sidewayZmoose

hello, i am new to the forum and would appreciate some feedback on an engine build idea i have. i plan to buy a 4.8 (LR4) and a 6.0 (LQ4) bore the 6.0 block to a 6.2 (0.065 over), drop the short stroke crank from the 4.8 in the 4.065 bore block and have a high rpm destroker. this is an engine i’d want to put in something like a foxbody notch or a tri 5 chev. unfortunately those vehicles are a tad out of my price range and impractical for a daily driver. in the mean time i am going to buy a 2wd automatic
s-10 to LS swap. i’m thinking i could just use the stock 6.0 crank and rods with the 4.8 pistons in the 4.8 block. this would create a higher compression 5.3. with a medium size cam, stock truck intake with a larger throttle body, and headers this should create a decent street motor (engine i know i know.) any guesses on power. i’d also like to be able to run it on 87 octane. i’ve heard a 5.3 with 4.8 pistons and stock 706 heads would have about 10.5 to 1 compression but i’m not certain as i haven’t calculated it myself. would it be possible to run this combo on 87?

Ls7colorado

iTrader: (3)

sounds like a disaster IMO.
A 6.0 will rev well passed 7000 rpm without a 4.8 crank witch is about as high as you will want to be before getting into an extremely expensive valvetrain setup. So there is NO NEED for a 4.8 crank if you want revs. If your wanting to hit 8000rpm + for some reason and run a solid roller cam and spend thousands on the rest of the valvetrain then go for it.

The flat top 5.3 would be a great idea, but then you kill it with an 87 octane tune......

Enigma540

i concur with this. The only reason to go with a short stroke in the ls platform would be to meet some class restriction. And in that situation, if a mustang is out of your budget, the cost to assembly a stable valve train will also be out of your budget. I don't understand why some think you need all sorts of black magic to turn rpm's in an ls platform. Big block chevys have been turning 7000+ with insanely heavy valves, large strokes, and heavy lifters for decades. Other than rod bolt concerns, there's no reason to be afraid of turning a 3.662 stroke crank well over what you could turn a 4.25 stroke 80 pound crank with 180 gram valves.

sidewayZmoose

8 thousand rpm is the goal. i realize the valvetrain will be extremely expensive but there is no real timeframe on this build for me. if it isn’t possible to run 4.8 pistons in a 5.3 on 87 octane with the 706 heads it seems to me i have 2 options. simply swap to the 6.0 heads to lower compression which i don’t think is the best option as from what i’ve heard although they have big valves the actual design of the ports isn’t ideal. or i could buy different pistons and still use the 706 heads. if i were to go this route i think boring it out to a 5.7 would make the most sense as i’m already going to be spending the money on pistons so i might as well get some extra cubes. any feedback is greatly appreciated!

Ls7colorado

iTrader: (3)

I mean, if you just wanna spend alot of money on the bottom ends for no real reason then go for it!

AwesomeAuto

What is with the massive influx of guys from the import scene who come here with RPM being their main goal?

sidewayZmoose

the reason is revving to 8 grand. but i’m more looking for advice on what to do with the left over parts. i’ll have the 6.0 crank and rods and the 4.8 pistons. which would be a great combo but i want to run it on 87 octane fuel as this engine will be going in my daily. i’m not sure if i’ll be able to run that bottom end with 706 heads and their tiny 61.5cc chambers. should i use the 317 heads off the 6.0 or buy different pistons with a dish? if i were to go the latter route would it be worth it to the block bored to ls1/6 specs (3.898 inches) for the extra cubes or would stock 5.3 3.78 inch bore 7cc dish pistons be fine? or will the 706 heads and flat top pistons be fine on 87 octane? obviously it won’t make as much power as it would if i were to run it on 91 but would it run okay or would i run into detonation issues? of course i’d love to build it with flat top ls1 pistons, ported 706 heads on 91 but unfortunately i’m on a shoestring budget lol.

sidewayZmoose

i can’t speak to that as i’m more of a domestic guy. the appeal of high rpm for me is the sound (obviously) and being able to make more power with less displacement.

Ls7colorado

iTrader: (3)

The way I see it your just going to have left over parts... no need to tear apart a 5.3 just to put flat tops in it witch will raise the compression and then put larger CC heads on it to lower the compression....?? Just doesnt make sense, especially when a Lm7 can be bought for $500 ish...
And you still dont need a 4.8 crank in the 6.0 to rev to 8,000, it might help it live a little longer since the piston speed will be lower if your going to be holding it at 8,000 rpm for LONG periods of time. Otherwise its just lost power.

kott0n

I dont know but Detroit Speed has a LS powered 3rd gen they spin to 8500rpm and it sounds AMAZING.

