Destroked 6.0 / Big bore 4.8
 

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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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.

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...

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.

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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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.

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.

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.

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.

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...

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

Does the 4.8 rev high in the truck?

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

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

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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My main obstacle for this swap is fitment, I know it can be done but I don’t have much knowledge on fabricating engine mounts. I know this is a pretty basic thing to get over but it’s still my greatest obstacle, wiring I find to be quite easy and I’ve already looked into this. Custom driveshaft I’ve had worked out already, and there’s conversion plates for the t56 transmission to bolt onto the 1UZ, not to mention a whole slew of other transmissions that would fit this swap. If you know of any mounts that can be ordered or just blueprints for mounts, I could pull the trigger on the 1UZ right now....


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High Performance Academy on YT has covered a high revving 1UZ 86. Start here.

https://www.youtube.com/watch?v=Zih4ZrAAAlM

Thanks for the link but I’ve already picked HPA’s resources on this car clean, I reached out to them and they explained again that they really had no involvement with the car prior to the wiring and tuning stage of the build. I know it’s honestly a pretty trivial thing for a swap but I really just want a set of engine mounts that I can buy so I don’t need to fabricate them. The guy who actually built HPA’s car is on this forum and has a thread on the build, while it is helpful, he doesn’t have much on the engine and tranny mounts included in his documentation. I’ve tried reaching out to him but since he’s sold his car to HPA he’s gone MIA on the forums. I’ve looked pretty hard, but do you know of any mounts I could order for the swap? Do you know any users on this forum that would be good to discuss this swap with?


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All I keep seeing is Surfab custom. I think if you want plug and play, stick with Chevy. The 1uz is too uncommon to not have a bit of fab work.

https://www.youtube.com/watch?v=J2MrGWaYBX0

Yeah you’re probably right, a guy can dream tho


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I thought HPA mentioned that V8 blew in a more recent video.

They were running a VVTI model engine, the best one to go with is the non VVTI. The non VVTI has a slimmer power band stock but it’s been overbuilt like crazy, like some of the thickest stock rods I’ve ever seen.


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They were also endurance racing and hanging around 8k rpms, that’s gonna be rough on any engine haha


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I'm waiting to see what they do next, though. I remember reading some other person's work on an intake manifold or supercharger for a SC-400 project, manual transmission and going for sky high revving machine, which I liked a lot. I think it was in a clublexus forum, and might be mixing several projects in mind since I can't find the link. Neveetheless, still rooting for them.

Who cares if it revs. You're gonna be so much stronger than the fa20 even if you set the rev limit at 4 grand. Lol

If you have and are competent with a welder then there are probably a million tutorials on how to make engine mounts from static/fixed mounts to polyurethane. You could make a universal mount with multiple holes to move the engine forward and back, or you could make a slot in the mount. Just like a car's wheel, where the holes don't hold the wheel onto the hub; the friction between the two surfaces locks them together. The engine mount hole is to align it into position and so the bolt can camp the two surfaces together, but it is the surface friction that maintains its position, so slots, loose holes, etc wouldn't be the end of the world if precision fitment is a concern.


These are some BRZ to LS mounts.




https://www.cxracing.com/image/cache...02-650x650.jpg


Here are some mounts for a 1UZ into a Tacoma. You could buy those and hack off the half that mounts to the Tacoma and make them fit the 86.


https://www.cxracing.com/ESK-1UZ-TACOMA9504


https://www.cxracing.com/image/catal...9504-car-9.png

I like the way you think sir, I can weld but my skill level is sub par. But that’s why I have a little brother that’s a superb welder I guess haha.


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High revs= more fun lol but yeah I get what you’re saying, the main goal of the high rpm limit is to widen my power band and yes I will sacrifices some peak power, but I’d rather my power come on early


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When your car pulls like a f*cking freight train from 2K-7K rpm, the redline becomes pretty freaking irrelevant.

Going from a 7400 rpm redline to 7K wasn’t that different and well worth the trade off for torque. I am glad I have a valvetrain built to handle more revs than 6500 though. Mine should be fine to spin to 7400 but not much point with the cam I’m running. I have the shift light set to 6850, shift at 7K and rev limiter set at 7300. I find this works out very nicely.

If you have a boosted FA20 making a bunch of power I’d get use to shifting at 7K anyway if you want your engine to last. Not sure it’s worth it to build a destroked LS revving to the moon. If that’s what you’re looking for I’d go K swap.

