3" or 2.5" duel exhaust (what's better?) and X-pipe
11-10-2010, 01:38 PM
#41
Drifting
Member Since: Jul 2006
Location: Sault Ste. Marie Ontario
Posts: 1,871
Likes: 0
Received 6 Likes
on
6 Posts
There may be some science involved and you could probably calculate a couple of HP here or there with a certain size motor and a certain size pipe.
I have never been to the drag strip and heard anyone tell someone they would go faster with a smaller exhaust system.
Which one of these sounds more reasonable ?
A) A 200hp motor with a 3 inch exhaust, a 400hp motor with with a 2.5 inch exhaust and a 600hp motor with a 2 inch exhaust or:
B) A 200hp motor with a 2 inch exhaust, a 400hp motor with with a 2.5 inch exhaust and a 600hp motor with a 3 inch exhaust
Personally I switched to a 3 inch exhaust when I hit the 550HP mark, a little common sense goes a long way here without all PHD BS
I have never been to the drag strip and heard anyone tell someone they would go faster with a smaller exhaust system.
Which one of these sounds more reasonable ?
A) A 200hp motor with a 3 inch exhaust, a 400hp motor with with a 2.5 inch exhaust and a 600hp motor with a 2 inch exhaust or:
B) A 200hp motor with a 2 inch exhaust, a 400hp motor with with a 2.5 inch exhaust and a 600hp motor with a 3 inch exhaust
Personally I switched to a 3 inch exhaust when I hit the 550HP mark, a little common sense goes a long way here without all PHD BS
I like the way you think Wayne
11-10-2010, 01:43 PM
#42
Team Owner
11-10-2010, 01:52 PM
#43
Race Director
Thread Starter
Like OMG!!!!!! when i changed out the springs it made an improvement,,, and it was noticeable... thought that was it...but after further work, and your help (thank you) Holly $h!t!!! I wish you could take it for a spin.... I took Beejay out in her last week... this girl moves like.... wow
She pulls all the way through, and not just pulls, it feels as if the faster she goes the more power she makes... straight through 6500.... just wow.... i will not be surprised if i hit well over 440+hp at the rear on the next dyno pull.... thx again Geroge... p:-)
She pulls all the way through, and not just pulls, it feels as if the faster she goes the more power she makes... straight through 6500.... just wow.... i will not be surprised if i hit well over 440+hp at the rear on the next dyno pull.... thx again Geroge... p:-)
11-10-2010, 02:06 PM
#44
Team Owner
Like OMG!!!!!! when i changed out the springs it made an improvement,,, and it was noticeable... thought that was it...but after further work, and your help (thank you) Holly $h!t!!! I wish you could take it for a spin.... I took Beejay out in her last week... this girl moves like.... wow
She pulls all the way through, and not just pulls, it feels as if the faster she goes the more power she makes... straight through 6500.... just wow.... i will not be surprised if i hit well over 440+hp at the rear on the next dyno pull.... thx again George... p:-)
She pulls all the way through, and not just pulls, it feels as if the faster she goes the more power she makes... straight through 6500.... just wow.... i will not be surprised if i hit well over 440+hp at the rear on the next dyno pull.... thx again George... p:-)
I would like to know what your final pushrod preload depth came out to with the dial indicator? IMO it is so much more accurate than somebodys touch + a 1/2 turn
11-10-2010, 02:36 PM
#45
Race Director
Thread Starter
Do you have a rev limiter? Bad things can happen when you have a motor that can just power past the intended red line. I use the Crane HR6 or some number like that and I have the MSD digital ETech pro distributor set a few hundred RPM above my Crane multi spark unit.
I would like to know what your final pushrod preload depth came out to with the dial indicator? IMO it is so much more accurate than somebodys touch + a 1/2 turn
I would like to know what your final pushrod preload depth came out to with the dial indicator? IMO it is so much more accurate than somebodys touch + a 1/2 turn
as far as a rev limiter, i have a MSD unit with built in rev-limiter, I have it set at 6500, and I have hit it a couple of times because the engine is still increasing in power on it pulls even at 6500, so it throws me off on the shift.... my C5 is not even close...I feel no valve float, no leveling off of power, nothing like that... just a steady continually increasing power...up through 6500..... it has been amazing.... in first or second i can hit it and just about anywhere in the RPM range the rears will start to light up... and im not talking about dropping the clutch... just pushing the gas..... makes me SMILE:-)....
