I have a 68 camaro with close to 500HP and am wondering what size exhaust to get. The guy at buckys said i would be fine with 2 1/2" I was thinking 3". Also the headers i have probably arent the best. They are the patriots and the collectors that came with them taper down to like 2 1/4. I can probably get collectors for whatever size i want but what size? I am going with flowmaster mufflers unless ??

It sounds like with 500 hp that it will only be a weekend driver in which I would go with the louder and less restrictive 3" exhaust.

Ya i dont have to drive it to work everyday or nothin.

I think 2 1/2 will be fine for 500HP. 3" is hard to fit. Are your headers like a 3/4 length ? That would be good for ground clearance.

Tom I too have a 500hp/510tq 408" in my '67(the wife's car). AED 750 (Holley DP) carb, MSD, 1 3/4" primary tube DOUG's headers. I could not imagine running 2 1/2. I have 3" to the X pipe, and 3 inch all the way over the rear end and existing at the rear of the rear wheel. Sound great, runs terrific. Hell on tires!

Ya i think its got to be 3" thanks guys. Do i need the x pipe?

Ya i think its got to be 3" thanks guys. Do i need the x pipe?

Yes, X>H.

Yep 3", with an X. Fit great on a BBC too.
http://epitomesrebuild.com/images/242.JPG

The late John Lingenfelter helped us prove this over and over with his legendary Corvette exploits. People were often amazed how he would run 600 plus horsepower Vettes with 2 1/2" exhaust. If 4" would have made John go faster, he would have run it.

http://www.borla.com/faqs/

Is this the same motor you ran without oil?

The late John Lingenfelter helped us prove this over and over with his legendary Corvette exploits. People were often amazed how he would run 600 plus horsepower Vettes with 2 1/2" exhaust. If 4" would have made John go faster, he would have run it.

http://www.borla.com/faqs/

Is this the same motor you ran without oil?


Right now I am running my ol race motor 500+ and 2 1/2 x and magnaflows,I agree with onovkind67(guys are running 700 hp and 2 1/2 ,3 in. is for the Wow factor or BIG BIG hp turbo setup from what I have read and been told,I dought you would see any performance gain ,but Tom do what you think best for you...did you meet up with Mike yet ??? Two Tacoma guys ,meet and have a :beers: or a pop you both are doing the same thing with your cars Drag Racing....:)Happy Motoring

Go with 3" you won't be sorry. 2 1/2" might get the job done but, you know 3" will.

We haven't met yet. I have been on jury duty and its been rough. They won't let us out until 4 and not a minute before. We were dead locked and they herded us back in there and said, deliberate until you come back with a verdict.
They won't even let us leave for lunch. They provided us with lunch but we're in this stuffy room and we weren't allowed to leave.
I'm finally done.

So maybe I can get out there this weekend, Tom doesn't live far from me.

As far as Bucky's.....
WARNING!!
Bucky's, Walts and Pro Max are all the same. They are all related family members that are the owners. Therefore, they likely have the same policy's.
The work I had ProMax do on my car was bad. They did not weld the exhaust into place, they screwed it with big lag screw looking things into the sheet metal. It rattled loose and started making noise. I saw what was up and they were not very friendly about fixing it. They fixed it, it rattled loose again. :mad:
So I took the loss and just went elsewhere.
Do yourself a favor and don't go to those businesses. I recommend an independent shop.

As far as X pipes. Some sort of cross feed is very very helpful. I was a non believer with my 468. I went with an H pipe and it was night and day smoother running.

I beleive you would gain more with some good headers and 2 1/2" pipes with an x-pipe than you would if you kept them headers and went with 3" pipes.
Also I read somewhere that the x-pipe out performed the h-pipe.
I will try to find that and get back to you.

My 2 1/2" exhaust and 3 chamber Flowmasters are working pretty well for me. I wanted to make sure I did not have interior resonance and got just what I wanted.

My first hand experience and opinion. Go 3", you will never have to upgrade again if you someday drop a bigegr motor or whatever. You never know what the future may bring.
Go with Dynomax straight thru welded mufflers, flowmasters make less power and are louder. I have had them both on my 3", the Dynomax made way more power, 50-75 hp(in my case) and were quieter.

I have had them both on my 3", the Dynomax made way more power, 50-75 hp(in my case) and were quieter.

Did you actually check this hp increase on a dyno?

My friend had a 2-1/2" Flowmaster system with Dynomax Ultraflows. We uncapped it on the chassis dyno and he picked up 4 HP with cutouts after the H pipe opened. That car was 455-460 HP at the wheels.

