Aluminum rods + 4.375 crank in aluminum block.

[fekbmax]

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. 

[XR7]

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.

[blykins]

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.

[gt350hr]

  +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.

[gdaddy01]

what about the new rods you were talking about , Brent ?

[blykins]

what about the new rods you were talking about , Brent ?

They would be for a standard FE journal, not a BBC journal.

[Ghoughton]

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???

[fekbmax]

Thanks guys. Just gonna stick with the crower rods.

[blykins]

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

[blykins]

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.

[cammerfe]

What about using the 'Honda' journal. Bearings are available and they have been used for some time in MOUNTAIN MOTORS, (

KS

[Dumpling]

Didn't they use titanium rods in some corvettes?

[gt350hr]

     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.

[cammerfe]

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

[gt350hr]

   +1 sometimes they are essential!