440 problems/quenching?/advice needed

AJ/FormS said
Now here's a little math; Let's start with a stock stroke and bore+.030. That would be 4.35 x 3.75. That calculates out to a 921.7 swept. If in fact the engine was previously 10.75Scr(post 36), that requires a total chamber volume of 94.53 cc.; 909/(10.75-1)=94.53
Since we know(or you say) the block is zero decked and you have flat-tops with no reliefs, it's easy to figure the chamber volume is 94.53 less the gasket.I have to guess at the gasket bore; say 4.40 and the thickness of .038,well that makes about 9.5cc. so that tells us that he the PO was using 94.53 - 9.5=85cc heads. That was his combo, and it makes sense, if he started with 90cc

Now your combo with the same 9.5cc gaskets and 78cc heads comes to
{921.7 + (78 + 9.5)}/87.5 = 11.53Scr
The Wallace calculator puts this at a Dcr of 8.7 and the cranking compression pressure at 177psi, with an ICA of 70* degrees using that 292/509 cam.
Now that is for sure testing the limits of pump 93. But guess what; you have the .038 quench going for you and by your own admission you're not into racing. So if you're not interested in the max power, then there is no reason to run max timing. You can run 34* or 32* of power timing if that is what it takes to kill WOT detonation.
Now let's talk PT(part throttle) detonation. At 8.7Dcr this is again pushing it, But guess what; you have not done any timing loops. There is a ton, a TON of tuning you can do to get it out of detonation at PT. A TON.
Detonation is also load sensitive. Let's take an engine that is on the edge of detonation with full timing, that is stuck in a chassis with 2.76 gears and a 2400 TC. So then you put in 3.55s and a 2800 TC, and move the detonation up several hundred rpm. Then take out 1 or 2 or 3 degrees of power timing and problem solved. But guess what; you may be able to run full PT timing and have a dynomite engine , at anything short of peak torque! See what I mean about tuning.So you can start your tune with carburetion.If the engine cannot ingest a full load of air it will not experience a full load. So a smaller carb than optimum is on the table.Well that is not said right, but the result is the same. Take the 850 off and try a 750 or a 650.Or something with a load-sensitive secondary.

Now lets put those open chamber bad boys on there with a 284/484 cam. Let's say they come in at 90cc. The Scr will be (921.7 + 90 + 9.5)/99.5 = 10.26Scr and the Wallace calc. puts that at a Dcr of 8.06,with a ICA of 66*, and pressure of 161. Phew you dodged a bullet. This is pretty safe. But guess what; you are still stuck with the problematic rocker gear.And you have lost completely, all the Quench benefits, which may have allowed the prior 11.5SCR.And you may have given up some terrific PT benefits.Which you are wanting.

I know which combo I would want under my hood. But I am willing to measure stuff and calculate stuff and tune it til it wails.

Quote from Doosterfy,(post 70)
"There are plenty of guys, engine builders in particular who will steer people away from pushing it. Its been my experience over the years (I've been at this since the 70s) that keeping compression and/or cylinder pressure up makes a car much more fun to drive, much better off idle throttle response, less throttle opening to propel the car, it sounds better and the car will simply have more snap to it. I got talked into staying at 9 to 1 or lower twice and both times I was very disappointed with the results after spending my time and money building the engines".
(My experience as well. AJ)
Sorry for the novel; it was a lot shorter in my head.

OOps, One more thing, If the big 440 gets tirespin, it is no longer loaded.Wrap your head around that for a sec.

Sounds like you have a more in depth understanding of engine theory than I do. IDK if you read the entire thread. A few things to consider that he has told us. Its not a race car and he never plans to race it, its a cruiser. He had some unknowns with the valvetrain and suspected there was a bunch of mismatched parts in the valvetrain and turns out he was correct about that. He also said he wants to avoid using anything other than pump gas and wants the engine to be easy to deal with. He's also a novice builder, at least with Mopar. I agree with most of what you're saying and can't actually pinpoint any one thing you said that I disagree with. If I understand what you're saying correctly, you are saying that dropping the compression by swapping to open chamber heads will likely net him no gains in avoiding detonation because he will be giving up quench which is good at reducing it (detonation). That is a good point as are the points you made about tuning as far as timing and fuel curve. With what he had going on in the valvetrain I think trying to tune it would have been nearly futile. If it were mine, and its not, I would have left the heads on, corrected all the valvetrain issues, got it up and running and got on the tuning to see how it ran and if it would tolerate pump gas. My guess is that with iron heads and nearly 11.5 to 1 it would not without going to a much longer duration cam, which is something I think he does not want. My guess and its just that a guess or estimate is that with the open chamber heads, a moderately sized hydraulic cam and good tuning he'll be right near the detonation threshold with 93 octane pump gas. I think if he kept the small chamber heads and ran the same moderately sized hyd cam the cylinder pressure would almost certainly put him into detonation. One thing I've learned is to start with the tuning as close as possible to where it needs to be the first time the engine is started. I've found that vacuum advance is more trouble than its worth with any cam that's larger (duration) than dinky. What I've been doing for a long time and getting good results is to run as much initial advance as the engine can handle and on most V-8s, including big block Mopars, it's about 20 degrees and a total advance somewhere between 36 and 40 degrees and to get all the advance in as soon as possible without causing detonation and that's usually about 2000 rpm. That means setting up the distributor before even installing it on the engine, preferably on a distributor machine and as soon as the cam break in is done setting the initial to 20 and leaving it as long as the starter can crank it and it does not ping at throttle tip in under load. once that is done I move onto the carb tuning and after that go back and start experimenting with the timing a little to see if there's any gains to be had, and finally back to the carb again. Before I learned all this, I remember chasing my tail turning the dizzy back and forth trying to get engines to run right only to find out (eventually) that the advance curve in the dizzy was way too wide. At this point I hope we don't overwhelm or confuse the guy with all this info. There is one magic bullet that would pretty much solve any detonation issues with this engine and that is a set of aluminum heads like Edelbrock rpms with 85cc chambers or 440 Source Stealths with 80cc chambers. Its his money and I have no idea what his budget is and/or it permits the investment in those. Your thoughts sir?