Mild 117 build cam
#21
My 79cc head’s currently have 1.940” intake and 1.575” exhaust and 0.650” springs and work superb with my S&S 585 cams and 97” big bore. The plan was to cc them to get required comp ratio required for the 117 upgrade.
I could just cc them and leave the valve size as the flow is spot on as designed for a cam with approximately 585 lift, that is, if you go off the theory that intake valve lift should be approx 25-30 percent of valve diameter…
or will I need bigger valves because of the extra cubes?
S&S recommend these heads upto 88” to 110” motors but I think that’s to do with chamber size more so than valve size?
I could just cc them and leave the valve size as the flow is spot on as designed for a cam with approximately 585 lift, that is, if you go off the theory that intake valve lift should be approx 25-30 percent of valve diameter…
or will I need bigger valves because of the extra cubes?
S&S recommend these heads upto 88” to 110” motors but I think that’s to do with chamber size more so than valve size?
#22
Read up on these.. It's a science..
https://www.rbracing-rsr.com/machcalc.html
https://www.rbracing-rsr.com/lovellgascalc.html
https://www.rbracing-rsr.com/machcalc.html
https://www.rbracing-rsr.com/lovellgascalc.html
#23
My 79cc head’s currently have 1.940” intake and 1.575” exhaust and 0.650” springs and work superb with my S&S 585 cams and 97” big bore. The plan was to cc them to get required comp ratio required for the 117 upgrade.
I could just cc them and leave the valve size as the flow is spot on as designed for a cam with approximately 585 lift, that is, if you go off the theory that intake valve lift should be approx 25-30 percent of valve diameter…
or will I need bigger valves because of the extra cubes?
S&S recommend these heads upto 88” to 110” motors but I think that’s to do with chamber size more so than valve size?
I could just cc them and leave the valve size as the flow is spot on as designed for a cam with approximately 585 lift, that is, if you go off the theory that intake valve lift should be approx 25-30 percent of valve diameter…
or will I need bigger valves because of the extra cubes?
S&S recommend these heads upto 88” to 110” motors but I think that’s to do with chamber size more so than valve size?
Your original post says 89cc S&S heads, are you now saying you already have 79cc S&S heads on it and are planning to use those?
The following users liked this post:
Max Headflow (11-24-2023)
#24
Yes my original post says 89cc S&S heads but I didn’t make myself clear from the get go, so here it is:
The bike is an 05 Dyna Superglide custom, I’m currently running:
S&S 97” kit
S&S 79cc heads (with the 0.650” lift springs)
S&S 585s chain
S&S hyd camplate & upgraded pump
S&S premium Quickee pushrods & tappets
06 up TB bored to 50mm with 4.9 injectors
Bassani Road Rage II B1 Power
3.37 gearing
Baker OD6
Barnet scorpion lockup clutch
According to BigBoyz calculator it’s at 10.33 static & corrected 9.27
Chain conversion
Lyndal twin disk setup up front
Lyndal rear
Legends carts up front, ohlins rear shocks
Metmachex Aluminium Swingarm
Lithium battery
Cast 13 spoke wheels (powder coated)
Turns out 109hp and 108tq
I’ve done all these mods myself, it was bone stock when I got her and you don’t need to be a genius to understand how heavily invested I am in this machine.
The original plan was to reuse the heads and cc them to 89cc.
Use a -10cc piston with 117 S&S cylinders and a 0.030 gasket to get 10:1 static.
Use an Andrew’s 57, 54 or woods 6G cam.
Use my exhaust.
Use my current 50mm TB and 4.9 injectors for what would be a ‘mild 117’….
Now after hearing lots of good info, I’ve been persuaded to avoid this ‘original plan’ and perhaps look at re-using my 585s and up the comp to 10.5 (by using flat tops and adjusting head cc’s in order to accommodate my 585s. Use the money I’ve saved by not replacing cams and invest that in a HPI 55/58 or similar…
Now the question remains can I use these S&S 79cc heads by just cc’ing them to my required 10.5 or will I need a valve job too? Or should I put ‘em on the shelf and grab some oem heads to modify?
I would prefer to reuse them as it would be wasteful not to.
Apologies for not being clear at the start, in my excuse, I was initially only asking for cam advice.
So there you have it…
The bike is an 05 Dyna Superglide custom, I’m currently running:
S&S 97” kit
S&S 79cc heads (with the 0.650” lift springs)
S&S 585s chain
S&S hyd camplate & upgraded pump
S&S premium Quickee pushrods & tappets
06 up TB bored to 50mm with 4.9 injectors
Bassani Road Rage II B1 Power
3.37 gearing
Baker OD6
Barnet scorpion lockup clutch
According to BigBoyz calculator it’s at 10.33 static & corrected 9.27
Chain conversion
Lyndal twin disk setup up front
Lyndal rear
Legends carts up front, ohlins rear shocks
Metmachex Aluminium Swingarm
Lithium battery
Cast 13 spoke wheels (powder coated)
Turns out 109hp and 108tq
I’ve done all these mods myself, it was bone stock when I got her and you don’t need to be a genius to understand how heavily invested I am in this machine.
The original plan was to reuse the heads and cc them to 89cc.
Use a -10cc piston with 117 S&S cylinders and a 0.030 gasket to get 10:1 static.
Use an Andrew’s 57, 54 or woods 6G cam.
Use my exhaust.
Use my current 50mm TB and 4.9 injectors for what would be a ‘mild 117’….
Now after hearing lots of good info, I’ve been persuaded to avoid this ‘original plan’ and perhaps look at re-using my 585s and up the comp to 10.5 (by using flat tops and adjusting head cc’s in order to accommodate my 585s. Use the money I’ve saved by not replacing cams and invest that in a HPI 55/58 or similar…
Now the question remains can I use these S&S 79cc heads by just cc’ing them to my required 10.5 or will I need a valve job too? Or should I put ‘em on the shelf and grab some oem heads to modify?
I would prefer to reuse them as it would be wasteful not to.
Apologies for not being clear at the start, in my excuse, I was initially only asking for cam advice.
So there you have it…
Last edited by pawhite; 11-24-2023 at 12:10 PM.
The following users liked this post:
Max Headflow (11-24-2023)
#25
That might work down at sea level where you can buy 93 octane from the pump, but c'mon out here into the west where it's hot as hell and I don't think you'll be telling people to run 11:1 compression on air cooled engines when it's 120 degrees outside on 91 octane. I'm not saying your advice to go bigger on a cam in a bigger displacement engine is a bad idea, but there is nothing old fashioned about telling people to not get ridiculous with camshaft and compression when they want reliability; any credible engine builder will be telling people that.
#26
How about posting a couple of pics of the bike; I would like to see it.
Last edited by djl; 11-24-2023 at 11:45 AM.
#27
Read up on these.. It's a science..
https://www.rbracing-rsr.com/machcalc.html
https://www.rbracing-rsr.com/lovellgascalc.html
https://www.rbracing-rsr.com/machcalc.html
https://www.rbracing-rsr.com/lovellgascalc.html
Great help 👍
#28
#29
As has been suggested more than once, sell the S&S heads and use the funds to purchase a set of OEM heads, preferably '06 up but since going out for porting and machine work (compression releases) the year really doesn't matter. Select a head porter, WFO Larry has been mentioned, give him a call (he will have good advice on cam selection as well) tell him your plan and turn him loose on your heads.
How about posting a couple of pics of the bike; I would like to see it.
How about posting a couple of pics of the bike; I would like to see it.
This is my latest one, No Tq in this one as the dyno guy had some issues with leads on the day?? but he assured me it was 108.69.
#30