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> Bus piston question, Wanna modify them
Joe Ricard
post Nov 7 2005, 07:45 AM
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So can I do this?
I just got a set of FREE bus pistons and 2.0L rods. the skirts look go and I want to use these to freshen up my motor on the cheap while I get a real motor put together.

I have heard form someone that cutting some of the piston crown off can help in bumping up compression. HOW MUCH???
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type47
post Nov 7 2005, 08:18 AM
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could you verify that bus pistons are a drop in into a 2.0L? something in the back of my (rapidly fading) mind equates bus motor to a 1.8L motor and i think there is something about the piston pin location on 1.8's being different than 2.0's. like, you can't put the same 96mm's p&c's on a 1.8 and a 2.0. i may very well be mistaken but....
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davep
post Nov 7 2005, 08:20 AM
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The pistons have a deep large dish that creates the low compression. Removing more marterial will further reduce the compression.

How could removing anything in the compustion chamber increase compression?
Decking the heads maybe, cutting the cylinders maybe, but it sounds the wrong way to me.

Bus 94mm pistons fit. The 1.8 thought is related to the head design.
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Joe Ricard
post Nov 7 2005, 08:54 AM
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Must be Monday Morning !!
can't ya'll "Read Red neck"????
Cutting the crown on the piston will reduce the volume of the dish
having a deck hieght of .037 as least I want to run as a target.
removing piston crown by a few thousands woul enable me to also remove some base shims. Thus retaining the deck hieght.
With a smaller dish volume the compresion ratio would be higher.
MORE POWER.
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Jake Raby
post Nov 7 2005, 09:40 AM
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BUT it will bring the top ring seriously close to the crown.... The top ring doesn't like that much heat.

Been there and done that when I was 14!

Find a set of euro spec pistons used- I think I have a few sets left after my Ebay blowout..
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SLITS
post Nov 7 2005, 10:01 AM
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And here I thought high ring placement on the piston was one of the keys to more power.............
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bondo
post Nov 7 2005, 10:15 AM
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Just embrace the low compression as an opportunity to go TURBO! (IMG:http://www.914world.com/bbs2/html/emoticons/smile.gif)
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Joe Ricard
post Nov 7 2005, 10:33 AM
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Jake if I were going to spend money on Euro P&C's then I would rather spend the same money on getting some cylinders bored for my Chinese 96mm pistons and some good rings.

I want a 2056. Hell I really want a 2316 Deliverd by our favorite UPS girl. BUT ....... I am the original CSOB so that won't happen.

But until then I'll probably just put these pistons in my engine with new rings and be happy. Hey I've been whipping the field on used Bus pistons I got from Slits like 3 years ago now.
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SLITS
post Nov 7 2005, 10:59 AM
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Oh the shame for deflating all those guys egos with your bus pistons....we should banish you for such a transgression. (IMG:http://www.914world.com/bbs2/html/emoticons/lol2.gif)

The only thing I really remember (or at least think I do) is the the deck thickness of the piston should be at least minimum of 0.120", other wise......
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Joe Ricard
post Nov 7 2005, 11:14 AM
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Ahh I'll measure them up tonight. I'm pretty sure the distance from top ring to crown is WAY more than that.
And If I burn them up Well Oh well....
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Aaron Cox
post Nov 7 2005, 11:15 AM
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why dont you use some of that brazing rod and fill the dish on the piston. Hell make it a domed piston with valve pockets (IMG:http://www.914world.com/bbs2/html/emoticons/laugh.gif)
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SLITS
post Nov 7 2005, 11:33 AM
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QUOTE (Aaron Cox @ Nov 7 2005, 10:15 AM)
why dont you use some of that brazing rod and fill the dish on the piston. Hell make it a domed piston with valve pockets (IMG:http://www.914world.com/bbs2/html/emoticons/laugh.gif)

Heliarc oh exhalted engineer....Heliarc.....
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Aaron Cox
post Nov 7 2005, 11:46 AM
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QUOTE (SLITS @ Nov 7 2005, 10:33 AM)
QUOTE (Aaron Cox @ Nov 7 2005, 10:15 AM)
why dont you use some of that brazing rod and fill the dish on the piston. Hell make it a domed piston with valve pockets  :lol:

Heliarc oh exhalted engineer....Heliarc.....

was a joke.

buy the right pistons in the firstplace (IMG:http://www.914world.com/bbs2/html/emoticons/rolleyes.gif)
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maf914
post Nov 7 2005, 12:18 PM
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Just fill the piston dish with JB Weld and sand it smooth! Instant compression boost. (IMG:http://www.914world.com/bbs2/html/emoticons/laugh.gif)
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Joe Ricard
post Nov 7 2005, 12:20 PM
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QUOTE (Aaron Cox @ Nov 7 2005, 09:46 AM)
QUOTE (SLITS @ Nov 7 2005, 10:33 AM)
QUOTE (Aaron Cox @ Nov 7 2005, 10:15 AM)
why dont you use some of that brazing rod and fill the dish on the piston. Hell make it a domed piston with valve pockets  :lol:

Heliarc oh exhalted engineer....Heliarc.....

was a joke.

buy the right pistons in the firstplace (IMG:http://www.914world.com/bbs2/html/emoticons/rolleyes.gif)

Well that would just blow my whole theme with this car.
"Bad Ass on a budget"
Ya think I don't know how to build engines? Just for reference This motor I built YEARS ago was in my son's 914. anyone remember the "Cool Blue Teener" went up in flames. Anyway he beat the Piss out that engine Probably 20K miles of neglect.
I put the motor in the yellow car shortly after I got home from Wa. state. I've beat this motor everyday of it's life. If I'm not rolling down the freeway @ 85 -90 for 350 miles per trip I am racing it at an Autocross somewhere. 24 events this year. best I can figure is the engine has 40K + miles on it. The used rings in used cylinders on used BUS pistons were near the wear limit when I put them in. 100 bucks shipped was a GOOD deal. Never planned on doing what I'm doing with this car.
I didn't do it with an inexhaustable budget either. (IMG:http://www.914world.com/bbs2/html/emoticons/cool_shades.gif)

Just cause you throw money at it don't make it better.
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SLITS
post Nov 7 2005, 01:11 PM
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Uh oh.....Is this a case of "Mississippi" in revolt?
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Joe Ricard
post Nov 7 2005, 01:17 PM
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QUOTE (SLITS @ Nov 7 2005, 11:11 AM)
Uh oh.....Is this a case of "Mississippi" in revolt?

NAh. Just that there is a place for everyone. some people just have to be put there once in awhile.
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SLITS
post Nov 7 2005, 01:21 PM
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Iffin' ya need another set, I do believe I have some.....free for shipping from CA.


Back in my days (IMG:http://www.914world.com/bbs2/html/emoticons/laugh.gif) to build compression, you just cut the top off of a piston at the first ring land and bolted it to the other piston....wella, instant compression increase (IMG:http://www.914world.com/bbs2/html/emoticons/smile.gif)
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Joe Ricard
post Nov 7 2005, 01:26 PM
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I actually need ONE good cylinder. then I can match it up to the other 3 I have with no broken or very thin fins.
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SLITS
post Nov 7 2005, 02:15 PM
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QUOTE (Joe Ricard @ Nov 7 2005, 12:26 PM)
I actually need ONE good cylinder.  then I can match it up to the other 3  I have with no broken or very thin fins.

Sorry Joe, all I need is 3 2.0L bus pistons

(IMG:http://www.rccauto.com/engine/bus.jpg)

Yours iffin ya wants dem!
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