My block might go 020 over, but I already had new KB 9.68:1 pistons for my other 030 over block (this is a better block now).
So I may be in the market for a better set of pistons, so I'm looking around for now.

What is the most compression I could run with a set of Edelbrock E-Tec 170cc heads (vortec style chambers) and not detonate on 92 octane? I figure with iron vortecs, stay under 10:1, but what is safe with aluminum heads and the vortec style chamber? 10.75:1?

I guess it might depend on cam specs. I'll have my cam card for my custom cam on Monday when it arrives, 220/226 @.050" .525"/.544" 112/109 is what it is. Not sure on advertised dur. specs.

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'71 RS/SS project: full roller 406sbc / 9.76:1 w/ E-Tec Al. heads / 750 Competition AFB / big 4 whl discs, 1-5/16 VSE ft & 1" Rancho adj. rr sway bars / 4 speed 3.23 posi / 81 Z28 & dual snorkel vette Air Induction

I wouldn't doubt you could get 10.5-10.75 with aluminum heads, the right cam, and good quench. I run 9.75 with aluminum heads with a very short duration cam on 87 octane, so I'm pretty sure you could get close to your goals on 93.

IMO it very much depends on what your looking for. Judging from the cam specs were talking a street car with gumption and not a weekend warrior at the track. You really only need around 9:1 to support that cam. More compression isn't going to make or break the package. If it were a situation where you are strictly looking for ET, I would keep it just under 11:1 and deal with having to de-tune the motor to tolerate pump fuel on the street,,, dump a mix of leaded race fuel into the tank for the track. But if it is strictly a pump gas, daily driver,, I'd keep things under 10:1 just for the sanity of it. There is no sence in fighting an octane/compression problem over 10-20HP on the street. You can EASILY find ET that 20HP would make by fine tunning the motor, picking a gear ratio and lsunch/shift rpm that best suits the combination, sticky tires, weight distribution/reduction. You see where I'm headed. Don't shoot yourself in the foot and make the car unfriendly to drive just for the sake of compression.
Just for giggles I modeled a 406 in Engine Analyzer using E-techs, a hydraulic roller cam similar to the duration you list, gave it plenty of carb, exhaust, pump 93 octane and 9.0:1 compression. Then with making no changes but bumping the compression up to 10.5:1,,, it made 14 ft. lb. of torque and 16HP more. I doubt sincerely you can feel 14 ft. lb. of torque in the butt-o-meter on street tires.

So all I'm getting at is I have no doubt you could go to 10.5 or more and have no problems if the quench, tune and octane is there. But is it really worth it??? 14 PEAK ft. lb. of torque for $0.30 or $0.40 a gallon!

It's your motor and your combination. You should build it like you want. Just wanted to offer a little sanity check on considering how much compression is 'too much' compression.

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Proud member of the "bright side"
Track toy (http://www.small-block-chevy.com/nova.htm) 9.94 @ 133 n/a Small Block

Weekend Grocery getter (http://www.small-block-chevy.com/md_toy.htm) 12.3's through the mufflers on DOT's, in street trim

alrighty, thanks marv. I figured before I went out and bought the E-Tec heads with the money I got from the Fastburns, I should make sure I didn't want to get something with a larger chamber to run flattops and 10.75:1. I was pretty set on the E-Tec's. Went from 2 yrs ago wanting vortecs, to wanting either fastburns or e-tecs, got a deal on fastburns unfortunately! Figured those out, hurried and sold 'em... still sold on the vortec chamber style and reverse dome piston for a street engine. I guess I'll stick with the setup I have, but if my engine will in fact go .020" over (I was just checking it out my "509" 400sb, minor pitting in one cylinder, hardly any ridge at all on any of them, stock bore), I may jump from the 22cc D-dish KB's to the 18cc D-dish KB's, which will still have me at mid 9's in compression.

What kind of power numbers did you get for that Engine Analyzer dyno run?

Thanks!

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'71 RS/SS project: full roller 406sbc / 9.76:1 w/ E-Tec Al. heads / 750 Competition AFB / big 4 whl discs, 1-5/16 VSE ft & 1" Rancho adj. rr sway bars / 4 speed 3.23 posi / 81 Z28 & dual snorkel vette Air Induction

go flattop 2 valve relief and be happy!