Small block Chev (classic) exhaust notes/tuning physics etc

[faytmorgan]

Somewhere in a dark corner of the "internet" lies a video of somebody that somehow crossed the leads from the header pipes so instead of all the primaries going into one collector some go into the other side collector...that produced a very exotic sound.

Can someone tell me a little more about his process?

180 degree headers are NOT going to fit in my car so I am starting to try and find other options that will make a higher pitched more exotic (Ferrari like etc) sound (not rice...).

Working with a 327 Chevrolet. I love the sound of muscle, the car is not muscle and should not sound that way, or to the best of my ability to capture it. The complete setup of the engine.
4.040 bore (3.25 stroke) inches (we are going to magnaflux the block to see if it is capable to go to a 4.060 bore)
team g intake single plane manifold
jegs 195cc intake port, 64cc chamber heads aluminum strait plug(these heads are getting worked and will be put on the flow bench soon)
the cam will be setup for the intake/heads/headers that are selected in the end result. The cam will put the engine in the 3000rpm-7000rpm range and a redline of 7500, albeit will be designed around the intake/heads/headers flow etc.
The compression will be at 10.5:1, so as to utilize pump gas.
Forged crankshaft (small journal block, two bolt) cross plane style crank shaft I am not going to swap in a 180 crank (flat plane) as per Ferrari spec much too much work and $$ to do such a thing.
I have yet to decide if I should pony up for 6" rods or just stay 5.7" rods
the rockers are at a 1.6 ratio.

The engine is designed around the fact that I wanted a specific rpm range, the car is very light and tires are very limited. The max tread width I could find in the max rim size available was 8.5 inches. The section width of the tires are 245mm. The rim itself when measured end to end was 240mm. The car will weigh in at about 2800lbs. The donor car is a 1978 Datsun 280z five speed which is going through a sbc v8 conversion. The drivetrain (axles, transmission, and differential) that are available can hold to the hp (which I realize is tq(rpm)/5252). So the rpm of the motor has been raised to the 7000rpm mark to best match the transmission ratios and differential ratio as well as to produce more peak hp than low end tq. Too much tq will just cause the tires to spin and cause premature part failure.

ratios
1st gear 3.06:1
2nd gear 1.63:1
3rd gear 1:1
4th gear .7:1 (more of an overdrive)
Differential 3.545:1

The tires are 245/50r16 at a speed rating of 97w. The speed rating limits the tires to 168mph.

One issue that I have found is header clearance. So I need to know what header type is going to best suit this as well. From my understanding "shorty" tubes with a larger diameter (about 1 and 3/4 of an inch) would be beneficial to the rpm I am going for rather than long tube headers. The kit (jags that run) comes with sanderson block hugger headers to avoid the steering shaft that is in a inconvenient location.

I found this on the Ferrari forums.

"An American V8 with a cross-plane crank doesn't fire alternate banks consistently. The firing order means that you sometimes get successive exhaust pulses into the same manifold. In a dual exhaust, this means inconsistent pressure pulses in the two sides.

Look up "beat frequency". When you have two frequencies that are almost -- but not quite -- the same, the difference causes a low frequency pulsation (beat frequency) that gives the American muscle car its distinctive low frequency rumble.

The same thing happens in twin engine aircraft when you don't "synchronize" your props -- the rpm difference between the two props makes for a low frequency throb you can feel as an intermittent vibration.

With pure alternate bank firing, the Ferrari engines have identical pressure pulse rates into both exhaust manifolds, so the exhausts are "synchronized". After that, it's just a matter of tuning the exhaust paths.

So, no, a Ferrari type exhaust on a cross-crank engine will not replicate the Ferrari exhaust note.

Some newer GM V8 engines have cross-connections between the exhaust sides to reduce the exhaust "rumble"."

I would like to know more about the cross-connections that are done on newer cars if you guys know anything about that?

Also from my understanding (this may or may not be true) a "x-pipe" exhaust with chambered mufflers will help create the more European sound that I am looking for as well as help with the exhaust pulses. Any thoughts there?

Are there any other options I may consider? Let's please stay on topic and factual please.

Any educated answers would be greatly appreciated.