Heres the run down. You want horsepower or torque?? The smaller the exhaust the better low end you will have but if you go for 3" you will have a better high end because she will breathe better. I have 3 inch on my camaro because its a 383 spinning 7500 and at that high of rpm it wants to breathe, but if you arent seeing high rpm with your 406 then no i wouldnt i would do 2 and 1/2 because it will be better all around rpm power. X pipes are good they actually scavenge the exhaust out of the bank that isnt firing and creates a vacuum affect which is good for some power. Although i dont have it on mine because i like the sound and the ability to tune one bank of cylinders seperate of the exhaust. Really i think the x pipes again are a lower rpm affect.

Really i think the x pipes again are a lower rpm affect.

Is that why they are used in NASCAR racing?

I would think an X pipe and good flowing 2.5" muffs would be enough. Look at Greg O's 406.... If he is running 95+ in the 1/8 with 2.5's then I would think it should be fine.

In reality you'd never notice the difference on the street.

If you race regularly go 3".

In reality you'd never notice the difference on the street.

If you race regularly go 3".
:yes:

Did you actually check this hp increase on a dyno?



No, that was the butt dyno! 50-75 hp is pretty close I would say.

3" is not going to hurt performance at all (low or high RPM). I think people are making a much larger deal out of this than need be. As long as your headers are correct for your application, that's the main thing (primary tube and collector size). Too small of exhaust after that can hurt performance, too large really won't hurt you. Is 2 1/2" too small, probably not, if you run an X or H pipe with the 2 1/2" you'll be fine. In either case you have to do what works best for you. With a 2 1/2" it will not be as deep (all other things equal) but, it will tend to be more raspy. What sound do you like?

I copied this from a Car Craft article on their site , it was an article based on a comparison between h pipe and x pipe . . . . .

". . . wondered if the open headers were costing us a little low-end torque due to a lack of backpressure. To find the answer, we took the car to Magnaflow Performance Exhaust’s research and development center. After discussing our combination and the way the car is used (100 percent at the track), Magnaflow built a system based on its universal X-pipe crossover and a pair of its stainless steel street series mufflers.
For any performance exhaust system, some type of crossover connecting the two sides of a dual exhaust system is important because it acts to balance the two banks of the engine. The common H-style crossover is good at balancing sound pulses between the two halves, but does little to promote scavenging because the exhaust gases tend to follow the path of least resistance, which is straight through each pipe rather than taking the 90-degree turn through the H-pipe into the other half of the system. In an X-pipe system, however, where the two sides of the system intersect, the gasses have no choice but to intermingle as they pass through the junction. This promotes improved scavenging effects by smoothing out uneven exhaust pulses from the engine’s firing order. It also helps quiet down the exhaust, resulting in a mellower, less raspy tone. According to Magnaflow, the faster acceleration of the gasses through an X-pipe causes them to flow in a linear fashion parallel to the walls of the tubing rather than tumbling. This “laminar” flowing gas is much quieter than tumbling gas, resulting in an exhaust tone up to 8 decibels quieter than a traditional H-pipe.
We left the car at Magnaflow for about a week, and when we came back we found that after some preliminary testing, the guys had built a really trick system consisting of 2-½-inch tubing from the header collectors into the X-pipe, 3-inch out of the X flaring into 3½-inch tubing running for about 26 inches before necking back down into a pair of 3-inch mufflers with turn-downs. The theory behind this design is that it will keep the velocity of the exhaust gases moving quickly through the headers into the X-pipe to maximize the scavenging effect, while the larger-diameter tubing ahead of the mufflers prevents the gasses from stacking up as they pass through the mufflers to avoid excessive backpressure in the system.
Sounds good, but would it work? To find out, we tested three exhaust-system configurations on Magnaflow’s in-house Dynojet. For a baseline, we ran the car with open headers and saw 333 hp at 6,300 rpm and 304 lb-ft of torque at 5,200 at the rear wheels. Next, we ran a 2-½-inch bolt-together system consisting of a BBK short off-road (http://www.carcraft.com/techarticles/exhaust_system_installation/index.html#) H-pipe designed to fit the company’s full-length headers connected to a set of race-type 2-½-inch welded mufflers with turndowns. Our Mustang’s carbureted 302 didn’t like this combo, as power fell to 323 hp at 6,300 rpm and 295 lb-ft of torque at 5,200. The increased backpressure also richened up the air/fuel mixture by about two carburetor jet sizes.
Finally, we swapped on the stepped X-pipe setup and were impressed to see power levels equal to the open headers: 335 hp at 6,300 hp and 302 lb-ft at 5,200. That’s a gain of 12 rear-wheel horsepower, although it turns out we weren’t really giving anything up or gaining anything extra from the open headers. So the car’s happy, and our ears are even happier! "

They just did a test in one of last months mag's on 2.5" vs 3" on a 500HP motor. The difference was like 4HP. Now if your gonna step your combo up later then 3" for sure.

