What is that exhaust sound ?
Printed From: Unofficial Allis
Category: Allis Chalmers
Forum Name: Farm Equipment
Forum Description: everything about Allis-Chalmers farm equipment
URL: https://www.allischalmers.com/forum/forum_posts.asp?TID=33464
Printed Date: 05 Apr 2026 at 1:44pm
Software Version: Web Wiz Forums 11.10 - http://www.webwizforums.com
Topic: What is that exhaust sound ?
Posted By: Larry Miller
Subject: What is that exhaust sound ?
Date Posted: 07 Jul 2011 at 9:23am
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I have several tractors - some do this more than others. It is the sound the exhaust makes when you throttle down from high rpms. But I hear it when at low rpms and idle. It is not a miss like a bad plug or wire and it is random - not like one cylinder does it every time around. Don't hear it at all under load or higher rpms. Just wondering, Larry Miller ------------- I used to be young and stupid, now I am not young anymore. |
Replies:
Posted By: Boogerowen
Date Posted: 07 Jul 2011 at 11:04am
| Imagination !!!!! |
Posted By: John (C-IL)
Date Posted: 07 Jul 2011 at 2:05pm
| At low RPM the fuel system isn't operating very efficiently, it could be either a lean or rich mixture. It could also be the valves passing some compression. I've heard it too, you get to thinking there is something wrong with the engine when all it really needs is a few more RPM. |
Posted By: Lonn
Date Posted: 07 Jul 2011 at 3:02pm
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Turn the radio up! ------------- -- --- .... .- -- -- .- -.. / .-- .- ... / .- / -- ..- .-. -.. . .-. .. -. --. / -.-. .... .. .-.. -.. / .-. .- .--. .. ... - Wink I am a Russian Bot |
Posted By: steigerbro24
Date Posted: 07 Jul 2011 at 6:52pm
| My model b makes soft popping sounds. it could be the straight pipe on it or just some thing but I don't worry about it too much. |
Posted By: Alvin NE WI
Date Posted: 07 Jul 2011 at 6:59pm
| wife says I make a popping sound much too ofter when I slow down. |
Posted By: q4016lanz
Date Posted: 07 Jul 2011 at 7:05pm
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May be a burnt out valve by the sound of it ------------- 15 allis chalmers tractors 9 lanz bulldog tractors 2 water cooled deutz 9 john deeres tractors 14 Aus made orange chamberlains I spent most of my money on old tractors I wasted the rest |
Posted By: ACD19farmboy
Date Posted: 08 Jul 2011 at 7:14pm
| Our C does that when its not under load or just idling!! it is allways making a tinging sound when the flapper/rain cap gits banged back and forth!! lol |
Posted By: DaveKamp
Date Posted: 09 Jul 2011 at 4:22pm
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That is music you'll never hear anywhere else. People are getting so used to hearing modern port-fuel-injected, high compression, electronic ignition with computer managed fuel mapping, ignition advance and knock control... One of the things that I've always been observant of, is the sound of every type and model of engine I hear. Some of it has to do with a sick love of machines, and the physics and principles of operation, but the rest is probably the result of being a part-time musician with an endless love for unique sounds. If you listen to a Model A Ford, you'll hear it's sound, which PARTLY is characteristic of the long, skinny exhaust, slow speed, but also it's flathead, low compression, mechanical points, firing order and chamber shape. Bore and stroke affect the timbre of sound, but rate of exhaust ejection and intake draught are also integral to the sound. The very first memory of my dad 'working' on a car, was when he was installing a freshly rebuilt engine into the chassis of a '29 Ford Tudor... I stood alongside while he and a neighbor lined up the mounting surfaces and started the bolts, and I watched while the electric starter groaned it over for the first time since rebuild. It sounded nothing like the 455 in the big Buick wagon, and nothing like the neighbor guy's VW Bus. I blueprinted and 'built' a 250 Chevy inline six several decades later, and it's nothing like the Model A, or the big Buick, or the wheezy-whistle of the flat four. Here's some things to think about when you hear it... The Model A, and the Fordson, and the early Waukesha and Continental fours, you'll see they're all flatheads, low compression, short-duration camshafts, very conservative timing, small carb throat, and skinny exhaust. The short-duration camshaft and skinny intake passage means high intake velocity at low RPM. Good, 'cause these engines didn't run fast. The A has a 'hissing' sound to the intake, because the Zenith carb's venturi is very restrictive, and running at a right angle... with a choke plate really close to the venturi... oh, and no air filter to 'quell' that noise. Henry didn't believe in air filters, or oil filters, or hydraulic brakes... or... Okay, so compare automotive engines of the mid-late '30's with say... the WC engine... Start with overhead valves... adjustable rocker arms... long, long stroke, moderate duration on the cam... centrifugal advance and air filter... full pressurized lubrication, in comparison, the WC engine was a musclebound heavy-breather... of course, it had to be! When a Fordor rolled down the road heading to church, that 40hp mill was actually only being asked of oh... 10hp or so in order to make 40mph... splash lubricating all the way. The WC