2270 Engine Questions, Crank and Rods Options

[yeahmag]

I'm getting close to having all the parts for the 2270 build, but have a few questions:

• Crank brand: DPR, Scat, or AA? AA and Scat are new forgings but cost a bit more than the DPR crank. DPR is well respected in these parts.
• Crank size: Seem like a shame to leave it at a 2270 (78mm) when I could go up to a 2316 (80mm). Chevy journals.
• Rod length and type: Planning on 5.325" and Chevy journals for both clearance and the better bearing availability. Can I go longer for a better rod angle?
• Rod brand: Anyone have a preference? They all seem to be in the $400 range these days.

This will be primarily an autocross engine with some weekend drives. I also drive to events. The engine needs to be able to spin to at least 7500RPM even if it's not making power up there.

Here's the rest of the config (all of these parts are in hand):

• JE 96mm pistons with AA barrels
• Type 4 Store 9550 cam (86b/86c variant)
• Set of beautiful Finch heads I scored from Len Hoffman years ago
• Tangerine Racing 1.75" header
• 48 Dellorto Carbs with a 38mm vent (probably need to go to a 40mm vent)
• Dry sumped (either CB or ideally TP)

[Jack Standz]

I'm getting close to having all the parts for the 2270 build, but have a few questions:

• Crank brand: DPR, Scat, or AA? AA and Scat are new forgings but cost a bit more than the DPR crank. DPR is well respected in these parts.
• Crank size: Seem like a shame to leave it at a 2270 (78mm) when I could go up to a 2316 (80mm). Chevy journals.
• Rod length and type: Planning on 5.325" and Chevy journals for both clearance and the better bearing availability. Can I go longer for a better rod angle?
• Rod brand: Anyone have a preference? They all seem to be in the $400 range these days.

This will be primarily an autocross engine with some weekend drives. I also drive to events. The engine needs to be able to spin to at least 7500RPM even if it's not making power up there.

Here's the rest of the config (all of these parts are in hand):

• JE 96mm pistons with AA barrels
• Type 4 Store 9550 cam (86b/86c variant)
• Set of beautiful Finch heads I scored from Len Hoffman years ago
• Tangerine Racing 1.75" header
• 48 Dellorto Carbs with a 38mm vent (probably need to go to a 40mm vent)
• Dry sumped (either CB or ideally TP)

Thoughts:

Keeping weight of reciprocating mass low helps the motor spin-up faster and balanced.

Light car, light flywheel.

Yes, get a quality forged stroker crankshaft. Suggest getting one without heavy counterweights or full circle that adds weight. Our project 2615 (102 "nickies" & 80mm stroke as 78mm wasn't available) has the larger type 1 journals.

Sleeve lifter bores and use type 1 tool steel lifters (53 versus 137 grams compared with type iv lifters).

Empi forged I-beam rods are stronger and lighter than H-beams rods (5.5" are 564 grams on our scale). https://empius.com/products/empi-pro-series...5-16-rod-bolts/

Have everything (dynamically) balanced together. Flywheel, Rods, pistons, crankshaft, etc.

Crower springs and lightweight retainers. Check your heads as they may have these already.

Best wishes for your project.