Ideal compression for a 57h

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Oct 30, 2014 | 05:26 PM

#11

ridedaddy

Thread Starter

Road Master

Joined: Mar 2013

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From: chatham il

Ok so the final conclusion is........? Is it a good idea to install a .030" hg to get a few hp/tq or will the gains be to minimal concidering the cam doesn't need the extra compression?

Oct 30, 2014 | 06:00 PM

#12

slyedog

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Joined: Aug 2013

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From: Hawkeye state

Quote:

Originally Posted by ridedaddy

Ok so the final conclusion is........? Is it a good idea to install a .030" hg to get a few hp/tq or will the gains be to minimal concidering the cam doesn't need the extra compression?

If our getting the heads reworked then do it per the machinist doing them advice. If no headwork not worth the time.

Oct 30, 2014 | 09:16 PM

#13

HD Pilot

Elite HDF Member

Joined: Sep 2012

Posts: 3,791

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From: N Texas

Quote:

Originally Posted by slyedog

If no headwork not worth the time.

But a big bore and the .030" hgs would be worth it.

Oct 31, 2014 | 06:12 AM

#14

Hillsidecycle.com

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Joined: Dec 2007

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Ask target64 what a good set of heads, and big bore can do!
Scott

Oct 31, 2014 | 07:08 AM

#15

98hotrodfatboy

Seasoned HDF Member

Joined: Mar 2010

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From: Poolville

for real

Definitely the nastiest harley I ever heard............period...........

Quote:

Originally Posted by Hillsidecycle.com

Ask target64 what a good set of heads, and big bore can do!
Scott

Oct 31, 2014 | 07:13 AM

#16

Melman

Tourer

Joined: Apr 2014

Posts: 420

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From: Bradenton,Florida

I do stand corrected (got the info from the local H-D mechanic...should of known better!) but if the wethead is running 9.7 what is the air cooled motor CR?

Oct 31, 2014 | 10:12 AM

#17

djl

HDF Community Team

Joined: Jun 2006

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From: san antonio

Per MoCo specs, 9.6.

Nov 1, 2014 | 09:49 PM

#18

Pigbacon

Road Captain

Joined: Aug 2014

Posts: 624

Likes: 0

From: Central Arkansas

What exactly would happen if someone tried to run a 57 with 10.5 to 11.1 compression?

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Nov 2, 2014 | 06:46 PM

#19

HD Pilot

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Joined: Sep 2012

Posts: 3,791

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From: N Texas

Quote:

Originally Posted by Pigbacon

What exactly would happen if someone tried to run a 57 with 10.5 to 11.1 compression?

I am not a tuner but at 10.5:1 the 57s would have a Cold Cranking Pressure of 205 psi and at 11.1:1 the CCP jumps to 220 psi - detonation would surely be knocking at the door, better have a great tune and premium gas at the least.

Last edited by HD Pilot; Nov 2, 2014 at 06:49 PM.