Destroked 6.0 / Big bore 4.8

[DeathToocher]

Originally Posted by GrabTheWheel

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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[Swift]

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!

[Rex1585]

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.

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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[DustinS]

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.