Tom Sifton

[c.o.]

I've been kicking around the idea of putting a 45 flat tracker together at some point. It's all a pipe dream now but I've been doing a little reading on hopping these little flatties up. Tom Sifton comes up consistently when it comes to performance. Have any of you folks ever seen the inner workings of an engine that he put together?

[Steve Slocombe]

Dear Cory, my understanding is that Tom Sifton started his flathead tuning in the 1930s, and the 1935 VLDD and 1936 VLH show relieving around the valve seats which must be at least inspired by him. On these 80 cubic inch bikes the inlet manifold was also enlarged a little, and a 1 1/8" venturi fitted to the carburetor rather than the stock 1 1/16" one. The 35VLDD was also advertised with special inlet cams as a $9 option, which must be the hook cams used for racing - no more lift but lots of duration. In a letter to dealers of 19 August 1935, J Kilbert also announced the VLDD had a special muffler with 2" tube, R-7 Hot Shot spark plugs, con rod bearings specially fitted for high speed service, motor specially assembled and road tested, and high compression cylinder heads of latest improved design. For 1935 only, Harley released 7.3 and 8.6 cubic inch heads, as well as the stock 9.3, 10.5 and 12.5 types. Aluminium heads were also tested, but never went into production as the 1930-35 seven bolt Big Twin heads were superseded by the nine bolt heads in 1936. It looks like the August letter worked, as the few surviving 35VLDD bikes have high engine numbers.

[Steve Slocombe]

Dear Cory, the same 19 August 1935 Harley letter also describes the 35RLDR small twin. This had 'larger intake ports, larger special manifold with 1 1/4" carburetor, intake ports, manifold and cylinder heads polished, and motor specially assembled by one of our expert motor men and block tested'. It was recommended for 'the seasoned rider who wants a sport job with dynamite for TT racing and other Class C competition', and reported that 'RLDR type motors cleaned up the first three places in the 200-mile race at Oakland'. So we see a confident company coming out of the 1932/3 worst years of the Depression, plus hand built special motors from the factory already compromising the spirit of run-what-ya-brung Class C racing.

From memory we then see new cylinders for the WLDD in 1939, again for the WLD and WR in 1940 with canted-in valves, then aluminium heads, flat tappets, roller bearing cams, and so into the KR years. Tom Sifton seemed to concentrate on gas flow (rather than increased compression ratio), hotter cams and bigger carbs, and that's what I'd do starting with a stock flathead today.

[D.Mac]

I've been kicking around the idea of putting a 45 flat tracker together at some point. It's all a pipe dream now but I've been doing a little reading on hopping these little flatties up. Tom Sifton comes up consistently when it comes to performance. Have any of you folks ever seen the inner workings of an engine that he put together?

Cory, In the late '60's a buddy of mine was putting together a 45, and we had the privilege of pawing through Tom Sifton's personal stash and buying some very cool parts from him. The thing that impressed me the most, was looking at the cam chests of several motors he had built. Everything that rotated was drilled and lightened, everything ran on bearings-no bushings, and the cams were radical. His workmanship was impecable. His cam designs and cylinder work blew the competition out of the tub. I have a book on hopping-up Ford flatheads, that has a page showing an HD drawing for relieving cylinders. I believe HD was using Tom Sifton's proven designs for thier recomendations.
Doug.

[redfred84]

Cory,
Our late, great Guru, Francis, "Cliff", Clifford won the Reno time trials with a speed of over 106mph on his 101 Scout. I forget it this was before the war, or after. But upon winning the meet, with a record speed at the time (Reno is at high altitude), Tom Sifton approached our local hero, and offered him a seat on one his bikes. "Why would I wanna do that? I just waxed you guys!" was his reply!
Cliff was a gem.
RF.

