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Reload this Page K-321 rebuild/reassembly help needed.
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  #31  
Old 09-11-2014, 02:27 PM
J-Mech J-Mech is offline
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That's the way to do it Sam Mac! On the dyno to give them rings plenty of back pressure to seat.
Rings don't need back pressure to seat. They need run. You could break them in by hooking an electric motor up to the engine and just spinning it. Temp plays an important factor, but not as much as use.
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  #32  
Old 09-11-2014, 02:45 PM
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dvogtvpe dvogtvpe is offline
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I think you need cylinder pressure under load to get ring seal. if you were to use a electric motor is would do the same if not worse than leaving it idle?
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  #33  
Old 09-11-2014, 03:02 PM
J-Mech J-Mech is offline
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I dunno Don......

I didn't put a lot of thought into that statement TBH. But thinking more about it now....

I think that ring/piston expansion under load (from the heat) has more effect than anything. I agree that I wouldn't let a new motor idle.... but only because with it idling the cylinder temps would be so cool it wouldn't allow for proper expansion. If you were to spin a non running engine and just let the friction heat the block (so block at operating temp) I think they would seat. It's not like combustion pressure puts more outward force on the rings. A new ring in a piston should be tight, so you shouldn't get any more "rocking motion" out of a ring under load, than not under load. I really think engine/cylinder temp plays more of a role than load. I do also understand that cylinder temp is DIRECTLY affected by load...... Hmmmmmm

I believe my flippant remark about the electric motor is debatable.....
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  #34  
Old 09-11-2014, 03:12 PM
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dvogtvpe dvogtvpe is offline
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do you know the theory behind gas ported pistons?
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  #35  
Old 09-11-2014, 03:21 PM
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Allow cylinder pressure to hold the ring to the cylinder wall?

I am in unfamiliar area here as I don't build high performance engines.... but I'm going to say that using a gas ported piston lets you run less ring tension because when it needs the tension the ported piston allows for it. Thus reducing unnecessary drag?...... How close am I, LOL!?
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  #36  
Old 09-11-2014, 03:23 PM
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the more cyl pressure you develop the more pressure that makes it down behind the top ring to push it outward to create a better seal. you may achieve the same result with no cyl pressure it would take allot longer. a gas ported piston just makes it easier to get the pressure behind the ring to create a better ring seal.
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  #37  
Old 09-11-2014, 05:40 PM
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the more cyl pressure you develop the more pressure that makes it down behind the top ring to push it outward to create a better seal. you may achieve the same result with no cyl pressure it would take allot longer. a gas ported piston just makes it easier to get the pressure behind the ring to create a better ring seal.
Bingo! We have someone that knows what he is talking about.
Pic is the dyno run from my last road race engine. It was built to have a wide power band. Nothing wild just a nice wide power curve. It also had to live for the season. It did what it was designed to do and then some.
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  #38  
Old 09-11-2014, 08:51 PM
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that's a nice solid torque curve.
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  #39  
Old 09-11-2014, 09:41 PM
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Bingo! We have someone that knows what he is talking about.
Pic is the dyno run from my last road race engine. It was built to have a wide power band. Nothing wild just a nice wide power curve. It also had to live for the season. It did what it was designed to do and then some.
I'd say you have the nice wide power band you were looking for. That's very impressive.
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  #40  
Old 09-12-2014, 06:56 PM
rickx rickx is offline
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It runs! I installed the rebuilt K-321 and it started right up. No noise, no smoke, just ran "normally"! I've got 2.5 hours on it now and all seems well.
I could not have completed this rebuild without the help of this group! Thank you for your patience and expertise. Is this a great site , or what!
Bottom line: Rebuild kit( +.010 piston, rings, -.010 rod, valves, one crank bearing, gaskets) - $140.00. Machine shop( bore, turn crank, lap valves) - $100.00. $240.00 total, not counting shop supplies, carb. rebuild, etc. Note - my second machine Shop estimate was for $320.00! Pays to look around.
Thanks again, Guys!
Rick
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