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Old 12-22-2008, 07:22 PM   #1
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Default Glow plug distortion?

This is what my glow plugs look like after a couple of litres, is this glow plug distorted? Engine runs fine and holds a good tune.
What could cause this?

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Old 12-22-2008, 07:33 PM   #2
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looks rich what plug what engine?
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Old 12-22-2008, 07:35 PM   #3
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im not sure about the distortion but the plug is wet so that means its rich. could be the wrong plug for the engine, could be its rich but not enough head clearance? Ill let one of the engine gurus tackle that part but its definately looks rich.
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Old 12-22-2008, 07:53 PM   #4
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Yeah its rich as I had it idling for a bit too long on the box just before I took the plug out.
Its a GO .25 port motor using Mcoy MC-8 plugs, the reason for the 2 washers is because the GO motors use shorter threaded plugs. The Mcoy plugs are a bit longer.
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Old 12-22-2008, 09:03 PM   #5
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Quote:
Originally Posted by herb99 View Post
Yeah its rich as I had it idling for a bit too long on the box just before I took the plug out.
Its a GO .25 port motor using Mcoy MC-8 plugs, the reason for the 2 washers is because the GO motors use shorter threaded plugs. The Mcoy plugs are a bit longer.

if its a turbo head button go with p3, if its a standard use a p8
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Old 12-23-2008, 02:50 AM   #6
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Quote:
Originally Posted by losi_racer View Post
if its a turbo head button go with p3, if its a standard use a p8
I don't know how helpful this is, as firstly it is obvious he has a standard plug. If he were a newbie your answer would just confuse him. You mena a P3 or #8 by the way... the "P" designates turbo plug
Secondly, OS plugs are not necessarily the answer as he has a tuning problem.
Thirdly, sorry to insult but you previous tuning ideas were 100% incorrect as is evident from other threads.

Now to his question

(1) Go engines seem to like LRP plugs, try a LRP #6 or #7, or if you can't get them a RB #6 or 7. A A3 or A5 may be a tiny bit hot, maybe a #8 will be better.

(2) The problem is very hard to diagnose as the pics make it look rich, but he said it was idled for a long time. (How long?) If it was only idled for along time ONCE, on the last run, then that would not have caused much extra colouration so we can assume the plug pretty much looked like that during running

(3) yes that filament is distorted! A lot....
A distorted filament means too lean, too high compression for the % nitro u are using (doubt it.. you are not usuing like 16% or something with no shims are u???) or the plug is too hot for that motor!!!! You are so close to ruining the engine you have to do something now!

(4) if the plug body is so black (meaning rich) and the filament is distorted (usually meaning lean) as I see it, there is only two things that can cause it:
(a) your bottom is waaay rich and your top waaay lean.. or...
(b) you have entirely the wrong plug, possibly coupled with the above tuning issues. I have no idea about McCoy plugs so can't offer an opinion on them: I just know that LRP and RB #6 and OS P3 work well in the Go Tech .21's

Point (a) may be an issue: you realise that Go engines prefer to be tuned almost totally on the LSN and pretty much leave the HSN alone? As an Eg the .21's only have the HSN turned in about 1/4 turn from factory set, and the LSN is played with a lot.

(5) it is hard to see ... not 100% on this one... but the plug body does seem to show some pitting which indicates detonation (caused by lean run or hot plug or too much compression). In the first few pics it looks like pitting.... in others it is not so obvious... and the colouration of the plug may be masking it a bit.
I'd be interested to see the head button as that will really show it up.


Perhaps take the motor to somebody very experienced in racing and even better a Go Tech owner....

IMHO

Last edited by Mark_Australia; 12-23-2008 at 03:22 AM.
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Old 12-23-2008, 07:12 AM   #7
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Check the rod play too. If the rod fits the crank loose the piston can go past the normal tdc and mash the plug element. Yours isnt as mashed as some Ive seen but its still worth a look.
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Old 12-23-2008, 07:41 AM   #8
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I agree with Mark for the most part - at some point this engine looks as though it was run very lean in spite of the other signs that it's also been running rich. It's been my experience that, in situations where there's too much compression or detonation, the plug coil is pushed into the plug housing. I believe it's simply too lean. I also agree on the plug type - it's clearly a standard plug, so discussion of a turbo plug is just confusing. Almost any plug can be used in these engines. Yes, some plugs are better suited than others, but if the engine is tuned properly, even a hot plug that is typically unsuitable for a big block engine WILL function properly and not become distorted. The MC8 plug from McCoy is on the hotter end of plugs for a big block engine, but not uncommon, so I don't think it's related to the plug. The tune of the engine is suspect IMO.
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Old 12-23-2008, 09:56 AM   #9
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I'm not worried about the color, what worries me is the distortion. Distortion is caused by one of three things.

1. Too much compression

2. too much RPM

3. Too hot a plug.

Since offroad motors tend to do better on hot plugs let's ignore #3 for now.

If you have been really twisting the motor hard (like doing speed runs in the parking lot) then either change gearing (up a tooth on the clutch) or let off the gas.

If RPM isn't the problem then either drop the nitro % or add a head shim.
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Old 12-23-2008, 01:22 PM   #10
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i say it's too lean somewhere, and my need to be shimmed. The plug is distorted from the compression, and the white carbon residue is from being too lean most likley on the low speed. It has dark coloring likes if it's been idleling for a long period of time then when you go out to run hard it cooks on to the plug and all that deposit is also on the head button which is not doing any good for your next plug. So I would pull the head button and clean off the fuel burn.
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Old 12-23-2008, 01:59 PM   #11
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I would also say to check your bearings and rod for slop. like PTP Racing said slop can cause excess compression. I had to find that out the hard way. I had an engine distort plugs like that right before the bearings went. Now I know better lol. But with the other signs in those plugs it seems to me you problem may lie with tuning. I don't think the plug is too hot as the mc-8 is a medium plug and I run them all the time. I would probably look into some of the tuning issues that people have listed. I would say wayyy rich on the bottom and wayyy lean on the top but thats just my guess.
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Old 12-23-2008, 02:55 PM   #12
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Thank you for all the help and suggestions.
I took it for another run with a new plug, as the other one had too much build up from idling, this plug is 3 tanks old.
I was doing a far amount of high speed runs, the element is sticking way out of this one.
I will try adding another head shim to lower compression.


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Old 12-23-2008, 03:19 PM   #13
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The way it's sucking the plug out makes me think it's an RPM problem. If you are going to be doing speed runs you need to change your gearing. Go up a tooth on the clutch and you will see more top speed and engines will last MUCH longer. If you can't change the gearing then adding a shim will definitely help.
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Old 12-23-2008, 09:16 PM   #14
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My Bet would be on the fact your have a worn big end on the conrod. My dragsters are prone for doin it (sucking the plug in/distorting the element) when they get a bit worn out... Being a Go engine would make me think so even more so becuase of the fact they have a rediculous piston-liner fit when they are new and you probably didnt replace the rod after run in... Ive been wrong before but try replacing your rod. Or winding the motor over to top dead center so it locks up and try and move the fly wheel to see how much play is in the big end. If you have more the 2 or 3 degress there's your problem right there. Tune may also have something to do with it but no tune up will mask a flogged out rod...
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Old 12-24-2008, 04:01 AM   #15
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Just smoked my new GRP .21 .Same condition except you stooped exactly 5 revolutions before your element fell into the cylinder and tested its hardness against the port windows. You are very lucky. You need to keep that plug as a good luck charm.
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