Not that I would ever spend the money to build one but man does it sound good.

G Atsma

Not sure I would spend a ton of money on the main objective of SOUNDING good. RUNNING good, oh yeah.
But your 8k rev goal will only be met with a VERY high dollar valve train. Just to sound good???

00pooterSS

iTrader: (40)

That's a **** load of money to spend for the sake of being different and how it sounds. I think usually when people want to do this they don't truly understand the full picture of cost and special needs of a high rpm build. If you're building on a budget you can go a whole lot faster for a whole lot less money if you don't try to do it with RPM.

I love the sound of a high revving v8, but not only is it a bank account draining idea due to valve train needs, rod and rod bolt needs and overall attention to detail throughout the engine, you also have to cam for it, gear for it, and modify the auto trans for it.

As for building a motor to run on 87. Just leave it stock if you wanna run 87. It blows my mind to see so many people invest so much time and money in modding then want to run 87. It's completely *** backwards and pointless. It limits power and fuel mileage and everyone wants to do it to save money.... The higher octane allows more timing that nets more mpg and evens out the cost. I've done it, and I've done the math.

Ls7colorado

iTrader: (3)

Also, if you cant afford to run 91/93 then you certainly cant afford to be modifying the engine. Let alone make one that will live at 8000+ rpm

Matt_ws6

Remember what horsepower is. It's simply (RPM*Torque)/5252. Most stock-like destrokers have to rev to the moon simply to make up for the lack of torque that is made. You mentioned a daily. For a daily, you want usable power as soon as possible. The idea of a destroked motor is cool, but for most applications it's not optimal.

AwesomeAuto

I missed the 87 octane part. LMAO.

You can rev a gen 4 5.3 to 8000 RPM. Why go through the trouble of creating one through a destroked 6.0?

00pooterSS

iTrader: (40)

Full agree

sidewayZmoose

the destroker won’t be going in my daily. the 5.3 i build out of leftover parts will be going in my daily. i think i’m just going to bite the bullet, use the 4.8 pistons and run it on 91 (the highest octane available in my area.)

sidewayZmoose

the 339 ci destroker (4.065 x 3.267) is a long term project eventually going in a tri five chev or a foxbody. i am looking for advice on what to do with the left over parts. i’ll have a 4.8 block and pistons, 6.0 crank and rods (same as a 5.3), 706 and 317 heads, and two cathedral port truck intakes. i’ve been convinced to run it on 91 so i think the best cheapest option would be to use the 6.0 crank and rods with the 4.8 pistons to create a higher compression 5.3 with a stock truck intake (anyone know if that’ll clear an s-10 hood?) and 706 heads. i’ve also been toying with the idea of getting the 4.8 block bored out to 3.898 inches and using stock ls1/6 pistons. obviously this would add a fair bit of cost to the program but would it be worth it?

sidewayZmoose

if i do end up keeping the truck intake i’ll definitely get a larger throttle body (what size would be best?) and the s-10 swap kit i’m looking at comes with headers. any cam suggestions for a 5.3/5.7 with 706 heads?

00pooterSS

iTrader: (40)

Titan 4 is an excellent all around cam for a 5.7
Plenty big enough with excellent manners.
But if you want high rpm you can look at going a bit bigger, however the truck intake would just kill all the potential in a sense. TBSS is an okay truck manifold and the LS6 is okay. But you'd really want a FAST if you're gonna go that far with a cam and high revs. Or a MSD or even something like a sniper/high ram etc.

I'm not 100% sure if you can do 4.8 pistons on 3.622 stroke. I've always just though yeah sure that works, but all 3 of those have around .005 - .007 piston out of the hole measurements in stock form, and if you increase the stroke on the 4.8 setup the pistons would have to come up and out further. Makes me wonder if 4.8 rods are longer. Never read into it though.

I'm not sure on the hood clearance. You may be able to dig around in the conversions/hybrids forum for answers on that

I feel like we're all kicking the **** out of you for your ideas, not trying to if it's coming across like that. And I know it kinda is.

There's a lot of questions in one thread that can have a ton of answers for each idea so it's hard to cover them all.

Also, you don't need to destroke these things to rev them. You could rev out a gen 4 rodded motor just fine.

Replacing dish 5.3's with flat top 4.8's is always a good plan. Compression is good. The 706 heads are good too.

Larger throttle body on a truck intake, or any intake really that it isn't designed for is a complete waste of time. The opening in the intake is only so big, a larger throttle body cannot and will not outflow the size of the hole in the intake. You have to increase the size of the hole in the intake by cutting off the nose of the intake and putting a different larger nose on it to make any use of a larger throttle body.

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