11-10-2010, 03:29 PM
#46
Race Director
This from CarCraft.com They ran 2 1/2" from the header to the x-pipe, and 3" from the x-pipe back to the mufflers....BUT, this was only a 330hp engine at the rear wheels...
http://www.carcraft.com/techarticles...ion/index.html
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 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!
http://www.carcraft.com/techarticles...ion/index.html
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 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!
11-10-2010, 06:39 PM
#47
Safety Car
Member Since: Nov 2005
Location: Lompoc, CA. Santa Barbara County
Posts: 3,932
Received 543 Likes
on
198 Posts
Can't believe i am going to say this....but no...... the engine is done, other than maintenance. It is the quickest and fastest engine I have ever built. it SMOKES my C5, and will keep up with many of the C6Z06 cars to ~140... run out of RPM...
no, my new $$$ is going to go to a new Richmond 4+1 transmission (overdrive!!!)... running down the freeways at 3-4Krpm has got to stop...about the only thing left to do to this engine is put a bigger one in.... and that is not going to happen. (wife would have a hart attack!!)
so, 2.5" or 3"
no, my new $$$ is going to go to a new Richmond 4+1 transmission (overdrive!!!)... running down the freeways at 3-4Krpm has got to stop...about the only thing left to do to this engine is put a bigger one in.... and that is not going to happen. (wife would have a hart attack!!)
so, 2.5" or 3"
Wait till you see the composite intake manifolds Airflow Research was showing at SEMA. The water passages and base plate bolt to the motor, and you can switch from dual plane to single plane plenums in minutes. No muss, no fuss. AFR said the dual plane will make 15-20hp more than RPM Air Gap. 10 lbs lighter too. When I order mine, should I put you down for one too?
I never had my car on a dyno, but I got a Physics degree 30 years ago, and I am a Rocket Scientist, and I stayed at a Hilton in Vegas last week. I could be just as full of BS as the next guy that didn't stay at the Hilton. So, here is my $.02 worth. Exhaust gas going down 10 feet of pipe will move out faster and more efficiently with less restriction. Mufflers are a source of restriction. Smaller cross section pipe is a source of restriction. Bends are a source of restriction. But....restriction reduces noise. Race cars running at WOT a lot of time will perform best with open big *** headers. Not practical with cars driven on the street. My best performing and practical exhaust system was 2.5" pipes with 3" mufflers. But I only have a little bitty 350 cubic inches. Someday I will have a 427 small block. I will have 3" pipes and 3" mufflers, and never start it before 8am. In a nutshell, bigger is better. Like my biker friends say, size does matter. Mae West said, too much of a good thing is Wonderful!
Why are you even considering off the shelf exhuast systems anyways? Take that puppy to someone that can bend and hang pipe and tell him to give you the biggest, least restrictive, freest flowing exhaust system he's ever put on a Vette. Just don't start it at 5am.
Bee Jay
PS Pauls motor pulls like a freight train. Size does matter. You should see him Manhandle and drive the crap out of his Vette one minute (no mercy on the tires, shifter or clutch), and tenderly hold his brand new baby the next minute. All with the same hands. Awesome.
Bee Jay
11-10-2010, 08:06 PM
#49
Racer
Member Since: Jan 2010
Location: Christchurch Canterbury
Posts: 367
Likes: 0
Received 1 Like
on
1 Post
YEA RIGHT!
Wait till you see the composite intake manifolds Airflow Research was showing at SEMA. The water passages and base plate bolt to the motor, and you can switch from dual plane to single plane plenums in minutes. No muss, no fuss. AFR said the dual plane will make 15-20hp more than RPM Air Gap. 10 lbs lighter too. When I order mine, should I put you down for one too?
