I've been playing with the VE calculator that pianoprodigy tweaked. What is the optimal SCR & DCR that one should target for when running on 92-93 octane with a stock block? I've ordered my cam and am saving up for the AFR 205's. I'm trying to figure out how much, if any, to have them milled when I order them.

 

I have read that for pump gas you want your DCR around 8.5:1

 

im goin 11.3scr 8.64dcr

 

I would play it safe with 8.4-8.5 max.

 

I've found that 11.0:1 for SCR and DCR 8.3-8.5 for 91 gas is the max you should go. So I'd imagine you'd be a little higher.

 

I'm running 11.88 SCR and 8.68 DCR on 94 Octane (US grade).
Also keep in mind that as SCR goes up colder plugs should be used.

 

peace

 

when i was h/c on the stock bottom i had around 9.0 dcr on 93 octane and had zero issues but that was in the spring time also and with a head that had a slightly lazier runner than an afr 205.i would shoot for 8.7- 8.8 dcr with a set of tr6s or similar.you can always back the timing down a few degrees if you have alittle spark knock.

 

Just worry about DCR and let the SCR come out to whatever DCR you choose.
I run 8.7 DCR with 93 octane, you should be fine with 8.5-8.6.

 

I'm looking at a DCR of either 8.45 or 8.66. At what point should I look at using a cooler plug (like a TR6)?

 

8.64-1 here since 2003 with no problems. Daily driver alot of the time. 93 octane with no problems. No knock has ever been monitored while data logging on the dyno or on the street.

 

You mention running a colder plug as the ratios get higher. What happens when you through nitrous into the mix? I am already running TR6s for the bottle.

 

Not sure; I don't plan on spraying.

 

I ordered some TR6's for my setup, just haven't installed them yet. I would run the TR6's for your setup as well.

 

Stock pistons I'd shoot for 8.5-1 or so. We have run 9.2-1 DCR on 10.6-1 SCR before but the compression is pushing it on stock piston/rod combo.