FE Power Forums
FE Power Forums => FE Technical Forum => Topic started by: fekbmax on April 20, 2021, 09:36:38 PM
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Has anyone used GRP (or other) 6.700 aluminum rods with the scat 4.375 crank in a pond aluminum block ? Wondering how much clearancing had to be done. Mostly concerned with the camshaft tunnel area and bottom of cylinders.
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Not that exact combo, but had trouble with clearance from the big end of the rod to the cam lobes (only a .440 lobe) on a couple of the rear 4 cylinders. That was with a 4.375 crank and Callies Ultra 6.700 BBC steel rods! With aluminum rods there would be even less clearance I would have to guess. Might help if you go to a 2.100 or 2.00 inch rod journal but then that is a custom crank (and rods). Other than that, might check clearance around the oil pump boss. Haven't had any clearance trouble with 4.250 in a Pond aluminum block, but again with Ultra steel rods. That one had a .480 lobe in it.
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I don’t see how the rods would fit. They're huge. Aluminum rods with the 3.50” stroke crank in my 352 got close to the block.
I've never had any issues with a 4.375" crank in any FE block and if the correct steel rods are used, then you don't have to grind on anything. Aluminum is a different story.
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+1 Aluminum rods are simply too "bulky" to clear with the 4.375 stroke. "Modern" steel rods can be lighter than an aluminum rod too.
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what about the new rods you were talking about , Brent ?
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what about the new rods you were talking about , Brent ?
They would be for a standard FE journal, not a BBC journal.
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I’m using 6.8 GRP rods with a 4.125 stroke in genesis block. No clearance issues. Tightest spot was a couple cam lobes. .457 lobe and the closest was .100....Sooo maybe a 2.00 or 2.100 would work with a 4.375???
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Thanks guys. Just gonna stick with the crower rods.
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I’m using 6.8 GRP rods with a 4.125 stroke in genesis block. No clearance issues. Tightest spot was a couple cam lobes. .457 lobe and the closest was .100....Sooo maybe a 2.00 or 2.100 would work with a 4.375???
That’s good data.
I think the extra stroke would make thing go downhill fast though. In a SBF, an extra quarter inch of stroke can make you go from a drop-in-no-touch assembly to having to grind part of the oil filter pad away LOL
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Thanks guys. Just gonna stick with the crower rods.
You’ll find a K1 or Molnar rod would be lighter and as strong.
I still use steel rods even on very high rpm stuff, high hp stuff.
The weight is certainly a benefit but IMO the other real benefit of aluminum is that it can absorb a lot of loading.
The only reason I’m having some made for my 352 is because if I want to stay with the stock stroke and add compression, I’m looking at a 1.920” piston that’s as heavy as an anvil. R&R is making me a set of custom aluminum rods and they are drilling me some bearings since there are no drilled FE bearings available.
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What about using the 'Honda' journal. Bearings are available and they have been used for some time in MOUNTAIN MOTORS, ( :))
KS
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Didn't they use titanium rods in some corvettes?
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Yes LS7 Corvettes have Ti rods. Crower makes allot of ti rods for 440+ci dirt late model engines. Just pack up a wheel barrow full of money to buy a set. 10,000 rpm pro stock engines use steel rods for more power and longevity.
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Aluminum rods provide a degree of cushioning effect that is beneficial any time high-end cylinder pressure is expected, such as when using power adders. Look inside a Top Fuel engine.
KS
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+1 sometimes they are essential!