As far as a 1UZ swap unless you love doing fab work or just really need to stand out and be different I don’t see the point. Having one of probably only half a dozen completed LS swaps in the whole state of California already makes it feel pretty rare. Most 1UZ swaps you see were done in other parts of the world where LS stuff is harder to come by.

To me unless you are drag racing or on an unlimited budget no reason to go with any other engine aside from K swap or LS. I love that in 20 years I should still easily be able to source LS parts. There’s also plenty of crashed 86’s to get parts if need be. Aside from torque the massive availability of parts makes the LS a winner in my book.

From talking this over with my coworker (big LS guy) and reading your post, you’re honestly right. Although it’s a cool idea, having a 450hp FRS is already good enough haha


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I would try and compare weights. There is data on here and probably a sticky. Point is that if you can get a "junkyard" LS in an aluminum block of any kind should be a good thing. Talk to your buddy about what parts are interchangeable etc etc. There is numerous valvetrain upgrade kits to hold higher rpms. Hell...throw some ITB's on it!

So there are a lot of variables that need to be taken into account.

For starters, the stock 4.8 crank is pretty rugged. Guys are running 1000+hp turbo builds on stock bottom ends and having no issues.

There is a lot of math involved in this work.

For example. The stock LS1 bore is 3.898 while the stroke is 3.622. The connecting rod is 6.098in.

The 6.0 is a 4.0 in bore and the same 3.622 stroke. It is also an iron block as previously mentioned. It also has the same connecting rod length.

The 4.8 is 3.780 in bore block, and has a 3.267 stroke, and most of them are cast iron. Connecting rod length is 6.275in.

The LS3/LSA block is the preffered route, as they are aluminum, and have a bore of 4.065 and a 3.622 crank, with a rod of 6.098, and the bore size would allow the much larger 2.165 intake valves. However, bigger means more weight....which is the antithesis of what you want on a spinner.

Now here is the complex part of it all. The block height of all of these engines *should* be the same height. When you short stroke the engine as mentioned, you need to make either the piston height taller, or the connecting rod longer, or some combination of the two so you can maintain a proper compression ratio.

But wait, there is more. When you change the connecting rod to stroke ratio, you change the engine speed at which the engine best fills the engine with air/fuel to make power. The higher the rod-to-stroke ratio, the higher the RPM the engine makes power. Effectively, you won't create a larger power band. The power band is measured from peak torque, to peak power.

Now, lets say we all of that figured out, just like in the hotrod article you linked. You need the valvetrain and the head surface area mated to work at those speeds. A high flowing head is going to be ideal, but the intake runner size could be crucial to drive ability, as is the quench area, but I will stay out of that in-depth discussion, as it gets pretty muddy and very cam specific. I haven't even touched on the camshaft topic yet, because those require certain compression ratios, vacuum, etc to operate. There are some off the shelf parts that will likely work, and well. However, that information would require someone who has the knowledge and experience to build an engine as such. Valvetrain stabilization is available, things like shaft mounted rockers, but the other bits are valve weights, retainer weights, retainer design, etc. It starts a toilet bowl of because of part A, I now need parts b, c, d, and e.

Lets say all of this is fairly easy to figure out and build, without too much insanity. My initial estimate for an LS3/LSA block to build is around 12k. That is just the engine build to *roughly* be assembled. It isn't taking into account the various machine work, or unforseen costs related to the 8k+ rpm loads.

Lets now say you have the engine, what about the clutch and flywheel, another part that often gets over-looked. You would want something that is not to terribly heavier, or light, to make this partially driveable on the street.

Now the even more difficult part. The majority of the transmissions used on LS engines aren't built for 8k+ rpm shifts. The syncronizers would be getting tortured, and not last to terribly long, likey a custom rebuilt, or even built transmission would be required.


A great example of what can be done.

https://www.youtube.com/watch?v=lgMoTQLebTs


I was/am planning on going this route at some point if the S/C route doesn't give me what I want. Because I think it would be absolutely mental. I miss the sound of a V8, but I love the chassis dynamics of the 86.

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I looked extensively into this as I had a bored out ls3 block with my 418ci stroker build and bought a 4.8 crank. Pistons/rod combo becomes tricky while keeping proper quench. The more I looked into it, the more it became apparent I was better off keeping a stock stroke LS3 with lightweight crank/rods/pistons, a set of well built LS3 heads with larger valves, Comp Conical Valve kit, Shaft rockers, link-bar lifters and a good intake manifold. Will rev to 8k rpm and have a better power band than a de-stroker build.