An example of the sound (which btw I have heard corvettes (cross plane cranks) as well as the larger v8 bmws (cross plane cranks) create, I just don't know enough about exhaust to know what is done to create this as well as keep performance as well. Hence the posting.

Link of a Ferrari 348 engine sound
http://www.youtube.com/watch?v=g2Cx...PL3320E3F23893E064&lf=results_main&playnext=2

If there is more information needed about the car I will do my best to provide the information.

Fayt~

 

[mender]

Short of a flat plane crank or 180 degree headers, no, you will not get the even exhaust pulsing you are after. An X-pipe will be the best you can do.

Since you have only a 3.25 stroke, the 5.7s are fine; a redline of 7500 means better rods anyways and I usually put in 6.0s when upgrading.

Have you considered using a Supra turbo motor/drivetrain? That would give you the smoother sound and have more than enough power.

 

[faytmorgan]

It is extremely more expensive to work with import motors than a sbc. The sbc is the least expensive motor to build. I also already have about 2300 into the motor. I am looking for a 500 plus hp engine that could produce and even tq curve through the entire range so I needed the proper amount of displacement as well. I was going to do a 283, but the piston availability was very small and expensive compared to 4 inches or more.

It was less expensive to build a 327 than the l28 that the car came with. I was going to supercharge the 2.8 L6 the car came with but mega squirt is not my friend. I like to try and keep the fuel delivery process simpler with a carb.
--------------
Could I take shorty headers and connect the primaries necessary? One big problem people have found with 180* headers is that the length necessary before the collector limits the usable rpm range.

 

[mender]

Better set your sights a little lower, a very good street 327 will be doing well to top 400 hp.

The long tubes are needed to cross over to the other side of the engine to produce the even pulsing and there aren't any shortcuts.

 

[faytmorgan]

Better set your sights a little lower, a very good street 327 will be doing well to top 400 hp.

The long tubes are needed to cross over to the other side of the engine to produce the even pulsing and there aren't any shortcuts.

You are incorrect about the 327s maxing out at 400hp.

As just an example.
http://www.chevyhiperformance.com/t...7_small_block_chevy_engine_build/viewall.html

The heads I have are knock-off afr 195cc comp heads.

 

[faytmorgan]

v8 m3 - these have a cross plane crankshaft. Love this sound. I was under a 545i today (same engine) they use shorty headers and a x pipe. I don't know what the deal is with the muffler though. I don't know if the ITBs that they run would affect it that much really, because I have heard vettes sound like this.

m3 Header
http://www.porscheboost.com//images/imported/2012/01/404364_10150626271018169_103189758168_11-1.jpg

Does anyone have any info on this?

 

[faytmorgan]

http://www.corvettegarage.com/product/corsa-touring-exhaust-system-for-c5-and-z06-corvette.html

Check the sound bites out

 

[2milehi]

Any chance that you can get a camshaft ground so that the firing order changes to cause alternating banks of cylinders firing?

...Looked into this further and it appears not to be possible due to the dual-plane crank. Never mind

 

[mender]

You are incorrect about the 327s maxing out at 400hp.

As just an example.
http://www.chevyhiperformance.com/t...7_small_block_chevy_engine_build/viewall.html

The heads I have are knock-off afr 195cc comp heads.

I never said they maxed out at 400 hp, I said a good street 327 would be doing well to top 400 hp.

The most recent SBC in that displacement range that I built was a 343 that made 664 hp at 7200 rpm; quite civilized in behavior considering, and some people might be tempted to put that on the street but it was built for a local GT-1 racer.

I'm building him a 422 for his street car that should make close to 600 hp but be much nicer to deal with. Still will be on what I would consider to be the ragged edge of being streetable though.

As per the article, a 254/260 cam hardly qualifies as a street cam for most but it depends what you're willing to live with.

 

[mender]

Any chance that you can get a camshaft ground so that the firing order changes to cause alternating banks of cylinders firing?

No; the crank dictates the movement of the pistons, not the camshaft. Unless equipped with a 180 degree crank ("flat" crank) or 180 degree headers, the exhaust will have the distinctive V-8 sound.

ETA: seems you already found that out.

 

[turbo]

What is wrong with the sound of a Chevy small-block? Spend a day at the strip and watch those 283 wheel-standers run and listen to them. Who needs $$$$$$$$ foreign cars?