Heres my experience, of course totally unscientific. I ran a 11.70 @ 114.02 with a 1.637 60', 7.41 1/8 with full length 2.5" pipes, 2 chamber flowmasters and an H pipe. I changed exhaust only, nothing else, to 3" pipes and a Dr. Gas X, 3" magnaflow muffs, and dumps at the axle. first run after doing that, literally nothing else changed on the car, it went 11.49 @ 116.52, 1.623 60', 7.29 1/8. The only change was the days I made the pass, and the slower pass was actually made in Oct, the fast pass was done in the heat of August (well as hot as it gets around here).
I knew the car was laying down a bit up top before the exhaust, and obviously that was the case, you can see where the change was in the two passes. And actually, around town and idling it's no louder than before, however when you mash the throttle it does get a bit louder than it used to. I always get comments on how the cars ET does not match the look or the sound, (very quiet).
I attribute it to several things in addition to just the tubing size, the header had 3" collectors, the X and the Magnaflows. I was very pleased with the seat of the pants feel right off the bat.

Thanks for sharing your first hand experience Sean!

Tacoma :you out there ,lots of good info for you ,PM MKpatrick ,he's done with jury duty,you guys live within miles of each other ,wish I was closer hookup too,but with my work schedule 7 days a week and 1 weekend off a month its hard ...we will soon Happy Motoring

Tacoma :you out there ,lots of good info for you ,PM MKpatrick ,he's done with jury duty,you guys live within miles of each other ,wish I was closer hookup too,but with my work schedule 7 days a week and 1 weekend off a month its hard ...we will soon Happy Motoring

Yeah I could run by there today.

Thanks guys for all the info. The headers i have are probably not the greatest but they will have to do for now i think. As far as the exhaust i am going to go with the 3". I have had pick ups with way leas motor and had 3" exhaust so i dont see what the advantage would be to go smaller now.

Is this the same motor you ran without oil?
Yes :o

Well it seems that to do this right it is going to cost well over $700 and I just dont feel right spending that kind of coin right now until i get her going and make sure there is no long term affects of the prior no oil error :) So i just went out and bought some..............Cherry Bombs.
I know, I know Its kind of a waste of money, but i am hoping it will quiet her down enough so that it only sounds mildely obnoxious while i work on getting the engine smoothed out.

That will. I got my exhaust put on at a local shop for 150 and that included glasspacks. I have 22 inch 3 inch diameter glass packs because my car is lowered and nothing else would fit. I brought the noise down to the point that i didnt have to wear ear plugs anymore but the neighborhood knows when i start her.

Tom,
You have/had several choices. You could have just had the shop dump the exhaust at the rear axle and then when you were ready they could add the tailpipes. You could buy a 3" pre-bent system and install it yourself, then just have it tack welded once you get it all clamped. What were you getting for well over $700? Seems a bit steep to me.

My 2 1/2 x pipe with Magnaflows to stock hangers was 905.00 include tax ,cause I had him go to the stock hangers I bought and put on ,he said it would of been couple hundred cheeper ,if he could of done the hangers himself but I did not want that (it took 2 trys to mate to the stock hangers as if you are a degree off in bends it would look like crap he showed me )so I did not mind paying the xtra ),and I must say the exhuast system looks like a piece of art work ,It was his last appointment on a friday started at around 4 and finished at 8 pm...Happy Motoring

A little over $1800.00 (Hooker Super Comps/JetHot coated included) and I did all the work, welded everything except the tips. My nephew did those for free. God! It runs good.
http://epitomesrebuild.com/images/242.JPG

Yes it does Fred ,very nice,I guess if ya add the price of the Hedman headers from jet hot 500.00 and and the 905.00 = 1,405.00 as long as a guy's happy thats the main thing ...Happy Motoring

Jerome, with the freight, the headers were a touch under $800. These are the 2 1/8". Then the pipes, then the stainless tips, the paint, fill the acetylene tank,,, lordy. I think I figured low! But NO SALES TAX! All bought on the web, except the gas. Happy Motoring back at ya!

$700 was from Stans Headers, a pretty respected Exhaust builder around here. That was for 3" Mandrel bent and Magnaflow mufflers. Every other exhaust place in the area (Midas, Buckys, ProMax, Walts ect) do not mandrel bend.

