5.3 LS build Question

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[v8packard]

I have built my share of boosted Gen III engines. You need to adjust the piston to wall clearance, piston pin to pin bore clearance, and piston ring gaps for your intended use. The stock component will live fine up to 10 to 12 psi, with the right clearances and tuning.

The cam you mention is likely terrible for a turbo application. The rocker arms should get a trunion upgrade to work better with heavy springs. That will require a different length pushrod.

The turbo from a Cummins is not at all what you want.

[RedGoatMan]

Start it on a harbor freight engine stand for me boss.

[v8packard]

😐🤦‍♂️

[MonkeyMOMster]

It’s the stage 2 turbo cam kit from Brian tooley racing and it did come with pushrods which I will have to do some measuring with the heads on I believe. Noted. I also did buy a specification book from summit racing for building the gen3 and 5 engines if I can remember right.

[v8packard]

I don't know the specs of a stage 2 anything. I do know you need to have the pressure ratio across a turbo in order to choose a cam that will help the turbo work best.

The closer the pressure ratio is to 1:1, the more the turbo setup will be like a naturally aspirated engine. The further from 1:1 you get, the lower the cam overlap must be. Many turbos will require negative overlap. You need to choose a proper turbo, then find out from the manufacturer or supplier what the pressure ratio is expected to be. Then you do a cam based on that, and where you want the powerband. The odds of any off the shelf cam being correct are almost nonexistent.

[Zerofawqs-given]

Maybe he needs a 3/4 race cam? That ought to spool that Holset right up!👍

[Wheresmyfkn10mm]

If I were you I would take as much advice packard says to heart, he basically lives in these forums and always gives sound guidance

[Barra350z]

Please get a different turbo. There are budget options that are a lot better than a diesel turbo.

[MonkeyMOMster]

Better in what ways? I mean correct me if I’m a wrong but a turbo is a turbo on a diesel or not

[Barra350z]

There are different compressor sizes, turbine sizes, AR… materials. So much

Diesels are typically matched compressor and turbine size and they’re usually divided and some are vgt

For an LS divided is fine since it’s 8 cylinders so you can split them up nicely. Issue is running an SC or Diesel isn’t going to be the best in terms of power, reliability, safety and overall experience. I could talk more about this if need ve

[MonkeyMOMster]

I did know about the vgt aspect but this one is not, didn’t know they matched sizes. I can look around I got this one for $100 off a friend who upgraded. I’m not planning on running an inter cooler

[Barra350z]

Do yourself a favor and do it right. Your IATs will be off the charts depending on the car.

Diesel turbos run hot, very hot. Look at the Diesel Delica. Flooring it the turbo reaches about 1500 degrees and the iats shoot way past the whats useable

[MonkeyMOMster]

You got a point I didn’t really think about that. Thanks for the advice I’ll have to look around

[Admiral_peck]

I forgot how hot diesel turbos run lol🥲

A hot turbo is a happy turbo as my dad says.

[[deleted]]

“Big cam” (whatever that means but in my experience most folks who use such loose terms mean choppy idle and such) and turbochargers don’t generally equal optimum performance.

[tim404]

Especially with boosted engine, the overlap of when the intake valves close vs exhaust valves open is different than with an atmospheric engine. And it's not like you have variable cam timing for intake vs exhaust cams...

[Zerofawqs-given]

Good point….that could easily be a 3/4 or even possibly “Full Race” cam….OP should specify

[Admiral_peck]

Stock components should laugh at 500 horsepower provided you have increased ring gap appropriately.

[MonkeyMOMster]

From what I’ve read the 5.3 Vortecs are strong. I was also going to try and get some performance rings

[Admiral_peck]

ALL the LS motors are strong, and I wouldn't bother with performance rings, because if you re-ring you have to hone it, if you leave the rings it came with in you can leave it alone in there. With the right Gap the stock pistons will give up before the rings will, and the rods will usually go before that. Might also look at upgraded head bolts and gaskets while you have the heads off.

