Dear Oppo: Teach me about RPMs and V8s.

Illustration for article titled Dear Oppo: Teach me about RPMs and V8s.

Teach me about rod/stroke ratio, bearing types and strengths, crank/piston/rod material strength, and the relationships between piston velocity (mean and peak) and piston acceleration.


Does increasing the bore of the engine cause more stress on the reciprocating parts, outside of them being heavier? Which is better, lighter, weaker components, or stronger ones? Which is the limiting factor?

The firing order of a cross-plane crank makes manifold tuning supposedly difficult. Explain how this could be a problem at over, say, 7000 RPM, or does it become less of a problem?


What type of camshafts are best for 7000+ RPM? Solid rollers? What is "valve lash"? Does higher RPM mean more lift is needed to, or just more duration?

Do carburetors actually work better at sustained high RPMs than fuel injection (aka, why Nascar uses them)? Or is this a myth? What about for track use?


Can a 2-bolt main block be converted to a 4-bolt main?

Which saps more power: added weight of a longer stroke, or added friction of a proportionally higher RPM?


What are the primary differences that let race (circle track) engines sustain high RPMs vs street engines that stay primarily in the low RPMs?

How does a turbo or supercharger affect stress on high RPM motors? Is more-boost-less-RPM worse, or less-boost-more-RPM worse?


Does a tall deck height become a problem if you don't need the long stroke?


Let's say I want a good V8 engine with 8500-9000rpm shifts. I want to make peak power between 7500 and 8500. Don't ask why. Just go along with it.


My options are:


1. Ford 302 Mexican Block (4" bore, 3" stroke, short rods, short deck)
2. Ford 289 "Hi-Po" (4" bore, 2.87" stroke, slightly longer rods)
3. Ford 351W (4" bore, 3.5" stroke, long rod, tall deck, stronger mains)
4. Ford 460 (4.36 bore, 3.85" stroke, extremely tall deck)
5. Ford 429 (4.36 bore, 3.59" stroke, basically the same as the 460)



1. Chrysler RB Block (extremely tall deck, 3.75 stroke, 4.14 (383) to 4.25 (426) bore)
2. Chrysler B Block (3.375 stroke, shorter deck (but larger than 351W), 3.889 (313) to 4.14 (393) bore)
3. Chrysler LA Block (3.31" stroke, smaller bore spacing, 3.91" (318) to 4.04" (340)


In trying to go for short-stroke-wide-bore-highest-safe-RPM build possible. Ignore the amount of power the engine could put out and go just for the "character" of the engine.

Any good GM motors (I know the least about them) that I should add to the list?

Right now it looks like a 289 Hi-Po block, or a 302 with a 289 crank, would be the place to start, but it also looks like that would yield the least power for the RPMs. Also, since it's the smallest engine of the group, would it actually be worse since more parts would need beefed up to handle the speed?


For example, and RB block may have a longer stroke, but if the engine parts are stronger, not just heavier, could it take the same RPM and have a larger displacement?

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