School Me on LS Motors

[RDF1]

I'm not at liberty to discuss the application yet, and the project is still very much in the bench racing phase. I do endurance racing, but this engine won't be for my usual venue.

The goal is an engine that can survive producing 650 HP all day long, and without requiring a rebuild after every event. For reliability we'd like to produce that much power under 6500 rpm. As much as I say "stock bottom end", I'm not opposed to beefier rods and lighter pistons if required, but stroking is out of the question and any boring will be a cleanup bore.

I just read up a bit on the shaft rocker setups, and having run a shaft rocker on my Cadillac, that's the route I'd want to go on this. Valvetrain stability will be the #2 requirement, after bottom end strength.


Definitely FI, and likely an aftermarket ECU. It might be Megasquirt, or we might pop for a Terminator X. It'll depend on funding. There is a chance we might get someone who has the time and experience to play with a factory ECU, but that remains to be seen.

Holley Dominator
Dual widebands if your doing FI

For shaft rockers we use these, And plug the rear of the shaft, Run Pressurized oil thru the shaft to force feed the rocker bushings. Helps keep everything cool during substained high rpm runs. Also run Johnson 2110R lifters and make dang sure your pushrod length is perfect.

(this is for Cathedral heads but they make them for LS3 heads as well)

Comp Cams Max-Lift BSR Shaft Rocker System for LS1/Cathedral Port

Late model performance specialists, offering parts at competitive prices, LS1 LS2 LS3 LS6 LS7 LS9 LSX

www.tickperformance.com

So where did the 650hp # come from?

You could do a simple 370ci engine (6.0L iron block bored from 4" to 4.030") with a stock crankshaft, decent rods like Eagle FSI's and a DSS racing piston to match the compression you want from the cylinder head combustion chamber size. I suggest LS3 heads.

Then for your FI, plan out the engine build, then figure out what size turbo (think about the right size compressor with a larger turbine to keep drive pressure down for higher rpms).
Then talk to Martin Smallwood for your cam design to get the power/rpm you want.

Ive put several 370 engines together with a 88-91mm turbos that make 1400hp with ease on E85R fuel.

 

[Road Trip]

I have near zero experience on LS motors, but I may be getting involved in a project where we will need to build a "serious" horsepower naturally-aspirated LS on a strict budget. The engine will almost certainly not be using a factory ECM.

What do I need to know about the differences in generations? What differences are there in the blocks? What's the best non-forum website for an LS newb to study? What's the best forum for LS engine builds?

I found myself in a similar situation not too long ago. The lingo the LS community
uses assumes that everyone knows it...also gave me that 'outsider looking in'
feeling in the beginning.

When it comes to engines, no matter what the physical displacement,
the actual displacement (ie: torque production) that you get when driving
depends on the bottleneck in the air flow circuit. And that bottleneck
is always the heads. Given this, for me I decided to navigate the LS
family starting at the intake port:

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Ahhh, now at least I have a place to start from.

And this article was very helpful, helping answer some common sense questions like
"Did the LS2 come next after the LS1?" And since you are living my dream (that is,
giving yourself the challenge of everything be sourced from the Treasure Yard) ...be
sure to check out the Spotter's Guides located partway down the article.

Bonus: From a Corvette forum, here's a "Complete History of GM's LS Small Block V8
Engines". Just another perspective, with really tasty engine pics. (link)

Hope this proves helpful --

 

[618 Syndicate]

Holley Dominator
Dual widebands if your doing FI

For shaft rockers we use these, And plug the rear of the shaft, Run Pressurized oil thru the shaft to force feed the rocker bushings. Helps keep everything cool during substained high rpm runs. Also run Johnson 2110R lifters and make dang sure your pushrod length is perfect.

(this is for Cathedral heads but they make them for LS3 heads as well)

Comp Cams Max-Lift BSR Shaft Rocker System for LS1/Cathedral Port

Late model performance specialists, offering parts at competitive prices, LS1 LS2 LS3 LS6 LS7 LS9 LSX

www.tickperformance.com

So where did the 650hp # come from?

You could do a simple 370ci engine (6.0L iron block bored from 4" to 4.030") with a stock crankshaft, decent rods like Eagle FSI's and a DSS racing piston to match the compression you want from the cylinder head combustion chamber size. I suggest LS3 heads.

Then for your FI, plan out the engine build, then figure out what size turbo (think about the right size compressor with a larger turbine to keep drive pressure down for higher rpms).
Then talk to Martin Smallwood for your cam design to get the power/rpm you want.

Ive put several 370 engines together with a 88-91mm turbos that make 1400hp with ease on E85R fuel.

He wants to do it n/a.
In not sure 650 hp is possible from a stock bore/stroke LS keeping it under 6500 rpm, let alone on a small budget.

