This is definitely premature. But, should be a fun discussion!
Say we have a stock, good condition truck 5.3 from 2001. Pre dod. We want 400+hp/tq, broad powerband, reliable, and able to turn 8k on a regular basis.
Application would be a gearing limited track car with a 1:1 final drive in the trans.
What would it take to do it as chap as possible, and reliable?
Are we talking sustained high RPM, or tickle 8k on occasion without sending the rotating assembly into the stratosphere ?
In reply to Appleseed :
Sustain 6k+, tickle 8k on occasion without taking a piston potshot at mars
I would rather try this with a 4.8 due to the much more favorable rod/stroke ratio. It seems like oil return and valve float will be the primary challenges.
I'm perhaps the least qualified to speak on the topic, but isn't one way to do it by "de-stroking" the 5.3 with a 4.8 crank?
Relevant to my interests as an LS/LQ is the plan for the e36 coupe.
Didn't Hot Rod or another mag build a 9k rpm LS using a 6.2 block & 4.8 crank? IIRC they used a lot of custom $$ parts to keep it alive.
dyintorace said:I'm perhaps the least qualified to speak on the topic, but isn't one way to do it by "de-stroking" the 5.3 with a 4.8 crank?
A 4.8 is a destroked 5.3
https://www.motortrend.com/how-to/1901-554-hp-from-low-buck-junkyard-48l-lr4-ls/
Looks like a cam & springs swap + a custom tune, maybe with an aftermarket EFI controller, should give you what you're looking for with a 4.8. A call to the cam vendor of your choice would probably help verify this.
Force is the enemy. F=ma
Peak piston acceleration for a 4.8L @ 8000 is about the same as a 5.3L @ 7415.
Peak piston acceleration for a 5.3L @ 8000 is about the same as a 4.8L @ 8630.
Lightweight all the things that move.
While 400 hp is easy enough, 8k rpm and 400 ft-lb may be mutually exclusive in this context.
.
Final drive changes would probably be a cheaper way to pick up mph, than rpm.
Oh wait, I misread, I thought it was 6k on a regular basis. 4.8 with a custom rotating assembly? Doesn't seem worth it unless you really want to go full tilt with the thing.
Making anything spin to 8k regularly that didn't come from the factory that way isn't going to be cheap. Especially still making power up there.
You know the old:
Cheap, reliable, fast............pick two.
I've already gotten the 5.3, so that is why were going here.
Cam, compression and mild porting will get me power up to 6500 or so. However, the delta with my trans between 6-8k is 30mph in 3rd, 40 in 4th. Maybe not needed at every track, but i can see where it'll help.
The budget and reliability is the key. I am, after all, trying to run for pennies a lap.
I think the thing that would concern me (even if you get it to not explode at 8000) is where it will make power.
First, you'll need some serious heads if they even make them. It takes a truckload of flow to support 8000 rpms with 5.3L. Those heads will also remove a truckload of low-end torque. The required cam, exotic valvetrain parts, and related parts will mean it will idle at 2500 and not make any real torque until 5000. You're going to need about 14:1 compression and a steady diet of a fuel with about 110 octane rating and a very careful ignition curve.
My point is, naturally aspirated you are going to have a fixed torque curve and a HP curve. It's not that you can't rev it that high, it's that it won't make power that high unless you go pretty nuts with the other parts. I think you'll find that if you just do the normal cam/heads to make - let's say - 500 hp, you'll stop accelerating at maybe 7000 because the power curve has fallen off so far that friction and aero is greater than the HP needed to keep accelerating. It's not just revving that high, it's selecting the exoticum parts to make power that high.
Budget, 8k rpm V8, and reliable is going to be a tough challenge.
Lightweight rods, heavy duty rod bolts, cam, valve train, push rods, intake and headers to match would be a start.
I think you can spin one to 8k on a reasonable budget. I just don't know if it will be close to your power goals if keeping it NA
Starting with a less than optimal engine for the stated goal is not going to make this easier. Horse trade for a 4.8?
I don't see this ending with the desired result. It'll either be much more expensive or much less reliable than what you want. RPM is the problem; torque can always be increased by forced induction, probably for less money than any other solution. I realize that may change the category the car is in... which brings up the question: what type of drag racing is this for? Is it officially-classed racing, or just a run-what-you-brung casual event to impress friends?
Sell 5.3, buy 6.0, use tork instead of RPM. That'll cost you less than trying to make the 5.3 outperform a bigger engine.
I've had a built up 5.3, a mostly stock 5.7 and a 6.2 that's bone stock other than the ASA cam. The 5.3 and 6.2 were in the same car, the 5.7 was in a different car that weighs about the same. The car is much faster with the 6.2. It was the gap in performance between the 5.3 and the 5.7 that made me change it out. The big engine was worth something like 18 mph down the straight at High Plains.
The nice thing about the LS engines is that they're all the same size, so a displacement increase is a simple thing. About the only caveat is the number of teeth on the reluctor wheel, that's determined by your engine management. And you can swap those.
Everyone worried about the bottom end, but nobody talking about keeping the valves happy at 8000rpm.
Relevant? He doesn't take them over 7k rpm, but he gets your desired power/torque from a mostly stock 5.3 and a cam swap
buzzboy said:Everyone worried about the bottom end, but nobody talking about keeping the valves, heavy roller lifters, oil-filled pushrods, and rocker arms happy at 8000rpm.
Amended that for you.
Thought experiment time: Assume 2 otherwise identical cars.
Car A -- HP -- Car B
3500 -- 245 -- 4000
4000 -- 280 -- 4571
4500 -- 315 -- 5143
5000 -- 350 -- 5714
5500 -- 385 -- 6286
6000 -- 420 -- 6857
6500 -- 455 -- 7429
7000 -- 420 -- 8000
3.27 --- FD --- 3.73
Aside from engine pitch, these two cars will go down the track exactly the same: accelerating at the same rate, shifting at the same time, and hitting the same speeds. However, the engine in car A will be more reliable for less money than the engine in car B.
In reply to Curtis73 (Forum Supporter) :
I would have thought the LS7 would have the answers for a high RPM valvetrain. Besides, those failures don't usually take out the entire engine the way a rod does :)
It's fun doing the math on loads on the rods as RPM goes up. It's exponential.
Dusterbd13-michael said:This is definitely premature. But, should be a fun discussion!
Say we have a stock, good condition truck 5.3 from 2001. Pre dod. We want 400+hp/tq, broad powerband, reliable, and able to turn 8k on a regular basis.
Application would be a gearing limited track car with a 1:1 final drive in the trans.
What would it take to do it as chap as possible, and reliable?
This has been done. It's on UTube so it's free to see the results. Actual on the chassis Dyno results.
Go to nivlac57 and look at his 4.8 vs 5.3.
But 4- even 500 hp can be done with a stone stock junkyard engine. Just add boost. A $140 Amazon turbo and you're there. I think they even sell a whole kit for about $500. Don't have to even take it apart if it's over 100,000 miles. Ring gap opens the required amount if you use E85.
Nothing magic about High RPM except the damage that happens when parts fail.
You'll need to log in to post.
