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Old 01-17-2009, 04:34 PM   #1
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Default Con-rod

Would like to know will there be any negative effect if the rod's hole is facing the rear plate instead of the carb side? Thanks!
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Old 01-17-2009, 08:18 PM   #2
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To say the least you will wear out the crank pin as well as the rod end. No lube will be following the passage properly.
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Old 01-17-2009, 08:46 PM   #3
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To say the least you will wear out the crank pin as well as the rod end. No lube will be following the passage properly.

+1. The hole location is important to ensure proper lubrication of the crank pin
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Old 01-18-2009, 12:14 AM   #4
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At that moment wear is no problem.....
Less lubtication on the crankpin makes it hot and heat will make the aluminium rod weak so it will break....
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Old 01-18-2009, 04:01 AM   #5
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oh no...
checked mine and mine was facing the wrong way!

about half a gallon of nitro has gone through already. maybe i was drunk when replacing the rod...
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Old 01-29-2009, 12:21 AM   #6
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can anyone explain to me "when is the correct moment to change your con-rod?"...economically please......still beginner...

and do new con-rod give yougood idling or best performance?...or both?...thanx man...
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Old 01-29-2009, 12:26 AM   #7
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can anyone explain to me "when is the correct moment to change your con-rod?"...economically please......still beginner...

and do new con-rod give yougood idling or best performance?...or both?...thanx man...
generally and usually replace the conrod after engine has been break-in.

after that it can be every 1-2gallons or never at all...just dont run too lean!
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Old 01-29-2009, 12:38 AM   #8
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Quote:
Originally Posted by abul View Post
can anyone explain to me "when is the correct moment to change your con-rod?"...economically please......still beginner...

and do new con-rod give yougood idling or best performance?...or both?...thanx man...
Depending on the motor.....
If you run high performance onroad engines it is wise not to wait long after running in. I normally run 1 or 2 races after running in and after that every 5 liters. I run Novarossi (based) engines)
Offroad engines can run with easy up to 10 liter before changing the rod.

Cheap RTR engines must be used until they are dead and then it is better to buy a new one.
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Old 01-31-2009, 11:31 PM   #9
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can anyone explain to me "when is the correct moment to change your con-rod?"...economically please......still beginner...

and do new con-rod give yougood idling or best performance?...or both?...thanx man...
If you ever come across any of my other posts, you'll quickly learn I tend to run counter to the other posters. So take what I say as an alternative view.

I don't let gallons/liters or hours dictate when to change parts on an engine. I go by measurements. As the rod and pins wear the head clearance and port timings will change. Once they fall out of tolerance for my desired application, then the engine goes under the scalpel. (if you didn't take measurements when the engine was new, you won't have any numbers to compare against)

As the engine accumulates hours, the rod bushings & pins wear in to one and other. As the surfaces become lapped during break-in the load becomes better distributed between the rod bushings and pins. As the fit improves the rate of wear slows down. Once a new rod is introduced to used pins, the new rod and old pins cut into each other and accelerate the wear on the parts.

So what I'm saying is don't change anything unless you have a good reason. IMO a few (3-4) gallons isn't a good reason. If your engine isn't running like it did when it was new, it's because of the wear. Reshim the head to account for the lost clearance, lengthen the pipe for the increased port timing. Changing a rod prematurely will only hasten the death of a mis-diagnosed engine problem.
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Last edited by chunk t; 02-01-2009 at 03:34 AM.
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Old 02-01-2009, 05:21 AM   #10
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In an onroad application con rod failure is the problem. The crank end comes apart. (junk engine) The best way is to be safe and change it on a regular basis. A long back stretch can really stress a rod.
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Old 02-01-2009, 05:37 AM   #11
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Quote:
Originally Posted by chunk t View Post
I don't let gallons/liters or hours dictate when to change parts on an engine. I go by measurements. As the rod and pins wear the head clearance and port timings will change. Once they fall out of tolerance for my desired application, then the engine goes under the scalpel. (if you didn't take measurements when the engine was new, you won't have any numbers to compare against)
Tricky.... With onroad engines the material of the rod gets tired/weak what you never can measure (without damaging the rod). The rod can measure fine, maybe as new but can snap in a blink at the next time you start the engine.
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Old 02-01-2009, 09:03 AM   #12
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Tricky.... With onroad engines the material of the rod gets tired/weak what you never can measure (without damaging the rod). The rod can measure fine, maybe as new but can snap in a blink at the next time you start the engine.
I'm a boat guy. my engines run 50-65% nitro at a CR of 10:1, turning 30,K+ RPM under a much higher load than any car engine. if a rod shatters during use it's most likely because of excessive sleeve pinching and improper break-in's. If a particular brand of rod has a history of shattering, replace it in the beginning and do your break-in with the rod you intend to run.
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Old 02-01-2009, 10:32 AM   #13
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Thats a complete different story as you did seem to figure in the earlier post.

Such a story does not belong in a car onroad forum....
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Old 02-01-2009, 10:49 AM   #14
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Quote:
Originally Posted by chunk t View Post
I'm a boat guy. my engines run 50-65% nitro at a CR of 10:1, turning 30,K+ RPM under a much higher load than any car engine. if a rod shatters during use it's most likely because of excessive sleeve pinching and improper break-in's. If a particular brand of rod has a history of shattering, replace it in the beginning and do your break-in with the rod you intend to run.
More load perhaps, but fewer RPM. On the big tracks we can hit 50,000 rpm. RPM is a rod killer.
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Old 02-01-2009, 01:06 PM   #15
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Roelof, if you think my comments are irrelivant, that's cool with me.

Sean, I get what you are saying, and I agree; RPM will stress the rod & pins, and will cause fatigued or damaged parts to fail. But load or RPM, both can cause damaging wear if the components are not properly matched, the fuel lacks the right % oil content and the temps get out of hand.

My point goes back to my earlier comment (which I guess I didn't articulate correctly) that IMO changing a rod as preventive maintenance too often or too early in life will accelerate the wear on the crank & wrist pins.

To help add some perspective to 50K rpm road engine vs a 30K rpm marine engine. Think of each road rpm as a whack with a tack hammer, & each marine rpm as a whack with a sledge hammer.

all is good.
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