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Author Topic: Compression too low for 600 cam?  (Read 833 times)

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ltank

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Compression too low for 600 cam?
« on: May 30, 2019, 01:01:06 AM »

My S&S V124LC has 10.2:1 compression. The S&S cam description "S&S 600 Cam - Originally designed for the legendary S&S 40th Anniversary engine, the S&S 600 cam has proven to be an exceptional cam in any large displacement engine with 9.5:1 to 10.5:1 compression - Good power across the rpm range - Requires high lift springs and normal clearance checks."
 I went Big Boyz EVO Calculator and figured my Corrected compression ratio is low than expected.
Will it damage my motor by being under compressed? According to S&S description I should have been good. Thanks
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johnsachs

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Re: Compression too low for 600 cam?
« Reply #1 on: May 30, 2019, 06:46:33 PM »

My S&S V124LC has 10.2:1 compression. The S&S cam description "S&S 600 Cam - Originally designed for the legendary S&S 40th Anniversary engine, the S&S 600 cam has proven to be an exceptional cam in any large displacement engine with 9.5:1 to 10.5:1 compression - Good power across the rpm range - Requires high lift springs and normal clearance checks."
 I went Big Boyz EVO Calculator and figured my Corrected compression ratio is low than expected.
Will it damage my motor by being under compressed? According to S&S description I should have been good. Thanks
Usually the LC 124 twin cam engines are shipped with the S&S 585 easy start cams. 45 degree intake closing, and avg. 89 cc heads.
I just cc'd a new set of the 124 LC S&S TC heads for a shop when I changed the new beehive valve springs to dual springs.
If you're going to get involved, you might want to check the cc's of your heads compared to the S&S Twin Cam heads.
John
« Last Edit: May 30, 2019, 06:51:27 PM by johnsachs »
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ltank

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    • CVO3: 1989 FXRS, 1990 Custom 100" Shovelhead/ EVO
Re: Compression too low for 600 cam?
« Reply #2 on: May 30, 2019, 10:37:48 PM »

 My V124LC custom built from S&S has the -10cc dished pistons and 585 cam but it starts running out of go about 4700 rpm. The 600 cam has more duration and should pull to at least 5500 rpm. S&S didn't add the High lift Springs or roller Rockers that normally come in the V124.  My shop added the roller Rockers and S&S but a Beehive spring failed after 477 miles and now has Fueling Endurance high lift Springs. The 600 cam runs good but I don't know if the 10.2:1 is good enough now and should consider putting in the  10.8:1 flat top pistons for a 9.3 corrected compression. Thanks
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ltank

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    • CVO1: 2000 FXR4 S&S V111, CustomS.S. 2-1 exhaust, Primo-Rivera OD 6 speed, 49mm Custom Front End Ohlins 30mm Fork cartridges , Hyperpro Shocks, Barnett Scorpian Clutch
    • CVO2: 1983 88" Shovelhead Won the World of Wheels 1985 Sept 85 Issue of Hot Bike Mag
    • CVO3: 1989 FXRS, 1990 Custom 100" Shovelhead/ EVO
Re: Compression too low for 600 cam?
« Reply #3 on: May 30, 2019, 10:38:52 PM »

Heads are 91cc
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MCE

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Re: Compression too low for 600 cam?
« Reply #4 on: June 12, 2019, 06:36:26 PM »

Run the numbers on the BB calculator, see what the cranking compression ends up being. Should be around 190 for optimal TQ.
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