Marco
Just for curiosity, I plugged some numbers into the Dynamic Cr calculator.Not knowing the exact numbers other than 360cid,11.5cr, and 250*@050, I worked the formulas backwards(using a cam spec of 295* advertised,on a 106Cl, and 3*advanced, and .030 O/S and arrived at an estimated Dcr of 8.5@ sealevel.
My combo is also a 360(+040), A static CR of 10.7,and a Dcr of 8.4sealevel.My combo (Eddies) has been quite happy on 87E10 for 15 years.
So I think we are both right in the ballpark; You with 93octane with 8.5Dcr and iron quench heads,and me with a little less octane, a similar Dcr and aluminum quench heads.
Im pretty sure I could run a bit more Static on 87, but its not worth it to me to find out.My little 366 pulls hard enough for me.
Valiant 1
Using the assumption that iron heads will support 8.5Dcr@sealevel on 93, as Marco points out, I plugged some numbers into the Dcr calculator for you. Using a 4.07 bore. 11.75 static requires a TOTAL chamber volume of 65.7cc. This would require a cam of 305/106/4A to net a Dcr of 8.5sealevel.
Thats a pretty big cam! Thats about what?
[email protected]. To support that cam will require lots of drivetrain mods.
Now Im not saying that you cant successfully run a smaller cam, at a higher Dcr. Im only saying that we(Marco and I) have run successfully at 8.5 Dcr-sealevel.
For instance, if you are at 1000 ft altitude, this will drop your Dcr to 8.3 .This would then allow you to go to a 297* adv cam; which would boot the Dcr back up to 8.6. Thats about a full cam size smaller.
Now going back to Post #1, where you say "mild solid cam". Thats a bit vague and subject to personal opinion, as to what is mild. I have a mild cam. Its a 230*/050 Hughes.I call it mild.The next guy might not.Lets say you have a cam about like mine. That would be about 280 advertised.That cam on a 110LDA and 4*A would get you about 9.2 Dcr. That might be iffy on 93,even with a tight quench, and aluminum heads.But guess what, if you retard it to 4*after, the Dcr drops to; wait for it; 8.5@sealevel.
So now we have a pretty good idea of what to do if you encounter detonation.
And we have learned an awful lot about Dcr theory. After all that 280 cam is 25 degrees smaller than the 305 we started with.
Theres one thing to bear in mind, running the cam 4*retarded may/will require some chassis changes.You might not be able to get that beast off the line easily/quickly/naturally enough to suit your driving style.
I would suggest, that for now, stop worrying about it. Put the 93 in it and take it for a good long ride.Get to know her. Dont boot it the first time you have an opportunity. Work up to it, being ever vigilant of detonation.Find out what it doesnt like. Take a notepad along,and use it. Dont depend on remembering everything.Then make some timing changes to initial,or total, and/or the rate of advance. Leave the vacuum advance defeated, until much later. If you have to run too little power-timing, or you cant have it til 4000rpm or something. Then you can think about retarding the cam-timing,or running different fuel, or reducing the Static cr.
BTW, if you have the tool, how about doing a compression test and posting that up?
So. Go out and collect some data.
If you can successfully run 93 in your combo, I for one,would certainly like to learn about it. I might even consider bumping my static up,too.
And one more teaser; I have run my combo at over 8.8 Dcr without issues, on 87E10.
Most guys say aluminum heads are worth a half a point. So that means iron heads might run ok on 8.3/87octane. If you add .3 for midgrade and another .3 for 93octane, that seems to indicate that iron might be ok at up to 8.9 with a tight quench. You might not be as far away from successfully running 93 as you think. Theres even options we havent talked about yet.
Drive!
