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> Cooling fan ?, Anyone know the degrees per blade?
ottox914
post Feb 17 2006, 09:41 PM
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Messing around with some updates to the 914, no problem finding TDC, but my other timing marks are hard to find. As a means to double check my work, anyone know how many degrees per fan blade? Yes, I've tried Mr Search to no avail.
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Dave_Darling
post Feb 17 2006, 10:15 PM
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Check the photos in the "914 timing" article on the Pelican site. You can see where the marks are in relation to the fan blades. There's also a template you can print out...

--DD
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ottox914
post Feb 18 2006, 07:37 AM
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Good answer dave, but not exactally what I was looking for. I was probably a little vague, so I'll try to ask again with more info-

I'm installing an aftermarket efi system, (I'll post details once it runs) and don't need to know where the stock timing marks are. I know where TDC is, but need to set a base timing different than a factory referened mark on the fan. As I know where TDC is, how many degrees are referenced per fan blade, so I can approximate where and what my timing is being set at, since I don't need/can't use the factory timing marks?
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Mark Henry
post Feb 18 2006, 09:01 AM
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What system are you running? I take it you have some sort of programmable ignition?

On my SDS I made a mark at 10 degrees BTDC that you saw through the timing hole in the fan shroud. You then started the engine and at idle you set the baseline crank-fire timing with a strobe. After that you use the program to set your timing.

Guessing at fan blades is a poor method for setting the baseline.
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swl
post Feb 18 2006, 09:27 AM
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The template on the pelican site is great tool. You can use it to do a much better job estimating degrees than blades would. That said, the diagram on pg65 of the haynes manual is pretty accurate I think shows 4.5 blades in 27degrees.
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Jake Raby
post Feb 18 2006, 10:36 AM
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Pop out the number one spark plug and the corressponding valve cover.. Rotate the engine clockwise until the intake valve on #1 opens fully and then closes fully.

Then use a drinking straw in the spark plug hole to feel the piston as it travels up the bore to TDC. When you have found the point where the piston is highest and dwells there for a second that is TDC, remove the timing plug and using a nling, sharp chisel or screw driver stamp a mark.

You are done and within a degree of where TDC really is if you do the job accurately.

BTW, there are 4 different 914 fans- you can't use the blade method due to this unless you are a half asser!
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Mueller
post Feb 18 2006, 10:47 AM
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QUOTE (ottox914 @ Feb 18 2006, 06:37 AM)
Good answer dave, but not exactally what I was looking for. I was probably a little vague, so I'll try to ask again with more info-

I'm installing an aftermarket efi system, (I'll post details once it runs) and don't need to know where the stock timing marks are. I know where TDC is, but need to set a base timing different than a factory referened mark on the fan. As I know where TDC is, how many degrees are referenced per fan blade, so I can approximate where and what my timing is being set at, since I don't need/can't use the factory timing marks?

actually, Daves answer was spot on (IMG:http://www.914world.com/bbs2/html/emoticons/smile.gif)

what you "you" need to do is print out the template (make sure it's 1:1) lay it on the fan and measure how many degrees from one blade to another with the template...measure the diameter of the fan and just do the math...Dave Hunt also posted a link to a downloadable degree wheel that'll help with the setup as well....
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McMark
post Feb 18 2006, 11:42 AM
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How about an adjustable timing light? Then you only need to know TDC. (IMG:http://www.914world.com/bbs2/html/emoticons/confused24.gif)
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spare time toys
post Feb 18 2006, 11:47 AM
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Cant you count the number of blades and devide 360 by that number to get how many degrees of rotation it would take to move 1 fan blade? Like if you have 10 blades it would take 36Deg. of rotation to move one blade.
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Cap'n Krusty
post Feb 18 2006, 12:02 PM
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Measure the circumference of the fan, divide by 360. That'll give you the exact length of each degree. Based on the number of degrees you need, measure the distance and mark it. How hard can that be? The Cap'n
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davep
post Feb 18 2006, 06:22 PM
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QUOTE (spare time toys @ Feb 18 2006, 09:47 AM)
Cant you count the number of blades and devide 360 by that number to get how many degrees of rotation it would take to move 1 fan blade? Like if you have 10 blades it would take 36Deg. of rotation to move one blade.

No, there are posts and there are blades. I don't think there is an equivalence between posts and blades that is useful.
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alpha434
post Feb 18 2006, 06:53 PM
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. 8.875
(diameter)/2=4.4375(radius) - 2in (sector)/2 = 1 - 1/4.4375 = inv SIN
13.02 deg. X 2 = 26.04 deg.
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alpha434
post Feb 18 2006, 06:54 PM
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That's measured along the circumference. Just use a tape measure and you'll be close.

(IMG:http://www.914world.com/bbs2/html/emoticons/cool.gif)

2 inches= 26deg
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