Help with DCR please!
Help with DCR please! I am trying to figure out my DCR, but for some reason I keep coming up with over 10 with the calculator I found. Here are the specs of my setup:
AFR 205's milled .024" down to 62cc, futral F13 cam (230/232 .595/.585 112+4), Cometic .040"...(not sure what the bore of the gaskets is...I got them from AFR p/n 6846 so whatever it is I'm not sure), .008" piston out of hole, stock block and stock pistons, and according to my cam card, the intake valve close is 43 ABDC. I think this is all the info you need...
If someone could please calculate this for me that would be great. I think I calculated the SCR correctly and it came out to 11.37:1.
Thanks in advance!
AFR 205's milled .024" down to 62cc, futral F13 cam (230/232 .595/.585 112+4), Cometic .040"...(not sure what the bore of the gaskets is...I got them from AFR p/n 6846 so whatever it is I'm not sure), .008" piston out of hole, stock block and stock pistons, and according to my cam card, the intake valve close is 43 ABDC. I think this is all the info you need...
If someone could please calculate this for me that would be great. I think I calculated the SCR correctly and it came out to 11.37:1.
Thanks in advance!
TECH Regular
Joined: Oct 2005
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Your cam will have an intake centerline of 112 minus 4 = 108°, so the valve will close at [108 + (230/2)] -180 = 43° ATDC, so plugging the info into a DCR calculator such as: http://www.rbracing-rsr.com/comprAdvHD.htm will give a DCR of ~ 10.33:1. However this calculator works from the 0.050" lift point, which, although it may be accurate re when effective air flow through a valve begins, is not the basis upon which the common "9:1 DCR max. for good pump fuel" rule of thumb is based. The 9:1 rule is predicated on 'advertised' or seat-to-seat timing, which for a typical hot street hydraulic roller is ~ 50-55° more duration. Therefore, your calculation might look like: [108 + (282/2)] - 180 = 69° and the DCR calculation would give ~ 8.75:1
TECH Fanatic
Joined: Mar 2003
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Originally Posted by MadBill
... the common "9:1 DCR max. for good pump fuel" rule of thumb is based.....
Don't want to steal this thread, but I wish we could have more info on DCR vs. 93 octane fuel and the limits there of....
my motor supposedly had a 9.0 dcr and ran great on 93 octane.it did spark knock alittle at low rpm part throttle but that was because i needed to do alittle fine tuning.too bad a rod decided to start knocking 