I never had my car on a dyno, but I got a Physics degree 30 years ago, and I am a Rocket Scientist, and I stayed at a Hilton in Vegas last week. I could be just as full of BS as the next guy that didn't stay at the Hilton. So, here is my $.02 worth. Exhaust gas going down 10 feet of pipe will move out faster and more efficiently with less restriction. Mufflers are a source of restriction. Smaller cross section pipe is a source of restriction. Bends are a source of restriction. But....restriction reduces noise. Race cars running at WOT a lot of time will perform best with open big *** headers. Not practical with cars driven on the street. My best performing and practical exhaust system was 2.5" pipes with 3" mufflers. But I only have a little bitty 350 cubic inches. Someday I will have a 427 small block. I will have 3" pipes and 3" mufflers, and never start it before 8am. In a nutshell, bigger is better. Like my biker friends say, size does matter. Mae West said, too much of a good thing is Wonderful!
Why are you even considering off the shelf exhuast systems anyways? Take that puppy to someone that can bend and hang pipe and tell him to give you the biggest, least restrictive, freest flowing exhaust system he's ever put on a Vette. Just don't start it at 5am.
Bee Jay
PS Pauls motor pulls like a freight train. Size does matter. You should see him Manhandle and drive the crap out of his Vette one minute (no mercy on the tires, shifter or clutch), and tenderly hold his brand new baby the next minute. All with the same hands. Awesome.
Bee Jay
Wait till you see the composite intake manifolds Airflow Research was showing at SEMA. The water passages and base plate bolt to the motor, and you can switch from dual plane to single plane plenums in minutes. No muss, no fuss. AFR said the dual plane will make 15-20hp more than RPM Air Gap. 10 lbs lighter too. When I order mine, should I put you down for one too?
I never had my car on a dyno, but I got a Physics degree 30 years ago, and I am a Rocket Scientist, and I stayed at a Hilton in Vegas last week. I could be just as full of BS as the next guy that didn't stay at the Hilton. So, here is my $.02 worth. Exhaust gas going down 10 feet of pipe will move out faster and more efficiently with less restriction. Mufflers are a source of restriction. Smaller cross section pipe is a source of restriction. Bends are a source of restriction. But....restriction reduces noise. Race cars running at WOT a lot of time will perform best with open big *** headers. Not practical with cars driven on the street. My best performing and practical exhaust system was 2.5" pipes with 3" mufflers. But I only have a little bitty 350 cubic inches. Someday I will have a 427 small block. I will have 3" pipes and 3" mufflers, and never start it before 8am. In a nutshell, bigger is better. Like my biker friends say, size does matter. Mae West said, too much of a good thing is Wonderful!
Why are you even considering off the shelf exhuast systems anyways? Take that puppy to someone that can bend and hang pipe and tell him to give you the biggest, least restrictive, freest flowing exhaust system he's ever put on a Vette. Just don't start it at 5am.
Bee Jay
PS Pauls motor pulls like a freight train. Size does matter. You should see him Manhandle and drive the crap out of his Vette one minute (no mercy on the tires, shifter or clutch), and tenderly hold his brand new baby the next minute. All with the same hands. Awesome.
Bee Jay
Well said, if you need back pressure to make power, you need to change engine builder!
Bigger has always made more power for me, the limitation being practicality of tube size under a car for clearance etc
11-10-2010, 10:45 PM
#50
Racer
Member Since: Jun 2006
Location: Easton PA
Posts: 476
Likes: 0
Received 0 Likes
on
0 Posts
Question: Why ISN'T a bigger pipe always better?
Answer: Don't be fooled! Bigger is not better! Many people think that having the biggest diameter pipe is the best way to make power.
Not true. Due to a variety of factors, extensive testing is required. We've dyno'd extensively and our systems yield optimum power increases. Some manufacturers claim even higher horsepower numbers.
It is a fine line to reduce backpressure while maintaining good exhaust velocity. It is not about getting the biggest pipe, it is about getting a more efficient pipe diameter while maintaining exhaust velocity.
