I have an older nelson that runs very well but never really gets up to where I think it should be... From what I've seen others turn with the same prop I figure I'm at least 800 rpm off what I should get on the ground. I have adjusted the sleeve and head from high to low and have seen very little if any change in rpm. I guess my question is what should I see when dropping the head or sleeve and conversly what should I see when raising them. I do know that I need to get some more shims because my selection is limited but I saw no change from .194" @ .013" to .190" @ .010".... Is the thing in need of some parts or what?

I would like to get some test flights in this weekend and would like to have the engine at least close. I give up enough time with my thumbs I can't afford giving it up on the engine too....[]

Any help would be appreciated.

Thanks.

Lee,

What prop/props are you trying to run? And, what rpm are you peaking those props.....

Randy

So far I have been testing with a 8.8x8.75, thought this would be a good standard to test with. Since the start of my testing I have not even been able to crack the 19k mark except at full lean so I figure about 18.5k to give some room to unload. So I figured there must be something wrong concidering I've seen engines that turn this prop about 1000 rpm better(19.4 -19.6k) and still have room to unload. I don't know, maybe the thing is just tired.... It's my first year in 428 so I'll probably just run it until it won't run anymore but it would be nice to at least be in the ball park.

Lee,

Are you removing the flashing from the edges of your props? I have a series of "Speed Secrets" Articles that will soon be posted here and on the NCPL website. One of the articles devotes a lot of time to preparing a prop for racing. Getting a prop ready for racing is a little different than for sport flying. I've seen a good 200-300 rpm gain from a properly prepared prop to an old crusty, dinged up prop.

I would really like to take a look at your engine before you write it off. A new top end (pison and sleeve) may be all it needs. Considering where you got the engine, it may not even be broken in at this point. Jerry doesn't normally "let em spin" on breakin, so it may need a few tanks on the ground at about 24,000 rpm. At this point, I'd try and get the sleeve at about .191 and the head at about 12-14 until you get it worked out. If you leave it at .010 on the head, you could burn it out before you get it working. A higher head spacing won't hurt you much, and will be a lot more forgiving as you learn to set the needle on these things.

I ran two older engines on Saturday with that same prop and one peaked at about 19,200 and the other at 19,500. They will soon be going up for sale in the marketplace.

The older style piston liners ran a little bit higher on the timing, the majic set-up we used to run was 195 and 10
If its old and tired, you might try 193 and 8 or 195 and 8, the higher compression can sometimes get back a little rpm from the motor.
The position of the ports was raised by 5000 to keep from having to place so many shims under it, so the old 195 and 10 is now 190 and 10, so the old set-up you have it at would be 185 and 10 with the new pistons and liners, that is usually for bigger props and more torque... To get more rpm on the smaller prop IE 8.8x8.75, try the 195 and 10 or 8...

PS... Ground rpm is not everything... I have seen motors that do not do that well on the ground, but go like stink in the air,
This last Winterfest, I set my own personal fast time of 1:08 with a motor that only turned the 8.8x9.25 at 18,700rpm, but went like stink in the air... My other motor with a higher timing turned it 19,500rpm, but was slower in the air, slower by testing it on the same plane and taking an average of lap times...

Static Rpm does not mean its slow in the air, these ground rpm's can be decieving, in my opinion, its very hard on a motor to run it lean on the ground searching for a high rpm number... You can do damage and hurt the piston liner while trying to make it show a good number on the tach, I turned off my tach this last race and just went with lap times, glad I did, I do not like to see low numbers either, when I had low numbers on my number 1 engine, I turned off my tach and never tached it again the whole weekend...

That all being said, the motor could have too many runs or lean runs on it and may need a new top end, that will surely bring it back to life!!! Break it in carefully and do not step on it hard until after at least 10-15 runs, some like 20 runs...

Hope that helps,
JZW

Thanks for all the info...

I never let the engine get past where it wouldn't pinch up a little because I was worried about leaning it too much. I will admit that when I raced with this engine the last race in October it was no slouch by any means but I still think that there is something a miss, I just need more. Dave, I will bring it out on Sunday and let everyone look it over real good.... I don't have the right shim to get it to 191 so right now it's back up at .194 and the head is still at 10. Come to think of it, I don't think I have the shim to get the head to 12 either... I guess it's time to call Performance Specialties and get an assortment of them.

Diggs, If you are talking about the nelson that I sold you....that engine has 1 run for 45 seconds on it that I ran,,,asside from whatever dave put on it when he rebuilt it,,,and I agree. I know of an engine at the nats that only turned 17200 on the ground, and was one of the fastest engines in the air, so ground RPM means NOTHING!..
Prop it and run it.

Pete,

This isn't the one I got from you.... That one is on the shelf waiting for some warmer weather The more I think about it maybe I will just run it and not worry about it. I don't (yet) fly a tight enough course to have it make that much difference anyway. []

If all else seams good... check your head... it is easy to overtighten and distort the head dome... which ruins the plug seal costing about 500 RPM. Had that problem with one last year.

I do have an extra head.... How would a guy test for that?

I'm taking it with me over to the NCPL guys to let them check it out for me... Heck, maybe I'm measuring it wrong. I will say that would be the first mistake I've ever made

Just try swapping heads with your good engine and see if there is an rpm improvement. Its tough to actually see that a head is bad, the proof is in the rpm numbers.

