Grand sport (1963) race car headers

[Clem Z.]

Re: Grand sport (1963) race car headers

Someone told me that the guy that was Kustom (made headers for GM) is somewhere doing headers again. Clementine might know who and where.

Also, I think that Kevin McKay had a set of headers made, with the flattened collectors, for the LeMans L/88. You might want to contact him and see who did it.

some header builders will fab the headers on the car. i don't know if jerry s is still doing that. i know nothing about what kustom is doing.

[Clem Z.]

Re: Grand sport (1963) race car headers

some header builders will fab the headers on the car. i don't know if jerry s is still doing that. i know nothing about what kustom is doing.

jerry's website says they still do custom header work. if you talk to jerry tell him i said "HI" as i have not see him for a few years since i quit going to trade shows.

[Scott P.]

Re: Grand sport (1963) race car headers

Jerry, here is another place to check, Ed will give you 20 minutes on headers design anytime. Scott

http://www.headersbyed.com/

[Jerry G.]

Re: Grand sport (1963) race car headers

Great website, i'll call him on Tues. It's interesting that the Grand Sport header that Jim posted a photo of has what appears to be a "venturi" collector. seems like they knew something back in the sixties

[Duke W.]

Re: Grand sport (1963) race car headers

I think Ford was onto something with the GT40 "bundle of snakes" exhaust system. Supposedly the complexity was justified by greater power and/or greater power bandwidth. They have what appears to be a "venturi collector" with diverging ("megaphone") tail pipes, which was common, in that era, on racing motorcycles, both two and four-stroke.

Chevrolet also tried such a system on a ZL-1 Corvette, and it supposedly improved output compared to typical independent four-into-one on each side racing systems of the day, but you can imagine the complexity of fitting such a system into a Corvette chassis with two pipes from each bank crossing over to the other. I recall seeing pictures of it in a magazine circa 1969.

On a cruciform crank V8, the exhaust pulses are not equally phased on each bank. A pair fire 90 degrees apart and a pair are 270 degress apart, but combining the inner two cylinders from one bank with the outer two from the other bank yields equal 180 degree phasing at each collector.

The other way to get equal phasing - on each bank of a V8 - is two use a flat crank, but then you get an unbalanced horziontal shaking force that can only be balanced out with auxiliary balance shafts.

The classic Cosworth DFV, all Ferrari V8s, and current F1 V8s use flat cranks (and no balance shafts), and I don't believe there is a crossover between the two banks' exhaust systems. They are completely independent - essentially two inline fours 90 degrees out of phase.

Crossovers between the collectors on cruciform cranks V8s with typical four into one systems on each bank supposedly come closer to the output of a 180 degree system.

Duke

[Clem Z.]

Re: Grand sport (1963) race car headers

I think Ford was onto something with the GT40 "bundle of snakes" exhaust system. Supposedly the complexity was justified by greater power and/or greater power bandwidth. They have what appears to be a "venturi collector" with diverging ("megaphone") tail pipes, which was common, in that era, on racing motorcycles, both two and four-stroke.

Chevrolet also tried such a system on a ZL-1 Corvette, and it supposedly improved output compared to typical independent four-into-one on each side racing systems of the day, but you can imagine the complexity of fitting such a system into a Corvette chassis with two pipes from each bank crossing over to the other. I recall seeing pictures of it in a magazine circa 1969.

On a cruciform crank V8, the exhaust pulses are not equally phased on each bank. A pair fire 90 degrees apart and a pair are 270 degress apart, but combining the inner two cylinders from one bank with the outer two from the other bank yields equal 180 degree phasing at each collector.

The other way to get equal phasing - on each bank of a V8 - is two use a flat crank, but then you get an unbalanced horziontal shaking force that can only be balanced out with auxiliary balance shafts.

The classic Cosworth DFV, all Ferrari V8s, and current F1 V8s use flat cranks (and no balance shafts), and I don't believe there is a crossover between the two banks' exhaust systems. They are completely independent - essentially two inline fours 90 degrees out of phase.

Crossovers between the collectors on cruciform cranks V8s with typical four into one systems on each bank supposedly come closer to the output of a 180 degree system.

Duke

flat crank V-8 engines are quick but the vibration would put the drivers hands to sleep and even crack the welds on the oil pan. they changed the GM olds indy engines to flat (180 degree) cranks to get away from the NASCAR sound of the 90 degree cranks. i have heard that back in the flat head ford days they used flat cranks and fired 2 cylinders at the same time. we tried 180 degree headers on stock cars and other than the sound the cars were not any quicker but sounded like they were quicker. they still sell 180 degree headers both in over the top or under the engine style.