 

[PlayingWithTBI]

In not sure 650 hp is possible from a stock bore/stroke LS keeping it under 6500 rpm, let alone on a small budget.

build an 800 HP mill and install a rev limiter

 

[618 Syndicate]

build an 800 HP mill and install a rev limiter

How you gonna get 800 hp from an n/a stock bore/stroke LS? Even on 50% funny fuel you're looking at a rebuild every session, something he explicitly doesn't want....

 

[Road Trip]

The other day my son came over to help tile the kitchen. He showed me some pictures of a 6.2 where the valve spring broke, the valve stem got bent and the valve itself puked out the intake port. He said he's had a few 6.2s come in like this. IDK personally but, he says this is a known issue with their valve train - just saying

You must be registered for see images attach

You must be registered for see images attach

You must be registered for see images attach

You know, personally I love the sound of a V8 at really high rpm.
Naturally aspirated DZ302s, HiPo289s, 340 TAs,
Can Am BBCs, they all give me the Schurkey limp, if you
catch my drift.

But at the same time, when I'm talking to friends or customers
about what they are trying to do with their engines, I always
start with this: RPM = Ruins People's Motors.

Most folks equate too much rpm with bottom end failures.
Using ARP fasteners & following tried-n-true recommendations,
I've never personally had a catastrophic failure down low.
(Maybe I simply haven't built enough power yet? :0)

On the other hand, I have experienced several failures with
the valvetrain. The one that scared me the most was a
friend's '73 C20 Camper Special that had a 454/Turbo 400
in it. After an idyllic WOT day in the mud bogs, the motor developed
an intermittent skip, with a new noise under the driver's side
valve cover in time with the skip.

When we pulled the valve cover I felt a little queasy, for one of
intake valves had broken the outer spring, leaving only the
inner spring keeping the valve from dropping into the bore
with instant widespread destruction resulting. :-(

We limped it home just off idle in 3rd, and thankfully our
guardian angels saw fit to get us back to home base
without further incident.

The silver lining? It gave us the excuse to open up the
7 year old big block & make a good thing better.
(My all time favorite truck...until the one I now have. :0)

Misc. thoughts:

* Intake valve springs are always the ones that fail
first. (They weigh the most, and are hardest to
maintain control over.)

* The sound of a valvetrain is an important clue as
to what's really going on under the valve covers.
(Especially if you are running solid lifters.)

For example, I had put together a high-winding
engine with the normal upgrades: triple valve springs,
roller hydraulic cam, aftermarket roller rockers 1 step
better than stock, etc. I ended up with not 1 but 2
intractable problems -- the first was that the valves
would float like clockwork at 6200 rpm despite the
triple springs that came with the cam, and second,
the stupid valvetrain sounded different at each &
every rpm...and not in a good way. (Note: The
rest of the motor was set up to pull like a Ducati
all the way up to 7500rpm - I was not a happy
camper!)

Trying to get a better understanding of what
kind of valvetrain dynamics I was fighting, I
waded through countless screens of armchair
conjecture & confident nonsense.

*Finally*, I came across the magic word: The Spintron!

Can't find the pic of an old Tektronix analog scope showing the valve float, but it looked kinda like this:

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Further digging around, and I stumbled across some ultra slow mo/stroboscopic videos showing
real valves and the shimmy shake that they do at high rpm. Here's a few links for your
viewing pleasure:

* Valve spring oscillation at 8500 rpm. (May want to turn down the sound.)

* Who knew that the valve stems oscillated side to side like this?

* And the granddaddy slow mo Spintron video. (Very informative, but caution: may cause nightmares)

****

OK, I should stop here & regroup. Seeing the carnage in your son's photos reminded
me of some of my own ad-hoc 'test to failure' episodes in my misspent youth. :0)

To summarize, back when Ford wanted the GT40 to last the full 24 hours as well as beat Ferrari
at their own game, the overriding rule was for the drivers to adhere to a strict rpm limit, despite the fact
that the engine was capable of more on the dyno.

No matter how fast you are, you still can't win if you aren't running at the end.

Great photos by the way. If you get a chance, show your son those videos on my behalf.

Cheers --

 

[alpinecrick]

That does it--I'm installing beehive springs in my L31s..........

 

[0xDEADBEEF]

To summarize, back when Ford wanted the GT40 to last the full 24 hours as well as beat Ferrari
at their own game, the overriding rule was for the drivers to adhere to a strict rpm limit, despite the fact
that the engine was capable of more on the dyno.

You must be registered for see images attach

 

[Erik the Awful]

I fully understand that 650 HP might not be achievable with junkyard parts and a 6500 rpm rev limit. I've already spreadsheeted three different-budget-level builds and submitted it to a couple other guys for review. Our actual power level is going to depend heavily on how much cubic dollars people are willing to spend. The bare minimum build is clocking in around $3,800, and the "stretch goal" build is about $10,500.