Just don't go to the county fair they might keep you

You're killing me Splatt.... I'll bring all my stuff with me on Sunday and we'll see what happens...

I have a friend in my club that has a tool... a machined plug that fits perfectly into the inner dome of head and glow plug hole. If the plug seal is deformed... it will not seat completely on the bottom of dome and rocks.... good seal... seats perfect and will not rock. Amazingly simple. I don't know where you get one of these other than your local machinist friend (I suspect it came from one of two of our local machinist/racers).

that sounds like a neat tool Dmyer, I assume one of the Edmunds made it?

Can you post a picture or two of what it looks like? Sounds like something worth having.

I happen to have a laith at my disposal if someone could get me the demensions.... I suppose a guy could measure up a new head and use that but it would be quicker if someone already had the numbers.

I bet Dave or Henry know what the head dimensions are... I have seen an rpm increase from installing a new head, look for pitted head, a sign of lean runs... The distorted head chamber is the compbustion chamber, so if it is damaged and or altered, it will run slightly different than one that is pristine...

P.S. I mentioned the older timing in my earlier post, that would be an engine from a few years back, like maybe 1999 to 2000, somewhere around then is when the change was made in the ports, so if the engine is 3-4 years old, its probably the new stlye, if its 5 years or more is probably the old style, so disregard my earlier statements about timing if its newer than about 5 years???
JZW

To be honest I couldn't tell you how old it is. The other Nelson I got from Pete is probably in the 5 year old time frame but this one I believe is newer than that.

MY engine was definitly the old case,,,but all the "guts" are from Dave Shadel, I can only assume that he put the latest and greatest stuff in it..you know what happens when I assume [&o]. I am curious to how it runs for you Lee.
I have been reading all of the post's on the "monster" pitch props and I will share my idea's on it (not that my oppinion means much).
I used to run a little less pitch than some guys for 2 reasons. I was a good pilot and flew a decent course, but NOT a perfect course for 10 laps.
1) a lower pitch prop accelerates faster than a higher pitch, if you make any mistakes in your flight pattern, the lower pitch prop will get you back on course quicker and is also faster to come off the ground.
2) 2 stroke engines love to turn RPM and do NOT like to be lugged down. when you load a big prop. the "lean" range gets smaller and I found it harder to get that good engine run.
Ok..call me lazy but I flew to have fun and didn't have extra time to spend to get the "perfect" race set up so i probably gave up some MPH in order to keep the "fun factor" in it

I'm all about fun Pete I don't imagine I wil run anything other than a 8.8x8.75 this year. I too have an issue with flying the perfect 10 laps

Do not take offense to this Storm, I like guys that run the smaller props and get more rpm out of them... They give me practice when I come around to lap them... he he he... I did a lot of testing with lap times and my data recorder, there is no question in my mind the 9.25 is faster... I showed anywhere from 5-7mph faster and another 3mph faster than that with the 9.5nn.... that is in good conditions on the west coast... Even when I horsed the plane around with the 9.5nn, it was down to about the range of the 8.75, but then with a good lap, I would be right back above the best the 8.75 could do on my plane...
Rocket Ray validated what I see in qm in rpm, one prop peaking at 24,500rpm on the ground was 5-7mph slower than a prop that peaked 23,200 on the ground.... Rpm is not everything in my opinion and in all my testing in 428, the 9.25 is clearly faster... Just went 1:08 with it, the best I ever did with a 8.75 was a 1:13.... They do take some getting used to when needleing. I never peak it out on the line, I set it in the pits, shut it off and then start the engine on the line throttled back... I never go wide open until right before the flag drops, this seems to help a lot. Those big props can overheat the engine quick!!! So if you are not good at needling, I do recommend the smaller props because they are eaiser to needle and do not get as hot as fast....
P.S. In Hot Humid conditions, the 8.75 can be the better choice...

No offence taken at all!!!....
I just flew what worked for me. I have seen too many new pilots so concerned with making sure that they run just as big a prop as the so called "experts" !
And its always fun to lap someone..especially when they are running the BIG props!
I had to throw that in there

John and Storm make great points. The 9.25 is probably the fastest prop out there, it also has the smallest room for error. It is tricky to set right on the line, and can not be allowed to get hot on the line. The 8.75 is the easiest prop to use for the relative newcomer and probably will allow most racers to put in consistent times.

Would you rather finish 4 heats all in 2nd place, and 2 heats in 1st with the 8.75 (20 points)

or,

4 heats in 1st place, and 2 heats in last place (due to bad needle settings) with the 9.25 (18 points)

Don't let the big guns make you think you have to run the heavy props. I know Travis and Randy will typically start most races with the lighter props and work their way up as the contest goes on. The lighter props will work better in the mornings, and the heavier props tend to be a little faster in the afternoons. Then again, if your all over the sky, the big props won't do you any good.

Good point Dave... I think at least for the start of the year I will stick with what I can needle. That "little" prop should get me flying quicker and to #1 quicker, after that I suppose the big guns will pass me but that's ok, must of the time they have at least one cut anyway

For me, this year is all about getting the couse down the best I can. Then maybe I'll start trying some other stuff.

Don't forget about landing, landings are always good.

Say I was thinking, make sure the rear muffler bolt is not too long, it can block the backpressure passage. Make sure to blow through it.