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Glenn73
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Joined: May 30, 2011
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Location: West Jordan UT
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 Posted: Wed Jun 13, 2012 9:55 pm Post subject: Is my compression too high? |
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Ok. So I had to get a new motor due to a ruined crank and using
http://www.csgnetwork.com/compcalc.html I get 11.4-1.
Its a 1776cc with AA P&Cs, Stock crank, rods, rockers, heads, and a mild cam (an ACE 262 special grind).
Also running 34-3 carb with a 009  (I know not the best combo) and a stock muffler.
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1973 SB 1776cc
Sat from 93-2008
Work in progress. |
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KopfenJager
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Location: Oregon
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| Posted: Wed Jun 13, 2012 9:58 pm Post subject: |
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post your measurments, that seems realy high for a 1776.
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Glenn73
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| Posted: Wed Jun 13, 2012 10:04 pm Post subject: |
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It has a 0.060 base shim and a 0.040 copper head shim.
So it is at about 0.10 deck.
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1973 SB 1776cc
Sat from 93-2008
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KopfenJager
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| Posted: Wed Jun 13, 2012 10:15 pm Post subject: |
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what do the heads cc out to be?
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Glenn73
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| Posted: Wed Jun 13, 2012 10:22 pm Post subject: |
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43cc I dont know how I missed that part
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1973 SB 1776cc
Sat from 93-2008
Work in progress.
Last edited by Glenn73 on Sun Jul 08, 2012 10:14 pm; edited 1 time in total |
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SRP1
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| Posted: Wed Jun 13, 2012 10:26 pm Post subject: |
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So .100" deck, what head cc?
With a head cc of around say 54cc's, your at 7.3:1
I would shoot for a deck of .050-.070" for a compression ratio of 7.7-8.1:1
depending on your build criteria.
Like I said "what head cc?" is the key question in determining your actual
deck height and final comp ratio.
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Last edited by SRP1 on Wed Jun 13, 2012 10:29 pm; edited 1 time in total |
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GDOG57
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Location: Gilbert,Arizona
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| Posted: Wed Jun 13, 2012 10:29 pm Post subject: |
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Just punch in your numbers here:
http://www.cbperformance.com/enginecalc.html
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SRP1
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| Posted: Wed Jun 13, 2012 10:30 pm Post subject: |
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| Glenn73 wrote: | | 42cc I dont know how I missed that part |
Ahhh your at 8.6:1 right now, and your deck height is ridiculously huge.
I would have your pistons dished, then bring the deck height down as close to .060" as you can. .100" deck and it will be a ping monster.
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Last edited by SRP1 on Wed Jun 13, 2012 10:34 pm; edited 1 time in total |
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Splitdog
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| Posted: Wed Jun 13, 2012 10:33 pm Post subject: |
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Perfect.
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Glenn73
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| Posted: Wed Jun 13, 2012 10:33 pm Post subject: |
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Oh thank you I must have punched the numbers in wrong to get 11.4-1 
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1973 SB 1776cc
Sat from 93-2008
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KopfenJager
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Location: Oregon
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| Posted: Wed Jun 13, 2012 10:59 pm Post subject: |
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If I plug in 90.5mm bore, 69mm stroke 42cc heads and .010 deckheight I get 11.2 to 1 CR. So the question is, what is the final deck height after all the shims and gaskets etc. How far do the pistons sit down in the bore? .010 is EXTREMELY tight deck  . At .040 deck your still pushing 10-1CR. At .060 deckheight you about 9.6-1 CR. Those chambers seem pretty small to me to run on pump fuel.
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modok
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| Posted: Thu Jun 14, 2012 12:30 am Post subject: |
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| "stock" 113 heads with the step cut out are usually around 47cc, are you sure your heads are 42? that's small! |
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66brm
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| Posted: Thu Jun 14, 2012 12:35 am Post subject: |
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Perhaps the anti Berg creator has struck again!!!!!!
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| modok wrote: | | I am an expert at fitting things in holes, been doing it a long time |
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Glenn73
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Location: West Jordan UT
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| Posted: Thu Jun 14, 2012 11:06 am Post subject: |
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| Quote: | KopfenJager
So the question is, what is the final deck height after all the shims and gaskets etc. How far do the pistons sit down in the bore? .010 is EXTREMELY tight deck |
It sits at .100" deck.
| Quote: | modok
"stock" 113 heads with the step cut out are usually around 47cc, are you sure your heads are 42? that's small! |
They were on a 1600cc that bummed out on me and left impressions where the cylinders were. When they got cut for 90.5's they got cut a lil deep.
| Quote: | | I would have your pistons dished, then bring the deck height down as close to .060" as you can. .100" deck and it will be a ping monster. |
Actually it doesn't ping. I run nothing under 91 octane.
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1973 SB 1776cc
Sat from 93-2008
Work in progress.
Last edited by Glenn73 on Mon Jun 18, 2012 2:13 am; edited 1 time in total |
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KopfenJager
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| Posted: Thu Jun 14, 2012 3:12 pm Post subject: |
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Ok 8.6 Cr.
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Alstrup
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| Posted: Thu Jun 14, 2012 3:19 pm Post subject: |
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Get your deck height down to 0,043 - 0,050" and find yourself another set of heads.
Runing that much deck (0,100) makes for a lazy running hot running, polluting SOB.
T |
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Alstrup
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| Posted: Thu Jun 14, 2012 3:21 pm Post subject: |
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PS. that cam can handle a tad more CR. if needed, as long a s the timing is under control. 8,4 is no problem.
T |
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Glenn73
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Location: West Jordan UT
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| Posted: Mon Jun 18, 2012 2:11 am Post subject: |
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Ok. So now that its been noted that it is an ok CR What kind of carb and distributor combo should I use?
I am open to going to Dual carb.
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1973 SB 1776cc
Sat from 93-2008
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KopfenJager
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Location: Oregon
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| Posted: Mon Jun 18, 2012 9:08 am Post subject: |
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If you ever think that someday you will want a bigger engine with bigger heads , cam etc. Go duals. Weber 44Idf's can cover most engine combo's if jetted right with the proper venturi. Other carbs can work well, but none work as good as a set of properly tuned duals.
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