DCR and Octane

[Dezertxj88]

Ok gurus, shoot some wisdom my way..

I kicked the turbo idea after talking understanding it more..thought my safc II would work to tune it and it won't...so kicking the idea! My 4.2L is just going to be run n/a.

3.935 bore
3.500 stroke
12cc dish (11.5cc-true, just added a extra .5 for the piston ring height)
.043 head gasket
-.005 deck clearence


Since I'm not spending on the turbo setup, I have bought some bolt on roller rockers:) Awsome And will be doing a cam, probably the comp 232. Which will give me a 9.73 static & 8.35 dynamic. I wanted to run 87oct. in the winter and am fear that it won't happen with a 8.35 dynamic..I'm right at sea level give or take...what say you? Too high?

Cruise rpm is 2000-2200rpm..pending 65-70mph. Looking for power from about 1500-4500rpm if possible.

[Cheromaniac]

If your head chambers are 57cc the SCR will be close to 10.0:1. I suggest you build around my wilder mini-stroker recipe to avoid pinging problems but either way, your aim to run it on 87 octane is rather ambitious. Even with the lower DCR afforded by the longer duration 68-235-4 cam, it's likely you'll need 91 octane.

[Dezertxj88]

If your head chambers are 57cc the SCR will be close to 10.0:1. I suggest you build around my wilder mini-stroker recipe to avoid pinging problems but either way, your aim to run it on 87 octane is rather ambitious. Even with the lower DCR afforded by the longer duration 68-235-4 cam, it's likely you'll need 91 octane.

Head is slightly bigger than 60cc..using ls1 valves, polished chambers. I was hoping to get 87 during winter, and 91 in the summer. If I have to run 91 all the way no biggy, was just hoping lol.