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FastPete71 Samba Member
Joined: December 19, 2010 Posts: 170
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Posted: Thu Apr 19, 2012 7:40 pm Post subject: Head CC |
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How many cc will you loose by flycutting the step out of 043"s ?
Mine are 54cc now
Thanks |
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modok Samba Member
Joined: October 30, 2009 Posts: 26740 Location: Colorado Springs
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Posted: Thu Apr 19, 2012 7:49 pm Post subject: |
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(bore divided by two)squared, times pi times step
all units centimeters
if the step is .15cm and stock bore then it would be 8.6cc |
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mark tucker Samba Member
Joined: April 08, 2009 Posts: 23937 Location: SHALIMAR ,FLORIDA
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Posted: Thu Apr 19, 2012 8:31 pm Post subject: |
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are you replacing it with a copper gasket? if so then it would be the differance between the gasket thickness& the step depth .or pretty darn close since the step is wider than the gasket(wider as in across the bore size steps are usualy wider than the gasket.)just cc it so you wont wonder till the end of time.and have a peice of modocks square pie he made for the morlocks who think it's cake. |
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blue77bay Samba Member
Joined: February 11, 2006 Posts: 631 Location: Brisvegas Australia
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Posted: Thu Apr 19, 2012 11:45 pm Post subject: |
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mark tucker wrote: |
are you replacing it with a copper gasket? if so then it would be the differance between the gasket thickness& the step depth .or pretty darn close since the step is wider than the gasket(wider as in across the bore size steps are usualy wider than the gasket.)just cc it so you wont wonder till the end of time.and have a peice of modocks square pie he made for the morlocks who think it's cake. |
LOL man u crack me up _________________ I like hammers. Lots of hammers. Hammers and me go way back.
A large hammer collection is like an instant problem solver
Mark tucker wrote:,wack off as needed |
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Little Harry Samba Member
Joined: November 15, 2011 Posts: 340 Location: Marquez, Texas
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Posted: Fri Apr 20, 2012 5:42 pm Post subject: |
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Not trying to thread hijack but this raises a question that I have. I have been doing a lot of reading/research on the forum trying to learn as much as I can about engine building (air cooled specific). One question I have is this...Why is it that a lot of people elect to remove the step from the heads?
I am in the process of building a 1679cc (88mm bore X 69mm stroke) using aircooled.net's thick wall 88's. I haven't selected my cylinder heads yet but I was debating whether a stock set of heads or the stocker plus set (L3's) with the step removed from aircooled.net.
What is the reason the step is removed and is there any benefit on a motor that is the size of mine with a stock camshaft?
I am sorry for all of the newbie type questions but this is just something I have been pondering. |
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modok Samba Member
Joined: October 30, 2009 Posts: 26740 Location: Colorado Springs
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Posted: Fri Apr 20, 2012 5:51 pm Post subject: |
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well, if you don't cut it out you'll be stuck running .100" or more from the quench pads, one way or the other, because the bigger piston won't fit inside the step
running tight has been the way to go since......the beginning, but vw put the step in there to lower HC emissions......which was stupid, and they still make them like that, just to piss us off probably
It is simpler to cut it out
Last edited by modok on Fri Apr 20, 2012 5:57 pm; edited 1 time in total |
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Little Harry Samba Member
Joined: November 15, 2011 Posts: 340 Location: Marquez, Texas
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Posted: Fri Apr 20, 2012 5:57 pm Post subject: |
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Thanks Modok, so all it really boils down to is an emissions thing, makes sense. |
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modok Samba Member
Joined: October 30, 2009 Posts: 26740 Location: Colorado Springs
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Posted: Fri Apr 20, 2012 6:10 pm Post subject: |
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exactly, it was added for emissions
Why they did that instead of just making the pistons shorter is what I find puzzling.
You can sometimes make use of the step in some combinations, setting it up so the piston is even with the top of the cylinder, but this requires that the ID of the step be bore size, and is really only worth doing on strokers. |
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FastPete71 Samba Member
Joined: December 19, 2010 Posts: 170
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Posted: Fri Apr 20, 2012 6:51 pm Post subject: |
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Im cutting it out because im on a tight budget for this build, and the pistons I have the 5cc dish in them. So compression is 7 to1 yuck.
So the eaisest way to get it to 8 to 1 is removing the step and maybe a bit more. I will be ccing the head tomorrow after the step is gone and see if I need more.