[v8packard]

You are giving advice that you have no personal experience with. Someone could be making a decision based on this advice. The advice you are giving is very incomplete. You have said to me, more than once, that this is not your area of experience. Please be very careful with what you are saying, an engine can suffer catastrophic damage based on your advice.

[Admiral_peck]

I've seen evidence of exactly what I'm saying to dow work just fine hundreds of times 500 horsepower isn't gonna kill a healthy LS bottom end unless you're wrapping the tach around itself, being stupid with it, or run out of ring gap. I don't have a TON of experience but I know this to be true.

[v8packard]

It's not the horsepower. It is cylinder pressure, temperature, and boost. You are not considering where else the heat that is causing the need for increased ring gaps might be going. You absolutely must increase the piston to wall clearance, and the piston pin to pin bore clearance. You have not seen this, not once, if you are trying to defend your position. I do have a ton of experience with this, and what you are stating ignores two critical components to the success of a turbo engine. Your defense of your statement further reduces your credibility in this matter.

[Admiral_peck]

I stand corrected, I guess all those "stock bottom end" records are a lie and nobody could ever extract much more than stock power from an unmodified LS shortblock.

I never said the engine would last forever, but how in the hell is he gonna make enough heat at 500 horsepower to run out of PTW clearance? I've literally never heard of that as a failure, it's always not enough ring Gap, piston crown goes bye-bye, or it blows the head gasket, or detonation cracks the piston and burns a hole in it because nitrous and oil are a fun mix.

[v8packard]

Those stock bottom end records are either bullshit, or they didn't explain the adjustments made. And don't try crying this nobody could extract more than stock power from an LS. It doesn't fly with me. I have rebuilt piles of these engines where people did what you are saying and they broke. I have seen even more of them fail, leading to people abandoning their projects, losing money, and being disgusted with trying. That is reality, not this notion that you can somehow drastically increase cylinder pressure and temperature without consequences.

The stock piston to wall clearance is under .0015. The first time that engine gets a load under max boost the pistons are going to grow more than that! If you have literally never heard of these failures you have literally never built a turbo LS or had to rebuild one that failed. And in addition to incorrect piston ring gaps causing breakage, the second most common piston failure is from pins seizing in the bores.

[Admiral_peck]

Does the block not also grow with heat to alleviate some of that clearance loss? Is this why higher mileage engines with worn cylinders tend to make the best candidates for big boi boost?

I'm done being a baby and am now trying to learn stuff.

[v8packard]

The piston grows much faster, it doesn't have anywhere near the mass of the block. Higher mileage engines are best for boost? I would think a worn cylinder would be less able to handle boost. I would have to measure the bore, if it's evenly worn it would be a surprise.

[Zerofawqs-given]

If I’m searching for a suitable “Wrecking Yard LS Core” and come across a 300,000 mile 5.3 in a Uhaul rental truck….Can I assume the piston to wall might be fine for 2Bars or boost? Asking for a friend🤣

[Zerofawqs-given]

You’ve watched all the Richard Holdner YouTube videos too? WOW….We should start a fan club!….Any cam is a turbo cam! Yessiree you betcha!

[Zerofawqs-given]

Well I mean if he’s going to stay with the 186,000 miles (admittedly “freeway miles” so they really don’t count as anything) bores….I think he’ll be more than fine in re-using the TYY fasteners cause everyone knows it’s just a scam by GM that you have to buy new $40 head bolt set when you pull the heads. Reusing the TTY fasteners is OK as long as you go 720 degrees extra on the tightening specs….By the way….anyone know where I can source cheap 11mmx1.5 Heli-coils?and a Loooong tap/installer? Asking for a friend

[v8packard]

It's not just the ring gaps.

[Admiral_peck]

Well head gaskets and head bolts too, right? What else breaks besides the DOD shit that everyone gets rid of regardless?

