and a bit more in torque. I'm not agreeing with him that 2 1/2" behind the collector is enough.

Red Mustang this is the Pontiac guy that I am talking about. I had no question really just a comment. The cost of a near loss free system would be high. Since going larger might not cost much more why not ? My projects hang around for years and they always get faster as I get bored or learn more not slower. I think the exhaust system should be built better flowing than required now to allow for future power gains without sinking more money into the exhaust.

 

[prostreet6t9]

Red Mustang this is the Pontiac guy that I am talking about. I had no question really just a comment. The cost of a near loss free system would be high. Since going larger might not cost much more why not ? My projects hang around for years and they always get faster as I get bored or learn more not slower. I think the exhaust system should be built better flowing than required now to allow for future power gains without sinking more money into the exhaust.

X2 :thumbup:

 

[wmhjr]

Red Mustang this is the Pontiac guy that I am talking about. I had no question really just a comment. The cost of a near loss free system would be high. Since going larger might not cost much more why not ? My projects hang around for years and they always get faster as I get bored or learn more not slower. I think the exhaust system should be built better flowing than required now to allow for future power gains without sinking more money into the exhaust.

I'm that guy. With this car and motor I'll never add nitrous. I've got some custom suspension under it, and there isn't much room to begin with under the back side of a '66 a-body without hacking it up. 3" is the max for me, and even that is real hard to do well on the tailpipes. I'm "probably" going to use a "Dr Gas" type ovalized X-Pipe behind the collectors, running to my electric cutouts and mufflers. Probably 3" to either just before or just after the mufflers. Then probably 2 1/2" tailpipes. With the car being lowered about an inch, the billet adjustable upper control arms, the Moser rear end and the limited space to begin with on a '66 GTO, I'm concerned that I won't be able to get the 3" to fit correctly.

Edited:

Also forgot to mention - this is a convertible. I can't put all the power I'm building on the pavement as it is without twisting this thing into a pretzel. No nitrous or blower for me - I'm already probably wasting about 75hp.

 

[red65mustang]

LOL,,,70 posts is way beyond my memory's recall capability...

 

[willys36@aol.com]

72 posts .

 

[RustoRod]

I'm that guy. With this car and motor I'll never add nitrous. I've got some custom suspension under it, and there isn't much room to begin with under the back side of a '66 a-body without hacking it up. 3" is the max for me, and even that is real hard to do well on the tailpipes. I'm "probably" going to use a "Dr Gas" type ovalized X-Pipe behind the collectors, running to my electric cutouts and mufflers. Probably 3" to either just before or just after the mufflers. Then probably 2 1/2" tailpipes. With the car being lowered about an inch, the billet adjustable upper control arms, the Moser rear end and the limited space to begin with on a '66 GTO, I'm concerned that I won't be able to get the 3" to fit correctly.

Edited:

Also forgot to mention - this is a convertible. I can't put all the power I'm building on the pavement as it is without twisting this thing into a pretzel. No nitrous or blower for me - I'm already probably wasting about 75hp.

You need to look at www.torquetechexh.com. They have 3" & 3.5" mandrel bent kits for GM A bodies.

 

[wmhjr]

You need to look at www.torquetechexh.com. They have 3" & 3.5" mandrel bent kits for GM A bodies.

Thanks - appreciate it. But the issue isn't mandrel bent kits. Even Pypes has a full mandrel bent 3" kit specifically for my car. So does Ram Air Restorations. The problem is two-fold. First, the kits are designed for stock ride height and I'm lowered about an inch. Second, the larger ones are really really tight in the tailpipe section where they loop over the rear axle housing next to the upper control arms. I'm running a Moser rear end with heavier duty (and larger) UCA mounts, and billet adjustable (and larger) upper control arms. '68 and newer A-body cars make it somewhat easier, but the '66 is real tight. I'm not putting anything on that is not mandrel bent, but I think 3" up front and 2 1/2" in back is probably best. The Dougs headers have a 3" collector so I doubt that going larger than that even to the cutout will make any difference.

 

[prostreet6t9]

Thanks - appreciate it. But the issue isn't mandrel bent kits. Even Pypes has a full mandrel bent 3" kit specifically for my car. So does Ram Air Restorations. The problem is two-fold. First, the kits are designed for stock ride height and I'm lowered about an inch. Second, the larger ones are really really tight in the tailpipe section where they loop over the rear axle housing next to the upper control arms. I'm running a Moser rear end with heavier duty (and larger) UCA mounts, and billet adjustable (and larger) upper control arms. '68 and newer A-body cars make it somewhat easier, but the '66 is real tight. I'm not putting anything on that is not mandrel bent, but I think 3" up front and 2 1/2" in back is probably best. The Dougs headers have a 3" collector so I doubt that going larger than that even to the cutout will make any difference.

