220 GPU timming advice

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gat2013
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220 GPU timming advice

Post by gat2013 »

I cleaned the mag because it was not hitting on all 6. Well when i put it back together I put number 1 at top dead center and droped the mag back in, it fired up but seems to be of a little. Basicaly i did it like a car motor not thinking that I had to take in considerasion that the mag is a impulse an now it is firing when the piston is on the way down. So how many degrees does it need to be before top dead center. My question is how to put the motor back in time correctly like i said it is off you can tell by the way it starts a little hard but it will start up and run. Someone told me that you can count the flywheel and back it up by the theeth but I am not sure so I figured i would ask you guys that have ran this engine. Or can someone give me any site or link to get info on a 220 GPU just on the engine in general. Any help would be great thanks.

Glenn

Larry
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Post by Larry »

A standard single mag GPU is supposed to be timed at 30 deg. btc. When I time mags I have a degree wheel with a free floating pointer that attaches to the prop and then you set the deg. wheel with a piston stop that screws into a spark plug hole. Then you use a buzz box that attaches to the mag grounding lead and lets you know when the points close. You can use the flywheel teeth method if you know where tdc is and mark it on the flywheel. You then take the total number of teeth on the flywheel and divide by 360 and you know how many degrees of timing you have per tooth. Then just count 30 deg. of teeth from your tdc mark, but you still need a way to know when the points close, I would suggest useing an ohmmeter, you don't want to backfeed power into the mag. This should get you pretty close to what you need, sorry guys for the long post.

Larry

rjonesboy
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Post by rjonesboy »

Larry, How many degrees BTDC are you supposed to time a dual-mag GPU? Thanks, Jonesboy

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Airboatcapt2
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220 GPu

Post by Airboatcapt2 »

Hey Rjonesboy are you located in TX?
Are you bobs son?
If so, I tried to e-mail your dad but it didn't go through with the e-mail he gave me.
Thanks,
Faron
Faron Floyd
American Airboat Corp
Orange, Texas
www.americanairboats.com
409-920-0716 Cell
Airboatcapt2@aol.com

rjonesboy
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Post by rjonesboy »

Sorry Airboatcapt2, I'm from Punta Gorda, Fl, and Lakeport (Okeechobee) most weekends.

ricmey1
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Post by ricmey1 »

rjonesboy, time dual mags the same 30 degrees before tdc.

Larry
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Post by Larry »

With hi-comp. pistons I time my dads dual mag GPU at 27 deg. We tried 30 deg. first but there was a hint of detonation while driving, so I backed it down a bit. Engine runs a bit cooler and it doesn't detonate when hot. A stock low comp. dual mag GPU would be fine at 30 deg. timing.

Larry

gat2013
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Post by gat2013 »

The fly wheel on the motor is a chevy flywheel and starter but does it matter what kinda flywheel you have on it? Or just count the theeth and do it the way you said? Oh the motor has HI COMP pistons in it also so 30 degrees BTDC is still ok or should I try a different degree first?

Larry
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Post by Larry »

If you have a single mag engine I would leave it at 30 even with the hi-comp pistons, you need the exta timing to get the flame front all the way across the piston. Counting the teeth method works with any flywheel setup, We run lycoming flywheels on them that already have timing marks in them so that makes it real easy.

Larry

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