Destroked 6.0 / Big bore 4.8

[DeathToocher]

So after a lot of consideration and a lot of jumping back and forth on whether I want to mod the stock engine or which engine I want to swap in, I have come to the conclusion of sticking with the tried and true LS swap. With all the support for a GT86 LS swap it seems like the obvious choice. The one thing I considered a drawback (although it’s a pretty trivial thing to consider a drawback) is the fact that the LS engines do not rev high at all. This led to my discovery of “destroking” a 6.0 block by running a 4.8L crankshaft. I plan to run an LQ4 block, a forged 4.8 crank, forged LS3 rods and pistons, LS3 heads with hollow stem valves and beehive valve springs (to take care of valve float at higher RPM), and a mild LS3 comp cam. I’d like to buy a full LQ4 setup and sell the accessories and wiring harness for a few extra bucks to stick into a bad ass serpentine kit. I plan to run a FAST intake manifold. Wiring I’m hoping to have provided by Sikky but haltech is my back up. Looking at what my stock FA20 with 44k miles on it is worth, this build won’t hurt the wallet too badly. With similar setups, I’m seeing results of a 8-9k redline and nice 480-600hp. Anyone have experience with a similar build? If not, thoughts?


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[Mike_ZN6]

I don't have any experience with this, but what you are describing is basically my dream build for this car. I think you should go ahead and do it and make sure to make a build thread.

[ZDan]

IMO fascination with "destroking" is misplaced. You lose more displacement (linearly w/ stroke) than you gain potential revs (only gain with square root of stroke). Pretty straighforward to build a 7500rpm LS2/3 and 8000 is also doable.

I replaced the 7000rpm 2.4 liter (peak power at ~5500) in my 240Z with a 3.1 liter stroked L28 that reliably revved to 7200rpm and made peak power at 6500.
No ragerts...
You can have both revs and displacement...

[Westen86]

I work with a Chevy guy that says the 4.8, 5.3 and 6.0 are all the exact same block. Just buy a 4.8, and put 6.0 heads on it. Or whatever. But dont start with a 6.0.

[DeathToocher]

Originally Posted by ZDan

IMO fascination with "destroking" is misplaced. You lose more displacement (linearly w/ stroke) than you gain potential revs (only gain with square root of stroke). Pretty straighforward to build a 7500rpm LS2/3 and 8000 is also doable.

I replaced the 7000rpm 2.4 liter (peak power at ~5500) in my 240Z with a 3.1 liter stroked L28 that reliably revved to 7200rpm and made peak power at 6500.
No ragerts...
You can have both revs and displacement...

To simply gain a higher rev range, did you essentially just upgrade your bottom end and upgrade your valves / springs and then have it tuned to the rev limit you wanted?


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[ZDan]

Originally Posted by DeathToocher

To simply gain a higher rev range, did you essentially just upgrade your bottom end and upgrade your valves / springs and then have it tuned to the rev limit you wanted?

Custom cam, springs, professionally ported cylinder head (piggy-backed someone else's race development), 3x2 45mm carbs
Stock forged diesel crank, stock L24 rods, stock KA24 pistons w/ valve reliefs machined.
Primary tuning (distributor advance curve and main/air jetting) by me, pro did further driveability tuning of carbs.

I chose to limit it at 7200 to have some headroom above the 6500rpm power peak. It held together over dozens of track events and 10s of thousands of street miles.

[Summerwolf]

Should probably do some reading on ls1tech.

I've had several lsx vehicles. Not quite sure a destroked motor and those rpms are exactly what you're looking for. I spun a 5.7 pretty high with a heads and cam combo but still had a ton of torque at lower rpms as well. Do a ton of research on this.

There are also different blocks so do your research there as well, they're not "all the same" as stated above.

[Summerwolf]

Originally Posted by Westen86

I work with a Chevy guy that says the 4.8, 5.3 and 6.0 are all the exact same block. Just buy a 4.8, and put 6.0 heads on it. Or whatever. But dont start with a 6.0.

Besides being different bore sizes this would drop your compression....

Also the 6.0 has a built in casting that's different to support the bore size. Not all blocks are the same. Let alone the differences between a truck block, aluminum block, and then other differences between certain versions.

[Westen86]

https://www.hotrod.com/articles/make...0-4-8l-engine/

[PulsarBeeerz]

Originally Posted by Westen86

https://www.hotrod.com/articles/make...0-4-8l-engine/

That was an interesting article. I like how their $200 4.8 was over$7k all said and done. Lol Kinda like K20/24 swaps.

[ZDan]

Worth noting the 4.8 is an iron block, so +85 lb. (ish) more weight on the nose of a car that's already too nose-heavy stock.

I'd go forged-bottom-end crate LS2/LS3 with a cam and basic valvetrain mods, should be able to get 'er to rev to 7500rpm without much worry. Do confirm with LS experts of course...

[Westen86]

Im no LS expert, Im just dropping my humble opinion in. Im a 1UZ kinda guy.

[Irace86.2.0]

Does the 4.8 rev high in the truck?

I think this is a 2V problem. Not a piston speed problem.

The LS7 is a 7,011 cc (7.0 L; 427.8 cu in) engine, based on the Gen IV architecture. The block is changed, with sleeved cylinders in an aluminum block with a larger bore 4.125 in (104.8 mm) and longer stroke 4 in (101.6 mm) than the LS2.

Peak output is 505 bhp (512 PS; 377 kW) at 6300 rpm and 470 lb⋅ft (637 N⋅m) of torque at 4800 rpm with a 7000 rpm redline.[16] During GM's reliability testing of this engine in its prototype phase, the LS7 was remarked to have been repeatedly tested to be 8000 rpm capable, although power was not recorded at that rpm level, due to the constraints of the camshaft's hydraulic lifters and the intake manifold ability to flow required air at that engine speed.

https://en.m.wikipedia.org/wiki/LS_b...l-block_engine

[DeathToocher]

Originally Posted by Westen86

Im no LS expert, Im just dropping my humble opinion in. Im a 1UZ kinda guy.

Me too, 100% but I’ve never fabricated engine mounts before. A 1UZ GT86 was what I wanted but I can’t seem to find many helpful guides. Do you have any experience with this? I have someone who could help me with mounts but I’d like to get the mounts right the first time so I don’t need to pull the engine again.


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