milling heads for comp ratio increase

B3422w5 said
You will take some heat for the 5-8% comment regards power, but sometimes the overall flavor of the combination changes by having more compression, and that allowing things to work better and make more power.
My current car/ combination is a perfect example. Stock 360, pistons 028 in the hole, 50 thou head gasket, comp 292 cam, stock eddie heads..... single plane Mopar intake..... car ran 12.17 best with 4.10 gear and 8 inch 4500 flash convertor.
Replaced cam to 260/264 Howards cam( similar lift), dual plane intake, took heads off, had them mildly ported, setup up with new springs, etc, for new cam, milled them to 57cc( about 45 thou) and reinstalled with 28 thou head gasket. No other changes.... cam, intake, mildly port heads, mill for compression, thinner head gasket...... car ran 11.26
This in spite of the fact the cam i installed i am aware is probably one step too big for what i have( i was in a hurry and it was on the shelf when i made these changes)....... a bandaid would be more convertor and maybe gear, convertor change is in the works as we speak
So here we have a decent bump in compression allowing a motor to be able to make more power( lots more) with just a couple easy changes. I suspect this thing will get in the 10’s yet, its gonna love the convertor swap with that big cam

thanks for well written post, I love reading about these real life experiences! Obviously people here are not happy with those numbers I gave - I'm not defending myself, just recounting what I read; it's not from my experience, nor am I laying that down as law, and possibly taken alone, they are out of context. Yes, even with my limited experience I can see that over 5% power increase would be hard to get from just a one point CR increase alone. But lets look at the big picture, these are percentages, not HP numbers. So in a low horsepower stock engine (whatever that is, not necessarily Mopar or even a V8, or maybe not even a car engine), perhaps it IS possible to get 5 or more PERCENT increase in power/torque from that CR increase. But talking Mopar A engines, it probably does apply.

B3422w5 It's a well written post because you have put in writing from a more balanced perspective; CR increase as part of a combination of changes that work better together. That's probably what I also should have said (well I think I did mention it somewhere) that with my 273 engine, obviously I am doing more than just that one thing of increasing comp.! I am using a bigger than stock solid cam (approx 0.47), heavier springs /w dampers, M1 high rise dual plane (port matched to heads), small 4 BBL carb, headers with twin exhaust, and also a 2600 stall in a shift kitted 904. Plus upgraded ignition. So all considered, it's important that I get the CR up from approx 8.5:1. Even 9.7 or 9.8:1 maybe. We have 98 octane fuel here and as I mentioned will be running a fuel additive as the valves seats are not induction hardened.

B3422w5, that performance from that 360 is incredible, almost a flat 12 from just those few changes. The gearing and heads would be the biggest factor (and I assume big port headers and 2.5" system?) but did you bolt them straight on from the box, or check all the valves and seats for sealing etc? Also the 292 cam, was that a Comp Magnum or Purple shaft? They recommend 3000-3600 stall for those cams. So when you say "more converter" do you mean less stall? As 4500 is pretty dam high. And incredible to see almost a whole second faster with the extra work done.