Valve spring limitations vs Cam selection
I read on Allpar that the factory 5.9 CR was 8.9 and Evan (who put together the Magnum-swap website) stated "I have checked many Magnums and all are between 8.8-9.3 factory. it all depends on how deep the pistons are, .040-.08".
Mine were .050 down. Perhaps I was being hopeful at 9.4 using the .028 Mr gasket and the EQ's 62cc.
Without measuring these numbers are guestimates and I can't measure until I get my parts back.
BTW.....I sure do appreciate all of your input.
No problemo, JP1.... good to go into this with all the data. I was figuring the piston depth at .060" which is the book spec on the FME Catalog website for the H655CP, and assuming the nominal deck height of the Magnum. The .028" thick head gasket would help about 0.2 point on SCR/ and DCR.
If you want good low RPM torque when you drop below 2800-3000 RPM or thereabouts, then SCR/DCR become your key to that. You're transitioing from the higher RPM's, where the exhaust draw-through reeeealy is working well to fill the cylinders, to the lower RPM's where that draw-through effect just plain craps out, and the higher compressions are all you have to make cylinder filling decent, to keep your torque up.
nm can he swap pins?
or take some out of the pistons
side grind the rods thats a diy with a good kitchen scale and I'll tell him how to hang them
He
could get some weight out of the pistons, but how much is hard for me to say, not seeing them. 50 grams out of that is very tough unless you start shaving the crowns down a lot, and the crowns are probably not the old style thick ones, so maybe not much there to remove.... and it would destroy the CR again LOL. Grinding down the rod's beams and small ends would get a fair amount out, but then you really ought to weigh them end to end to keep things reasonably equalized. Maybe 10-12 grams out of the pins max; those are already pretty light, and not very cost-effective for those few grams IMHO; a new set will cost more than a simple balance job of the crank and LA damper/flexplate to a new bobweight.
Of course, using an LA damper may be a different pulley so that is a possible issue; IDK if the is OP planning on the serpentine belt pulley or the earlier V-belt type. The flexplate ought to be interchangeable as long as the weight is corrected.
IMHO, this is the most cost effective to get back to balance: rework the external weights. If that becomes a possible route, then speak up JP1 and we'll see what can be done. I have some ideas already on how to do it.