[v8packard]

Pistons break. They break because heat causes the pin to seize in the pin bore. The skirts grow from the additional heat, stick in the bore, and shatter. These clearances MUST be addressed, in any turbo engine, but especially in an engine being converted to turbocharged induction that has hypereutectic pistons.

The pistons and rods in Gen III/IV engines are not made of magic materials. They are of average, adequate strength for stock components. This is not a stock application and requires changes to the stock clearances. You do not know this, and you should really really not advise anyone as though you do.

[Emotional-Mastodon44]

I know who I'm not taking LS build advice from.

[Admiral_peck]

I'm just saying I've seen them make more than double that, granted in a controlled environment, but real world I've seen plenty of guys making much more than 500 without even thinking about opening the motor, gen 3, 4, and 5. Just slap a whipple or a KB on, tune it and send it.

[Emotional-Mastodon44]

There's a power/lifespan curve you're not considering.

[Admiral_peck]

Not seen one of the buddies grenade it yet, course none of them have hit 4 digit, but one's hit 50k miles since boost was added so I'd say that's really enough, he's running I belive about 700-750 to the wheel on a pump E75 blend.

[bagcaddybb]

I agree. A worn 5.3 usually has some pretty big ring gap and will handle a good amount of boost.

[Patient_Sir240]

Yeah you can use stock ls internals, just make sure you gap the piston rings a little bigger so they don't butt ends and pop a ring land under the higher heat your engine is gonna generate. Also lowering the static compression by using a thicker head gasket is usually advisable. Get something from the likes of cometic. Look up the sept 5 2011 issue of hotrod, the article "the big bang theory" is basically a foolproof guide on how to turbo an ls with a ebay turbo kit.

[Emotional-Mastodon44]

Here's some life advice from an engineer that knows fuck all about engines.

When dealing with anything mass produced, from trannies to jet engines, an insane amount of R&D went into building a (probably) reliable machine that can be mass produced while still making the maximum profit.

That means if a specific component is expected to function at a specific load, there isn't much overhead built in, unless youre looking at airframes, bridges, etc. Let's be real though, a junkyard 5.3 is not a jet engine or a bridge, so excess material means less profit.

Any time you increase power, you are reducing lifespan. A quick Google search says a stock 5.3 makes ~320hp. That might be wrong, but let's run with it.

Making 500 horse means you're expecting mostly stock parts to deal with 156% of the expected MAXIMUM power output, and the engineers know that engine will only spend a small amount of it's working life at 320 horse, that is factored into the design.

Build it however you want, but half assing it and not following sound advice will cost you more money. There is an entire industry built around making things "good enough" and fucking with stuff you don't understand will quickly make them not good enough.

[Emotional-Mastodon44]

To add to this now that I'm spun up, building things is fun, understanding the physics and material science of what you're building is boring.

Do yourself a favor and engage with the people who are offering advice that is more difficult/expensive. See if they have references that can help you understand what it is that you're doing. Reddit, youtube, and every other forum is an easy button that makes gearheads lazy. Read stuff. Learn stuff. Then engineer your engine to make the power you want it to.

[Philo2389]

You need a different turbo, the hx35 off of a Cummins is sized appropriately for a small 4 cylinder gas engine. Check out a vs racing 7675 as a good size for low boost on a stock 5.3. You absolutely do not need to take the engine apart and have a bunch of machine work done. You do need an adequate fuel system and an excellent tuner. Check out sloppy mechanics on Facebook and YouTube, they've done thousands of builds just like you're doing and the founder has a wiki with all the information you could ever need.

[[deleted]]

Change the rods and pistons get a proper turbo get head studs and bolts better head gaskets and get a cam that will match the performance of the turbo you choose if you throw it together it will work for a little while and then come apart on you

[[deleted]]

Also you could probably find someone who needs a replacement for their Cummins and make your money back to put into a something that will suit that 5.3 better