 

[mender]

Some people like the smooth sound of equally spaced pulses:


I'm one of them.

 

[faytmorgan]

"To replicate the Ferrari exhaust note exactly will take 1) Single plane crank with shorty equal length headers and a short overall length exhaust system, (shorter length is higher pitch). 2) 180 degree headers of equal length, as short as possible with the primaries to retain as much high pitch as possible along with as short of overall length. This will get you 90% there. 3) 8 into 1 headers all primaries being equal length, again as short as possible. 4) Some mufflers such as Spintech have a unique of absorbing the tones that give the domestic V8 that old boat drumble giving a more distinct crisp smoother "raaaaaaaap" to the exhaust note with a hint of off beat rumble. Listen to youtube sound clips of c-5 &C6 Vettes with spintechs for an example.

Not positive about diameter and it's effect on exhaust note/tone. Pretty sure smaller equates to higher pitch due to higher velocities, if that is indeed the case, finding that balance of small but so small it is restricting.

Spintech is a chambered design, I don't recall if they offer a Stainless version, if so Stainless will last much longer than mild steel, 15+ yrs. Not sure how long the mild steel versions would last, 5 years?

So shorty equal length headers that as soon as possible go into one collector, an x pipe, and then to a chambered designed muffler. Do muffler lengths and tips change the pitch? I am not sure, I would suspect it would, but only slightly. Most likely would the tone coming from the shell of the muffler/exhaust as it rings from the sound traveling within, most likely noticeable only standing right next to the muffler if..."

 

[Highspeed]

Faytmorgan, I know a couple people with Dat-conversions (Mopar and BBC powered) and they can be a lot of fun. First off, you need the flat crank or 180 headers for the sound. There is no short cut. You can try some fart-cans, but it will probably sound like a school bus instead of a Ferrari. 8) X-pipes will change the sound, but not transform it. They are good for the torque curve though. What is your plan for this car? Is it a street car, a part-time strip car, strip only? Given your desire for pump gas, I'd guess a street-strip car, so I'd have to lean toward Mender's comment that 500hp is a bit optomistic. Not at all impossible, but you may have overlooked that the engine in your noted article had 11.5:1 compression and used a pretty aggressive (pass the gas-can please) solid-roller cam. You can't even come close to the opening rates of that cam if you're thinking hydraulic; it will pass everything but a gas station if you go to the big solid cam. Is that a 4-speed stick or auto trans?

I don't understand why you want it to sound like something it's not, but that's your decision. Good luck to you!

Tongue-in-cheek...there is a device my sister bought me that keys on your alternator frequency and plays Ferrari-like rpm sounds through the radio in tune with the engine rpms. How about that? 8)

 

[mender]

The gear ratios he listed are for a 700-R4 (automatic) and unless he has a 3500 rpm stall convertor or higher it'll be pretty doggy off the line with the combo he's been indicating.

 

[Highspeed]

Yes, that's why I asked. A high-stall, lock-up converter isn't cheap either. There are a few challenges here, but it could be a very nice car.

 

[faytmorgan]

I don't need off the line power, nor want it. The car doesn't weigh that much. I am limited on tire, and the rear axles won't hold to tq, they will hp but not tq. Hp is a function of rpm and tq, if the tq comes in later and more gradual they will be fine. Also 700r4s are not known for strength, this one has been built, albeit all the same.

As for the rest of it. Do you guys have any thoughts on diameter sizing before I will be choking the motor?

 

[Fahlin Racing]

If you want something different, read Smokey Yunick's Best Damn Garage in Town particularly the exhaust section with a race car he built and holes he drilled in the header. More labor intensive with what he did, but you won't hear anything else like it. Not sure it will work the same with a street car application though.

Your exhaust note is made during the blowdown phase, if you want to attempt to manipulate that area.

