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tightness btw cylinder head and crank case

tightness btw cylinder head and crank case

Old 12-21-2005, 11:10 AM
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Default tightness btw cylinder head and crank case

Hi, all. I have been reading the posts with interest over some months, but I just joined as I believe I would have any questions in future including this one below;

I own an old OS engine, which I took it apart and now I am trying to put it back in. There is a cylinder head which I need to bolt in with six cap screws to the crank case, and I would like to know how tight I should tighten up the cap screws.

Is it 1) as tight as possible but stop just before I damage the threads or 2) just so such that no air leakage (or no bubbles/foams are seen when engine is running) is observed?

I am asking this question because with every OS engines just bought off the shelf, the cap screws tightens just a bit more when I turn the screws counterclock-wise; so I am trying to think not to screw in too much as that is not what OS factory is shipping their product out.

Many thanks for your answers and opinions in advance!

Regards,
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Old 12-21-2005, 12:29 PM
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you dont need to torque them down real hard, and you want to tighten them in a cross pattern, much the same way you would lugnuts on a car..
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Old 12-21-2005, 02:29 PM
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you might describe it as heavily snug
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Old 12-22-2005, 03:44 AM
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Red face Thanks... but are there any....

Thank you very much for your kind responses!

Is there any reason why I should tighten it as 'heavily snug' and/or 'not with too much torque' and not screw them down as tight as possible?

What could be the problem with tightening them as far as possible (max. possible torque) but stop just before I damage the threads?

Many apologies for such trivial questions, but this is one of those questions that's killing me and my friends!

Kindest regards,
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Old 12-22-2005, 10:33 AM
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Originally Posted by hkkimst1
Thank you very much for your kind responses!

Is there any reason why I should tighten it as 'heavily snug' and/or 'not with too much torque' and not screw them down as tight as possible?

What could be the problem with tightening them as far as possible (max. possible torque) but stop just before I damage the threads?

Many apologies for such trivial questions, but this is one of those questions that's killing me and my friends!

Kindest regards,
simple.....
how are you going to know where that max possible torque is just before it breaks?

its best to tighten it down snug and call it good..
also with the heating up and cooling down the motors go through the metal need some space to expand and contract..
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Old 12-23-2005, 10:44 PM
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Don't tighten one screw any more than another. Make A LOT of short, brisk passes on each bolt before cranking them down with the last snug turn. When you see, or feel, resistance on the head bolts stop and go to the bolt directly across from it. After about a turn or so at a time switch in the cross pattern mentioned earlier.
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Old 12-24-2005, 11:11 PM
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Originally Posted by hkkimst1
Thank you very much for your kind responses!

Is there any reason why I should tighten it as 'heavily snug' and/or 'not with too much torque' and not screw them down as tight as possible?

What could be the problem with tightening them as far as possible (max. possible torque) but stop just before I damage the threads?

,

the engine blocks are cast aluminum, not steel. aluminum is very sensitive to overtightening and steel is not. you can tighten steel the same everytime but aluminum weakens everytime you stress it so if you overtighten the first time, the next time snugging the bolts may strip the threads. this is is just what i learned a few years ago when i was a newbie to nitro engines.
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Old 12-24-2005, 11:20 PM
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go snug but not tight... i've stripped the case on an v-01b by overtightning...
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