The Cherry Bombs actually sound pretty good. Quieter than i thought they would be.

go with 3' and an xpipe use any good welded muffler there is no secret formula for power they all have a different sound, It's just what you perfere. As far as pro-max thay are good I race with a lot of the guy's there. Walt's is not owened by walt it's owned by a corp. in Cali. But Like all large chains go one shop could have good muffler guy were another may have a hacker.

I did a lot of research on exhaust systems before putting one on our 73 Camaro with GM 383/425 engine.
The goals were to run at Laguna Seca road course and meet their sound requirements which are 92db with the mic mounted on the K-wall at exit of turn 5.

I first exchanged emails with Stainless works, they built the exhaust for the Mule when it had a 600hp injected non-turbo engine. They put 2.5" mufflers and exhaust system on it. They first tried 3" but there was no benefit from actual dyno testing.

I couldn't consider Flowmaster mufflers, they are too loud from other racers local track experience, plus I've read that they really don't flow all that well in the 50 series we would have to use to try and meet the sound restrictions.

I chose Walker mufflers with 2.5" in/out. They make a 3" muffler but it necks down to 2.5" internally anyway and I had a better idea.

I bought a 3" X pipe kit from Summit, the exhaust cools as it travels rearward and the X pipe combines exhaust pulses from all 8 cylinders, so more exhaust can flow through each muffler because each "sees" 8 pulses each. I bought two Flowmaster reducers from 3" to 2.5", and put those right before each muffler for a smooth transition and to stay 3" as long as possible to allow the pulses to spread out and the exhaust to cool as much as possible before entering the mufflers.

After that it's all 2.5" and uses Flowmaster mandrel bent tail pipes. We autocross and want the largest rear tires we can fit, so going super large on the tail pipes was out. Also reading I've done says the exhaust is cooling as it travels rearward and smaller tail pipes are not detrimental. The pipes run all the way to the back splash pan. The sound is nice and quiet but throaty when you get on it like a late model Corvette. The car barely passes the sound limit. I'll have to make turn-down elbows for the tips to kick the sound away from the mic, because a change in weather can easily put us over the limit. Horsepower torque and throttle response is way up compared to the 2.25" system we had on before, which I expected. We actually lost power over the old restrictive system on the first dyno test, because I'd jetted the carb leaner to compensate for the smaller exhaust. We had to jet WAY up to get the power back. We are up over 4 jet sizes from what the carb came with.

This system meets our goals which are quiet on the street and track, with good HP with max ground and rear tire clearance. We run a 295X17 rear tire in stock wheel wells.
The Summit X pipe worked but had to be chopped up. A Dr Gas X pipe with 3" inlet and 2.5" outlet looks like it would be a better choice, and less of an "X" angle would help.

If you want big, go big, you probably don't have the concerns I have, but I'm just putting in a good word for the 2.5" system. I plan on doing a similar system on my 67 Camaro with 427 injected SB and 600+ hp.
David

www.PYPES.com

and if anybody reading has MORE pictures on installed/hung PYPES 2 1/2" Crossflow system I would like to SEE!!!!!!!!!!!!!!!!!!!!

Tom,
$700 is not bad at all for a madrel bent system. There are not many shops that have a madrel bender (they are VERY expensive). I assumed it was just a typical muffler shop. You syill might want to check into a pre bent system. Camaros are so popular you can buy off the shelf systems.

Jerome, with the freight, the headers were a touch under $800. These are the 2 1/8". Then the pipes, then the stainless tips, the paint, fill the acetylene tank,,, lordy. I think I figured low! But NO SALES TAX! All bought on the web, except the gas. Happy Motoring back at ya!

Fred I hope your Thanksgiving was good,I have pictures but not here at work ,I will try to get my girlfriend to E mail me some pics. then I will photobucket them,TT If there's anyway you can get your car to the Renton Highlands ,Lifetime muffler brake radiator ,Kevin is the guy in my neck of the woods,people come from miles around, the guy is GOOD...down south its Stans, I here is good .he's been there since the beginning of time...Good luck and Happy Motoring
http://gilbertautoparts.com/frame.html ZZ383 premium,Fred what ya think I am ordering with in the next week or so ,I am excited ,like a 51yr.old in a candy store :hurray::yes::thumbsup: Happy Motoring
Parameter Specification
ZZ383/425 Parts
Horsepower: 450 @ 5,600 RPM
Torque: 488 @ 4,400 RPM
Max. Rec. RPM: 6,000 RPM