[Duke W.]

Re: Grand sport (1963) race car headers

Ford flatheads and I think all earlier V8s had flat cranks. Given the technology of the day they were easier to fabricate - either cast or forged, and I don't think the math to balance the first order rocking couple on a cruciform V-8 was worked out until the 1930s. I ran across a technical paper on the subject written about that time in the U. of Wisconsin engineering library when I was a grad student, circa 1969.

I remember a couple of high school buddies who had Ford flatheads. The engines felt rough and were totally out of breathe before 4000 revs.

I think the new Olds and Cadillac OHV V-8s of 1948 and 1949 were the first mass produced cruciform crank V-8s. They were definitely high-tech at the time.

About 20-25 years ago I recall seeing an IROC race from Daytona with Firebirds. They had to be running 180 degree exhaust systems as they sounded a lot faster than the Cup cars of the era. No doubt they turned slower lap times than the contemporaneous Cup cars, but the Firebirds sure made a great shriek - more like a thoroughbred European sports car than a hunk of yankee iron.

A buddy used to own a Ferrari 308 and the horizontal second order unbalanced shaking force wasn't noticeable until about 7500 when I felt a strong buzz through the seat. The redline was 7800, but it was too far beyond the power peak at that point, and 7500 was about the optimum shift point. You didn't need to watch the tach - just shift when you felt the seat buzz.

The new Ferrari 458 is up to 4.5 liters, still a flat crank with no balance shafts, AFAIK. I have not ridden in one, but they must have reasonably tamed the vibration with a sophisticated hydraulic mounting system.

Duke

[Dick W.]

Re: Grand sport (1963) race car headers

flat crank V-8 engines are quick but the vibration would put the drivers hands to sleep and even crack the welds on the oil pan. they changed the GM olds indy engines to flat (180 degree) cranks to get away from the NASCAR sound of the 90 degree cranks. i have heard that back in the flat head ford days they used flat cranks and fired 2 cylinders at the same time. we tried 180 degree headers on stock cars and other than the sound the cars were not any quicker but sounded like they were quicker. they still sell 180 degree headers both in over the top or under the engine style.

I remember years ago when everyone in NASCAR was running 180 degree headers, Smokey Yunick wandered thru the pits and made the statement, "boys, if you work hard enough with those headers, the car will run as fast as it would with the headers you replaced". The trick to making those headers work was a tweaked cam profile, connecting rod length, and tweaking the intake system. There were a few extra horsepower to be had when you ran them, but it was very expensive and hard to gain.

[Clem Z.]

Re: Grand sport (1963) race car headers

I remember years ago when everyone in NASCAR was running 180 degree headers, Smokey Yunick wandered thru the pits and made the statement, "boys, if you work hard enough with those headers, the car will run as fast as it would with the headers you replaced". The trick to making those headers work was a tweaked cam profile, connecting rod length, and tweaking the intake system. There were a few extra horsepower to be had when you ran them, but it was very expensive and hard to gain.

180 degree headers require long tubes so they limit the RPMs you can use.

[Jerry G.]

Re: Grand sport (1963) race car headers

So longer headers limit RPM? I guess that makes sence, longer tubes mean more back pressure.
I wonder if anyone has done dyno tests on the Grand Sport header design Jim posted vs a modern set of headers.

[Clem Z.]

Re: Grand sport (1963) race car headers

So longer headers limit RPM? I guess that makes sence, longer tubes mean more back pressure.
I wonder if anyone has done dyno tests on the Grand Sport header design Jim posted vs a modern set of headers.

here is a good website on header design. http://www.burnsstainless.com/techarticles.aspx

[Duke W.]

Re: Grand sport (1963) race car headers

So longer headers limit RPM? I guess that makes sence, longer tubes mean more back pressure.
I wonder if anyone has done dyno tests on the Grand Sport header design Jim posted vs a modern set of headers.

The shorter the pipe, the less time it takes for the pressure wave to reach the exit and reflect back as a rarefaction wave. There's a simple formula usually called the "organ pipe formula" to compute the time, which can be related back to RPM and valve timing so the rarefaction arrives at the exhaust port during the overlap period. This is the simple part of header design and how you come up with the 30-36" length for older racing engines.

Modern unrestricted Cup engines probably use noticeably shorter primary pipes given that they rev as high as 9500. They would undoubtedly be too short to cross over as required to achieve 180 degree phasing in each collector, and a flat crank would probably shake the cars apart.

The "exhaust box" as seen on Cup cars is discussed by Phillip H. Smith in his classic book "The Scientific Design of Intake and Exhaust Systems", which was first published in the sixties.

