Yeah I know
I've watched quite a few dyno runs.
Dale.
I've watched quite a few dyno runs.
Dale.
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Yeah I know
I've watched quite a few dyno runs.
Dale.Comment
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Re: Exhaust pipe diameter
Scott you are in a good situation to evaluate the 2 inch versus 2 1/2 inch exhaust system and post your evaluation.
Since your 70 350/350 has the standard 2 inch exhaust when your engine is broken do a dyno run and test the system. Then using your stock manifolds buy the factory type 2 1/2 inch exhaust pipes and dyno them. With the results we will know about the torque and horsepower of both.
I have a original owner 68 L79 327/350. It came from the factory with 2 inch exhaust manifolds and the 2 1/2 inch exhaust pipes are reduced to two inches where they connect to the engines exhaust manifolds. I have replaced the exhaust throughout the years with the 2 1/2 inch replacements.
I have a 70 that when I decided to retire the 69 style exhaust side pipes I decided that I wanted to use the 2 1/2 inch exhaust pipes like which came on my 68. Sinc I was putting all new under the car exhaust I had to change out the exhaust pipe support bracket located at the transmission mount to fit the larger pipes. I had the original engine 350/300 which has a good amount of torque and was satisified with the new system. Since I have put in a ZZ crate engine using the same 2 1/2 inch exhaust system. My 70 has the turbo 400 and I like the performance I have, mayby it could be better the the 2 inch system.Comment
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Re: Exhaust pipe diameter
Scott you are in a good situation to evaluate the 2 inch versus 2 1/2 inch exhaust system and post your evaluation.
Since your 70 350/350 has the standard 2 inch exhaust when your engine is broken do a dyno run and test the system. Then using your stock manifolds buy the factory type 2 1/2 inch exhaust pipes and dyno them. With the results we will know about the torque and horsepower of both.
I have a original owner 68 L79 327/350. It came from the factory with 2 inch exhaust manifolds and the 2 1/2 inch exhaust pipes are reduced to two inches where they connect to the engines exhaust manifolds. I have replaced the exhaust throughout the years with the 2 1/2 inch replacements.
I have a 70 that when I decided to retire the 69 style exhaust side pipes I decided that I wanted to use the 2 1/2 inch exhaust pipes like which came on my 68. Sinc I was putting all new under the car exhaust I had to change out the exhaust pipe support bracket located at the transmission mount to fit the larger pipes. I had the original engine 350/300 which has a good amount of torque and was satisified with the new system. Since I have put in a ZZ crate engine using the same 2 1/2 inch exhaust system. My 70 has the turbo 400 and I like the performance I have, mayby it could be better the the 2 inch system.Comment
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Disagree with JoE...Listen to Duke!!!
All other variables being equal, you'll get better performance with the bigger exhaust. Look at the Trans Am cars now. They are using 4" and 5" pipe. Kind of like the saying, "No exceptions for cubic inches, go faster go bigger"
Just a thought....Comment
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Disagree with JoE...Listen to Duke!!!
All other variables being equal, you'll get better performance with the bigger exhaust. Look at the Trans Am cars now. They are using 4" and 5" pipe. Kind of like the saying, "No exceptions for cubic inches, go faster go bigger"
Just a thought....Comment
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If you're going for groceries
at Trans-Am speeds of well over 125 MPH then YES build horsepower and forget bottom end torque. Your wife and the other pit crew members will get you rolling by pushing your car down the street and away from the pits. Any High School kid knows that bigger is MUCH better when it comes to horsepower because all they have to do is read the Summit catalog.
Those hundreds of GM engineers, technicians, dyno operators and designers just didn't read Summit's books and therefore didn't have a clue about how to build a power train. That's OK however because we can vastly improve on GM's engineering right here on the Technical Discussion Board!
Dale.Comment
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If you're going for groceries
at Trans-Am speeds of well over 125 MPH then YES build horsepower and forget bottom end torque. Your wife and the other pit crew members will get you rolling by pushing your car down the street and away from the pits. Any High School kid knows that bigger is MUCH better when it comes to horsepower because all they have to do is read the Summit catalog.
Those hundreds of GM engineers, technicians, dyno operators and designers just didn't read Summit's books and therefore didn't have a clue about how to build a power train. That's OK however because we can vastly improve on GM's engineering right here on the Technical Discussion Board!
Dale.Comment
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You missed the point....
