7A-FE Compression Ratio, Looking at changing the CR of my 7afe when I rebuild. Options

[PaukST]

Hey all, I'm trying to decide what to do with my 7AFE (have to take it apart due to a rod knock anyway). I've kicked around a few ideas (or maybe a lot ), and I'm currently researching what an increase in compression ratio might do. Does anyone have any info on this? I'm unsure of the potential difference in performance, and I can't seem to find any hard data on what pistons (4age, smallport 4age, 4agze) result in what CR. I've been trying to make sense of these tools and formulas - http://www.csgnetwork.com/compcalc.html http://s-86.com/s-cr.html and http://s-86.com/s-cr-chart.html - but I'm having a hard time digging out the relevant numbers. Doing the math myself or using the calculator I come up with significantly different numbers than their little handy chart, so I don't know what to think. Is this a futile exercise? Will I even be able to notice a performance difference over the stock 9.5:1 without having to use higher octane?

[Special_Edy]

Just have it decked. Do the stock rebuild.
You are supposed to have the cylinderhead resurfaced anytime you remove/reintall it, which basically involves them grinding a layer of metal off of it. You can specify to the shop how much you want removed if you would like more taken off than the minimum amount needed to bring the head back to specification. I have a '64 chevy straight six in my garage that has an 11-1 CR and all it took was a shop grinding a little off the heads.

As for detonation, there are several factors that can make it happen or help you avoid it.
Ignition advance- more advanced = more power but more likely to detonate. Retarding it will help cure detonation
Fuel octane- Lower octane fuel has more energy per gallon, but lower octane is more likely to knock. Basically octane rating is the fuels resistance to combustion. Increasing octane will reduce detonation.
Air to fuel ratio- should be close to perfect with our EFI systems, but a lean mixture is more likely to knock and a richer mixture will be less likely. Lean mixtures burn hotter and can damage the insides of your engine while rich mixtures will foul your plugs and catalytic converter.
Spark plugs- hotter plugs will burn fuel better, but are more likely to predetonate. Moving to a cooler plug(one that dissipates heat better and stays cooler) will reduce the likelyhood of knocking but will be more susceptible to becoming fouled.
Anyways, theres a few tidbits there I wouldnt worry about overdoing the CR the only thing you should worry about is the clearance between valves and pistons if you do go with a non-standard piston

[richee3]

Fuel octane- Lower octane fuel has more energy per gallon, but lower octane is more likely to knock. Basically octane rating is the fuels resistance to combustion. Increasing octane will reduce detonation.

Quoted for reiteration. Maybe one day the myths will be dispelled....

OP- I would say you're better off with a standard rebuild. The 7A with a higher compression ratio will still not be a high output engine. Even with cams, SAFC, etc. it still wouldn't put a lot of power to the ground. Why be forced to pay for premium fuel for only a little more power than a 5S? If anything, I would personally lower the compression ratio and boost it later.

That's just my opinion, what I would do if I was rebuilding a 7A. Truth is, I'd love to know what a higher compression 7A can do. The sensible side of me says stick to proven methods to make power for the 7A, but that doesn't make me any less curious.