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Engine Break-In during Cold Weather

Old 02-29-2012, 05:19 AM
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bhughes89
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Default Engine Break-In during Cold Weather

Anybody know if it's safe to perform engine break-in during cold weather, i.e. winter months? I just finished my HPISavage XSSwith 4.6 "Big Block" and, being a nitro first timer, I'm eager to break it in and run it around.

Keeping in mind that I'm a nitro first timer, my intuition tells me that trying to break in my engine during cold weather will result in one of two extremes. My first thought is thatthe colder ambient temperaturewill simply hinder the break-in process since it will keep the engine cooler than break-in temperature. On the other hand, I feelthat if great enough, the temperature difference between ambient and the inside of the cylinder head will cause too much stress on the head and crank case, possibly fracturing it.

Any thoughts on my intuition?
Old 02-29-2012, 05:31 AM
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HerrSavage
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Default RE: Engine Break-In during Cold Weather

Your(and most peoples', including mine before I learned otherwise) basic intuition is wrong. Nitro engines are kind of counter-intuitive in this regard. Colder air has more O2 in it, so it actually means you need a somewhat RICHER setting in colder weather. This theoretically is good for break-in even in at least one regard: most RTR engines are sete WAY too rich from factory. So if breaking in in cold weather, you should have to lean it less to get it running right initially...

As for whether to break in, depends how cold you mean. If not below freezing, I think you can do it fine. Key to a good break-in is preheating the engine before you start.

This is how I would do it:

1.) Take out plug, look down in hole. Rotate flywheel to point where piston is at BDC - bottom dead center - i.e. it's bottom-most point. With the piston at BDC, scratch a notch in your flywheel at 9:00. This way you will always know where BDC is. Put plug back in.

2.) Wrap head in several layers of alu foil, followed by a sock with a rubber band.

3.) Pull fuel tube off pipe and blow into it, while keeping your eye on the tube that goes to the carb. Once you see fuel hit the carb, stop blowing. This primes the engine.

4.) Prop hair drier over the engine at a slight angle, and leave on high for ten minutes or so. Don't put it straight down, as you might fry the hair drier. Check temp at glow plug. You're aiming for 180-200F.

5.) Once there, start the engine.

6.) OK, so engine is started. Plop the truck on the ground at first and see if it keeps running. Give gentle little blips to the throttle as necessary if it sounds like it's going to cut out. What you want now is for it to hit 200-225F for say two or three minutes. Once it hits 200-225F, shut it down. Immediately rotate flywheel to 9:00. Take off alu foil and sock. Let the engine completetly cool with the piston at BDC. Go do something else for 10-15 minutes... Repeat ten times or so. This is "heat cycling". The whole heat cycle process for an RTR engine should be 4-6 tanks or so. Each cycle you can put a bit more fuel through it. Just keep an eye on temps so they stay in that range. If they're too cold, lean the HSN a tiny bit at a time (1/12 turns or so..) Run, hit 200ishF, shut down, complete cool down with piston at BDC, repeat.... That's heat cycling.. Try not to floor it too much in the first half gallon. After that, letter' rip...

Preheating the engine makes starting much much easier, and is good for your engine.

As for colder air temps, again..., you actually need a RICHER setting (HSN basically..) generally, since cold air has more O2 in it. As long as it's not too cold, slightly colder temps can even make things easier, as the engine will cool faster. Nitro engines I think generally like slightly colder air because of the denser O2 levels..
Old 02-29-2012, 10:13 AM
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bhughes89
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Default RE: Engine Break-In during Cold Weather

Ah, this makes sense. And your procedure sounds quite similar to everything I've read and watched.

My only other issue is that the crank shaft is nearly impossible to turn right out of the box. I most definitely cannot rotate the flywheel by hand, and it is extremely difficult to rotate it via the pull starter.I'm assuming this is normal because the engine is not broken in and also not lubed with nitro fuel. Is that correct?In any case, it is quite difficult to get the piston to BDC becauseof theimmense resistance to rotation.I don't have accurate control over the crankshaft or flywheel position since the only way I can rotatethe assemblyis with the pull starter. Does any of this sound normal for an engine fresh out of the box?
Old 02-29-2012, 10:20 AM
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HerrSavage
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Default RE: Engine Break-In during Cold Weather

It gets much easier to turn when it's hot - that's the point of preheating..(also the point of heat-cycling.. - so the piston will fit up in the sleeve better. That pinch will go away with more and more fuel and heat cylces through the engine..)

To make it easier to turn cold, take the plug out - or just loosen it..

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