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pablovent
Samba Member
Joined: July 14, 2010
Posts: 900
Location: Chile
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 Posted: Mon May 09, 2011 1:46 pm Post subject: deck high decision |
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Hi...for my 2187cc need a better decision!!
for 8,5 Cr have two options:
1.- 3,2mm deck high with 51cc heads or
2.- 2,5mm deck high with 56cc fly cut heads.
what is better decision?? |
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56Speedster
Samba Member
Joined: May 14, 2009
Posts: 66
Location: UFO Capital
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| Posted: Mon May 09, 2011 2:25 pm Post subject: |
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| Option 2 |
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slalombuggy
Samba Member
Joined: July 17, 2010
Posts: 9340
Location: Canada
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| Posted: Mon May 09, 2011 2:27 pm Post subject: |
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#2 . Way more efficient combustion.
brad |
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pablovent
Samba Member
Joined: July 14, 2010
Posts: 900
Location: Chile
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| Posted: Mon May 09, 2011 6:12 pm Post subject: |
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| slalombuggy wrote: |
#2 . Way more efficient combustion.
brad |
exist a problem with 2,5 mm deck high??..... |
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DarthWeber
Samba Member
Joined: November 24, 2007
Posts: 7542
Location: Whittier,CA
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| Posted: Mon May 09, 2011 6:24 pm Post subject: |
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| pablovent wrote: |
| exist a problem with 2,5 mm deck high??..... |
Yes and no. Optimum deck should be between 0.040" (1.00mm) and 0.060" (1.50mm). Your motor will run fine with 2.5, it's just not ideal. Nothing to lose sleep over. What cam are you planning on running and are you way up in the Andes or closer to ocean level? |
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kielbasa
Samba Member
Joined: November 28, 2007
Posts: 1443
Location: Garbage Grove, CA
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| Posted: Mon May 09, 2011 6:39 pm Post subject: |
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I run a .060 deck and .031 copper head gasket.10:1 comp. I don't see any problem with big deck. Seems to work bitchen.
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offrdbus70
Samba Member
Joined: August 23, 2006
Posts: 512
Location: Pine Valley-SD
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| Posted: Mon May 09, 2011 8:27 pm Post subject: |
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| kielbasa wrote: |
| I run a .060 deck and .031 copper head gasket.10:1 comp. I don't see any problem with big deck. Seems to work bitchen. |
I had a .120 deck and it seemed to run bitchen. Right up until I changed it to .038
Now it runs amazing. Starts right now. Ultra crisp and torquey.
No big decks for me anymore!
MG |
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RockCrusher
Samba Member
Joined: August 03, 2010
Posts: 4596
Location: Parkesburg, PA
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| Posted: Mon May 09, 2011 8:33 pm Post subject: |
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| offrdbus70 wrote: |
| kielbasa wrote: |
| I run a .060 deck and .031 copper head gasket.10:1 comp. I don't see any problem with big deck. Seems to work bitchen. |
I had a .120 deck and it seemed to run bitchen. Right up until I changed it to .038
Now it runs amazing. Starts right now. Ultra crisp and torquey.
No big decks for me anymore!
MG |
 Another convert....
RC
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modok
Samba Member
Joined: October 30, 2009
Posts: 27747
Location: Colorado Springs
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| Posted: Mon May 09, 2011 10:31 pm Post subject: |
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| pablovent wrote: |
| slalombuggy wrote: |
#2 . Way more efficient combustion.
brad |
exist a problem with 2,5 mm deck high??..... |
I do not believe it matters if you do #1 or #2
2.5mm or 3.5mm will run the same
we like to have 1-1.5mm for best performance,
If more than 2mm and squish/quench effect is lost, so 2 or 3mm will run the same. |
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pablovent
Samba Member
Joined: July 14, 2010
Posts: 900
Location: Chile
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| Posted: Tue May 10, 2011 8:15 am Post subject: |
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| modok wrote: |
| pablovent wrote: |
| slalombuggy wrote: |
#2 . Way more efficient combustion.
brad |
exist a problem with 2,5 mm deck high??..... |
I do not believe it matters if you do #1 or #2
2.5mm or 3.5mm will run the same
we like to have 1-1.5mm for best performance,
If more than 2mm and squish/quench effect is lost, so 2 or 3mm will run the same. |
best performance is high CR? |
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pablovent
Samba Member
Joined: July 14, 2010
Posts: 900
Location: Chile
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| Posted: Tue May 10, 2011 8:22 am Post subject: |
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| DarthWeber wrote: |
| pablovent wrote: |
| exist a problem with 2,5 mm deck high??..... |
Yes and no. Optimum deck should be between 0.040" (1.00mm) and 0.060" (1.50mm). Your motor will run fine with 2.5, it's just not ideal. Nothing to lose sleep over. What cam are you planning on running and are you way up in the Andes or closer to ocean level? |
Is for my buggy only for sand dunes use!!!....for solid low end torque and 1000-5000 rpm range use a c25 with 1,25 rockers!!!
i want 8,5 CR......if use 1mm deck high (ideal) the CR is too high...
i have a dual non ported 40x35,5 heads....single idf44 with 32 vents and heavy weight flywheel!!....
