The Jalopy Journal
Discussion in 'The Hokey Ass Message Board' started by 31Vicky with a hemi, Aug 6, 2012.
Very interesting subject I think.
as others have mentioned good compression along with a good cam grind
A 600 series Ford was much more likely an FE 361 engine.Short exhaust on old V-8 gas trucks echoing under the truck.GM trucks with duals on a 366 or 427 always did.
Fender well headers pointing down tend to shake the earth.
Its been said on here, compression, camshaft,
Awhile back. we built a car with a new crate engine, using a Thumper
Cam, sounded pretty good.
Doing a old gasser with a 11.5 to 1 small block Chev with same camshaft. It will get your attention, Biggest drawback is converter, and enough octane fuel. But gassers all have three pedals, right?
OK - compression & camshaft and or advanced .
So how how much compression, cam specs, how far advanced ?
Something must be backwards, 'cause the ground keeps shakin' my car whenever I get on the highway
5 star thread!!
I still think there has to be some physics involving the transfer of energy into the ground.
I wonder if a particular recipe produces low frequency sound waves (below human hearing) strong enough to shake the ground.
Excluding the drag strip for now....
Some of these cars that do the most ground shaking aren't the loudest of the bunch or the most radical. I don't notice any buzz from the car rattling like you do with those crazy steroid stereo bombs. I'll have to pay better attention to the exhaust to day for sure but I do believe they have full behind the tire tail pipes.
Cars that can shake the ground can usually burn rubber from a sixty mile an hour roll.
It hurts. They rumble everthing because of the liquid dynamite that get forced through them. 2 Fuel cars are louder than a field of Circle track cars
It called infrasound . Here's a link and a clip from it.
Man-made structures, such as engines, cars, buses, trains, motorcycles, and airplanes also produce infrasound. John Cody also noted that pilots exposed to infrasonic vibrations of jet chassis experience a reduction in "vision, speech, intelligence, orientation, equilibrium, ability to accurately discern situations, and make reasonable decisions."
Infrasonic vibrations, though harmful, can be pleasantly stimulating in mild levels. The effects of brief, mild exposure can give a feeling of invigoration for hours. While a person may FEEL invigorated and euphoric, his body is being subjected to an elevated heart rate, elevated blood pressure, a release of endorphins, and the "fight or flight" adrenaline response. Feeling the effects of high-intensity/low-frequency sound can actually become an addiction, partially due to the release of endorphins in the body.
It was mentioned earlier. Compression, cam and timing.
I ran a big block ,4 speed Challenger that was quick for its day, roughly 11.20 ,maybe a little better, that could shake the ground.
Mom hated it when I was in the drive tuning for the weekend because all of her dish's and knick knacks were jumping on the shelves. Dad would just grin.
An old neighbor of mine had a 440 that'd shake the ground. The first time he brought it home my first thought on hearing/feeling it was a train passing through, except we're not close to the tracks. It had turn downs to go with a big old racer brown cam and high compression.
Agree with the possibility of smaller cubic inch engines may have more of a ground pounding exhaust note. Not trying to get OT but have noticed that most smaller displacement engines sounding better with HD motorcycles. Modified Sportsters always seem to have a much better sound than the modified "Big Twins" IMO
Yep , a high stepping 883 sounds a lot better than my 103. My 95 sounds better than my 103 too now that I think about it. But that 103 will put a whooping on both of them.
Compression/cylinder pressure are key to the depth of shake into everything from the ground you stand on to the bones in your body!! I've built many engines over the years, and compression motors are by far the most thundering. I've built everything from naturally asirated, turbo, supercharged, nitros engines, and compression/cylider pressure is what makes them thunder. There really is not much of a correlation with the thunder/pounding and output because depending on how the package is designed the results WILL vary.
One of my most recent ground pounders is a 393 ci sbf that really thunders bigtime, but it has a static compression ratio of 14.2-1. This is in a street driven, 1970 bronco that is the fastest naturally aspirated rig racing at the sand drags, racing uphill in the dunes, and holds it's own on the street amongst most street driven cars. It's biggest problem is short wheelbase, squirelly ride. With the lunati cam that is in it it does run on pump fuel with only 4 degrees of timing retardation, but add 116 octane race fuel and that thing really comes to life. Everyone that hears that bronco fire up and run cannot believe it is a small block, but it is, It breathed through 1 7/8" stepped to 2" primary tubes into a 4" collector and the exhaust is 3 1/2" flowmasters with total exhaust length 66" from head flange to exhaust tip.
Blew By You
One of the best sounding engines I ever heard was in a local unlimited-class mud-bogger. I could feel that thing resonating in my chest! Gotta be a big-block, I thought. Asked the owner. Really surprised me when he said........289 Ford.
I've always attributed it to compression. I remember that most of the hot engines decades ago had a much better sound than I usually hear today. But 11:1 - 12:1 compression wasn't at all unheard of back then. A late model with only open exhaust always seems to have that "fake" sound you mentioned.
There's a lot of physics going on in the sound of an engine. Anything you are able to perceive as noise is actually a pressure differential in the atmosphere. The only thing that's going to give that thump feeling in your feet and chest is a significant pressure differential.
You say that some cars are "quieter" but have more "thump." That's because the frequency of their soundwaves is low enough that you have trouble registering the high volume by ear, but you can feel it in your body.
There are a lot of things you can do to produce those low frequency tones, most of which have already been mentioned. Turn down the idle speed; reduce ignition timing; increase compression; run a cam with more overall duration and a wider LSA; run larger diameter pipes; use chambered mufflers; run a short exhaust system with turndowns after the mufflers.
All of these things are common on street-type small block nitrous cars. Listen for them at the track, they are the ones that seem to thump the most, at least in my experience.
Not to change the subject but while we are on the what makes it happen.
What makes a blown fuel injected engine have that awesome erratic idle?
Blower surge. From The Blower Shop's FAQ page,
This is exaggerated with injected cars that run mechanical fuel pumps since fuel volume is dictated by pump RPM.
Gotgas, I agree with you. I think it has to do with frequency that causes the feeling. I won't bore you all or try to act like I know everything, but look into Nikola Tesla and the resonant frequency of the earth. Here is a link that explains it well. http://www.excludedmiddle.com/earthquake.htm
Hmmm. I had a blown mechanical injected BBC in a car I build several years ago and was dissapointed that I could not get the car to do that. I was told I was not running enough boost (10psi). I fiqured it would not do it because the blower was not tight.
it's one thing experiencing this from a v8, it's another feeling it from 2 cylinders. get up close to a fuel bike in the pits at the all harley drags.
My wifes old cuda did that, but it was a 13:1 472 had single chamber flowmasters and 3" exhaust. It was a bad MOFO! It shook the ground and would just about kick the earth off its center of gravity when you could get the thing hooked up and get all of its power to the ground....Jim
a guy here in town owns a renault ft17 WW1 tank (except I think it is the american version, an exact copy of the french one), 4 cylinder 35 horsepower, I can't remember what he said the cubic inches were , but imagine 1 gallon paint cans attached to 2 foot 2x4's...I think it is something like 4 gal. to the mile.... anyway only 35 hp, max speed 5mph, and that thing literally shakes the earth!
also remember a dual quad 409 doing about the same...
That explains why some of the supercharged big block "cigarette" boats on the big lake here idle like a sea serpent breathing.
Although it sounds cool to some, a properly tuned blown engine will not surge when warm and ready to make a pass down the 1/4 mile. When your barrel valve/idle fuel setting is correct, the surge will go away as the engine reaches operating temp.
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