Technical > Matt Shaff's Engine Shop

Coupling 2 engines

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denverflatheader:
Hi Matt, my name’s Alan.  Got a question, a few have asked me and I really don’t know the answer.  I started a twin engine dragster build in 2011, powered by V8 flatheads.  The engine coupler design and fabrication was done by Landers Engineering in 2012.  They also splined crankshaft snout for coupler.  For my question, assume both engines built identical and dyno 250hp-300 ft. lbs. torque.
     
For back engine connected to transmission, that’s 250hp?  For front engine, connected via coupler, does that add another 250hp?  Would total be 500hp and 600 torque?  Will it hurt either engine’s internals or balance if they do not output identical hp and torque?  Do you have suggestions on clocking both engine crankshafts, like cylinder 1-1 together or……?

Here’s close up picture of coupler and at car show under construction.  Thanks for help and forum.  DF

Frontenginedragsters:
Denver:
 Can't say as I have ever been involved with "twins".
Keith [Roo-Man] can jump in here and help with this one.
The car is short and motors in the rear so it looks like not much flex in between the engines like a front engine car.
Horsepower wise it makes sense that you will get double. 8)
Lots of top gas cars from the sixties did well with "twins".
Good luck: Matt

denverflatheader:
Matt – Yes, 1.50” top/bottom rails, a little bit stiff…....  but not dead  : )    The est. hp is 2.5 times higher than stock engine output.  Key ingredient is camshaft and ignition for fh (one internal component, one external).  One friend told me his gas dragster went 171 on blown gas, he never forgets his mph, but couldn’t remember et as well, somewhere in the mid 8s.  What's important different for each of us.  Thanks Matt, will see if Roo comments. DF

janjon:
Clocking. That's a very interesting question. I wonder if there would be any noticeable difference in the effect of two cylinders firing together, such that the rearmost output sees their power combined at the same time, versus staggered so that the same flange sees twice as many evenly spaced single hits??? And could there be any bad effects as far as rapid and repeated loading and unloading at the coupling in the case of staggered firing??? Such that the splines might either stay loaded in the first case, or force reversals make them beat themselves up in the other??? And was the coupling timing designed and installed with any of that in mind???

denverflatheader:
janjon - coupler design allows almost infinite settings to clock the two engines.  I’m thinking of starting with both engines on #1 tdc.  I was thinking if the two engines don’t like where they’re clocked, maybe it’ll show up in the main bearings, and also in the ets….   DF

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