The "bare minimum" build includes new King XP bearings, new (not ARP) main and head hardware, trunnion upgrades, good pushrods, new lifters and guides, a Moroso road-race oil pan, and an LS3 intake - which would probably be our limiting factor for horsepower. And, dang it, I forgot to include good valvesprings in that estimate.

The "max build" has everything including having to buy a new block and crank.

The 50/50 build includes ARP hardware and a Holley intake, but also a junkyard block and (relatively) inexpensive pre-assembled LS3 heads.

I just got offered a cheap car, and I may swing that to my son and pick up his '94 C1500. If that happens, the tow-pig 350 in WCJr is coming out and if this project firms up I may get my feet wet with an LS build for WCJr. I'm picking up stuff fast. It looks like there are some LS specific tools I'll have to buy, but again, this is still very theoretical.

 

[Road Trip]

For example, I had put together a high-winding
engine with the normal upgrades: triple valve springs,
roller hydraulic cam, aftermarket roller rockers 1 step
better than stock, etc. I ended up with not 1 but 2
intractable problems -- the first was that the valves
would float like clockwork at 6200 rpm despite the
triple springs that came with the cam, and second,
the stupid valvetrain sounded different at each &
every rpm...and not in a good way. (Note: The
rest of the motor was set up to pull like a Ducati
all the way up to 7500rpm - I was not a happy
camper!)

OK. Armed with a newfound respect for what we ask the
valvetrain to accomplish when on the far side of the tach,
I compared & contrasted my basic setup with those who did
real RPM for a living and were successful at it.

After much research, I felt that the 'different sound
at every rpm' was because the stock-type roller rockers
were still a ball & socket setup. That is, the rocker arms
were literally doing the 'tempest in a teapot' thing as
viewed from above. After eliminating all other solutions,
I put on my big boy pants and bought invested in a set
of Jesel shaft-mounted rocker arms. Only 1 degree of
freedom. I felt like I was slathering caviar on a hotdog:

No, that's not a pencil. It's a graphite pushrod length checker, adjustable, Type 1, each

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Note: Using a pencil sharpener, I snuck up on the correct length to get rocker arm geometry right.
It actually worked...when the custom pushrods showed up, everything was on the money!

The other issue was the intractable valve float at 6200rpm.

To try to prove/dispove the theory that the hydraulic
lifters were pumping up at high rpm, I tried the old anti-pumpup
trick of backing off the lash one at a time (while the engine
was idling) to the just audibly ticking point & then retightening
to just quiet. The follow-on test drive was no change, no joy. :-(

The fix? We switched to a solid roller cam, giving the valve springs
a lot lighter lifters to work with. We also took away a little
duration and adding lift. (a skosh over .600"?) NOTE: We pulled
the engine after maybe 10 summers of this nonsense, and also performed
a balance & blueprint while we were throwing money at the valvetrain.

(zero-decked the block to tighten up the quench, hone, fresh rings &
bearings, each piston/rod assembly balanced to within 1 gram** of
each other, upgraded from the factory cast iron flywheel to an aluminum one
that weighed only 1/2 of the original, blah blah blah.)

And the result? First of all, the new valvetrain sounded like the
same little well-oiled sewing machine no matter how we revved
the engine. And after a short break-in session, the first pull
through 7500rpm was pure joy. It's like the rest of the choir
showed up. It may not have been a desmodromic setup...but
it sure acted like one. Now I know how the astronauts that
fixed the flawed Hubble felt -- Success! :0)

****

I share all of the above as a reaction to the pictures of that
dropped intake valve. The only reason I learned all this
stuff about our modern valve train is that the car we
built would start off pulling harder & harder as the rpm
would build...and then the valves would float --
Acceleratis Interruptus!

The moral of this story? Sometimes a really tough problem
is actually an excuse to fill in a hole in your knowledge base.
To be sure, all this truly s*cked at the time, for this was
supposed to be my signature build, and it was a bust.

Looking back a dozen years, I'm glad that I went through
all that. Today, I'm just glad I got to share those
valve shimmy shake videos with my hombres.

Hope they gave you some food for thought. May your
valves & pistons always timeshare the same space successfully!

****

**Interesting factoid: A pound is juuuuuust shy of
exactly of 454 grams. (What a great mnemonic! :0)

A single dollar bill weighs exactly 1 gram. I don't have
the old build notes handy, but I think each piston/rod
assy was ~1700 grams? So having all 8 assemblies
weighing within a dollar bill of each other means nothing
at zero rpm, but is a big deal when you are revving on the
far side of 100 revolutions per second.