You need big exhaust even on the street. Take the big block for instance. So many of them came thru with limiting cast iron manifolds. One of the first things you did to get anything, HP, torque, mileage, was put free flowing exhaust on it. AKA as headers. Most times you were increasing the size of the manifold, which goes hand in hand further down the system.....Comment
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You missed the point....
You need big exhaust even on the street. Take the big block for instance. So many of them came thru with limiting cast iron manifolds. One of the first things you did to get anything, HP, torque, mileage, was put free flowing exhaust on it. AKA as headers. Most times you were increasing the size of the manifold, which goes hand in hand further down the system.....Comment
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Actually, SAE gross...
Was run without the STOCK exhaust system, in fact, as I recall, they were allowed to draw a slight vacuum on the exhaust, which as you can imagine would inflate the power figures.Comment
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Actually, SAE gross...
Was run without the STOCK exhaust system, in fact, as I recall, they were allowed to draw a slight vacuum on the exhaust, which as you can imagine would inflate the power figures.Comment
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I Found the point....
Exhaust side scavaging is a VERY complicated engineering challenge involving the location of the lower RPM torque peak which superimposes with the intake side torque peak at higher RPMs to yield the over all torque curve which should be as flat as possible and as wide as possible for stret driven machines. The absolute torque value is compromised to achieve this characteristic.
The racing challenge is basically a no-brainer. Move the high RPM torque peak as far up in the RPM band as possible and make it as high as possible with a peak characteristic. Once you get going fast you can go really faster. This machine will fall on it's nose at low RPM or off-the-line! Such an engine is worthless on the stret. I've done enough street racing in my time with pimply-faced teen-agers who drive rumpety-rump Summit mean machines to know that most of them are a joke.
Concentrating on bigger ports, valves, cams, heads, and intakes will achieve the racing configuration for high RPM and great horsepower. (which is just a formula involving RPM and torque). When you just exhaust into the air, (the theoretically biggest exhaust pipe), you have an input side only engine. By engineering the exhaust side (manifolds, pipes, anti-reversion tricks, plenums, etc., you achieve the other half of the design goal for street machines.
I will risk a substantial wager that with a 300 HP 1962 Corvette I'll blow the doors off a 1962 Fuelie from stop light to stop light. I know because I've done it. The 300 HP produces more bottom end torque than a Fuelie and that's what wins short races.
Dale.Comment
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I Found the point....
Exhaust side scavaging is a VERY complicated engineering challenge involving the location of the lower RPM torque peak which superimposes with the intake side torque peak at higher RPMs to yield the over all torque curve which should be as flat as possible and as wide as possible for stret driven machines. The absolute torque value is compromised to achieve this characteristic.
The racing challenge is basically a no-brainer. Move the high RPM torque peak as far up in the RPM band as possible and make it as high as possible with a peak characteristic. Once you get going fast you can go really faster. This machine will fall on it's nose at low RPM or off-the-line! Such an engine is worthless on the stret. I've done enough street racing in my time with pimply-faced teen-agers who drive rumpety-rump Summit mean machines to know that most of them are a joke.
Concentrating on bigger ports, valves, cams, heads, and intakes will achieve the racing configuration for high RPM and great horsepower. (which is just a formula involving RPM and torque). When you just exhaust into the air, (the theoretically biggest exhaust pipe), you have an input side only engine. By engineering the exhaust side (manifolds, pipes, anti-reversion tricks, plenums, etc., you achieve the other half of the design goal for street machines.
I will risk a substantial wager that with a 300 HP 1962 Corvette I'll blow the doors off a 1962 Fuelie from stop light to stop light. I know because I've done it. The 300 HP produces more bottom end torque than a Fuelie and that's what wins short races.
Dale.Comment
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Dittos to Dale....
2" full-tube headers, "rumpy-rump" cam, open plenum high rise, and 1k cfm carb will pull great numbers on a dyno, and even wow the spectators at the strip, BUT; These levels are achieved at 5-6-7k rpm, so unless you are running 5.56:1 rear you won't see this rpm range much on the street. A stone-stock 2V smallblock makes more real-world power at stoplights than a LT1, for maybe the first 30 feet. I have seen the dyno sheets showing the power LOSS at 1500 rpm after the installation of headers. Engines which often see up to 5k would benefit from "tri-Y" type headers, but full-tube headers are actually a detriment in traffic power ranges. Save the headers for your weekend racer, run clean, deburred, port-matched manifolds on your driver or classic 'Vette.Comment
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