 

[faytmorgan]

http://victorylibrary.com/mopar/header-tech-c.htm

http://www.bgsoflex.com/bestheader.html

 

[Highspeed]

Faytmorgan, your links will get you in the ballpark. If you're buying off the shelf headers, and that's a pretty small shelf for a conversion kit, you'll have to go with the best compromise. Use your calculations to pick the best size for your application and needs. If you're thinking custom built headers, then your wallet is your guide. The person flowing your heads should have adequate software that will not only tell you the ideal cam specs for your heads/engine combo, but it should also define the header range for your engine to breathe most efficiently. I say range because it depends on where you are targeting the power curve. Ideally, the primary tubes would be constantly expanding (megaphone-like, to a degree), but that's a pain to package, build and even calculate. Second best would be stepped headers that have 2 or 3 primary pipe sizes before the collector. They are expensive and tough to package, but very adaptable to slip-on construction. Thirdly is the header you see every day with one primary size. Honestly, you're not building a highly-tuned engine looking for every lb-ft of torque it can make. It's a compromised design for general use. And that's fine, since most engines are. The headers simply provide a path of lower resistance for the gases...you're not tuning your power curve with them by more than a few hundred rpm. If anything, I'd keep an eye on the future, when you decide to add more power, and go with the pipes that are at the very top of your results from your calculations. You may need the flow later, and the worst case is that they move your torque peak up the rpm band a little bit now...which is what you want anyway given your traction concerns.

Fahlin, are you talking about the temp probe holes for the dyno that Smokey put in the pipes?

 

[faytmorgan]

Faytmorgan, your links will get you in the ballpark. If you're buying off the shelf headers, and that's a pretty small shelf for a conversion kit, you'll have to go with the best compromise. Use your calculations to pick the best size for your application and needs. If you're thinking custom built headers, then your wallet is your guide. The person flowing your heads should have adequate software that will not only tell you the ideal cam specs for your heads/engine combo, but it should also define the header range for your engine to breathe most efficiently. I say range because it depends on where you are targeting the power curve. Ideally, the primary tubes would be constantly expanding (megaphone-like, to a degree), but that's a pain to package, build and even calculate. Second best would be stepped headers that have 2 or 3 primary pipe sizes before the collector. They are expensive and tough to package, but very adaptable to slip-on construction. Thirdly is the header you see every day with one primary size. Honestly, you're not building a highly-tuned engine looking for every lb-ft of torque it can make. It's a compromised design for general use. And that's fine, since most engines are. The headers simply provide a path of lower resistance for the gases...you're not tuning your power curve with them by more than a few hundred rpm. If anything, I'd keep an eye on the future, when you decide to add more power, and go with the pipes that are at the very top of your results from your calculations. You may need the flow later, and the worst case is that they move your torque peak up the rpm band a little bit now...which is what you want anyway given your traction concerns.

Fahlin, are you talking about the temp probe holes for the dyno that Smokey put in the pipes?

I understand what you are saying entirely albeit I don't want anything more than 500hp. If anything I would rather put more money (after the fact) into the body. As in I would like to fab up a lot of carbon fiber for the car, which is something I have been researching as well. In example carbon fiber;hood, hatch, doors, fenders, cockpit, axles, drive-shaft, seats etc. I want to make them myself.

As for the header construction, I would be fabricating it myself. I may be getting a job at a large custom metal fabrication shop called Anderson & Dalen inc in Mn. The word is (from two friends who work there) that as long as I pay for materials I would be allowed to fabricate my own parts as well. Currently I am a mechanic working on a lot of Japanese and European automobiles. My understanding of said vehicles and their construction revolves around that.

What about anti-reverberation can someone clue me in on that a touch? I read some on that a few years ago the Honda guys got big into anti-reverberation headers. Little bumps in the primary tubes for whatever purpose etc. How could I apply this to my design?

Once I get the accurate flow numbers for my heads I will certainly post them as well. My engine builder's father just passed away from cancer so I haven't a clue when they will be available. I just found about his loss a few days ago.

 

[mender]

Interesting, I tried out the Bowling calculator and it agreed with what I was going to recommend: 1.75 OD primary tubes right around 32 inch tube length. For street you can add a few inches if you like.

That's what the header size is for one of the racing classes I build for that makes just over 500 hp so it's an easy call.

Do you mean anti-reversion?

 

[mender]

I don't need off the line power, nor want it.

Almost forgot this reply to the high stall converter.

It's also about getting the car to "idle" in gear without loading up and quitting on you.

