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Offline SeanStanley

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boring help?
« on: May 27, 2007, 03:13:23 pm »
hey there
right now I'm building a "supersport" 8hp engine for my brother for him to compete in our LC
the class allows all modifications, so i decided to try something i haven't before
i wanna take the piston out of a 11 flatty and put it in the 8
Ive traced the piston and it will fit, but how do i make the hole? can i use a milling machine with a large drill bit? And should i make it a tad bit larger to compensate for the rings?
Another question, will a shorter rod with a longer piston; will that give me more capabilities of higher RPMS if the "stoke" is short? Sorry for the questions, but another one. If i advance the timing after TDC, will that improve flow. This is my theory why. For example, a person throws a ball to you, you slam it back (this represents timing when spark is at TDC), but now they throw the ball, and you cushion it, then throw it back(timing a bit after TDC)
sorry for these questions, i tried searching.
any help appreciated
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AARLMG

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Re: boring help?
« Reply #1 on: May 27, 2007, 03:25:56 pm »
Yes, If you have a milling machine go for it.... BUT you have to have a special bit that bores. I am not sure of the actual name and I cant think right off the top of my head where to get it, but you need that. Also the plus of using the milling machine is that it is dead on straight its not crooked like the boring bits tend to get.
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Offline mowmaster

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Re: boring help?
« Reply #2 on: May 27, 2007, 07:45:09 pm »
As long as it is strait, go for it.
Also go 0.001 over for the rings and several honings.
Andrew
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Offline mightymowe

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Re: boring help?
« Reply #3 on: May 27, 2007, 09:24:53 pm »
The 11hp piston will not fit in an 8hp block you wont have any cylinder left. A short rod is not good for high RPM.If you are talking about ignition timing it needs to be before TDC and cam timing needs to be before TDC as well. To bore a cylinder it cost me only $35.00 not worth your time setting up a milling machine.
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Offline MTDrider1160

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Re: boring help?
« Reply #4 on: May 28, 2007, 09:12:53 pm »
Quote from: mightymowe on May 27, 2007, 09:24:53 pm
To bore a cylinder it cost me only $35.00 not worth your time setting up a milling machine.

Thats $35 that could be spent on other parts.
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Offline Squidd

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Re: boring help?
« Reply #5 on: May 28, 2007, 09:27:24 pm »
Remember... It's not just making the hole bigger....

It also has to be "perfectly" perpendicular to the crankshaft on both axis... unless your planning a slant cylinder bore....in which case you better know which way and how much you want it tipped... 
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Offline Shrek

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Re: boring help?
« Reply #6 on: May 28, 2007, 10:17:28 pm »
Why would you want a slant cylinder bore?
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Offline mowmaster

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Re: boring help?
« Reply #7 on: May 28, 2007, 10:30:10 pm »
Arc Racing provides this service. When you bore away from the valves you get increased throttle response and a higher top end. However, there is a longer flame travel, however if you bore closer towards the valves you get a better low end. Go to , or call ARCRacing.com
they can better explain this. :twothumbsup:
I'll be happy to answer anymore questions.
Andrew
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