Cam timeing on a 29 Indian Four

[partshunt]

Has anyone out there ever checked cam timeing on a 29 Indian 4 useing a degree wheel? The only data in degrees I have is for a 38-42 Four. Does anyone have this data for a 29 or will the 38 data apply the same? I realize its a different cam so there must be some kinda difference. Any input or advice would be helpfull...Joe

[harleytoprock]

Hi Joe, Did you ever figure out cam timing for your 29 Four? I ask as I'm been wondering also if the the 38 timing spec is the same as early. I'm sure you know about timing the cam with the "E" stamped on flywheel centered in the hole, #4 exhaust valve should just close. The procdure seems crude. Who knows if the "E" was stamped in the correct place. Another method is to center intake opening and exhaust closing around TDC with TDC being in the center. This method only works with symetrical timed cams.

[partshunt]

Hi, thanks for your response. The engine is assembled and back in the frame. Just preping the manifold to install. As for timeing, I dont have an "E' on my wheels. I have an "X, C And an "S' mark. I timed it as before acording to the riders manual same as I did five years ago but this time I used a degree wheel and the readings came very close to the 38 specs. I also timed the spark retard to the "S" mark as per the books and measered at full advace and I got 5/8" BTC as per specs. Its timed with #4 Exh just closed (tappet free) with "X" mark lined up and degree wheel made sense. As for the timeing marks on the gears, they match other samples inividually but in my timed engine, the cam marks are two teeth advanced. I believe if the riders book sez time it with #4 Exh closed, they must not have faith in the marks on the gears otherwise they would have called for you to time by those marks. They know your gonna have the timeing cover off anyway to pull the cam gear to time it....In general, my degree reading comes very close to the 1938 specs as well as generally most any 4 cycles engine readings....your thoughts if I missed anything...Joe

[harleytoprock]

Joe, your right, its an "X". I think the "E", I was thinking of, is on Hens. Do you recall how many degrees ATDC you got with the "X" mark lined up? The 5/8" BTDC for full advance ignition timing sounds right. I think its odd that your gear timing marks match other gears samples yet are off by two teeth. I'm not saying your out of time but just question why the gear marks have no value. If you aligned the gear marks would that advance or retard the cam position from where it is now?

[partshunt]

Here are my readings:-

Stock 1938 specs. followed by my readings.

Int opens 12 Deg. BTC mine is 12 Deg
Int closes 42 Deg ABC " " " 42 Deg
Exh opens 60 Deg. B Bot Centre. Mine...65 Deg.
Exh closes 8 Deg, ATC but mine is 25 Deg. ATC causing a longer intake flow thru.

The only thing I dont like is the late exh closeing but its normal for other 4 cycle engines in general. It will be in my older cam grind and an older probably possibly worn some camshaft. Whatever you change, will change everything else. as for the crank position on the "X" mark, I need to check my pics taken when timeing was set & checked. Will try to submit them in this forum if I can do it...Joe

[harleytoprock]

Hello Joe, According to the 1935 riders manual, "X" is 1 3/4" from "C" and "S" is 1 3/4" on the other side of "C". I confirmed these measurements on my flywheel which has a circumference of 31.250". Using a little math, I figure "X" is 20.19 degrees ATDC and "S" is 20.19 degrees BTDC. Were your "X" and "S" marks at 20.19 degrees before and after using your degree wheel? So if my calculations are correct the ignition timing is 20.19 degrees BTDC which is a bit conservative with modern fuels available. I would think that ignition timing could be safely advanced to 30 degrees at full advance and get a little more power. The 1938-42 overhaul manual states that the ignition timing is @ 45 degrees BTDC?? Sounds way advanced. On to cam timing. So Indian wanted the exhaust valve to close at 20.19 degrees ATDC with these early fours that have flywheel timing marks. Therfore you are very close on your cam timing. The manual also shows that a offset key could be made to make timing a bit more precise if needed. The 1938 cam specs are probably different because of larger ports and valves. Generaly speaking, if a cam is advanced the power range will be at lower rpm and if retarded the power will be at higher rpm. The advance or retard latitude being about 4 to 6 degrees from stock. Perhaps "4thcoast" could jump in and shed some light or any other 4 cylinder master.

[partshunt]

Thanks for your info and calculations mathwise. I didnt record degree readings from the marks but rather crank position and, timeing retarded as per riders manuals. When on the "S" mark and timeing set in retarded position, I advanced the mag and took piston position rotating untlil the points in the mag broke open, This position was .650" with the dial indicator angled slightly due to the head being cast in and acces was thru the intake pocket, manifold off. Very close to 5/8" . Also, the "C" mark is not dead centre as the cylinders on a 29 era engine are offset 1/4" and not directly above the crank centerline. Someone added lines adjacent to the original factory letter X C and S on my wheels and I verified that mark being actually truly TDC. All input is very welcome, maybe we can learn more about these engines but simply lineing up timeing marks does not always mean correct. If I lined up the marks on the cam to crank gear, then the exhaust valve closes close to TDC, too far off for my likeing. This engine burnt a hole thru #4 piston and just makeing sure everything is by the book...Joe.