engine hopup?

[chewyboy]

anyone here ever shave about .001 or so off the head of thier engine to get just a tad more out of it? i am kinda curious on anyones results.

 

[RobH]

This is not something anyone should try. Engines are designed very carefully. What you're describing is something along the same idea as removing the head shims. The distance between the glow plug and the piston is very precise. Changing that distance will have porr effects.

If you're looking for more performance for your engine, you could "port" it. This typically involves a dremel and your engine internals -- a combination that I'm not willing to create. You should leave engine mods to the professionals:

http://www.ebmods.com

-Rob

 

[bkunar5356]

i agree with RobH, this isnt something smart to try. a lot of thimes you can shave the heads on lawn mowers or other small engines and get good results but any 4-stroke engine like that has a seperate ignition that fires depending on the position of the crankshaft. a nitro engine fires depending on compression. if you change the well thought out and designed engine to make compression work to your advantage, you will have no luck. engine designers have already done as much as they can to make the engine better.

 

[chewyboy]

actually i've seen this done on an fs91. he wasn't quite getting enough power to pull out of some tricks very well so he took off .002 on his head. his compression went up and the power out of tricks was something else. this does work if you get it right i was just curious if anyone had tried it on an rc car and what your results were.

 

[GilBeQuick]

Here's my personal opinion. If you've got an engine you don't care about, and you're positive that you're going to purchase a new engine, go ahead and give it a good shot at porting it a bit. Check out www.nitrorc.com, they've got good pointers about porting in general in some of their articles. If you care about your engine and you don't want to possibly mess it up, then leave it alone.
I followed nitrorc.com's article on porting the pro .15 on an old pro .15 that originally came with the MAXX, and man did it make a difference....but I was also prepared to pick up a new engine if i totally fubar'ed it up.
When it's all said and done, it's your dollar, spend it as you like!

 

[sikz3]

here is a link to porting engines and tips as well.
http://www.affordablenitrotech.com/forum/index.php?act=SF&f=38

 

[chewyboy]

actually i wasn't thinking about modding the ports on it but actually shaving a few thousands off the head for greater compression. But thanks for the thoughts on porting it out too.

 

[robriguez]

The thought is the same with shaving as it is with porting Chewey.

If you are fully prepaired to shell out some $$ if the engine gets all messed up by trying to modify it then by all means have at it man. I'm sure we would ALL be interested in finding out if this mod actualy works. Let us know.

 

[totoyoo7]

i've seen some mods for some engines... but not for every engine in general, since all engines are not equal... there's a article i read at www.nitrorc.com that had to do with the modding of an ofna 12 redhead engine i think, made it a WHOLE lot faster in genreal, but i dont recommend you try it for any other engine... you'll just end up breaking it unless you know what your doing

 

[Akina'sMtx-2]

Originally posted by chewyboy
actually i wasn't thinking about modding the ports on it but actually shaving a few thousands off the head for greater compression. But thanks for the thoughts on porting it out too.

Few thousands is like shaving nearly the whole top of the sleeve or bottom of the head. What tools will you be using to measure the EXACT amount you will shave off? You need to be very precise to shave 1-hundred thousandth of a inch. Thats about the thickness of a hair. It can be done, but you gotta know what your doing first. I will have to go with Gilbequick, if it's a engine you don't care about, then it's worth a try, you will be able to learn how to port it also. If you want profession porting, i suggest you do a little more research, there are many porters out there, and I only would rely on a few, their names are mentions many time, I won't say any name because I want to be fair to everyone of them.

 

[StrechM]

Re-hash...Instead of shaving the head wouldn't it be easier to test your theory with some thinner combinations of head shims? My first thought is that you may loose some power by reducing the combustion area of a 2 stroke engine. I'm always wanting to move in the opposite direction by slightly increasing the combustion area and increasing the nitro content.

 

[GilBeQuick]

There's a great article about this in a recent RC Car Action (September) titled "Piston Power". I can't find it on their site, so I'll type out some of it. This should answer all of your head clearance questions!
-----------------
"How does head clearance affect performance?
Too Little head Clearance:
In a worst case scenario, a tight clearance may cause the piston to hit the cylinder head when the engine reaches it's full running temp and max rpm. And in some cases can cause excessive compression, which can lead to detonation, a blown plug, or an oveall lack of power with high temps.
------------------
Too much clearance:
-Can reduce power. It will cause an otherwise powerfull engine to perform poorly because it can't develop as much cylinder pressure as is possible. When the gap is too large the cylinder pressure is reduced, so less fordce pushes down on the piston. With extreme clearance, the engine may not be able to develop enough compression to ignite the fuel. Symptoms of too much clearance include an unstable low-speed mixture setting and a lower than avg. engine running temp.
-------------------
Which engines benefit the most?:
head clearance adjustments tend to benefit sport engines more than expensive comp. engines. Sport engines usually have much more clearance, and the reason is that it makes them easier to tune. The clearance on more expensive comp. engines are set a little more precisely to produce max power. To some degree all engines could possibly benefit from a clearance adjustment becaue the manufacturers don't typically have time to precisely set each engine.
-----------------

When should I increase clearance?
If you engine regularly blows or damages plugs even though it has been tuned to run at a reasonable temp. or if you often use a higher nito % than what's reccomended, add a 0.1mm head shim to increase clearance.
------------------

When should I decrease clearance?
Removing shims is a tricky subject. Engines' ideal clearance measurements differ, and each is based on internal components' tolerances. Only highly experienced engine tauners should reduce an engine's clearance signifigantly. In general, if your engine is easy to tune, runs well at low temps and rarely, if ever, blows a plug, you can probably safely remove a this (0.1mm) shim to boost performance.
Many engines have severl head shims installed on the head button, but some 9most notably OS) have a single shim that should not be removed. In those engines the shim acts as a gasket between the cylinder and the piston sleeve: you'll risk poor performance if you run an engine without any head shims. You may be able to replace the standard one with a thinner one, but you should always have at least one shim. You shouldn't reduce the head clearance less than .020 inch (0.5mm). If you reduce it too much, stretching and heat expansion could bring the piston dangersously close to the head once the engine is warmed.
The most important thing to remember when experimenting with the removal of head shims is to note which shims were in place from the factory and make only small adjustments at a time. Exercising caution means avoiding going too far in one direction or another."
By: Stephen Bess
-----------------------------


BTW, the article is on page 224 of the September RC Car Action.

 

[GilBeQuick]

Just wondering, but has anyone out there reduced the clearance too much and ruined an engine?

 

[chewyboy]

i have on a 4 wheeler engine once. I milled off a bit too much and when it got wound up the piston went nearly through the top of the cylinder. it wasn't a pretty sight. glad it was a dead engine anyway.

 

[Mugen-Racer]

The thing about shaving the head is that you've got to be precise and even. Any kind of air leak is gonna lead to negative results. There safer and easier ways to gain a little more power.

 

[scottericsonon]

here check out the hop ups here

but as was already said do NOT attempt this unless u already know what ur doing <then u dont need the link lol>

OR you prepared to buy a new engine if u royally screw it up

plus be careful wich engine u choose to do these mods

i pulled apart my fantom and found out everything was already at max

i tweaked the carb a little and it seemed to help tho

G/L and let us know the results

scott

 

[bkunar5356]

dude....am i missing something? what link?

 

[scottericsonon]

derrrrrrrrrrrrr

brain fart obviously

here ya go brother

http://www.nascart.com/defalt.htm

scott