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FastPete71
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PostPosted: Thu Apr 19, 2012 7:40 pm    Post subject: Head CC Reply with quote

How many cc will you loose by flycutting the step out of 043"s ?

Mine are 54cc now

Thanks
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modok
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PostPosted: Thu Apr 19, 2012 7:49 pm    Post subject: Reply with quote

(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
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PostPosted: Thu Apr 19, 2012 8:31 pm    Post subject: Reply with quote

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
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PostPosted: Thu Apr 19, 2012 11:45 pm    Post subject: Reply with quote

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
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Little Harry
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PostPosted: Fri Apr 20, 2012 5:42 pm    Post subject: Reply with quote

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
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PostPosted: Fri Apr 20, 2012 5:51 pm    Post subject: Reply with quote

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
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PostPosted: Fri Apr 20, 2012 5:57 pm    Post subject: Reply with quote

Thanks Modok, so all it really boils down to is an emissions thing, makes sense.
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modok
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PostPosted: Fri Apr 20, 2012 6:10 pm    Post subject: Reply with quote

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
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PostPosted: Fri Apr 20, 2012 6:51 pm    Post subject: Reply with quote

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
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PostPosted: Sat Apr 21, 2012 7:29 pm    Post subject: Reply with quote

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 Very Happy
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mark tucker
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PostPosted: Sat Apr 21, 2012 10:37 pm    Post subject: Reply with quote

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
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PostPosted: Sun Apr 22, 2012 2:55 am    Post subject: Reply with quote

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
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PostPosted: Sun Apr 22, 2012 8:39 am    Post subject: Reply with quote

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
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PostPosted: Sun Apr 22, 2012 9:43 am    Post subject: Reply with quote

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
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PostPosted: Sun Apr 22, 2012 2:54 pm    Post subject: Reply with quote

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
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PostPosted: Sun Apr 22, 2012 5:43 pm    Post subject: Reply with quote

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
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PostPosted: Sun Apr 22, 2012 5:47 pm    Post subject: Reply with quote

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
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PostPosted: Sun Apr 22, 2012 5:50 pm    Post subject: Reply with quote

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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