Comprression

[Don Dulmage <big-d@xxxxxxxxxxxx>]

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You can run  just over 10 to 1 safely with good gas (ie 94) or reasonable gas with octane booster. I do mean safely too . First though you need to know you need a good chunk of duration as well. I run typically 245 to 253 @ .050" in an hydraulic.
This reduces the physical compression or actual pressure in the cylinder at low speeds which is where the problem (if there is one) usualy shows up but allows the engine to make huge HP up range and since we have a good compression ratio makes it very drivable even at the low speeds. (900 rpm in gear idle with about 6100 max rpm)
Timing and by that i mean the distributor curve is very important. The distributor MUST be modified to bring in 32 degess Total by 2500 to 3000 rpm at the latest but must also have good control over the bottom of the curve so it will be retarded enough to start and be stable on Idle. 
Dave I think it was, just went through all this and has an excellant grasp of how to obtain it. 
(It is also in a little book called Old Reliable.) 
Do Not let Chevy or Ford guys do or advise you with dist curves etc. Their engines, because of combustion chamber design (or the shear lack of it), require far more advance in total and applying that to a Mopar is certain death or at least brings extremely poor performance. (barely drivable under heavy throttle, backfires pops spits etc)
Also a word of caution . Check your aftermarket vibration dampers for proper TDC. The new ones sold by MP are often way off (up to 12 degrees) and the ones I have used have a note in the box warning of this possiblitiy) The ones i am talking of are the new econo SFI units. 
If you want to run  less cam (duration wise) you will be disappointed at best and a 9.5 or 9.6 engine with a extreme energy type cam would be a better choice. However if you are willing to do it right like I said above, it will take hours to wipe the smile from your face when you go for a cruise.
Biggest trouble I have seen is using more than one cook to make the up the engine combination. Asking or using advise from three or four unrealted sources ALWAYS , IMMER, TOUT LES TEMPS, guarantees poor perfomance. Technical advice is often, by necessity, very specific.  Pick some one OF YOUR CHOICE and stick with his advice. How do you decide which one? Always someone who has done what your doing and you like thier results. Don't mix recipies unless you are willing (and can afford ) to fail several times to achieve your results. 
High ratio rockers
Interesting subject
In truth , it sometimes works and sometimes doesn't . More often not than yes. 
Why? 
Because first we need to understand why do other engine brands have high ratio rockers in the first place (ie the BB Chevy or most Fords.)
Because they have a smaller diameter lifter and are unable to obtain the valve action they need for big power without cheating a bit by raising the rocker ratio. 
Mopars have a huge dia lifter (comparitively speaking) which allows generous amounts of valve action (bigger diameter lifter can handle a much faster rate of lift than a smaller because the smaller lifter cannot handle that fast of a rise without the side of the lifter digging into the flank of the cam. It is really just that simple. Only other way to get the quick valve action is rocker ratio change)
Secondly, will the extra lift typically (.025 to .037") be an advantage to my engine? Extra lift does not automatically guarantee extra power. It only helps if the engine needs it or can use it. It is especially, with our motors, just often not necessary or advantagous. 
So why do the companies make them and promote them? So you will send them your money, son. That is why. 
I didn't, by the way, say they are always bad so please don't say that i did but, i will say there is often no advantage in many of the types of Mopar engines we would use and a knowledgable cam grinder (i think) would tell you the same. Often if a cam grind would benifit from a high ratio rocker they will say so, (Check the chevy section af a reputable cam manufacturer and you will see what i mean.) 
I have experimented with this quite a bit in the seventies and it was a bit of a disappointment to find they were not an instant power maker I had hoped for.
Disadvantages of high ratio rockers are it is harder on Cam wear, pushrods, etc because of the lever princples (which is what makes it work.) 
(BB Chevies were notoriuous for cam failure until the new piece two piece lifters were developed) Pushrod loads also rise and our BB mopar have VERY long pushrods.
Biggest problem I deal with is a tendency to apply all advice in magizines which is usually chevy specific (yes even our sacred Mopar mags have often done this unwitingly)  to Mopar engines. Often it just flat out doesn't apply. 
You don't ask a African cook how to cook Russian food do you? (or vice versa)Well, the same principles apply. 
There are some very good Mopar guys around today. I think Steve Dulcich who often writes for Mopar Muscle is one of the very best ever. He has an excellant comprehension of what he is doing and tests just about everything he talks about. That is the type of person i would want listen to . Some others, while semi famous, are smart mouthed and sometimes cute but in reality "Don't have the slightest idea of what they are talking about." When you work in this occupation for many years it becomes painfully obvious when someone is off track. So beware. 
 Supercharging I leave for another day although there is a description under the engine section on the Slant 6 website that i wrote short time ago.
Don

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