Shim Or Not To Shim?

[BigRed]

I have a question about shimming heads. I have a Fantom .21 05' edition and am running the standard button, running 30% fuel. Should I shim the head? I've been having problems with glows plugs burning out. And just recently had a wrist pin clip break and grenade my new engine (to many rpms, to long of a straight away) . I have a new piston and sleeve on the way and want to know before I start breaking in the motor again if i should shim. Thanks.

 

[mikeburgin]

are the glow plugs going because your to lean, or does it appear to be fine and there just grenading, if your not to lean then i wouild say you need to shim

 

[BigRed]

After a 20mn main the motor was running 240/w plenty of smoke.

 

[mikeburgin]

what sort of plugs u using

 

[Plaidfish]

the new 05s are standard heads again???
the 04 I had liked to run around 220 when it ran dry.....and it had plenty of balls.....Fantom says they are ready to run 30% but they had 1 single thin shim when I got mine....I added a thin one before I ran it......

 

[BigRed]

The 05's come with the turbo head, i didnt want to spend $10 a plug so i bought the standard head. It does come with one shim already, and yes Fantom doesn't mention antyhing about adding more shims. I think I'll do what you did, add one more just to be safe.

 

[Plaidfish]

anyone know if there is an exact science to shimming for higher nitro content fuels?
I hate just trying it and doing the "listen for poop performance" sound test....

 

[CorradoPsi]

for 30% fuel you want a head clearance of about .023-.028 inches to the edge of the combustion chamber. i also found out the hard way that fantom runs thier head clearance too low. i had one of thier small blocks that always ran hot on high nitro fuel, it wasn't until later that i found out it needed a shim to lower the temps, and it would have made more power too. it was detonating just enough to pit the head, but not enough to hear it. that motor didnt last as long as it should have, but i did get about 4 gallons out of it.

 

[FastEddy]

I have always used a shim with 30% IF... I have heat or plug issues. Some of my mills require it and some don't.

How exactly does one go about properly measuring head clearance?

 

[mikeburgin]

I have always used a shim with 30% IF... I have heat or plug issues. Some of my mills require it and some don't.

How exactly does one go about properly measuring head clearance?

Cutting the engine in half, or vernia

 

[Candyman]

I have always used a shim with 30% IF... I have heat or plug issues. Some of my mills require it and some don't.

How exactly does one go about properly measuring head clearance?

Actually I read a pretty nifty way if you can make it work. What you need is a thick strand of solder. Pull your glowplug. Bend the solder and a 90 degree angle so there's a small part after the bend. Put that part into the cylinder and then slowly turn the engine over TDC. The piston should smoosh the solder against the head. The solder is soft enough so it will deform and not affect the piston or head. Then, carefully remove the solder and measure the thickness of the flattened part with your calipers. And there you have it.

 

[mikeburgin]

Candy man your a braver man than me to be doing that, dont think id be wanting to put solder down my head, not to mention that means you have to have an engine that you can turn over easily by hand to start with

 

[olds97_lss]

Well, CandyMan's theory is sound. I think I read that somewhere a few years back.

Any idea of the temp of plug your running? I started this hobby with a 15 and ran hot (OS #3) plugs in it all the time. I didn't know any better when I got a 21 and ran the same in it. It pitted and pissed off the engine. Ran hot, kind of crappy, sounded funny and never gave me good power. Then I tried the OS A5 (cold plug) and it ran like crap. But I'm running 20%/12% oil. I ended up trying OS #8 (at $8 a piece...) and my OS 21 RG and Omega 21 Comp seems to really like that plug with the 20% fuel. Runs cooler, sounds better and I get a lot better power.

I believe your supposed to run a cooler plug with the higher percent Nitro to make it detonate later as the extra nitro makes it detonate sooner.

 

[CorradoPsi]

I have always used a shim with 30% IF... I have heat or plug issues. Some of my mills require it and some don't.

How exactly does one go about properly measuring head clearance?

candy mans method works, and I've seen plenty of guys use it, though i also am not a fan of it for the fact that your putting forien (sp?) material inside your engine. what if it gets caught in a port as you raise the piston, it will shear off and leave loose metal inside your crankcase, not to mention its unhealthy for your rod bushings.

the method i prefer is to grab your handy dandy calipers. take your head off the engine. remove any shims from the top of the sleeve and the inside of the head. now measure from the top of the sleeve to the top of the piston at TDC. write that number down. next measure the distance from the sleeve seating surface in the head, to the outermost edge of the head button. subtract that number from the first number. now whatever number you have there, you need to add shims to gain the clearance you want. if you want to know what your currently running, measure all the shims you removed from the engine and add them to your total.

 

[JatoFever]

I have 4 shims ??!!?? I bought an aftermarket head and it came with 4 shims and a big fat plug washer. The instructions said to use all 4 shims and remove them as the engine wears downs. WHAT does that mean?? Do I remove 1 every gallon of gas? Or do I say screw it and remove all but one right now after 1 gallon of fuel.
It also said the big fat plug washer was to be able to use short and long plugs?? What advantages would that have?
Right now I'm running all 4 shims should I remove some?

 

[Plaidfish]

leave em in if you have the snap you want when you accelerate......as the engine wears out remove one at a time.....every 3/4 to gallon sounds right....to me anyway

 

[JatoFever]

leave em in if you have the snap you want when you accelerate......as the engine wears out remove one at a time.....every 3/4 to gallon sounds right....to me anyway

So I just finished its first gallon last week. So I should remove a shim?? Or leave it alone cause its still running fine?

 

[mikeburgin]

leave them in till u start to otice a reduction in compression then take out

 

[Plaidfish]

if the Jato has a 2.5 then he's probably starting to loose it already....I'd be very surprised if the mill lasts long enough to remove 3 shims...LOL....actually if you follow all the instructions to the T then you'll get about 8 gallons...if it's your first mill you probably already overheated it once maybe more...cause that mill doesn't run right until it gets hot...I ran mine at 260 if I wanted real power from it......but mike is right leave it till you notice it's just not "punchy" anymore....

 

[niggle]

Actually I read a pretty nifty way if you can make it work. What you need is a thick strand of solder. Pull your glowplug. Bend the solder and a 90 degree angle so there's a small part after the bend. Put that part into the cylinder and then slowly turn the engine over TDC. The piston should smoosh the solder against the head. The solder is soft enough so it will deform and not affect the piston or head. Then, carefully remove the solder and measure the thickness of the flattened part with your calipers. And there you have it.

1:1 engine builders use a similar technique using something called "plastigauge" to check running clearances on main and big-end bearings when rebuilidng engines. Insert a thin strip of "plastigauge" plastic under the bearing cap and then torque it down, then remove the bearing cap and check the thickness of the deformed plastic strip with a micrometer.

The solder would need to be several mm thick though to check the head to piston clearance on a .21 engine. Even soft solder would require an enormous amount of pressure to deform a piece this thick and even though the alloy head and piston would survive I would be concerned about damage to the big-end bushing.