| [ Total Views: 566 | Total Replies: 7 | Thread Id: 15414 ] |
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 karmannghia60
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| posted on November 5th, 2003 at 07:52 PM |
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Shims under barrels
I know they are there to reduce compression but how do I determine whether I need them or not? What I have now is about 1.5mm.
Raf
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 vw54
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| posted on November 5th, 2003 at 08:20 PM |
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Now yr getting into the nitty gritty. Raf you have to work out the compression ratio using a formular. Dont throw them away
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Menangler
A.k.a.: Dave Becker
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| posted on November 5th, 2003 at 08:45 PM |
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Use this calculator to work out your compression,
http://www.csgnetwork.com/compcalc.html
You will need to know the deck height, the volume of the cylinder head, and of cause the size of your engine.
FAHRVERGNUGEN;
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Experienced when a car and it's driver are in mutual harmony, A unique driving experience, Pleasure, Satisfaction,
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LOWBUG
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| posted on November 5th, 2003 at 08:56 PM |
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Nice Work
Nice work Dave, what a great sight, everyone should have that in thier favorites
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karmannghia60
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| posted on November 6th, 2003 at 06:48 AM |
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Thanks. This is for an 1835 so it the following correct?
- bore 92mm
- stroke 69mm (standard)
- head gasket bore 92???
- compressed head gasket thickness (is this the thinkness of the shim?)
- chamber volume (is it 46x46x3.14x69=458.45cc?)
If I use the above with 2mm deck clearance I get compression of 1.97:1 which doesn't sound right. What am I doing wrong?
Raf
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karmannghia60
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| posted on November 6th, 2003 at 06:49 AM |
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Ah, and what is a reasonable CR for an daily driver 1835? Around 8.5:1?
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lugnuts
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| posted on November 6th, 2003 at 03:47 PM |
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Dunno bout the rest but chamber volume is measured not calculated and should be something between 40-60cc per chamber. |
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lugnuts
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| posted on November 6th, 2003 at 03:57 PM |
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Heres another calculater bit simpler without the H2O bull*hit. http://www.cbperformance.com/enginecalc.html
:thumb |
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 Bizarre
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| posted on November 6th, 2003 at 04:01 PM |
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http://www.aircooled.net/gnrlsite/resource/specgeninfo/calcs.htm
Here is a simpler one
For example
on MY motor
bore 90.5mm
stroke 69mm
deck 2mm
combustion chamber cc's 48
CR = 8.3
To measure the head you need to get it dead flat with the valves in and seated. Then get a syringe and measure the water going in. This will give you
your head cc's
Should be around 50-55cc.
Deck height you need to have the cylinders torqued down. Then measure the distance fron the top of the cylinder to the top of the piston.
The new wave of thinking is keeping your deck tight. Cant go too tight our you will bend something.
2mm is good. This "apparently" gives "squish"
If your deck is tight them you need cc's. If you need cc's and the heads have been fly cut then they need opening. Open too far and then you
need hemmi-ing.
Is hemi good???
Lets not go there. I actually have hemi cut heads.
I would personally have hemi heads than shims under the barrels and too much deck.
You see where this is going - round and round and round and round
To have an opinion you need to have built several motors and FELT the difference.
Or be like me. I have built one motor (several times) and read heaps and PRETEND i know.
IF you want to be real picky you will measure ALL FOUR cylinders. Not just one
Futue te ipsum!!!
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karmannghia60
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| posted on November 6th, 2003 at 04:37 PM |
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Thanks a lot. I got plenty to play with and learn by the looks of it
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