L31R complete or ZZ4 short block

[toolboxchev]

I cant decide which one???

I know they both have advantages.

Show me what you have done, or modified simply to make it work. Going to be repowering soon so I am looking for the finer details.

[Warrens69GMC]

I'm going to go ZZ shortblock, Summit heads 72cc and comp 08-502-8 camshaft

https://youtu.be/KFaw1_TJ7WM

[truckster]

From an economical standpoint I think the L31 makes more sense. Replace the cam with the HT 383 cam and you'll be right around 330 HP and 400 ft-lbs torque. You'll pay a lot more for the ZZ4 with not a lot of gain. The ZZ4 is designed for high-RPM performance, while the L31 is designed for grunt at the low end, where your truck needs it most.

[toolboxchev]

Part I am really having a problem with is specs.

L31 how many cc dished piston?

ZZ4 Does it come zero decked?

Cant seem to find this stuff.

[Warrens69GMC]

12cc dished pistone

normally the zz motors are approx .020 in the hole

[toolboxchev]

I am still leaning toward the zz4 due in part to the bottom end, flat tops, and ability to run mechanical fuel pump.

I will get a lot more in the end. But then again there is always the convenience. I still like being open to more choices in the long run. And a better end performer.

[toolboxchev]

So I found this interesting:

Here from Chevrolet Performance are these replacement partial engines for all ZZZ through ZZ4 series crate engines. These partial engines consist of cast iron 4-bolt mains with 1-piece rear main seals. Inside you have Forged 1053 steel internally balanced crankshafts, 5.7 in. powdered metal connecting rods with hypereutectic flat top pistons with offset pins. These are the same pins used in Corvette LT1 engines. Also included are rings, bearings and brass freeze plugs already installed. Does not include camshafts, timing chains, sprockets, front covers, oil pumps, oil pans, balancers, or flex plates. Compression ratios depend upon the combustion chamber size of the cylinder heads you use. Approximate compression ratios would be 10.0:1 with 58cc, 9.8:1 with 62cc, 9.6:1 with 64cc, and 8.5:1 with 76cc cylinder heads.

What does having offset pins compare with an L31 R Long Block assembly? Granted all pistons are not the same and as I dig the confusion grows! I am getting serious about this and do not wish to travel down a road blindly.

If someone with some engine building experience could chime in and shed some light I would appreciate it!

[toolboxchev]

Originally Posted by Warrens69GMC

12cc dished pistone

normally the zz motors are approx .020 in the hole

Yep, found the spec that say the ZZ4 block is not ZERO decked. Thanks Warren!