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Needle Valve and Head Gasket question????

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Needle Valve and Head Gasket question????

Old 08-30-2007, 08:17 PM
  #1  
agentorangeracer
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Default Needle Valve and Head Gasket question????

I have several interesting questions to ask, first to start off with, is the High speed needle, or the fuel inlet and needle valve w/ needle socket. When turning the fuel screw in, allowing less fuel for a better, leaner burn, your fuel is being forced threw one pressed hole drilled in the bottom of the needle socket, which has been run from the fuel tank to the fuel inlet. When taking the Needle assembly apart for proper cleaning, is it put back together by placing the two holes alighned even for fuel flow? In other words, do the two holes in the inlet and needle socket have to be even with each other when placed back together? Will this effect HP, and will the motor work correctly if the 2 holes are un-even? I have pictures of the Needle inlet and socket for prefrence.


Second question. If you have ever changed or taken your shim out of the head assembly, you will notice that the whole inner tube, or Head Button will slide right out. In between the head and head button, flows water, the only thing allowing space between the Head and head button, are 4 gaskets. There sized enough for just small amounts of water flow. The question is, if you could place much larger gaskets to leave more space in-between for more water flow, or would this effect the motor? I have also got pictures showing the the Gaskets between the head and head Button.

There was a picture of the two Heads, one put together with the head button on, and one without.

The four gaskets, and one main.
Old 08-30-2007, 08:57 PM
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Dan S
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Default RE: Needle Valve and Head Gasket question????

ok,
just so we make sure that we are talking about the same thing.

The red anodized piece is not a head but a water jacket or water cooled head, than you have your head button and than your crankcase.

Between your crankcase and head button you may or may not have a head shim (will go back to shims later).
There is no water that actually goes in between the crankcase and the head button, the water goes between the button and the water cooled head (red).

This is where I'm not sure as to where you want to had those rubber gasket, on thing, you can't put them between the button and the case and to had bigger ones between the button and the cooling jacket, I strongly believe it will not help in water flow.

The Head shims, head shims are there to either increase or decrease the compression. The more shims you add the more you decrease the compression and the more shims you remove the more you increase the compression.

Low Nitro content requires higher compression ratio (harder to burn), higher Nitro content requires less compression ratio (easier to burn).

in other words;

The compression ratio on model engines actually controls the ignition timing which is also effected by the nitro content of the fuel.

A glow engine is simular to a diesel engine. The compression ratio in model engine can be from as low as 7.5 to 1 to a high of 9 to 1. The compression ratio varies with the type of fuel, altitude, port timing, and exhaust configuration. Higher performance engines hold very close tolorances to assure the proper combustion point.

The basic rules are as follows:

If you engine is overheating...

It could be due to the compression ratio being too low for the fuel you are using. Lower nitro content require higher compression ratio. If the compression is too low the firing of the combustion charge will be too late or retarted creating poor burn and thus allowing a burning fuel charge to be released out the exhaust. This elevates the tempurature of the engine and lowers the performance.

If you increase the nitro content the conbustion will be advanced and can produce a more powerful and cooler running engine.

or

You can increase the compression ratio by removing a head shim (How to set squish band) and we are not gonna get into Squish Band/head clearance calculation.

On the other hand if you compression ratio is too high the engine will detonate. This the same as the ignition being too advanced in you car or if you run too low of an octane rating. Like when you car engine pings with regular gas.

If you want to run higher nitro fuel to get more power you may have to lower the compression ratio. You may need to add head shims. Detonation is basically the fuel charge exploding before the piston reaches the top of the stroke so the piston forces the explosion to be contained without expanding. It has no place to go because the inurtia of the crankshaft is forcing the the piston to move thru its proper course. Thus you get a ping which is the sound of all the clearances in the connection rod being driven together squishing the oil film out of te bearing. If you have detonation you can destroy your piston as the crown (or top) of the piston is subjected to exrteme heat and pressure because of the trapped exploding gasses.

Engines are designed to have the combustion expansion drive the piston down the cylinder, not have it trapped.

Note the higher the nitro content is not like a higher octane gasoline rating. Higher octane gasoline requires higher compression ratio as it actually burns slower than regular gas and requires more compression to ignite properly. Nitro actually lowers the compression ignition point of glow fuels.

Dan
Old 08-30-2007, 10:52 PM
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agentorangeracer
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Default RE: Needle Valve and Head Gasket question????

Ok, thanks for all that, do you have any idea about the needle settings that i asked about?
Old 08-30-2007, 11:15 PM
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Default RE: Needle Valve and Head Gasket question????

Thats one thing to which I am not certain about, so I rather not induce you in error.

Dan.
Old 08-31-2007, 05:10 AM
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Default RE: Needle Valve and Head Gasket question????

ORIGINAL: agentorangeracer
I have several interesting questions to ask, first to start off with, is the High speed needle, or the fuel inlet and needle valve w/ needle socket. When turning the fuel screw in, allowing less fuel for a better, leaner burn, your fuel is being forced threw one pressed hole drilled in the bottom of the needle socket, which has been run from the fuel tank to the fuel inlet. When taking the Needle assembly apart for proper cleaning, is it put back together by placing the two holes alighned even for fuel flow? In other words, do the two holes in the inlet and needle socket have to be even with each other when placed back together? Will this effect HP, and will the motor work correctly if the 2 holes are un-even? I have pictures of the Needle inlet and socket for prefrence.
Any chance you can reshoot the pics of the carb pieces so they're a bit more clear? Perhaps the camera can't focus from so close so maybe from a bit further away? It's too late to say this, but it's best to avoid disassembling a carb. I've seen people do this with airplane engins carbs and then not be able to get the engine running right. I'm not sure what cleaning you were doing, but I've found that denatured alcohol does a great job of cleaning off gummed up oil residue. This will nearly always work without disassembling the carb.
Old 08-31-2007, 06:18 AM
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Default RE: Needle Valve and Head Gasket question????

The fitting that I see looks like a banjo type, the black part should be groved or hollowed out inside the bore where the needle seat goes thru alowing fuel to flow all around the seat, I belive it was made like that so you can set inlet to any angle you want, so look at the black piece and I think you will see what I mean.
Old 08-31-2007, 10:21 AM
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agentorangeracer
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Default RE: Needle Valve and Head Gasket question????

I checked, and the black piece, whick is the inlet, has one hole for the fuel to travel threw.

It looks like when the inlet is wrapted around the socket needle it wouldnt let much fuel flow around in the socket, yet maybe your right, it could be so much of a tight fit for the fuel to be broke up in to small quantitys going in to the carb.

Oh, and Piper, thats a good question, after i took the needle assembly off the aqu.18, it wasnt running right at all, but the only reason I had did this was to get the motor cleaned out, anyways, I did it all the time to the dynamite.15's and they run ok...ok is all they are anyways tho huh. Well the question just came up, though I have always aligned the two hole together on the dynamite, i was thinking maybe the .18 wasnt running to great because of the alignment.

As far as the pictures go, Im using my Ampd Mobile cell for the pictures, not such a good quality photo, but the best I can do until I get a digital camera.

Ill try to put up some more pictures in a little while today, maybe I can get some better light going for me to see and show you guys what im talking about. Thanks!
Old 08-31-2007, 11:28 AM
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Dan S
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Default RE: Needle Valve and Head Gasket question????

Agent,

you have nothing to lose by aligning the two holes when you put it back together, the only thing that could happen is that it will work correctly.

Dan.

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