Board index Flathead Power-Technical Questions, Answers, and Suggestions Indians cylinder modification

cylinder modification

Post Sat Apr 07, 2018 12:06 pm

Posts: 147
Location: USA
Curious as to why I don't see any Indian cylinders being modified like the 45 Wr's or the K type harley motors. From a distance it appears that the Indians valve configuration is paraell and does not have the valves angeled but it seems like it would still be a good idea to modify the top of the cylinder by machining a channel from the intake valve seat to the piston to get all the fuel into the combustion chamber as possible and an exit channel for the exhaust gas. Thanks for looking at this ,always wanted to build an Indian.

Post Sun Apr 08, 2018 12:17 pm

Posts: 1474
Location: Ojo Caliente,NM,USA
once early flathead developers discovered that the lowered squish area over half or more of the piston was necessary to prevent detonation caused by the wide flat combustion area allowing the reflected sonic waves to create standing waves and light the whole charge at once. They were stuck with the lowered squish area restricting cylinder filling. Indian's engineers came up with a piston that popped up into the combustion chamber allowing the squish area to be raised removing part of the restriction. It worked pretty darn good Indian racers were faster than Harley's racers years after Indian was closed. Branch's reliving and domed piston along with the angled valves eventually produced more power.
Image
But this method isn't readily adaptable to Indian cylinders because the valves are so close to the cylinders and the rings come so close to the top, about 3/16 if memory serves. Once the valve seat is cut any deeper that the one in the picture you get the dreaded cylinder killer crack. There is just nowhere to put the reliving.
Dusty

Post Sun Apr 08, 2018 1:41 pm

Posts: 147
Location: USA
Thanks DUSTY DAVE,well spoken,so it seems that Indian was the initiator of the pop up piston. Were the top of the Indian pistons curved or should I say hemispherical. It also makes me wonder if a pop up hemispherical piston without the channeled ports being cut into the top of the harley cylinder might provide the same horsepower making the channeled cylinder ports unnecessary.

Post Sun Apr 08, 2018 9:22 pm

Posts: 1474
Location: Ojo Caliente,NM,USA
The Indian pistons were flat topped. I have a 741 bored and stroked to 42 cid with GS850 pistons that are hemispherical it was a real bitch to cut the heads to match. It runs real good but the ports and valves are still small and I don't have any other 42 cid 741s around to compare it to . I met a tuner in Sand Springs Oklahoma that welded the top of Harley pistons up so they popped up like Indian pistons before Branch and O'Brien developed all the KR stuff.
Dusty
Image

Post Mon Apr 09, 2018 1:59 pm

Posts: 3564
Location: Central Illinois, USA
That's some radius cutter, Dusty!

Mine had to be made itty-bitty and calibrate-able.
And a convex radius, instead of concave.
(Sorry, no pic, since my 'intellectual property' has already been stolen by the likes of Tedd, but I'll email direct.)

My toolpost works, but the scrap rate, at half a thou or less tolerance, is tragic.

....Cotten
PS: My stroked 741 motor project would have been given away to VI Moen by now, but nobody can pick it up for him at Davenport.

Nobody wants its "Warpath" Betor/ Honda/ BSA chassis stuff. Its junk honest. Trust me.
I'll donate it to the Dumpster Godz I guess.

Post Mon Apr 09, 2018 4:55 pm

Posts: 61
Because you haven't been looking hard enough.
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Post Mon Apr 09, 2018 5:15 pm

Posts: 61
Race Engines with this type of modification, are still running (and probably winning races) today. I've seen photo's of these engines.
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Post Mon Apr 09, 2018 6:31 pm

Posts: 1474
Location: Ojo Caliente,NM,USA
It originally had a straight tool but the ridiculously long radius ( piston dome had a little over 6" diameter)caused chatter and dig in so I ended up bending the tool down and grinding it to almost be a scraper then moving the holder up until the tool was on center. Seems like I ended up with the compound on a 45, Don't know why every picture I take of that lathe makes everything look off center I've tried different angles and distances. If I move all the way across the room it all looks right but is too far away to see what I want to show.
My concave is even more Rube Goldberg
Dusty

Post Mon Apr 09, 2018 8:06 pm

Posts: 1474
Location: Ojo Caliente,NM,USA
Indian 45,
Iv'e seen pictures of a few done that way but that one was the only one that wasn't cracked! Wonder if it was ever run? It would also take a special built piston to keep the proper squish clearance on the popup and move the top ring down to make room for the reliving.
Dusty

Post Mon Apr 09, 2018 9:03 pm

Posts: 61
Dusty

There has recently been (last two or three years), if not still racing today, a very fast Big Base Scout motor running this set up in the US. He Obviously had success with the sinking of valve seats. It's tempting to try it, but it shortens valve seat life and cylinders (or money) don't grow on trees. I've seen photo's of this engine, and I know it's fast.

Post Mon Apr 09, 2018 9:28 pm

Posts: 1474
Location: Ojo Caliente,NM,USA
And you cant be sure they aren't cracked until you either magnaflux or heat them with a torch. Fleebay photos can fool you. I would be interested to know what pistons and squish clearance the one you know about is running. I've heard of just leaving the top ring off and I've heard it was a bad idea not enough being built anymore to even get good rumors.
Dusty

Post Mon Apr 09, 2018 10:20 pm

Posts: 61
If a cracked engine wins races every time, I wan't one.

Post Mon Apr 09, 2018 10:23 pm

Posts: 61
Dusty

The point I am trying to make is. Just because you have never heard of it working, doesn't mean it's not real. the flea bay photo's of junk motor's are the only ones I will show you. Message me if I'm not making myself clear.

Post Tue Apr 10, 2018 12:27 am

Posts: 1474
Location: Ojo Caliente,NM,USA
Cracked cylinders don't win they just burn the valve at the crack and sometimes break the piston.


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