Ra12r
Zone Head
Posts: 919
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posted March 31, 2004 07:25 AM
Performance Gains from Base Gasket Removal
Lots of guys have removed the base gasket, and I am interested in you'all posting your "Actual" gains from this modification. The reduction in clearance, and the increase in compression has changed your performance by what amount??
Feel free to post the negative gains also.
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BA
Pro
Posts: 1592
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posted March 31, 2004 03:30 PM
 Edited By: BA on 31 Mar 2004 15:33
I think it's a fair question Ra12R, and as you probably realize, I've been reading my ass off concerning the whole 'base gasket' subject.
I know this much. Anyone can PLEASE bitchslap me if I'm wrong, just bring your facts.  lol!
Several people seem to have measured their base gaskets to be from .008" - .010" depending upon who you ask.
Also, I believe both Doug and Y2K (Jim) have concluded that this equals one half point. (.5)
That being said, Doug mentioned this last Dec.
"Now, given our theoretical engine, tests have shown that the actual power increase bears an almost linear relationship to the increase in compression.
So, if we raise the compression ratio one point, to 11:1, the resulting peak pressure would go up 10%...." Keep in mind he's talking pressure!
I recall reading more than once that for every 1 point increase in CR, you should get a 4% increase in peak HP.
So, if I'm making 200hp and THEN I increase my CR 1 full point, I should get 8 more HP, eh?
I'd be interested in hearing what others have heard, or learned firsthand.
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AnotherRedHead
Expert Class
Posts: 348
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posted April 01, 2004 09:46 AM
compression makes motors hard to start
My bike has only 8 to 1
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entropy
Moderator
Posts: 8671
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posted April 01, 2004 11:43 AM
quote:
compression makes motors hard to start...quote]
and not live too long... (15:1 +)
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BA
Pro
Posts: 1592
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posted April 01, 2004 01:34 PM
Entropy is most knowledgeable now about CR! 
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bossman12r
Zone Head
Posts: 513
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posted April 01, 2004 05:13 PM
So removing the base gasket should make a stock motor be around 13.1
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entropy
Moderator
Posts: 8671
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posted April 02, 2004 03:55 AM
Edited By: entropy on 2 Apr 2004 03:59
quote:
Entropy is most knowledgeable now about CR!
BA: hahahahahaha!
NOT most knowledgeable, but I have done a bit of homework.
With my set up adding/subtracting 1 base gasket (.010) = 0.3:1 CR difference
currently I have = 14.46:1 CR
remove 1 gasket= 14.77:1 CR
I am considering removing 1 gasket to decrease my squish height from .052" (current) to .042", which I am told is more or less optimum.
I don't want to increase CR but with the right fuel, 14.77 oughta be OK?????
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psycho1122
Pro
Posts: 1608
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posted April 02, 2004 06:57 AM
Edited By: psycho1122 on 2 Apr 2004 06:59
I do not run a base gasket on my 1270. CR is at 13.8-1.
Piston to valve is .050
Piston to head in quench area is .027
202 h.p. / 114 ft. lb. is the result! This a very tractable engine and runs EXCELLENT on 91 pump.
PROPER a/f ratio is key!!
NO OVERHEATING
NO DETONATION
NO HARD HOT STARTING
Cam Timing Helps 
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BA
Pro
Posts: 1592
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posted April 02, 2004 08:48 AM
PSYCHO! You soo didn't tell us what cam timing you are running!! Dude, I'm curious! What'cha got?!?! 103I/105E?
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entropy
Moderator
Posts: 8671
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posted April 02, 2004 09:08 AM
psycho
how thick is your headgasket????? are your pistons ABOVE the surface of the block at TDC?????
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MadMike
Moderator
FEAR THE BLACK FLAG!!!!!!!!
Posts: 6579
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posted April 02, 2004 02:42 PM
Holy shit psycho, how the hell did you do that?!!! what karl said?
you squish area is only.027??? wow. dangerous, I believe...
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200-MPH CLUB MEMBER!
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psycho1122
Pro
Posts: 1608
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posted April 04, 2004 09:46 AM
BA; Cam timing is 105 in./ 100 ex.
entropy; Head gasket is standard Muzzy/Cometic .030 . Actually, the pistons are just a vapor layer below deck! When this thing is running, no carbon can deposit on the exhaust side quench area.
Mad Mike; We clay check everything before assembly. The Mechanical limit for piston to head is .025! We are very close indeed, however- that's where the extra Torque comes from. She's a RUNNER! Even on a bad day it will pump out 198 h.p. w/ 114 ft. lbs.
Where do you like to run your piston to head clearances?
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Ra12r
Zone Head
Posts: 919
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posted April 04, 2004 05:50 PM
Psycho, your numbers are great and maybe the way you have assembled it helps it produce those numbers. Have you re-produced those results with the same combo on other bikes? Is some of your other clearances also on the edge?? Last question, have you checked your PSI??? Okay, one more,,,,,,are you using Muzzy "supplied" pistons????
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psycho1122
Pro
Posts: 1608
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posted April 05, 2004 07:10 AM
ra12r;
No reproduction on other bikes at this time...People feel the 12 is "Fast Enough" and don't see a need to spend the $.
Psi on this engine is 230 a hole COLD. Hard to check hot!
Full Muzzy pistons and rings!!
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NORTY
Novice Class
Posts: 47
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posted April 12, 2004 11:08 AM
quote:
So removing the base gasket should make a stock motor be around 13.1
Stock motor as delivered is 12.2:1
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