Swapping LS3 valvetrain to LS7

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Mar 30, 2022 | 10:08 PM

Z97

Thread Starter

Cruising

Joined: Oct 2020

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Swapping LS3 valvetrain to LS7

Curious as to those who know about this swap... The old google/facebook/youtube search isn't getting me too far with this one.

Have a LS3 being stroked out to a 416 build since it decided to spin a rod bearing (good times). Based on what I know the bore has to be 4.1 to run LS7 heads? Or there abouts?

Is it worth while to go LS7 valvetrain for extra power? Heads are currently stock casting ported by texas speed.

Any reading material or insight is appreciated!

Mar 31, 2022 | 09:11 AM

Orion2011

Burning Brakes

Joined: Jun 2015

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From: Shelbyville Kentucky

Not 100% sure but I don't think they are compatible. LS3 is 4.4" spacing

Mar 31, 2022 | 07:19 PM

farmington

Safety Car

Joined: Aug 2017

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From: North Myrtle Beach SC

Ls3 bore is 4.060. You can’t bore them .040.

Mar 31, 2022 | 08:35 PM

old motorhead

Le Mans Master

Joined: Dec 2005

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From: Southeast TX

As far as the valve train goes for the two engines, the lifters and some valve springs are interchangeable. That's about it.

Mar 31, 2022 | 11:24 PM

KW Baraka

Racer

Joined: Jan 2015

Posts: 375

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From: San Antonio TX

Quote:

Originally Posted by Z97

Have a LS3 being stroked out to a 416 build since it decided to spin a rod bearing (good times). Based on what I know the bore has to be 4.1 to run LS7 heads? Or there abouts?

Uh.....yeah.....it's been done.....LS7 heads on a bored/stroked LS3.

All this talk of LS7 heads requiring 4.100 bore is GM disclaiming so they're not liable for any damages.....

LS7 heads on a 6.2l block 4.07 bore. | Yellow Bullet Forums

KW

Apr 1, 2022 | 08:08 AM

grinder11

Race Director

Joined: Oct 2004

Posts: 12,864

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Quote:

Originally Posted by Orion2011

Not 100% sure but I don't think they are compatible. LS3 is 4.4" spacing

ALL LS, LT, SBC engines are 4.400" bore spaced. It's the smaller diameter of the cylinder that has interference with the large 2.200" diameter LS7 intake valves. IMHO, the OP would be way ahead of the game using ported LS3 heads, or aftermarket.......

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