There has to be a balanced design to enhance the maximum engine output, exhaust gas velocity, and sound. For example, imagine blowing air through a straw (comparing it to a smaller diameter pipe). This would take time to release all the air from your mouth, and you would feel pressure in your mouth while doing so. Now imagine blowing air through a paper towel roll (comparing it to a larger diameter pipe). You will relieve all your air much faster and feel little or no air pressure in your mouth because of the larger capacity of the tube. This is why it is important to get the correct size piping in order to relieve backpressure while maintaining thermal efficiency.
Use the guide below when calculating pipe size for custom exhaust work. Keep in mind that the goal is to improve exhaust flow. In most cases, just changing the restrictive OEM muffler and replacing it with the same size straight-through, Wide Open Performance MagnaFlow muffler will do the job.
To reduce additional backpressure, the OEM exhaust tubing can be replaced with mandrel-bent tubing of the same size or one size up from the OEM. As a general rule, you can enlarge the pipe diameter of your OEM exhaust system by 1/4 to 1/2-inch to increase your horsepower. However, any additional increase in pipe diameter is likely to decrease your performance; specifically, low end torque.
ENGINE SIZE HORSEPOWER MUFFLER INLET/OUTLET
Single Exhaust Dual Exhaust
150-200 CID
100 to 150
2" to 2-1/4"
2"
200-250 CID
100 to 200
2-1/4" to 2-1/2"
2" to 2-1/4"
250-300 CID
150 to 250
2-1/2" to 3"
2" to 2-1/2"
300-350 CID
200 to 350
2-1/2" to 3"
2-1/4" to 2-1/2"
350-400 CID
250 to 550
3" to 4"
2-1/2" to 3"
Use as a general guide for engine size and performance
source:magnaflow
11-10-2010, 11:07 PM
#51
Racer
Member Since: Jan 2010
Location: Christchurch Canterbury
Posts: 367
Likes: 0
Received 1 Like
on
1 Post
dude as i said earlier bigger isn't always better. but dint take my word for it..........
Question: Why ISN'T a bigger pipe always better?
Answer: Don't be fooled! Bigger is not better! Many people think that having the biggest diameter pipe is the best way to make power.
Not true. Due to a variety of factors, extensive testing is required. We've dyno'd extensively and our systems yield optimum power increases. Some manufacturers claim even higher horsepower numbers.
It is a fine line to reduce backpressure while maintaining good exhaust velocity. It is not about getting the biggest pipe, it is about getting a more efficient pipe diameter while maintaining exhaust velocity.
There has to be a balanced design to enhance the maximum engine output, exhaust gas velocity, and sound. For example, imagine blowing air through a straw (comparing it to a smaller diameter pipe). This would take time to release all the air from your mouth, and you would feel pressure in your mouth while doing so. Now imagine blowing air through a paper towel roll (comparing it to a larger diameter pipe). You will relieve all your air much faster and feel little or no air pressure in your mouth because of the larger capacity of the tube. This is why it is important to get the correct size piping in order to relieve backpressure while maintaining thermal efficiency.
Use the guide below when calculating pipe size for custom exhaust work. Keep in mind that the goal is to improve exhaust flow. In most cases, just changing the restrictive OEM muffler and replacing it with the same size straight-through, Wide Open Performance MagnaFlow muffler will do the job.
To reduce additional backpressure, the OEM exhaust tubing can be replaced with mandrel-bent tubing of the same size or one size up from the OEM. As a general rule, you can enlarge the pipe diameter of your OEM exhaust system by 1/4 to 1/2-inch to increase your horsepower. However, any additional increase in pipe diameter is likely to decrease your performance; specifically, low end torque.
ENGINE SIZE HORSEPOWER MUFFLER INLET/OUTLET
Single Exhaust Dual Exhaust
150-200 CID
100 to 150
2" to 2-1/4"
2"
200-250 CID
100 to 200
2-1/4" to 2-1/2"
2" to 2-1/4"
250-300 CID
150 to 250
2-1/2" to 3"
2" to 2-1/2"
300-350 CID
200 to 350
2-1/2" to 3"
2-1/4" to 2-1/2"
350-400 CID
250 to 550
3" to 4"
2-1/2" to 3"
Use as a general guide for engine size and performance
source:magnaflow
Question: Why ISN'T a bigger pipe always better?
