Thanks. My assumption is that none of us amateurs is likely to run a controlled-variable test of the groove(s), which happens to require a lot of work, more than for many things we could test. You would have to record combustion chamber volume before grooving, make your dyno pulls and establish the engine's spark timing and octane needs, then remove the head, choose one of the many, many possible goove configurations, reassemble the engine and check the new chamber volumes, and make the dyno pulls, rechecking the spark-lead and fuel requirements.
THEN you'd want to correct for volume, i.e., see what the engine would do with the grooves AND the original volume! How do you do this? You can't do it by decking the block and changing the squish, a dimension you would have wanted to pretty much optimize at the beginning of the testing because of its dramatic effect. The easy way to reduce volume would be to deck the head if you can, because otherwise you have to add metal to the combustion chambers. That isn't so hard on aluminum heads, but it reshapes the chamber, which would put all the results in question.
One of the previous posters, a groover, stated that grooving might not have much effect by itself, but would likely enable you to build the engine with more compression than you could otherwise do without running into detonation. If he's right, this is an enormously desirable finding, so you would definately want to take the head off and reduce chamber volume still further and test that. Again if you reshape the chamber to do this, you tend to lose your ability to directly attribute your dyno findings to the grooves alone.
And there's the problem of transferability. Do the grooves have the same effect in a swirl/tumble head design as in a non-swirl head? Would they augment the swirl or interfere? What about closed versus open-chamber heads, hemi heads, Heron heads?? What about shape of the piston crown? Do grooves do the same thing whether the piston crown is dished, flat-topped (and with which kinds of valve pockets?), or high-domed like old Hemi racing pistons??
No one amateur could do these tests; no manufacturer of aftermarket heads could either. Currently all we have is the collected annecdotes of the groovers worldwide, working on many different engines. As enthusiasts, their perceptions are likely to be skewed. As amateurs, their level of mechanical savvy varies wildly. Probably most are sober-miinded and well-intentioned; still, how many can you believe?
Most of us here are open to anecdotal evidence that is carefully observed by a knowledgeable observer who is appropriately modest about the repeatability and wider application of his findings. But most of us older guys are skeptics, having seen a variety of miracle carburetors, oils, spark plugs, and vapor injectors appear, with lots of anecdotal enthusiasm, and disappear under informed scrutiny.
A: One way to measure squish-height in an assembled engine is to poke a length of soft solder in a spark plug hole (you have to know where the squish area is and feel for it with the solder), hand-turn the engine so that the piston comes up to and past TDC and flattens the solder, then pull out the solder and mike it for thickness. Opinions vary slighty as to the desired squish range, which varies with engines and components. Do a websearch on squish/quench.
Q: Which of the groove websites do you recommend?
Be nice if your name was Rockefeller,too.Hehehehe.By the by,I seem to slightly remember how HP was figured BEFORE dynos came along.A weight of 2000lb was raised one ft in one minute(IIRC) to measureHP.Raise it for a SHORTER lengeth of time and divide the difference.There`s your "back yard dyno".
I think I'm probably making a rod for my own back, posting little tidbits like that.
to see if it would detonate as is with about 9:1 comp.