Thanks for all the answers. |
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FastPete71 Samba Member
Joined: December 19, 2010 Posts: 170
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Posted: Sat Apr 21, 2012 7:29 pm Post subject: |
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modok wrote: |
(bore divided by two)squared, times pi times step
all units centimeters
if the step is .15cm and stock bore then it would be 8.6cc |
Pretty close it took out 9cc so 8.2 now |
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mark tucker Samba Member
Joined: April 08, 2009 Posts: 23937 Location: SHALIMAR ,FLORIDA
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Posted: Sat Apr 21, 2012 10:37 pm Post subject: |
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modok wrote: |
well, if you don't cut it out you'll be stuck running .100" or more from the quench pads, one way or the other, because the bigger piston won't fit inside the step
running tight has been the way to go since......the beginning, but vw put the step in there to lower HC emissions......which was stupid, and they still make them like that, just to piss us off probably
It is simpler to cut it out |
I open up the step on my mill to a depth of .040 for most engines.I did my first mofoco heads on a rotery table, cut them down to the deck of the head for 87 bore with 78.8 crank, .060 head gasket and the piston stuck out of gasket .025 up into the head, dont remember the cylinder shims.080 I think, that was good for 11.5 cr on those cast pistons, ran it for 1 year like that with bugspray& fk8, then lowered the cr to 10.6, 3 more years run time then duell 44 hpmx went on it for about 2 years.it's now a 2028cc 10.4 cr wedgeported 42x37 mofoco 042's cb cam 2250 1.33 rockers. about 55000 miles as the 1874 cc motor,15000 sofar as a 2028.yes with the cast scat crank.and now the ultra thin berg/cima 90.5 specials.(new case too when the cc went up) you can configure it just about any way you want,as long as it works. |
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JustBuggy Samba Member
Joined: August 01, 2010 Posts: 849 Location: SF Bay Area, Ca.
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Posted: Sun Apr 22, 2012 2:55 am Post subject: |
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FastPete71 wrote: |
...... the pistons I have the 5cc dish in them. So compression is 7 to1 yuck...... |
What about trimming the edge of the piston off to get rid of the dish and raise compression? |
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FastPete71 Samba Member
Joined: December 19, 2010 Posts: 170
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Posted: Sun Apr 22, 2012 8:39 am Post subject: |
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JustBuggy wrote: |
FastPete71 wrote: |
...... the pistons I have the 5cc dish in them. So compression is 7 to1 yuck...... |
What about trimming the edge of the piston off to get rid of the dish and raise compression? |
Think about it that would lower it even more. |
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mark tucker Samba Member
Joined: April 08, 2009 Posts: 23937 Location: SHALIMAR ,FLORIDA
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Posted: Sun Apr 22, 2012 9:43 am Post subject: |
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then trim the cylinders so the piston gos farther up it.many ways to skin this cat, just watch for the claws&teeth. |
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JustBuggy Samba Member
Joined: August 01, 2010 Posts: 849 Location: SF Bay Area, Ca.
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Posted: Sun Apr 22, 2012 2:54 pm Post subject: |
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FastPete71 wrote: |
JustBuggy wrote: |
FastPete71 wrote: |
...... the pistons I have the 5cc dish in them. So compression is 7 to1 yuck...... |
What about trimming the edge of the piston off to get rid of the dish and raise compression? |
Think about it that would lower it even more. |
Not if you set the new deckheight ...... |
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FastPete71 Samba Member
Joined: December 19, 2010 Posts: 170
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Posted: Sun Apr 22, 2012 5:43 pm Post subject: |
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That dish is pretty deep. I bet .100 I wouldnt think about running it that.
Yes you could trim the cylinders and so on.
Top ring would be pretty close to the top of the cylinder.
Is it worth it? Naa |
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FastPete71 Samba Member
Joined: December 19, 2010 Posts: 170
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Posted: Sun Apr 22, 2012 5:47 pm Post subject: |
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I was close its .150 lol
Im not cutting my pistons and cylinders that much.
One thing affects another now pushrods etc. |
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modok Samba Member
Joined: October 30, 2009 Posts: 26740 Location: Colorado Springs
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Posted: Sun Apr 22, 2012 5:50 pm Post subject: |
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yeah, no fancy tricks needed for this little engine
If it was a stroker with some proper size pistons then maybe we play with steps |
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