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What about flat (180 degree) cranks in flatheads?

Discussion in 'The Hokey Ass Message Board' started by Magnus B, Feb 21, 2006.

  1. streetart
    Joined: Mar 1, 2006
    Posts: 22


    The rolling bones ran a crossfire in Bonneville this past summer , 300hp alchol fuel injection (Hilborn). Kong heads ... Snyder cam , flatheadjack crank and all the rest peformance pieces .... 296 cubic inches of balanced hell , A rod bolt broke on the 3rd past ,,, We packed it up and left early ...They do run , but bring your checkbook when you need it fixed .
  2. As I recall, the very earliest Cadillac V8s were flat crank) machining limitations at the time), and they would vibrate like crazy at certain rpms. The 90º crank solved that, and all production V8s have been 90º since then (AFAIK).
  3. rmeiners
    Joined: Jun 24, 2006
    Posts: 3

    from Michigan

    Wish I's been there to hear it run.
  4. Magnus B
    Joined: Jun 19, 2005
    Posts: 886

    Magnus B


    Dragging this old tread back up. I have not forgotten this thing. FAct is I think about it alot. Everytime I see a larger 4-cylinder crank I try to measure it to see if it might fit a flathead block. I saw a comment about a Farmall H crank might be close. But I don't have access to any over here. I guess it's among tractors and industrial engines one should look for a crank. Does anyone have access to older 4-cylinder engines and could take some measurements? Right now I'd like to know the dimensions the Farmall H crank of course.

  5. Mnhotrodbuilder
    Joined: Jul 12, 2010
    Posts: 1,142

    from Afton, MN

    I'm glad you brought this back up. I never get tired of listening about 180 degree, flat plane or single plane cranks. I have read they can have extra vibration if they are not balanced well and kept to a short stroke. This was because multiple cylinders are firing on the same side at the same time. Some old racers have said on different forums they are not worth the cost since they provide little to no extra horsepower. However, if you are like me, just doing something different and interesting makes all the trouble worth it or if you are going for a different sound like in a vintage sports car.
  6. hoop98
    Joined: Jan 23, 2013
    Posts: 1,362

    from Texas

    I have a research article from Coventry-Climax on their research with the 180 vs 90 cranks in their 60's F1 engines. As noted here the obvious application was the exhaust.

    Flathead Bank Firing Intervals


    With the flat crank you have 180 degrees separation on each cylinder in the bank.

    A 90 degree crank can get the exhaust tuning by crossing 2 cylinders from each bank to the other side. So called 180 degree headers.
  7. Magnus B
    Joined: Jun 19, 2005
    Posts: 886

    Magnus B

    As I see it it should have the same vibration as a 4-cylinder only worse since will have more rotational mass. But it does have the same unbalance problem as the straight 4. Keeping the stroke short and moving components light will help.

    In the case of a flathead a single plane crank is all about have each banks middle cylinders fire as far apart as possible. With the stock crank one they are very close. If I remember correct I think they are only 180 degrees apart. That means that with, for example, a 270 degree cam duration boh exhaust valves are open at the same time for 90 degrees. That can't be good.

    If a single plane crank will make more power or not, I don't know. I don't think so in the case of an engine with separate ports for each cylinder. But for a flathead??? I sure want to try.

    But right now I'm trying to find a crank I can modify. I know Flathead Jack have one. BUt for experimenting I don't really want to spendthat kind of money.

  8. Terry Buffum
    Joined: Mar 20, 2008
    Posts: 297

    Terry Buffum
    from Oregon

    Harry Duncan (Duncan Built Homes) sponsored several racers in the early 1950s in SoCal. One ran a Navy Blue chopped T coupe with 180 degree crank, Ardun heads at Santa Ana. I don't remember how it ran, but it blew up in spectacular fashion right in front of where my brother and I were standing at the fence!
  9. hoop98
    Joined: Jan 23, 2013
    Posts: 1,362

    from Texas

    A 180 firing order would be like thus;


    The siamesed ports would be separated so you could still get some scavenging...

    Attached Files:

  10. R Pope
    Joined: Jan 23, 2006
    Posts: 3,309

    R Pope

    All the early V8's had 180 degree cranks, including aircraft engines like the Hispano-Suiza and German Benzes. They were not real smooth runners, that's why the 90 degree cranks were developed.
  11. Rusty O'Toole
    Joined: Sep 17, 2006
    Posts: 9,613

    Rusty O'Toole

    All V8s had 180 degree cranks up until 1923. Same as a 4 cylinder. There were more than 20 makes of cars with V8 engines made in the US between 1915 and 1923, all with 180 degree cranks.

