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Author Topic: Can I tell if a Tower 40 has been retimed without taking it apart?  (Read 2767 times)

Offline Tim Wescott

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Can I tell if a Tower 40 has been retimed without taking it apart?
« on: March 19, 2013, 12:07:41 PM »
Subject line says it:  I've got a Tower 40 that I was given, and I'd like to know if it's been retimed or otherwise modded.  I'd rather not take it apart to measure things, if I can avoid it.

It'll run a nice solid 4-stroke, or a wet 2 blipping down into 4, for a whole flight without change.  Launch RPM is 8500 - 8750 on an 11-4.5 prop.

I'm wondering what I can expect from an engine that I know to be bone stock, and one that I know to be retimed.

Thanks.
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Offline RandySmith

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Re: Can I tell if a Tower 40 has been retimed without taking it apart?
« Reply #1 on: March 19, 2013, 12:35:27 PM »
Quote from: Tim Wescott on March 19, 2013, 12:07:41 PM
Subject line says it:  I've got a Tower 40 that I was given, and I'd like to know if it's been retimed or otherwise modded.  I'd rather not take it apart to measure things, if I can avoid it.

It'll run a nice solid 4-stroke, or a wet 2 blipping down into 4, for a whole flight without change.  Launch RPM is 8500 - 8750 on an 11-4.5 prop.

I'm wondering what I can expect from an engine that I know to be bone stock, and one that I know to be retimed.

Thanks.

Yes  , look closely into the exhaust port. at the intake ports, these are the ones in front and back of the sleeve, you should see if the ports have been ground on
if they used a dremel toll it will be easy to spot, if the used a mill, you may have to look closer, Most of the time if you can see brass color on the inside edge of the ports , it has been retimed, or re-angled , which is differant !

Randy
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Offline Mark Scarborough

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Re: Can I tell if a Tower 40 has been retimed without taking it apart?
« Reply #2 on: March 19, 2013, 01:22:10 PM »
One of the known mods for the FP 40 (tower 40 is pretty much a clone) is to cut the intake port directly across from the exhaust, the way I was shown was to cut what looks like two humps 50 thou tall into the top of the sleeve opening,, might look at that,, another reported option is to block the boost port
I am not recomending, nor condoning these mods, just things I have seen

Tim are you saying that your plane is flying at that rpm? that seems about a 1000 rpm slow for that pitch prop, I would have expected to see more along the lines of 9600 and that should be a rich two stroke,, from my experience with FP 40s,, but Randy Smith is MUCH more knowledgable than I,,
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Offline Jim Thomerson

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Re: Can I tell if a Tower 40 has been retimed without taking it apart?
« Reply #3 on: March 19, 2013, 01:24:24 PM »
I've flown stock Tower 40 and Tower 40 with blocked boost port on the same airplane and could see no difference in how they ran. 
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Offline Tim Wescott

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Re: Can I tell if a Tower 40 has been retimed without taking it apart?
« Reply #4 on: March 19, 2013, 01:30:30 PM »
Quote from: Mark Scarborough on March 19, 2013, 01:22:10 PM
Tim are you saying that your plane is flying at that rpm? that seems about a 1000 rpm slow for that pitch prop, I would have expected to see more along the lines of 9600 and that should be a rich two stroke,, from my experience with FP 40s,, but Randy Smith is MUCH more knowledgable than I,,

Those are the speeds indicated by my tach when I launch.  How much the engine is speeding up in the air, or if the tach is inaccurate, I don't know (the lights in my shop spin at 3600 RPM, though, so I think the tach is right on the money).

The airplane is leaning out a bit in the air as it reaches flying speed, so it is almost certainly turning faster after launch.  I can't really gauge how much, though.
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Offline Chris Wilson

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Re: Can I tell if a Tower 40 has been retimed without taking it apart?
« Reply #5 on: March 19, 2013, 03:13:53 PM »
Quote from: Tim Wescott on March 19, 2013, 01:30:30 PM
I can't really gauge how much, though.