 

[mender]

I understand what you are saying entirely albeit I don't want anything more than 500hp. If anything I would rather put more money (after the fact) into the body. As in I would like to fab up a lot of carbon fiber for the car, which is something I have been researching as well. In example carbon fiber;hood, hatch, doors, fenders, cockpit, axles, drive-shaft, seats etc. I want to make them myself.

As for the header construction, I would be fabricating it myself. I may be getting a job at a large custom metal fabrication shop called Anderson & Dalen inc in Mn. The word is (from two friends who work there) that as long as I pay for materials I would be allowed to fabricate my own parts as well.

Excellent; make sure you make friends with the lead fabricator and offer to mow his lawn or something if need be!

 

[Fahlin Racing]

Highspeed, I was talking about some holes Smokey incorporated on one of his indy car engines. I don't think they were used for the pyrometers on the dyno since he said they were 3/16" in diameter. He also used venturis at certain points in the exhaust system as well that assisted the engine in making power. Although he didn't seem to find something that would last a while with what he experimented with for periods of operation. But whatever he did in this period where he used the holes & venturis, it worked for the most part from what he wrote. It apparently made the engine sound like it was going twice the speed it was actually operating at.

 

[faytmorgan]

I can't find anyone who makes a equal length shorty headers for a sbc. If you guys know of anything please do let me know. I've called, hugger, hedman, hooker, sanderson, schoenfield, jegs, and summit.

The only set I could find were for a sbf made by bbk.
http://www.summitracing.com/search/Brand/BBK-Performance/Product-Line/BBK-Equal-Length-Shorty-Headers/?autoview=SKU

 

[mender]

A shorty header is basically a tube version of the stock cast iron exhaust manifold; neither are "tuned" but the shorty will flow more air, is lighter than cast iron and will fit in tight spots.

I'm surprised anyone makes an equal length shorty.

 

[mender]

Highspeed, I was talking about some holes Smokey incorporated on one of his indy car engines. I don't think they were used for the pyrometers on the dyno since he said they were 3/16" in diameter. He also used venturis at certain points in the exhaust system as well that assisted the engine in making power. Although he didn't seem to find something that would last a while with what he experimented with for periods of operation. But whatever he did in this period where he used the holes & venturis, it worked for the most part from what he wrote. It apparently made the engine sound like it was going twice the speed it was actually operating at.

The intent was to introduce extra oxygen and light off any excess fuel at the venturi. He made the venturis out of aluminum and slide them in and out until they melted, then made steel ones and reinstalled them at the same place.

Not sure how well they worked but he never seemed to be short on interesting things to try.

 

[faytmorgan]

I want short headers. Trust me. I have been doing a ton of research and this is what I need.

I may try and see how close the ford ports are to the chev and make my own plate and just weld it on to that header for the 5.0 if I have to.

The shorter the header, the smaller the primaries, the closer to the sound I want. The equal length is for performance and tuning ease.

 

[Highspeed]

I never followed Smokey enough to recall much about his indy efforts. I'm familiar with the de-stroked SBC turbo, but not enough to converse about it. The holes I were referring to were on a NASCAR engine and just for temp probes. NASCAR apparently thought it was cheating and said he couldn't run them. I respect Smokey; he thought deeper on engine function than most, thus was a pioneer and controversial. If you look at modern engines from the 80's on up you'll see the effects of his cross-ram work...most people just don't know it. Very interesting guy, and responsible for a lot of the information we have about airflow!

Faytmorgan, the sbf headers will not work on a sbc. Sbc heads have assymmetrical exhaust ports, except for some high-end aftermarket ones. There are lots of sbc shorty headers, and the equal length is really not that important as using them at all has just thrown any tuning of the exhaust right out the window. If you're using motor plates instead of mid-block mounts, you should have all kinds of exhaust room. You could fab up a header pretty easily. The anti-reverberation designs are claimed to help power at specific points (small ranges) in the power band. I've never dealt with them, so I can't help you much there.

 

[faytmorgan]

I never followed Smokey enough to recall much about his indy efforts. I'm familiar with the de-stroked SBC turbo, but not enough to converse about it. The holes I were referring to were on a NASCAR engine and just for temp probes. NASCAR apparently thought it was cheating and said he couldn't run them. I respect Smokey; he thought deeper on engine function than most, thus was a pioneer and controversial. If you look at modern engines from the 80's on up you'll see the effects of his cross-ram work...most people just don't know it. Very interesting guy, and responsible for a lot of the information we have about airflow!

