| [ Total Views: 900 | Total Replies: 18 | Thread Id: 92009 ] |
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 jaksc
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| posted on August 7th, 2011 at 06:51 AM |
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Compression Ratio
I'm having a go at screwing together a 1776 for everday use. What compression ratio do i need to run. Doing the measurements it is currently at 9:1.
How do i go about raising it or lowering it. Thanks Aaron
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Paulc1964au
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| posted on August 7th, 2011 at 08:05 AM |
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Am Interested to see if u r happy with the 1776 why have you selected a 1776
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hellbugged
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| posted on August 7th, 2011 at 08:07 AM |
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was it just a displacment change or other things as well?
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jaksc
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| posted on August 7th, 2011 at 11:03 AM |
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Had a 1776 built afew years ago by a reputed vw specialist. Had too much end float movement from when it was built. Had about 1000miles on it.
Stripped it down and couldn't find anyone to put it back together. Lots of brand new parts. So having a go myself. just need to be pointed in the
right direction. Aaron
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hellbugged
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| posted on August 7th, 2011 at 12:16 PM |
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So it's stockfish or big cam, heads etc?
Counterweighted balanced?
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hellbugged
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| posted on August 7th, 2011 at 12:17 PM |
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And how have you worked out the c.r?
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jaksc
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| posted on August 7th, 2011 at 12:26 PM |
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Basically stock. Aaron
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hellbugged
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| posted on August 7th, 2011 at 02:06 PM |
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spacers under the barrels or "flycutting' the heads or combo of both
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jaksc
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| posted on August 7th, 2011 at 05:13 PM |
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What compression ratio do i need? Aaron
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jaksc
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| posted on August 8th, 2011 at 08:22 PM |
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Anyone with some tech advice on what ratio I should use. What does it depend on.
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 Bizarre
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| posted on August 8th, 2011 at 09:04 PM |
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low 8's??
9 is a tad high for a stockish motor - but what would I know
It all depends on the cam, heads, valve size, deck height and a whole heap of experience.
Did you cc the heads??
Futue te ipsum!!!
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Ollie
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| posted on August 9th, 2011 at 11:31 AM |
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Go 14.5:1 and you'll just love it 
I lie.
As all above have mentioned, A good strong engine is the sum of it's parts, rather than one standout performance enhancement.
IMO a stockish 1776 would benefit from somewhere between 8 and 8.5:1 compression. It should give it that extra zap without causing too much stress to
the engine.
That said, I could be so far wrong It's not funny!
Ollie
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BiX
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| posted on August 9th, 2011 at 01:43 PM |
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My old 1776 with stock bottom end, mild port and polish and W100 cam had about 8.5/9 ish.
But in the end, that was selected by the engine builder based on the engine combo.
I have no sympathy for my car, only the wallet that pays for it!
Go hard or go home!!!!
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jaksc
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| posted on August 9th, 2011 at 06:09 PM |
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I worked out the ratio by
cyl volume + head volume + deck height volume
_______________________________________
head volume + deck volume
Stroke = 69mm
I am getting confused. Am i going to to much trouble. Just bolt the barrels down and forget about it. Thanks Aaron
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Bizarre
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| posted on August 9th, 2011 at 08:40 PM |
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check your answer against this calculator
http://www.aircooled.net/gnrlsite/resource/specgeninfo/calcs.htm
We are just saying 9 is on the high side
You could put a small spacer under the barrels or open the heads up a bit
The spacer mucks you deck height up and that mucks "squish" up
You could whack it all together and see what happens - you might just have to run 98 octane to keep pinging at bay
Futue te ipsum!!!
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Gracey
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| posted on August 9th, 2011 at 09:14 PM |
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Impossible to say without knowing what cam you've got.
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jaksc
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| posted on August 10th, 2011 at 07:01 PM |
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Bizarre, I used the calculator and came up with a figure of 8:1 ratio. I think I am going to go with just bolting everything up as is. There was a lot
more involved to this topic than I thought. Thanks for the help guys. Aaron
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RISKY4LIFE
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| posted on August 10th, 2011 at 07:26 PM |
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i think that you could run upto 8.5 for every day use if it was built right
but im no engine builder!
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Bizarre
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| posted on August 10th, 2011 at 09:08 PM |
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jus go for it and see what happens
Only way to learn 
Futue te ipsum!!!
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