Yeah you can, I believe that there is an audio application available for Iphones that will tell you exactly the rpm in flight.
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Offline RandySmith

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Re: Can I tell if a Tower 40 has been retimed without taking it apart?
« Reply #6 on: March 19, 2013, 03:23:40 PM »
"I'm wondering what I can expect from an engine that I know to be bone stock, and one that I know to be retimed."


  NO one answer,Anything from wonderful to horrible...depending on who did it and what they did, coupled with what you want and expect.

Randy
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Offline Tim Wescott

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Re: Can I tell if a Tower 40 has been retimed without taking it apart?
« Reply #7 on: March 19, 2013, 03:28:30 PM »
Quote from: Chris Wilson on March 19, 2013, 03:13:53 PM
Yeah you can, I believe that there is an audio application available for Iphones that will tell you exactly the rpm in flight.
Well I can't with the equipment that I happen to have.
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Offline Steve Helmick

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Re: Can I tell if a Tower 40 has been retimed without taking it apart?
« Reply #8 on: March 19, 2013, 10:56:52 PM »
Quote from: Tim Wescott on March 19, 2013, 12:07:41 PM
Subject line says it:  I've got a Tower 40 that I was given, and I'd like to know if it's been retimed or otherwise modded.  I'd rather not take it apart to measure things, if I can avoid it.

It'll run a nice solid 4-stroke, or a wet 2 blipping down into 4, for a whole flight without change.  Launch RPM is 8500 - 8750 on an 11-4.5 prop.

I'm wondering what I can expect from an engine that I know to be bone stock, and one that I know to be retimed.

Thanks.

Why not axe the guy that gave it to you? I'm pretty sure I launched his new eProfile today at Scobee field. If I remember right, he tried blocking the boost port and then unblocked it (JB Weld responds well to heatgun removal), head gaskets, and that's all. I know for a fact he tried the same on that XLS .36, and put it back stock.  H^^ Steve

 


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Offline Tim Wescott

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Re: Can I tell if a Tower 40 has been retimed without taking it apart?
« Reply #9 on: March 19, 2013, 11:43:23 PM »
Quote from: Steve Helmick on March 19, 2013, 10:56:52 PM
Why not axe the guy that gave it to you?

I did.  Then I waited.  Then I asked here.

Then he responded via PM (thanks Mike).  It may have an extra head gasket, maybe not.
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The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Offline Gene O'Keefe

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Re: Can I tell if a Tower 40 has been retimed without taking it apart?
« Reply #10 on: March 21, 2013, 12:44:59 PM »
  "Why not axe the guy "  ----- ebonics ?      LL~ LL~
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Offline Mark Scarborough

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Re: Can I tell if a Tower 40 has been retimed without taking it apart?
« Reply #11 on: March 21, 2013, 12:48:26 PM »
Tim, if you got this from Mike, are you running it with the same prop, same fuel, and same rpm as he did,, its a good starting point,,
fuel mix is FAR more important than a lot of people recognize
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Offline Steve Helmick

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Re: Can I tell if a Tower 40 has been retimed without taking it apart?
« Reply #12 on: March 25, 2013, 07:46:25 PM »
Quote from: Gene O'Keefe on March 21, 2013, 12:44:59 PM
 "Why not axe the guy "  ----- ebonics ?      LL~ LL~

Wuz jus' wunderin' if anybody on hear new how to spel!

Gene, you're renewing my faith. Texting is going to bring the art of spelling into the 16th Century.  :'(  Steve
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"The United States has become a place where professional athletes and entertainers are mistaken for people of importance." - Robert Heinlein

In 1944 18-20 year old's stormed beaches, and parachuted behind enemy lines to almost certain death.  In 2015 18-20 year old's need safe zones so people don't hurt their feelings.

Offline Mark Scarborough

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Re: Can I tell if a Tower 40 has been retimed without taking it apart?
« Reply #13 on: March 25, 2013, 07:48:34 PM »
Quote from: Steve Helmick on March 25, 2013, 07:46:25 PM
Wuz jus' wunderin' if anybody on hear new how to spel!

Gene, you're renewing my faith. Texting is going to bring the art of spelling into the 16th Century.  :'(  Steve

yo, don no what u be talkin bout there dude
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