Hot Rod Maytag Engine

[Mike Brown]

I have been pioneering my LSA powered belly tank at mile events for a decade.  I will continue with it as long as it makes sense.  While on a trip to Shipshewana Indiana I acquired a 1939 Maytag model 72 washing machine engine.  I was able to restore it to operating condition.  In the process I had two left over cylinder/head assemblies that were unusable due to scoring from the wrist pins because someone left out the Welch(dome) plug retainers.  I could not find oversized pistons for this engine.  I decided to build a hot rod version for potential mile land speed use in a small motorcycle/moped.  This is the beginning of the project. 

[Mike Brown]

This is a photo of my working model 72 Maytag engine.  Twin cylinder horizontally opposed two stroke with shared crankcase.  1-1/2" bore, 1-1/2" stroke.  Crankshaft induction.  Maximum designed rpm 1,650.  Rated horsepower 5/8.  I would really like to get 5-6 horsepower after modifications. 

[Mike Brown]

I machined a fixture for my lathe and machined the head off of the cylinder/head assembly.  The original engine uses a deflector on the piston head for scavenging.  The factory compression calculated to about 5:1. I will need a lot more compression to increase horsepower.  It also makes boring the cylinder for 40mm (1.575") chainsaw pistons much easier. 

[Mike Brown]

I will use 1/4-20 studs to hold the new high compression head to the cylinder then to the block.  Peak cylinder pressure is estimated at 80 bar or 1,160 psi.  Based upon the surface area of a 40mm piston there should be about 2,320 pounds of force lifting the head.  Calculations based upon grade 8 bolts they should have 2,640 pounds of clamping force each.  More than sufficient to keep this engine together. 

[Mike Brown]

I machined a pair of aluminum blocks for the new heads.  When the new pistons arrive I will determine the size and shape of the combustion chamber which will allow me determine the actual thickness that the head needs to be.  A mock up of the head with some all threaded rod to verify the stud clearance that was machined into the sides of the exhaust flange. 

[Stainless1]

Hotrod Maytag.... now there's a couple of words you rarely think of together.... 

[aircap]

Maytag engines are a blast from the past. My great grandmother washed her laundry with a Maytag powered washing machine. I saw her start it up when I was a little bitty shaver. She used it in a laundry house next to the chicken coop, and in the wintertime the laundry smelled like exhaust.

[WOODY@DDLLC]

When I were a pup, my brothers and I grafted a Maytag with a lawnmower carburetor on a 20" bike and smoked all the neighborhood Whizzers! I think that was the start of this whole affliction!

[Mike Brown]

This Maytag was built in March of 1939 and was restored to operation.  It is happiest at 1,450rpm.  It is not a "hit & miss" engine but has a centrifugal governor inside the crankshaft.  The induction is via ports in the crankshaft like remote control airplane engine.   

[tallguy]

Very nice!  Good luck with this project! 

How fast do you expect to go?  I used to get around on something similar to a Vespa scooter:  a 1960
Lambretta that purportedly had about 6 hp . . . good for about 45 mph.

[Mike Brown]

If I could go 45mph that would be a start. 

[Mike Brown]

I was searching for 40mm pistons that would work in this application.  I purchased a couple, the Stihl 021 piston was too short and the other too tall.  I decided that I would have to machine my own.  I have enough material to give it a go.  The material is 6061, not the best for pistons but OK.  I suspect that I will need to have it hard anodized or ceramic coated on the top. 

[Mike Brown]

I did plot the port timing.  I was surprised at the crankshaft induction timing being almost 180 degrees.  All of the ports are very small but when your maximum rpm is 1,650 that would be expected. 

[floydjer]

There is  nothing....Nothing...Better than having machine tools and an open mind...Bravo Sir,..Bravo.. Jerry. ( Index 745 and South Bend 13X60...And every hand tool known to man)

[Mike Brown]

I have a piston from a John Force top fuel funny car.  It has splendid design features to copy for this Hot Rod Maytag application.  In the center photo notice that the wrist pin bosses are not machined away but full length from the bottom of the piston crown to the bottom of the piston.  This design will be easier for me to machine.  There is also relief on the outside in the wrist pin area.  I will not have a cam ground piston to allow for uneven expansion so this will be my choice for relief.  A couple of other observations not applicable to my application.  Notice that the ring pack is located down from the top of the piston.  This somewhat limits maximum compression but keeps the flame front away from the rings.  Lowering the ring pack puts the oil rings well into the wrist pin openings.  The things they have to do to keep 11,000+ horsepower motors together for 4 seconds are nothing short of amazing.