What do I need to know for an 30.5CC upgrade

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kryptonite said:
its not that its not a good idea, its just a preferance. a 28.5 and a 30.5 head is the same(except machining). what gets the 30.5cc is the added 2mm stroke from the crank. with that extra lenght on the stroke comes less rpms. but an emense amount of low end torche. the 2mm crank is machined/balanced. when they do that, it lowers the case pressure cousing less rpm's. thats where the "stuffed" crank comes in. the fill the machined area with some sort of plastic to build up the case pressure, giving some of the lost rpms back(but not all). so a 28.5 with a 2mm stuffed crank is a 30.5. then "zen" 27.2 is really a zenoah 25.4 with a 2mm crank.. so as far as it not being a good idea, its debatable. some like the high revs and get the lower end torque with a pumper carb, lightened flywheel or a reed kit, yet still keeping the higher rpms. some like the high torque and can easly gear up. i have a ported 28.5 in my MT and i could use some more power. so a 30.5 is in order after the servo's.
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Holy moly my head ;)


Ok so then what about this one. Its a oneil 28.5 CC with a stuffed crank and a 36mm big bore kit.


http://store.5thscalecanada.com/index.php?main_page=product_info&cPath=14_107_114&products_id=33
 
yup. its the same. im not sure why they do that. i bought one of my mills as a ported 26.9. right next to it was a ported 27 for a few extra dollors. same exact motor. you can buy a zen 25.4 or you can get a zen 26.. same exact motor. i guess its like having empty seats on an airplane. check this one out its a 30.5 with a 2mm stroker. note how it has a 36mm bore, same as the 28.5 you have linked. stock stroke is 28mm's. with a 2+mm stroker you'll have a 30mm stroke. and that is, as you guessed..lol.. a 30.5.. so im not really sure why they list them like that.


http://www.oneillbrothers.com/rccar/itemdescription/30ccmotor.htm
 
Man this is getting confusing. BUt I am learning which is kewl.


SO if I go with the 28.5 which I can get for $250.80 CDN I should be good to go. A nice improvement in power and I shouldn't have to re gear correct?
 
O I have a feeling I am about to get flamed for this one :eek:


Does the size of the motor also have to do with the travel of the piston?? :( :(
 
kryptonite said:
oops.. ya, must have been too early this morning.. that headkit doesn't come with the 2mm crank.. my bad.
really? are you positive it was the new machined head? and you had a .40 gaskit? sometimes they would knock with the stacked gaskets, but i haven't seen(heard) of any machined heads with that issue.
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YES ,i have put just .40 and ran it fore 1 huor an puled the plug .pulled the pull start of and turnd it by hand and u can feel it hit the top of the cyl.those .40 very in thiknes. betwen .36 .38.i pintch a ring that way.unless its a esp modifyd .the race ported is not .even if it was i would still check it.
 
Wicked said:
O I have a feeling I am about to get flamed for this one :eek:
Does the size of the motor also have to do with the travel of the piston?? :( :(
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no flames here..lol.. but yes. there is a formula that takes your bore size and stoke wich equals the displacement
 
max 1 said:
YES ,i have put just .40 and ran it fore 1 huor an puled the plug .pulled the pull start of and turnd it by hand and u can feel it hit the top of the cyl.those .40 very in thiknes. betwen .36 .38.i pintch a ring that way.unless its a esp modifyd .the race ported is not .even if it was i would still check it.
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wow. thats interesting. so you got an esp machined head for a 2mm crank that still knocks with a .40 gasket.. that would meen your ports are off too. i thought the hole reason for the machining was to ba able to use a .20 gasket. when you stack the gaskets it throws everything off inside, including your coil gap.. i never had an esp motor. only O'BROS.. about 6 of them.
 
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