Answer: Don't be fooled! Bigger is not better! Many people think that having the biggest diameter pipe is the best way to make power.
Not true. Due to a variety of factors, extensive testing is required. We've dyno'd extensively and our systems yield optimum power increases. Some manufacturers claim even higher horsepower numbers.
It is a fine line to reduce backpressure while maintaining good exhaust velocity. It is not about getting the biggest pipe, it is about getting a more efficient pipe diameter while maintaining exhaust velocity.
There has to be a balanced design to enhance the maximum engine output, exhaust gas velocity, and sound. For example, imagine blowing air through a straw (comparing it to a smaller diameter pipe). This would take time to release all the air from your mouth, and you would feel pressure in your mouth while doing so. Now imagine blowing air through a paper towel roll (comparing it to a larger diameter pipe). You will relieve all your air much faster and feel little or no air pressure in your mouth because of the larger capacity of the tube. This is why it is important to get the correct size piping in order to relieve backpressure while maintaining thermal efficiency.
Use the guide below when calculating pipe size for custom exhaust work. Keep in mind that the goal is to improve exhaust flow. In most cases, just changing the restrictive OEM muffler and replacing it with the same size straight-through, Wide Open Performance MagnaFlow muffler will do the job.
To reduce additional backpressure, the OEM exhaust tubing can be replaced with mandrel-bent tubing of the same size or one size up from the OEM. As a general rule, you can enlarge the pipe diameter of your OEM exhaust system by 1/4 to 1/2-inch to increase your horsepower. However, any additional increase in pipe diameter is likely to decrease your performance; specifically, low end torque.
ENGINE SIZE HORSEPOWER MUFFLER INLET/OUTLET
Single Exhaust Dual Exhaust
150-200 CID
100 to 150
2" to 2-1/4"
2"
200-250 CID
100 to 200
2-1/4" to 2-1/2"
2" to 2-1/4"
250-300 CID
150 to 250
2-1/2" to 3"
2" to 2-1/2"
300-350 CID
200 to 350
2-1/2" to 3"
2-1/4" to 2-1/2"
350-400 CID
250 to 550
3" to 4"
2-1/2" to 3"
Use as a general guide for engine size and performance
source:magnaflow
I was talking from the collector back. Is it not header primary pipe size and length, as well as collector length where the tuning is done?
We had a ex nascar engine builder working for us, he explained in detail the cause and effects of lots of issues relating to cam choice, head flow primary and collector length depending on application, in summary ( which made good sense to us) anything after the collector (in a purpose build performance engine) the least amount of resistance the better.
11-10-2010, 11:45 PM
#52
Safety Car
Member Since: Nov 2005
Location: Lompoc, CA. Santa Barbara County
Posts: 3,932
Received 543 Likes
on
198 Posts
However, any additional increase in pipe diameter is likely to decrease your performance; specifically, low end torque.
I thought we were talking horsepower. You want low end torque, increasing exhuast restriction is not the best way to get it. Reducing pipe diameter will not increase horsepower.
Just my humble opinion.
Bee Jay
Bee Jay
I thought we were talking horsepower. You want low end torque, increasing exhuast restriction is not the best way to get it. Reducing pipe diameter will not increase horsepower.
Just my humble opinion.
Bee Jay
Bee Jay
Last edited by Bee Jay; 11-11-2010 at 12:01 AM.
11-11-2010, 01:52 AM
#53
Melting Slicks
If you need back pressure you have too much exhaust cam for your combination, period!
Primary pipe tuning is a choice of what is commercially available in headers for most folks, so let's concentrate on secondary tuning. The secondary tuning (behind the headers) is done with collector length and diameter. If your engine makes best power for your desired RPM range with 18" x 3" of collector (just numbers, yours may be much different), then you should have a box or chamber the 3" diameter collector pipe dumps into at 18" built into your exhaust system. This is not very feasible on our C3's because of room, they sit too low, and the heat under the floorboards would not be welcomed.
