crashinmike

Hello,
I am going to buy a pair of Nelson engines shortly. I am trying to decide whether or not to go with the ABC or AAC setup. I am told the ABC is more forgiving on the needle, but the AAC is not only lighter but lasts longer. I would sure appreciate the input from guys who fly AMA 428 on a regular basis.
I was also told I should set the engine at 192 and a spacing of .012" Sure would appreciate INFORMED input.

Crashin Mike

daven

My Feedback: (1)

My suggestion is to go with the AAC.

The weight difference is substantial (1 oz), and the piston/sleeve will last a long time if you do not injest sand or dirt through it.

I have not had any problems needling a AAC Quickee engine. As to head spacing, it kinda depends on your local, and standard weather.

My preference is about 190, with a head spacing of 14.

This seems to work well in hot humid weather tuning a big prop (9 pitch).

I would like to hear where others run them, but I am afraid most will not post their spacing.

Bozarth

My Feedback: (15)

I bought a new Nelson from Performance earlier in the year and if I remember correctly, only the AAC is now offered. I maybe wrong.

R.Bridge

But the AAC ! As far as timing and head clearance, Dave Norman is right. It kind of depends on the type of weather you live in? And almost as important it depends on your experience level.

I would say that if your new at? I would run about 192 (liner timing) and about 14 to 16.. When your needling it on the ground it will be less likely to get too hot. When you learn that running the motor about 600-800 rpm down from peak when you launch the plane... Then drop the head to 12...

I've been running 192 / 10 ....... That's what I ran at the Nats this last year.. Also, I always end up lowering the head when I get to the humid spots in the country... just following what the glow plug is telling me....

enjoy and remember, the better you take care of your motor the longer it will last.... lean is not good, too much prop is not good!!


RB

Jerry Knols

My Feedback: (1)

Hello.
I am seeing numbers here as far as 192 and a spacing of 10-12-14 etx. Would someone mind in detail explain the correct way to measure the numbers. I understand where the numbers come from, but how do you know when the piston is at top dead center and the sleeve has not lifted. My Nelson is so tight, it is darn near impossible to turn it over, let alone find TDC.
When I called Performance Specialties they said I should not be playing with the sleeve, and they were very short about it.


Thanks ,
Jerry

Bill Vargas

My Feedback: (5)

JK, click on the following link to Darrol website for a short LO-down about setting Liner Height using a Dial indicator for this particular maintenance proceedure/setup

http://www.darrolcady.com/Propellers...linertool.html

BV

Ed Smith

I have seen people banging their engines on a table top and even beating the head with a mallet just to try and force the piston to TDC in the liner. Would you believe on a new engine!!!

This is the no pain, no damage to the engine method. Remember where you heard it. All you need is a depth micrometer. no dial indicators or other gadgets.

Remove the head. Put the piston at BOTTOM dead centre. measure the depth from the top of the liner to the top of the
piston. On a Nelson it will be somewhere close to 0.897. From this figure take away 0.706 (The stroke) you now have your deck height. Shim the liner to get what you want. When you have established the DH measure the step in the head. Take this figure away from the DH figure and you now have your head clearance. Shim accordingly.

Ed S

MikeyD

Here is another idea, if your lucky enough to have ED at your race, and can find him at the motel, you can bribe him with a few drops of RUM to rebuild your motor.

TC
Mikey D

Jerry Knols

My Feedback: (1)

Hi Ed,
Thank you, boy is that simple, I have a good depth gage so this method will be a piece of cake. Why in the word don't they send something like this with the engine.
Just one more dumb question. I have been told to always do you numbers with out the shims and measure the shims separate. Then just do the match. Is that because it is too hard to compress them when you are taking the measurements.


My hat is off to you ED, You put it in nice simple terms, us beginners can understand.

Jerry Knols

Ed Smith

Ialways do it without the shims. I know then that there are no bent shims, springy shims or burred shims under the micrometer.

Ed S

crashinmike

Hello,
Well I have to tell you guys, this has been the most useful thing I have read on this pylon site. Whay can't there be more like this > Ed, Dave,BV etc thank you for taking the time to actually put up this info here.
Since this worked so well, I am going to try to start a new one.

Crashin Mike

Jerry Knols

My Feedback: (1)

Hi Ed,
Well I have my Nelson in front of me and I took the measurement as you suggested and it says the liner is sitting at 190 without any shims under it. Does that sound right?

Jerry

daven

My Feedback: (1)

190 with no shims sounds about right to me. There all a little different, but thats right in the ballpark.

Ed Smith

That is the correct figure for a 428 engine (0.190). Although I have never had a Nelson with no shim under the liner. To make sure,give the liner a tap with a wood block to ensure it is seated down. If the measurement is the same then OK. The thinnest liner shim I have seen is 0.003. In fact there seems to be only three sizes of shim, 0.003, 0.005, 0.008. So, although there is some variation it seems to be consistant.

Ed S