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What creates the loud rumble of 1960s muscle cars?

I don’t think Harley does it ‘intentionally’, they’ve always been this way, a consequence of the 45 degree cylinders combined with the ‘knife and fork’ connecting rods on the single throw crankshaft.

Ducati also has a single throw crank, with connecting rods side by side, but with cylinders at 90 degrees it results in a more even sound.

Originally they did not, but I recall reading that when they pulled Harley out of bankruptcy they considered changing the crank and decidied against it for reasons of its clearly identifiable characteristics. I recognize too that this setup enables a narrower engine with a big bore.

hondas sound like a bee hieve my 85 gti had a lower sound more bass but nothing like a late 60’s muscle car with a nice set of duels on it.

The truth behind Harley was that when they were considering changing their engine design to make it more competitive in racing, they were told in no uncertain terms by their very loyal and vocal customers that their sales would drop to zilch. They had a hard time just updating to the D engine design but that was eventually accepted.

Harley moved out of Milwaukee a couple of years ago and a lot of their customers swore they would never buy another Harley. Supposedly 12,000 used Harleys went on the market the day they announced the move. I never did hear the outcome of that decision but Harleys seem to be still selling well.

I don’t think they moved. They did have a large number of layoffs and closed some factories when the economic slump hit.

@EllyEllis:

Truth be told, it’s hard to evenly space the firing pulses of a 4-stroke twin unless you make it horizontally opposed.

We’ve mentioned the 45° v-twin; an inline twin can either: (1) oppose pistons 180°…which mass-balances, but a “fire-fire-pause-pause” firing pattern, or (2) not oppose pistons…giving no mass balance, but balanced firing. (or even something in-between, where neither is truly balanced.)

“We’ve mentioned the 45° v-twin; an inline twin can either: (1) oppose pistons 180°…which mass-balances, but a “fire-fire-pause-pause” firing pattern, or (2) not oppose pistons…giving no mass balance, but balanced firing. (or even something in-between, where neither is truly balanced.)”

Most British twins were/are the latter, with 360 degree cranks, while Japanese (Honda) twins were the former, with 180 degree cranks. Triumph has gone a step further, their latest Tiger scrambler took the twin from the Bonneville and replaced the 360 crank with a 270 crank to give it a unique sound.

Most British twins were/are the latter, with 360 degree cranks, while Japanese (Honda) twins were the former, with 180 degree cranks.
Let's not forget Honda's 52° v-twin, with its offset crank pin, and all the other variations of the v-twin.

Wouldn’t a parallel twin have an evenly-spaced firing pulse?

A parallel twin with a 360 crank (Brit bikes) would have an even firing pulse, but not with a 180 crank (Honda, etc.).

Yeah, but at the expense of unbalanced pistons…kinda a “double thumper.”

Having ridden both, 360-crank twins idle a lot easier…also allow the use of simpler “wasted spark” ignition.

Valve overlap, high duration cams, headers, glasspacks, etc. all contribute to the tone, but it’s the crank that makes the big difference.

If that was true then a 305 would sound not much different than a 502. Displacement and cam profile make a huge difference in rumble tone and volume.

Put an RV cam in a 454 and then take an identical motor with a radical cam. Even a deaf person could tell the difference. It changes the lope and volume significantly.

Displacement, cam profiles, and other factors will change the sound of the engine, but the loping idle and rumble of the american V-8 is still there. Radical cams will give the idle more of a “lope” because they are not ideal for low engine speeds. If you put a flat-plane crankshaft in a 454 the sound would completely lose that american V-8 signature.

This was a strange set up years ago. With 2 pistons running out of sync by a few degrees while sharing the same combustion chamber. They were quite powerful and smooth.

http://home.sprynet.com/~inniss/sears.htm

Dang it, I hate to to admit it-but I love that American V-8 sound the small block Fords with headers sure sound sweet( the configuration was kinda like a mini"Rat"
-Kevin

I have a 1965 Sting Ray 396-425. I love the way is sounds.

FCBIII

Not to take this in a direction off the map, but there have been concerns raised about electric or hybrid cars being too quiet so they surprise pedestrians. Didn’t I read someplace some years ago that someone was experimenting with a sound system to be able to choose how you wanted your car to sound. Just like a big boom box but you could pick the sound you wanted like a 57 Ford V8. Might sell, might not. Imagine a Prius with Ford V8 pipes though? Maybe the driver’s noses would even go higher in the air then. Kind of like balloons or baseball cards in you bike spokes.

I walk along a country road for my exercise and there are a couple of Prius owners that go by. My hearings not so good anymore but these have not surprised me yet. Tires still make a lot of noise, in fact most of the noise made by any vehicle is tire noise.

FCBIII, I do agree with you. That Corvette does sound good; real good. I was expecting to see the rear tires going up in smoke though… :slight_smile:

Many years ago I had a '59 Corvette with the 283 in it. It had dual exhausts that exited through the rear bumper and while not loud, it had a bit of a growl to it.
On a beautiful warm evening with the top removed I could drive that car around all night long just listening to the exhaust note on it.

The problem is at intersections when there is no tire noise. Letting drivers choose their own sounds would be fun but a bit confusing for the blind. Dibs on Good Humor truck.