Stroker Rod Fitment

Shamu70

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Hey guys, something I don’t understand. A 493 has, I think, a 6.76 rod & the block needs some minor notching. Yet a 512 has a 7.1 rod(?) & slips in without modification?
 

Davea Lux

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Hey guys, something I don’t understand. A 493 has, I think, a 6.76 rod & the block needs some minor notching. Yet a 512 has a 7.1 rod(?) & slips in without modification?

Some of the later 512 stroker kits have smaller throws that use the 427 chev sized crank throws with the smaller 427 rod bearings. This allows the crank and rods to clear without notching the block. Also keeps the mass of the rotating assembly down so that in theory, higher RPMs can be turned for more horsepower. This comes at the cost of a weaker lower end due to the smaller throws and bearing surface area. Usually an acceptable trade off for a race only engine where maximum horsepower is required.

Dave
 

Davea Lux

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Ok, so the 4.15 crank has larger throws AND bearing surface area?

Most likely yes, but you would need to check the technical specs to be sure. Most 490 strokers retained the factory sized throws.

Dave
 

CBODY67

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If the rods are of lighter weight, that would also play into the 512 pistons/pins possibly being heaver than the similar 496 pistons/pins? Less rotating weight can also mean faster "zings". The stock Chrysler pistons and pins are a good bit heavier than other similar engines' similar items, as I recall. Which is where the Ross lightweight pistons/pins used to come into play. with non-stroker race engines.

Curious, just how much additional torque and horsepower would the 512 build at the flywheel in order to justify cutting the crank? Everything else being equal.

Just some thoughts,
CBODY67
 
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70bigblockdodge

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You can get any of them with 2.2 chevy sized rod bearings/journals. Also get .990 piston pin. There is no reason not to get 2.2 big ends, it lightens everything. Sure, you can make the argument that the crank may be stronger with the big bearings, if that was a concern just buy a 4340 new stock stroke crank. 454 chevy engines have had a 4.25 stroke from day one and they have been making aftermarket forged cranks for them for a long time, and they can make big power so it's a moot point. Go with less weight and more common parts.
 

65Fury440

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On my 4.375 stroke kit, the closest spot is the rod bolt to the oil pickup boss, notched it maybe .060, not much at all.
 

Davea Lux

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The Chevy size cranks are not weaker. The metal now a days is way better. I have a 4.5 stroke crank and the oil pick up boss is ground down almost to the threads. Kim

If we are comparing say a 490 crank made with modern metal techniques and the 427 rod size against a 490 crank make 30 years ago with Mopar sized throws, yes the modern unit is stronger. If we are talking about a modern 490 with 427 throws against a modern 490 with Mopar throws, the heavier unit will be stronger, and probably a better choice for a street engine.

I still remember back when dinosaurs ruled the earth, Mr. Crankshaft and others made the early strokers by cutting apart two forged steel cranks and welding the pieces back together to get the longer throws. The 512 units had gusset plates added to the sides of the throws for additional strength, but they still broke a lot. Nice not to have those issues today.

Dave
 

oldkimmer

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I have a Probe rotating assambly for my 543 and also for my 505 kit. All the rods are good nowadays. They do have a horse power limit. Uy what suits ur build. My next builds will be K1 or Molnar. Kim
 

Dmopower

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I have a Probe rotating assambly for my 543 and also for my 505 kit. All the rods are good nowadays. They do have a horse power limit. Uy what suits ur build. My next builds will be K1 or Molnar. Kim

I'm not familiar with Probe assembly's. I am building up a 4" welded stroker 440 .030 engine right now. 6.76 Speed pro rods and Icon pistons. I had the crank welded up when the kids were still young and now that I have time I wanted to finish it up rather than walk away.

I am also building a 538. I have a K1 4.5" crank and 7.0 K1 connecting rods. I just wondered which rods you used as these K1 rods seem smaller than most at the big end and not in a weak way. I'll use diamond pistons. Using the shorter rod allows me to use 4.25" pistons. K1 stopped making the 7.1 rods.
 
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