Collector design is a lot more esoteric because of the interaction between the wave dynamics of the collected primary pipes. It's basically a black art. Collector pipe length also has an effect. Longer collector pipes usually flatten the torque curve somewhat. You trade a little peak torque for greater torque bandwidth. That's why Cup cars have relatively short collector pipes before they dump into the exhaust box. Then they can use whatever tailpipe length is necessary to the appropiate exit behind the driver. Tailpipe length has no meaningful effect as long as they are large enough to not cause excessive frictional loss. The "tuned" part of the exhaust system ends at the exhaust box inlet.

Dyno test data I have indicates that too small tubes do not produce much power increase though they do increase torque significantly. This was from a lab dyno test of a 327 LT-1. Headers improved peak torque by eight percent, but only 2-3 percent more power than the OE 2.5" manifolds, and the reason was excess friction in the 1 5/8" OD primary pipes. Each cylinder's exhaust had to traverse nearly three feet of primary pipe rather than being immediately dumped into a 2.5" pipe. The wave dynamics were mostly offset by pumping loss in the extreme upper rev range. (This header/manifold comparison test was done with no mufflers, and mufflers would narrow the spread.)

At the 500 gross HP level, primary pipes on a V-8 racing engine should be about 2" OD assuming about a .060" wall thickness.

Duke

[Dick W.]

Re: Grand sport (1963) race car headers

180 degree headers require long tubes so they limit the RPMs you can use.

Saw 9,000 + on the tell tale several times. The Chevelle that Smokey ran in '66 or '67 had a very tuned system. The exhaust was 21' from the seat of the exhaust valve to the end of the pipe. The underneath of that car looked like a drunken worm convention. T. A. Toomes was working with the Smoke back then and told me that they spent many days on the dyno optomizing that system.

[Michael H.]

Re: Grand sport (1963) race car headers

The shorter the pipe, the less time it takes for the pressure wave to reach the exit and reflect back as a rarefaction wave. There's a simple formula usually called the "organ pipe formula" to compute the time, which can be related back to RPM and valve timing so the rarefaction arrives at the exhaust port during the overlap period. This is the simple part of header design and how you come up with the 30-36" length for older racing engines.


Duke

I still have the primary pipe length formula from GM somewhere around here. The primary pipe length is calculated using the desired RPM and the time (in seconds) that the exhaust valve is open. (seat to seat/duration) From this, you can calculate the correct length that will be required to allow the positive wave to travel to the end of the primary pipe and back as a negative to the exhaust valve. I'm sure Duke will understand this.

Use a wave velocity value of roughly 1670 fps for your calculations.

As RPM increases, the time, in seconds, that the exhaust valve is open becomes less and less. That leaves less time for the positive/negative wave to travel to the end of the primary pipe and return to the exhaust valve. That's why, as RPM increases, less and less primary pipe length is required.

If I remember correctly, engineering recommended 34" primary pipe length for the 302 Camaro Trans-Am engine with the "140" cam. I think the peak HP came in around 7200 RPM?? (I'll dig out the dyno sheets)

The only part that's complicated is the math. Not the theory.

Of interest is the fact that in 1967-68, for the Trans-Am Camaro "engineering exercise", GM engineering leaned heavily on a well known 2 stroke engine engineer. Very few people at that time knew more about exhaust wave dynamics than the 2 stroke folks.

[Clem Z.]

Re: Grand sport (1963) race car headers

I still have the primary pipe length formula from GM somewhere around here. The primary pipe length is calculated using the desired RPM and the time (in seconds) that the exhaust valve is open. (seat to seat/duration) From this, you can calculate the correct length that will be required to allow the positive wave to travel to the end of the primary pipe and back as a negative to the exhaust valve. I'm sure Duke will understand this.

Use a wave velocity value of roughly 1670 fps for your calculations.

As RPM increases, the time, in seconds, that the exhaust valve is open becomes less and less. That leaves less time for the positive/negative wave to travel to the end of the primary pipe and return to the exhaust valve. That's why, as RPM increases, less and less primary pipe length is required.

If I remember correctly, engineering recommended 34" primary pipe length for the 302 Camaro Trans-Am engine with the "140" cam. I think the peak HP came in around 7200 RPM?? (I'll dig out the dyno sheets)

The only part that's complicated is the math. Not the theory.

Of interest is the fact that in 1967-68, for the Trans-Am Camaro "engineering exercise", GM engineering leaned heavily on a well known 2 stroke engine engineer. Very few people at that time knew more about exhaust wave dynamics than the 2 stroke folks.

those expansion chambers is what makes the HP on 2 strokes.