[Rooster]

There was a Tom Sifton-built racer at Dixon this past summer; it was either a 45 or a K-model, but danged if I can remember which! Do you recall that one, Red Fred? I know the owner and talked to him at length about the bike. I just went thru my pics, and that must be the only bike I didn't get a photo of...! :~(

[rwm]

tom sifton built a 2 cam jd racer.he used a single cam model and converted it to a 2 cam. i think the bike is on the west coast now. i would love to look inside the cam cover to see how it worked. legend has it that the bike was laps ahead.

[redfred84]

Nah, I didn't even know there was one of his racers there. The meets get pretty busy, especially our local one. Guess I missed it.
Drat.
RF.

[c.o.]

Tom Sifton seemed to concentrate on gas flow (rather than increased compression ratio), hotter cams and bigger carbs, and that's what I'd do starting with a stock flathead today.

Steve! Thanks for all the info!

I've discovered that Tom figured out a way to get around the uneven heating of the sidevalves by using rotating valve lifters. He also did some machining on the cylinder to enlarge the combustion chamber which in effect allowed the engine to rev higher. There were also modifications to the oiling system that forced the rider to hold it wide open all the way around the track so as to avert fouling the plugs!!! Great stuff!!!

[c.o.]

Cory, In the late '60's a buddy of mine was putting together a 45, and we had the privilege of pawing through Tom Sifton's personal stash and buying some very cool parts from him. The thing that impressed me the most, was looking at the cam chests of several motors he had built. Everything that rotated was drilled and lightened, everything ran on bearings-no bushings, and the cams were radical. His workmanship was impecable. His cam designs and cylinder work blew the competition out of the tub. I have a book on hopping-up Ford flatheads, that has a page showing an HD drawing for relieving cylinders. I believe HD was using Tom Sifton's proven designs for thier recomendations.
Doug.

Now that's a good story Doug! Thanks for taking the time to share it. I've read that Tom was reluctant to share his improvements with H-D at first but finally gave in. It's very cool that you got to meet the man and lay your eyes on his work.

[c.o.]

Cory,
Our late, great Guru, Francis, "Cliff", Clifford won the Reno time trials with a speed of over 106mph on his 101 Scout. I forget it this was before the war, or after. But upon winning the meet, with a record speed at the time (Reno is at high altitude), Tom Sifton approached our local hero, and offered him a seat on one his bikes. "Why would I wanna do that? I just waxed you guys!" was his reply!
Cliff was a gem.
RF.

Now Red Fred, we all know that Tom had to improve on H-D's design cuz Indian was cleaning up on the tracks....... That's the first time I've heard about Cliff's story. It shows the rivalry was there now don't it? Ed Kretz was also a thorn in the side of the folks in Milwaukee. It looks like it was a good thing that Tom Sifton decided to question factory technology or who knows how long it would have taken them to beat the bikes out of Springfield.... I had tossed around the idea of putting together a Sport Scout but the thought of making a "slow" H-D 45go fast is intriguing. There are a few flattracks within a couple hundred mile radius of me and it would be cool to hop a flathead and see if I could run with the more modern Brit and ***anese machines.....

[c.o.]

Rob being this is a JDH I guess it's not the bike you were referring to but cool nonetheless.



Rooster, it seems to me that Sifton made leaps and bounds with the K-Model.

[Tommo]

My guess would be either a FD or a FDCA of 1921 or 1922 vintage
F = magneto ignition
D = 74 cu in (1200cc) with 3 speed transmission
and
CA = alloy pistons
1921 or 22 because the forks don't have the rebound springs introduced in 1923 and unless some of Siftons magic that we can't see has been perfomed on it, it's definately not a "H" which signifys a Two Cam Motor

[fabercycle]

Cory,

" There are a few flattracks within a couple hundred mile radius of me and it would be cool to hop a flathead and see if I could run with the more modern Brit and ***anese machines"


Cory, Do you have flattrack racing experience? Because "with all due respect"....if you don't, you won't be hanging with anything.
Racing a fast bike is only half the equation.

[rwm]

this may be the bike.
http://www.pacificariptide.com/pacif...ydavidson.html