My heads in this moment have a 51cc .......but exist the option increased to 56cc unshrouded combustion chambers!!...is better??? |
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DarthWeber
Samba Member
Joined: November 24, 2007
Posts: 7542
Location: Whittier,CA
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| Posted: Tue May 10, 2011 9:02 am Post subject: |
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Given a choice between the two run 56cc chambers and 2.5mm (0.098") deck. The obstacle is that you are trying to run a small cam in a big motor so compromises must be made. Best route to go is open up the combustion chambers as much as possible while trying to maintain as much squish area as possible and run as tight a deck as you can. Would you be willing to change cams? Even a C35 would open up better deck/chamber volume combinations and with 2187cc's you would still have very good bottom end torque. What's your piston size and crank size? 2187??
A comment about your cylinder heads, you have unported 40 x 35.5mm heads. The ports are the restriction in the heads, adding big valves will not help at all. For your application a set of stock valve (35.5 x 32mm) heads with mild port work would have been a better match with the cam and carb you chose. Higher port velocity will give better bottom end and mid range torque. |
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pablovent
Samba Member
Joined: July 14, 2010
Posts: 900
Location: Chile
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| Posted: Tue May 10, 2011 9:16 am Post subject: |
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| DarthWeber wrote: |
Given a choice between the two run 56cc chambers and 2.5mm (0.098") deck. The obstacle is that you are trying to run a small cam in a big motor so compromises must be made. Best route to go is open up the combustion chambers as much as possible while trying to maintain as much squish area as possible and run as tight a deck as you can. Would you be willing to change cams? Even a C35 would open up better deck/chamber volume combinations and with 2187cc's you would still have very good bottom end torque. What's your piston size and crank size? 2187??
A comment about your cylinder heads, you have unported 40 x 35.5mm heads. The ports are the restriction in the heads, adding big valves will not help at all. For your application a set of stock valve (35.5 x 32mm) heads with mild port work would have been a better match with the cam and carb you chose. Higher port velocity will give better bottom end and mid range torque. |
then, unlike all others!!, i am interested in strength and power from real bottom, not high rpms all the time !!... I pedal hard and get out !!...... like a honda xr 400, but not a Honda CBR 400!! keeping the 2187 cc and the same central idf 44 carburetor ..... that combination of vents, heads, cam and rockers do you recommend? |
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DarthWeber
Samba Member
Joined: November 24, 2007
Posts: 7542
Location: Whittier,CA
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| Posted: Tue May 10, 2011 9:22 am Post subject: |
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| pablovent wrote: |
| ..... that combination of vents, heads, cam and rockers do you recommend? |
Everything except the heads. |
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pablovent
Samba Member
Joined: July 14, 2010
Posts: 900
Location: Chile
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| Posted: Tue May 10, 2011 9:25 am Post subject: |
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| DarthWeber wrote: |
| pablovent wrote: |
| ..... that combination of vents, heads, cam and rockers do you recommend? |
Everything except the heads. |
sorry, i dont understand!! |
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DarthWeber
Samba Member
Joined: November 24, 2007
Posts: 7542
Location: Whittier,CA
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| Posted: Tue May 10, 2011 9:28 am Post subject: |
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| DarthWeber wrote: |
A comment about your cylinder heads, you have unported 40 x 35.5mm heads. The ports are the restriction in the heads, adding big valves will not help at all. For your application a set of stock valve (35.5 x 32mm) heads with mild port work would have been a better match with the cam and carb you chose. Higher port velocity will give better bottom end and mid range torque. |
Pablo, run the combo of parts you listed at 8.5:1 CR, 56cc chambers and 2.5mm deck and you'll be fine.
Last edited by DarthWeber on Tue May 10, 2011 10:41 am; edited 1 time in total |
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vgajames
Samba Member
Joined: June 13, 2002
Posts: 805
Location: Texas
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| Posted: Tue May 10, 2011 9:29 am Post subject: |
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| kielbasa wrote: |
| I run a .060 deck and .031 copper head gasket.10:1 comp. I don't see any problem with big deck. Seems to work bitchen. |
Is that.060 deck height with the .031 copper shim or without?
If you saying you have .060 without the .031 copper shim then thats actually .091 " deck height.
ie... is someone has zero deck height and add's a .040 copper head shim they have .040 deck height. |
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kielbasa
Samba Member
Joined: November 28, 2007
Posts: 1443
Location: Garbage Grove, CA
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| Posted: Tue May 10, 2011 9:56 am Post subject: |
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Yes I have 91 deck..... sorry
_________________
Gotta give my props to:
Wolfsburg Motorsports
Dubbers Toy Box
Jeff's VW Speed and Fab
4inbore.com
Kielbasa Industries |
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[email protected]
Samba Member
Joined: August 03, 2002
Posts: 12785
Location: Salt Lake City, Utah
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| Posted: Tue May 10, 2011 10:02 am Post subject: |
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deck height is NOT the height of the top of the piston to the top of the cylinder.
Deck Height is the distance from the top of the piston to the DECK OF THE HEAD. All this "Zero Deck" nonsense is confusing people. There is no such thing.
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midtravelmidengine
Samba Member
Joined: August 06, 2009
Posts: 861
Location: Riverside, Ca
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| Posted: Tue May 10, 2011 10:32 am Post subject: |
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| [email protected] wrote: |
Deck Height is the distance from the top of the piston to the DECK OF THE HEAD. All this "Zero Deck" nonsense is confusing people. There is no such thing. |
THANK YOU!!!!
_________________
| modok wrote: |
| And I know you don't know because if you did you would know the reason for my knowing you didn't. |
| youngnstudly wrote: |
I just wasn't sure if I should recommend the 1/3 race cam, the 1/2 race cam, or the 5/8 race cam instead...guess it depends on how much of the race he wants to lead???
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