motor... when it was put to a field, it was gonna be asked of everything... everyday... all the time. And the farmer wanted it to use fuel at a 'sipping' rate. Okay, so about the sound... take an engine that's made to really work... hard... constant speed, mildly varying load... make it work hard and run on as little fuel as you can... lousy fuel perhaps... so you've got long stroke, a moderate duration cam, overhead valves, low compression, in a hemispherical chamber (upside down, of course!), put it at working speed and make it do it's thing... tune it to the leanest-reasonable point (where power stays high, but fuel use is low). Now, take an 'economizing' type carb, put it on there, and make it idle... slow... way slow... so it can calmly creep up to an unsuspecting implement, snag it, lift it up, and send it out to a field, where you'll throttle up, and drag that poor plow through dirt for eight-ten-twelve hours. At idle, the engine will be pulling immense vacuum... and there'll be JUST ENOUGH FUEL for it to run. On the Economizer, the fuel air ratio will be LEAN, particularly when you're drawing it into a BIG chamber. Ultra-lean mixtures don't like to light. HONDA experimented with solutions to this with their CVCC design (three-barrel carbeurators, extra valves, and all kinds of really cool ideas-in-progress)... you get cylinders that simply don't fire... too lean... it'd make the CVCC STALL if it wasn't set quite right. But the Allis... big flywheel, long stroke... piston speeds changed LOTS more than the CVCC motor... didn't spin as fast, but long stroke, big flywheel, if it didn't fire, it'd just push that mix out the exhaust. Into the hot exhaust... by the way... And as soon as a little oxygen made it to that really hot mix... "foomp" <clink> ... ... ... "foomp" <clink> :-) Real engines clink after they foomp. |
Posted By: Brian Jasper co. Ia
Date Posted: 09 Jul 2011 at 4:56pm
------------- "Any man who thinks he can be happy and prosperous by letting the government take care of him better take a closer look at the American Indian." Henry Ford |
DaveKamp wrote:Posted By: Brian Jasper co. Ia
Date Posted: 09 Jul 2011 at 5:02pm
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Ford was always bad about having a maze of vacuum lines, however it did allow them to meet emissions with out computers for 2 years after GM made the switch full line. Vacuum lines are going to bite them in the future on the 6.7 diesel in my opinion. Instead of using electronic actuators, they have a vacuum pump and lines to move the wastegate along with a few other things. ------------- "Any man who thinks he can be happy and prosperous by letting the government take care of him better take a closer look at the American Indian." Henry Ford |
Posted By: Dick L
Date Posted: 09 Jul 2011 at 6:25pm
| Right or wrong it is my understanding that all exhaust tubes in the manifold would need to be the same length out to where they are connected to the main exhaust pipe not have that stutter in the exhaust sound. Any lost HP from the standard manifolds would be at a minimum in most engines compared to the cost and space it would take to do away with the stutter. Least that is the way I understand it. |
Posted By: Jacob (WI,ND)
Date Posted: 09 Jul 2011 at 9:09pm
I'm with you Dave, I love to just listen to engines run/idle. Hit and miss engines come to mind, I could watch and listen to them for hours and not get tired of it. I guess that makes us sick huh? :) Pa-POP.... ca-click, ca-click.... Pa- POP! ------------- Jacob Swanson 1920 6-12; 1925,1926 20-35 longfenders; 1925,1926 15-25's; 1927,1929 20-35 shortfenders; C; B's; IB; WC's; WD; WD45 |
Posted By: DaveKamp
Date Posted: 10 Jul 2011 at 1:43am
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Hee hee... You're right about manifold length, Dick, but one thing that Allis did, that very few others... they used a different firing order, to make sure that the runner-length alternated long/short/long/short, rather than most others' long-short-short-long. They avoided firing adjacent cylinders, which many other engineers of the time avoided, citing the likelyhood of crankshaft twisting moments resulting in a broken crank. Apparently it wasn't that serious of an issue, 'cause the pullers go nuts with stroke, bore, and compression, and I don't hear long horror-stories about 'em grenading... I would NOT, however, be the least surprised to hear of a Ford N blasting a crank from such things... save the fact that they're simply not strong enough to even break themselves... :-) Zora Arkus-Duntov got a whole lot of recognition to firing-order alterations with his performance work on the small-block Chevy (particularly, the Corvette motors)... but Allis did that same thing some three decades earlier... In many respects, Allis WAS really ahead of their time. |
Posted By: beeman
Date Posted: 10 Jul 2011 at 4:21pm
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Guys, don't you love the way other gearheads listen to engines the way you do? 4 cylinder OHV gas burner Allis motors have a music of their own for me. When their governers are starting to "sense " being loaded and begin opening up......music!!! And throttling back coming down a grade.,letting the compression hold down the speed...still more music!! ------------- 1949 B 3930 Ford- Have owned other Orange ,green,red,yellow,dark green tractors and equipment. |