The size the exhaust and the flow of what the mufflers need to be to support your build depends on the horsepower output not the cubic inch. More HP = more airflow in and out. Some small engines make much more power than some big engines so process much more air. I built a 73.6 cubic inch engine that made 122 HP and 100 Lb Ft at the rear wheel (163 crank with 25% proven loss) using 1 3/4" primaries 36" long and a 2.5" collector 16" long that dumped into a one chamber muffler I built with near zero restriction for this engine. It did not make this power until I built this system, and it made a very wide power band. I was also working on the intake tract dimensions ( seperate inlets) and going back and forth from the dyno to Dynomation to build a correlation. Once I got a real world correlation, Dynomation accurately predicted the exhaust (and intake) dimensions, and that is what I built. This was my street bike (Buell) engine that I later sold and it went into a Bonneville bike that shattered the world records in it's class 2 years in a row. No one has come even relatively close to those records.
My point is not to pat myself on the back, but to show that exhaust is a science and you need to do a lot of work and study to make the best setup for your use and combination. It's not easy and it's just not cut and dry.
Primary pipe tuning is a choice of what is commercially available in headers for most folks, so let's concentrate on secondary tuning. The secondary tuning (behind the headers) is done with collector length and diameter. If your engine makes best power for your desired RPM range with 18" x 3" of collector (just numbers, yours may be much different), then you should have a box or chamber the 3" diameter collector pipe dumps into at 18" built into your exhaust system. This is not very feasible on our C3's because of room, they sit too low, and the heat under the floorboards would not be welcomed.
The size the exhaust and the flow of what the mufflers need to be to support your build depends on the horsepower output not the cubic inch. More HP = more airflow in and out. Some small engines make much more power than some big engines so process much more air. I built a 73.6 cubic inch engine that made 122 HP and 100 Lb Ft at the rear wheel (163 crank with 25% proven loss) using 1 3/4" primaries 36" long and a 2.5" collector 16" long that dumped into a one chamber muffler I built with near zero restriction for this engine. It did not make this power until I built this system, and it made a very wide power band. I was also working on the intake tract dimensions ( seperate inlets) and going back and forth from the dyno to Dynomation to build a correlation. Once I got a real world correlation, Dynomation accurately predicted the exhaust (and intake) dimensions, and that is what I built. This was my street bike (Buell) engine that I later sold and it went into a Bonneville bike that shattered the world records in it's class 2 years in a row. No one has come even relatively close to those records.
My point is not to pat myself on the back, but to show that exhaust is a science and you need to do a lot of work and study to make the best setup for your use and combination. It's not easy and it's just not cut and dry.
11-11-2010, 02:31 AM
#54
Navigator
Member Since: Nov 2010
Posts: 9
Likes: 0
Received 0 Likes
on
0 Posts
I've just got to add my 2 cents if you don't mind. I'm a Chevy guy and besides the 73 Vette I'm putting back together, I've got 3 other Chevys. An 85 Monte CarloSS with a 427 (.060 over makes it a 439) Runs about 520hp with 6spd manual and electric cutouts on a 2 1/2" system. When the dumps are open it sounds fantastic!! But, it runs and pulls a LOT better with the dumps closed. I've tromped on it in second gear with dumps open then closed the dumps and it almost feels like I shifted gears. It pulls that much better.
I've also got a 63 Nova SS conv. with a 350 vortec (and 'hot cam') and 3" Flowmaster exhaust. It sounded GREAT, but when I put 2 1/2" tailpipes on it, it's performance improved.
So, I would suggest, stay with the 2 1/2" system.
I've also got a 63 Nova SS conv. with a 350 vortec (and 'hot cam') and 3" Flowmaster exhaust. It sounded GREAT, but when I put 2 1/2" tailpipes on it, it's performance improved.
So, I would suggest, stay with the 2 1/2" system.
11-11-2010, 07:34 AM
#55
Racer
Member Since: Jun 2006
Location: Easton PA
Posts: 476
Likes: 0
Received 0 Likes
on
0 Posts
Hi,
I was talking from the collector back. Is it not header primary pipe size and length, as well as collector length where the tuning is done?
We had a ex nascar engine builder working for us, he explained in detail the cause and effects of lots of issues relating to cam choice, head flow primary and collector length depending on application, in summary ( which made good sense to us) anything after the collector (in a purpose build performance engine) the least amount of resistance the better.
