LT4 Long Block Help

Jaynu · 05-09-2025, 04:54 PM

New to this forum, looking for a little help. I am getting ready to purchase a LT4 long block from Chevy and I am looking for some details on two different part numbers.

First the GM#12700126 is listed as a 2016-21 Camaro LT4, then there is GM#12716403 is listed as a 2022-24 Camaro LT4. There is a significant price difference in the two. Does anyone know what the difference may be?

Was there possibly a change to the Cam phaser? And would that present any problem for a custom install using a terminator x to control the engine. This is the only clue of a difference i can find.

This engine is for an older restomod build so is not actually going in a Gen 6 Camaro. Any help would be greatly appreciated before I drop a lot of money on a motor.

Thanks

RobZL1 · 05-09-2025, 05:34 PM

Here is what I saw on the interwebs about the newer one:

• Intended as a service engine for 2022-2024 ZL1 . Can be used on earlier LT4 applications, however the cam phaser/actuator changed and we are NOT responsible for any issues you may encounter by installing this in an earlier vehicle!

I would imagine it's a moot point if you are using a standalone. Just my opinion. I thought they were the same, minus the oil pump updates and maybe some other part/vendor changes

KingLT1 · 05-12-2025, 07:46 AM

Just put a DOD/VVT delete cam in it, delete the phaser all together, and it won't matter.

Jaynu · 05-12-2025, 09:24 PM

Yeah, I think deleting is the way to go. Still don't understand why the 22-24 long block is $4k less than the 2016-21.

05-09-2025, 05:34 PM	#2
RobZL1 fo'shizZL1 Drives: 2017 ZL1 Join Date: Aug 2017 Location: ATL Posts: 1,849	Here is what I saw on the interwebs about the newer one: • Intended as a service engine for 2022-2024 ZL1 . Can be used on earlier LT4 applications, however the cam phaser/actuator changed and we are NOT responsible for any issues you may encounter by installing this in an earlier vehicle! I would imagine it's a moot point if you are using a standalone. Just my opinion. I thought they were the same, minus the oil pump updates and maybe some other part/vendor changes __________________ 2017 ZL1 M6 Black \| Maggie 2650 // 103TB // Big Gulp // CSP LT's & Ultra Cats // BMR MM // BC Forged KL13 Mods being installed- oil pump, cam, ported heads, dual in-tank, Goliath and XDI, corn, etc., etc.

05-12-2025, 07:46 AM	#3
KingLT1 Drives: 2016 1SS NFG A8 Join Date: Aug 2017 Location: 46804 Posts: 7,666	Just put a DOD/VVT delete cam in it, delete the phaser all together, and it won't matter. __________________ 2016 NFG SS A8/Whipple 2.9/Fuel System/Flex Fuel

05-09-2025, 04:54 PM	#1
Jaynu Drives: 2013 CTS-V Wagon, 1936 Chevy Master Join Date: May 2025 Location: Jax Florida Posts: 2	LT4 Long Block Help New to this forum, looking for a little help. I am getting ready to purchase a LT4 long block from Chevy and I am looking for some details on two different part numbers. First the GM#12700126 is listed as a 2016-21 Camaro LT4, then there is GM#12716403 is listed as a 2022-24 Camaro LT4. There is a significant price difference in the two. Does anyone know what the difference may be? Was there possibly a change to the Cam phaser? And would that present any problem for a custom install using a terminator x to control the engine. This is the only clue of a difference i can find. This engine is for an older restomod build so is not actually going in a Gen 6 Camaro. Any help would be greatly appreciated before I drop a lot of money on a motor. Thanks Last edited by Jaynu; 05-09-2025 at 05:24 PM.

05-12-2025, 09:24 PM	#4
Jaynu Drives: 2013 CTS-V Wagon, 1936 Chevy Master Join Date: May 2025 Location: Jax Florida Posts: 2	Yeah, I think deleting is the way to go. Still don't understand why the 22-24 long block is $4k less than the 2016-21.

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