    They had a 4 cylinder type secondary vibration at twice crankshaft speed and they also had difficulty getting even mixture distribution and smooth idle unless they used a 2 barrel carb.

    Each bank ran like a 4 cylinder. By having each piston and rod matched by another at 90 degrees they had a better balance than a 4 cylinder.

    Last production engine with a 180 crank was the 1930 -31 Viking made by Oldsmobile. It also had the first 1 piece crankcase and cylinder block a year before Ford. It had an ingenious vibration dampener to give it smoothness, I think they used the flat crank for cost reasons.

    W O Bentley asked Henry Leland why he made a V8 when he could have got the same power and performance from a big 4 cylinder?

    Leland replied, you are a man after my own heart. But you are overlooking the fact that I can sell an 8 cylinder car where I wouldn't be able to sell a 4.
  12. 777
    Joined: Jul 17, 2008
    Posts: 196

    from Pasadena

    Probably seen this before but mine The Sandy's Muffler Shop (Sandy Belond) roadster has a 180 degree crank in it, and a few other things.
    <iframe width="420" height="315" src="//" frameborder="0" allowfullscreen></iframe>

    Have no idea what people are talking about regarding rough idle and other nonsense.
    Exhaust note is sightly different but probably not enough to balance out the cost involved.
    BTW you'll need a roller cam, there are no flat tappets with the correct firing order.
    As mentioned before the exhaust pulse timing was the original reason for this modification in the Norden days.
    It makes more hp because it can turn more rpms because there is less rotating mass which also frees up hp.
    In real lay man terms think of it this way:
    Torque equals- clean powerful slow burning combustion strokes which takes time. think low rpm like a diesel
    Hp equals- many combustion strokes that aren't burning quite as efficiently (clean) but there are many more of them. think higher rpm small displacement.
    Basically quality vs quantity, pick your poison depending on your application
    and what is available to you gearing wise.

    I can't recall exactly how much lighter the 180 crank is but its a ton, which affords you the ability to do things like lighter pistons and rods because the bob weights can be smaller which in turn cuts down on aero drag in the sump
    and less stress on the main saddles. {I used Ti rods, casidiam pins and 2 ring slipper piston.} And if we were building real race cars, smaller counterweights would mean a shallower pan which means a lower cg because the crank can be brought closer to the racing surface. Hence the use in road racing, ovals, sprints etc.
    The Belond roadster has no main girdle and turns 7200 rpm. I also added a very light clutch assembly under 10 lbs. that's flywheel, clutch disc, floaters and pressure plate. Basically a 5-inch multi-disc carbon/ carbon button clutch out of an early 90's F1 car with a custom flywheel ring for the starter.
    For me I didn't care for the 3 main design and was looking for away around a girdle because I wanted to use the 33 pan he had used. So I wanted the least amount of mass I could get spinning around down there. Less spinning mass equals less stress on the block.

    All said it probably isn't worth the cost but I love driving things I can leave my foot in and I've beat this engine hard and it has given me flawless performance and everyone that has either been in it with me, driven it or raced against it has been floored by how well it runs and how powerful it is compared to other aspirated flatheads. BTW it will run right with street blown flathead, however I'd probably get my butt kicked by a proper blown engine.
    Last edited: Nov 27, 2013
  13. Magnus B
    Joined: Jun 19, 2005
    Posts: 886

    Magnus B

    Thanks you for posting. I had seen the Youtube clip, but was not aware of the fact it has a single plane crankshaft. I value your input, since you have tried it. I feel that my beliefs are confirmed. Better breathing, not that much more vibration and of course less rotational mass is a huge benefit.

    Since my last post I have found a company willing to make me a crank for way less then what I have seen available from another sorce. Well worth trying at least. Now I need to make a CAD drawing of it and send them. Also I need to decide on stroke of course. I like short stroke engines so I'm thinking I should stay with 3-3/4" stroke. But on the other hand why not go to longer stroke while I have the chance? I will stick with a 3 main crank. I don't want to mess with a girdle until the concept has proven itself.


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