I was talking from the collector back. Is it not header primary pipe size and length, as well as collector length where the tuning is done?
We had a ex nascar engine builder working for us, he explained in detail the cause and effects of lots of issues relating to cam choice, head flow primary and collector length depending on application, in summary ( which made good sense to us) anything after the collector (in a purpose build performance engine) the least amount of resistance the better.
11-11-2010, 11:37 AM
#56
Header tube diameter is determined by cylinder displacement and length is detemined by the rpm that is anticipated. Here we are talking about what comes *after* the collector. We want the pressure after the collector to be as low as possible. Any street exhaust system will have some backpressure and we want to minimize it.
There are tradeoffs to larger pipes. They reduce ground clearance, weigh more, cost more and do not dampen sound as well as smaller pipes thus a larger, heavier, more expensive muffler is required.
All this made Cheverolet put larger(2.5") systems on higher hp engines in the mid 60s and these engines were only making about 300hp at the wheels.
Like everything else exhaust size is a compromise but less back pressure will produce more power.
There are tradeoffs to larger pipes. They reduce ground clearance, weigh more, cost more and do not dampen sound as well as smaller pipes thus a larger, heavier, more expensive muffler is required.
All this made Cheverolet put larger(2.5") systems on higher hp engines in the mid 60s and these engines were only making about 300hp at the wheels.
Like everything else exhaust size is a compromise but less back pressure will produce more power.
11-11-2010, 01:07 PM
#57
Racer
Member Since: Aug 2006
Location: N. Alabama
Posts: 287
Likes: 0
Received 0 Likes
on
0 Posts
My engine builder is making a 400-425hp 355 for me and he was very adamant adamant about me only using a 1 5/8" primary tuber header with dual 2.5" exhaust, nothing bigger.
This guy ran the cylinder head program for Dale Earnhardt Sr and Rusty Wallace back in the early 90's when they were both winning. He is also one of a few authorized GTA series (road race) builders in the country and he is the engine builder for a Camping World truck race team (NASCAR). Everything he builds is dyno tuned and they have done many dyno trials with different exhaust systems. He knows what works best for most engine combos for optimal performance
This guy ran the cylinder head program for Dale Earnhardt Sr and Rusty Wallace back in the early 90's when they were both winning. He is also one of a few authorized GTA series (road race) builders in the country and he is the engine builder for a Camping World truck race team (NASCAR). Everything he builds is dyno tuned and they have done many dyno trials with different exhaust systems. He knows what works best for most engine combos for optimal performance
11-11-2010, 01:57 PM
#58
Race Director
I've just got to add my 2 cents if you don't mind. I'm a Chevy guy and besides the 73 Vette I'm putting back together, I've got 3 other Chevys. An 85 Monte CarloSS with a 427 (.060 over makes it a 439) Runs about 520hp with 6spd manual and electric cutouts on a 2 1/2" system. When the dumps are open it sounds fantastic!! But, it runs and pulls a LOT better with the dumps closed. I've tromped on it in second gear with dumps open then closed the dumps and it almost feels like I shifted gears. It pulls that much better.
I've also got a 63 Nova SS conv. with a 350 vortec (and 'hot cam') and 3" Flowmaster exhaust. It sounded GREAT, but when I put 2 1/2" tailpipes on it, it's performance improved.
So, I would suggest, stay with the 2 1/2" system.
I've also got a 63 Nova SS conv. with a 350 vortec (and 'hot cam') and 3" Flowmaster exhaust. It sounded GREAT, but when I put 2 1/2" tailpipes on it, it's performance improved.
So, I would suggest, stay with the 2 1/2" system.
11-11-2010, 05:09 PM
#59
Navigator
Member Since: Nov 2010
Posts: 9
Likes: 0
Received 0 Likes
on
0 Posts
The 427/439 in the Monte was on an engine dyno prior to installation at 522hp.& 498 lb torque. The Nova was never dynoed, but with 40+ yrs. I can pretty much tell an improvement in performance.
11-11-2010, 05:21 PM
#60
Race Director