Faytmorgan, the sbf headers will not work on a sbc. Sbc heads have assymmetrical exhaust ports, except for some high-end aftermarket ones. There are lots of sbc shorty headers, and the equal length is really not that important as using them at all has just thrown any tuning of the exhaust right out the window. If you're using motor plates instead of mid-block mounts, you should have all kinds of exhaust room. You could fab up a header pretty easily. The anti-reverberation designs are claimed to help power at specific points (small ranges) in the power band. I've never dealt with them, so I can't help you much there.

I am aware that I would have to modify the port side (of the header of course) that goes to the head to make them work with a sbc. I would have to take mounting plates for a sbc and route Also equal length is very important from every bit of research I have done. There are those that don't say it matters until about 9 inches or so. From a tuners standpoint I disagree, I have found on the dyno that the equal length does matter as far as ease of tuning them.

I have "d ports" as for exhaust ports on my head, which is traditional chevy ports.

As for room, there isn't much, most people use the sanderson block hugger headers. I don't them at all. Nor do I like the owner of sanderson for many reasons. The biggest was that I had inquired about headers when I had called there and she blatantly hung up on me, I had called back and asked for another tech. the tech then told me that she was the owner. I don't know what her deal is but I will NEVER by sanderson for that very reason on its own. Also I personally (prior to this) have seen product issues from them from my customer's cars that I have worked on, as well as at Z meets where people have complained about them. She also defends openly on her idea that equal length does not matter when from all the experience I have had, as well as ed at headers by ed (he has been doing headers since 1962) have found. I tried to explain to her that, that is what I wanted, and that from experience any header that is not equal length within .5 of an inch of one another that they suck to tune and they are not a quality header because of this alone aside from build quality.

I could go on with this topic but it really doesn't matter at this point.

 

[Fahlin Racing]

Yeah, I never knew about the holes and NASCAR, funny stuff though. Faytmorgan, I would just figure out the primary size, lengths and collector size and just build some. Just remember your exhaust system begins right at the exhaust seat's top cut.

 

[mender]

She also defends openly on her idea that equal length does not matter when from all the experience I have had, as well as ed at headers by ed (he has been doing headers since 1962) have found. I tried to explain to her that, that is what I wanted, and that from experience any header that is not equal length within .5 of an inch of one another that they suck to tune and they are not a quality header because of this alone aside from build quality.

I could go on with this topic but it really doesn't matter at this point.

With uneven exhaust pulsing the need for equal length goes way down. For example, the driver's bank of a SBC is 270-180-90-180 and is why it has the "harley" sound. The pulses just aren't going to arrive at the right time, so spending a lot of time getting the tube lengths within 1/2 inch is essentially a waste of time; the engine won't know or care fore the most part and in quite a few cases the engine will like the unequal lengths better especially for the street.

I recently dynoed an LS engine that's going into a hot rod and compared the headers that I built to look good and fit in the space available with length being of minor concern against a set of equal length headers from one of the race cars; my headers made more hp and torque across the board and were no different to tune.

Not at all uncommon in my experience.

 

[faytmorgan]

So I found out that the headers (from bbk) yes, are indeed equal. Albeit they are 17.5 inches in length, the primaries that is. According to the length equation from "headers by ed" {(CID * 1900)/(rpm_max * tube_od2)} the recommended length is 34.2 inches.

This being said, what is going to change in using 17.5 inch primaries vs 34.2 inch primaries aside from a higher exhaust note?

 

[faytmorgan]

To fitment, pics of them in a mustang.

http://customerpics.americanmuscle.com/view/sku/56011.php?sort=1

http://www.allfordmustangs.com/forums/attachments/94-95-tech/25070d1173998544-1994-mustang-gt-ignition-module-p1010125.jpg

Pictures of a used set from a forum
http://www.hardcore50.com/vbulletin/showthread.php?t=51387

I would have to make a down pipe of some kind. I would be bringing them down to an x pipe to spintech sportsmans to exit out the side.

This exhaust vid sounds 100% perfect to me, albeit its on a mustang. This is the goal of the setup, in that it sounds as close to that aside using a 5.0 block.