If you look at the tech for those guy's,They do mention that the customer will have to make a "DENT" in the control arm area to clear.

I've seen some 3" exhaust that after the muffler the Tail pipe was ran to exit behind the rear tire pointing down. Looked very nice,and sounded great. That might eliminate control arm problems.

I haven't tried one of the bolt on kit's, I would be curious how good they fit. Hopefully my other Camaro will be ready for exhaust in the next couple months and the exhaust guys around here are getting crazy expensive! Just might be the way to go.

 

[wmhjr]

If you look at the tech for those guy's,They do mention that the customer will have to make a "DENT" in the control arm area to clear.

I've seen some 3" exhaust that after the muffler the Tail pipe was ran to exit behind the rear tire pointing down. Looked very nice,and sounded great. That might eliminate control arm problems.

I haven't tried one of the bolt on kit's, I would be curious how good they fit. Hopefully my other Camaro will be ready for exhaust in the next couple months and the exhaust guys around here are getting crazy expensive! Just might be the way to go.

LOL! Dent the rear control arms? Even on stock, that sounds like a REALLY dumb idea. But try denting these... :nono:

Exiting right behind the rear wheel does nothing for the A-Body. You still need to get over the axle housing and around the control arm.

 

[prostreet6t9]

LOL,I'm not sure if they meant Denting the arm or pipe.I see your point as far as the control arm. They look like nice piece's,I woulnd't want to mess with those either.

 

[wmhjr]

Yeah, just yanking chains here. They mean denting the pipe. They do have some nice stuff, and seem to know what they're talking about. I'll probably get my driveshaft loop from them. The price is right.

 

[6426yy]

It's topics like these that keep me on this sight. I don't have a "real proof" example but my 07 Night Train was a completely different machine with a few simple bolt ons. I replaced the stock super restrictive exhaust with Hookers 4 biddens a power-commander and air cleaner assembly.

My buddies Nightster had a night and day difference with just the swap to Sweepers.

I read in one of my Harley rags that up to 8 foot pounds could be gained by simply putting a small bolt in a set of straight pipes. They used a screwdriver at the end of the pipe when it was on the dyno to prove their point to the customer who had to have straight pipes.

I had a guy complement me on my bike once but wondered why they used 4 one inch pipes in stead of 2 two inch. He said he taught a hydraulics class and said a 2 inch pipe will flow more. I really didn't have an answer I just like the style of the pipes. I think they look like something off a late-model.

Any ideas? sorry for the long post

 

[wmhjr]

Well, there are controversies in the harley world but not as much. Just before I started this '66 GTO project this past May I finished a Harley softail project. Took what was a stock '92 Heritage that I had rebuilt the top end with new heads, pistons and cam as well as carb. At that time I did a bunch of research and testing - including dyno testing - and ended up running D&D Fatcats (a 2-1 pipe). Great quality and great performance. That was more than a year ago.

But I took it much further last winter. Tore the bike down completely. Powder coated the frame. Chromed the rear swingarm. Put in a Jims 6 spd overdrive polished billet tranny. Performance Machine billet front/rear brakes. Spyke billet starter. Worked with R&R up in NH to build a 113" Evo hybrid. S&S case, crank, jugs. R&R billet heads, Super G carb, R&R custom grind cam, 11.2:1 w/forged custom pistons. All new tins including 5 gal fat bob tanks, repro bubble back bags - looks alot like a '58 DuoGlide. But runs close to 130lbs tq and 130hp on a DynoJet 250 - through my Bassani RoadRage 2-1 pipes.

Truth is that on a Harley V-twin, the more you deviate from the design of something like the Bassani Road Rage, the V&H PropPipe, or the D&D Fatcat 2-1's, the more your performance suffers. But this is a little different than the subject of this thread. Each of these pipes are essentially headers, and the 2-1 is the collector. The stepped header design is what makes it or breaks it.

The stock harley pipes especially on newer bikes combined with the fact that they're set to run REAL lean makes it so that moving to something like the street sweeper or the Fourbidden along with a powercommander or SERT is a real improvement, but most of that is because you're getting the air fuel a lot less lean and allowing the intake to open up a little. If you swapped pipes to a ProPipe or Road Rage, you'd be amazed at how much better it can be. If I put a set of sweepers on my bike and even retuned it, I promise you I'd lose at least 10hp and I'd make my torque curve a lot less flat. Doesn't mean they're bad pipes - or the 4bidden. Just that if you want to really optimize power, neither of them are real performance pipes. They have a cool look though.

Added: Specifically for the 4bidden, the 2 pipes per cylinder detracts from performance. You have only one round exhaust port per cylinder. A single round stepped pipe with equal lengths to the collecter is a more efficient and therefore power friendly design. It's probably not an issue for you at all - it's not a bad pipe. Kind of interesting.