robz

Since retiring from racing I decided to focus on dyno numbers.
I believe people underestimate the potential of these engines as well as the importance of having everything in the setup working together in harmony. Then there's fine tuning which is often overlooked as well. I feel that there's often another 15-20 hp left on the table from inefficient tuning.

So, I'm thinking 570-580 whp is possible through a GM Ls6 346ci H/C/I with all the details covered.
And I'm not talking about a "super high" rpm screamer which would make it much easier and less reliable.
I'm figuring peak whp might be around 7250rpms.
A Mamofied plastic production intake manifold would be an ingredient.


I'm basing my decision off of a compilation of all these:

- previous dyno numbers from numerous setups
- other comparable setups from the past and their mods
- MPH numbers from the 1/4 mile
- ET number from the 1/4 mile
- the potential of new mods and technology of today
- my experience with tinkering over the years
- my current cam-only setup
- a collaboration of the best online calculators (the least accurate measuring tool)

That's my opinion. I could be wrong.

LSOHOLIC

AGREE.....my only issue is the manifold you suggested. I don't believe a "space restricted" style manifold is max effort at all.
An epoxied Mast or Hi-ram would crush any "space restricted" Fast/ Edelbrock/ plastic intake of your choice.

My combo still run 243's and a crappy Fast 102....runs 135 in +700' air and has put down 537rwhp on a dynojet224, several time through a 4.10 gear and 275/50's.
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12.2, E85, light weight valvetrain, stock rockers, worked 243's, Fast 102, 102 TB, 4-vane Moroso pulling 12", short travels, fast lobe cam,.....etc..etc....stock bottom 346".

For comparisons it did 513rwhp at 11.6, pump 91 oct and no vacuum pump on the same dyno and same correction factor last year.

But as you know, it's just as much about the entire car as it is the power plant.

*****EDIT*******And for the record, this is a very street able car. Air conditioning, Heads up display, OEM Bose stereo w/Ipod adapter, cruise control...etc.

And I'm sure your aware of...but there is measurable rwhp in coatings, even on a stock bottom end combo.


Later this week when I find time....I'll get a little into the real details like....

Coefficient of discharge
Lift to diameter ratio
Plenum volume
Mcsa
Effective compression
Quench
Valve to bore ratio
Valve position vs piston speed
Throat %
Seat angles
Etc...etc....

The list goes on and on....but it's a proven formula...over and over....




Thanks....this is my opinion and there is a small chance I'm wrong....

.

63Corvette

There is a huge amount (+50hp or so) "free" horsepower abvailable with a negative crankcase pressure type of dry sump lubrucation. The more rpm, the more free hp you can recover.

LSOHOLIC

Agree...but your limited to an OEM ring pack. Which really limits your gain...both in parasitic gain and crank case windage control.

And when I think stock bottom.....I take that to mean the OEM oiling system as well.


Like I stated above I pull 12" @ 7400rpm. I feel I'm where I need to be on an OEM oiling system as well as risk vs reward on the ring pack.


If you wanted to get beyond the stock bottom....there is more than 25 hp available. Just roller bearings and DLC & Calico coating will net that. Not even discussing the rotating mass.


Thanks.


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Violence.Z06

They do have ls3 and ls7 heads for the smaller bore sizes but the limit is the valve size itself. would be WAY easier with a larger cube motor. But i dont think your numbers are to far off. Could be done with proper setup but limiting factor is bore size.

robz

No doubt. Just pointing out there's alot to be had with the 346 and readily available parts that are floating around these days.

How much hp can a well built, well matched set of heads make over the stock 243's?

Violence.Z06

Really depends. Like i said the limiting factor is the bore sizing. Are we talkin stock bottom end here with stock pistons? Or are we talking a built bottom end?

LSOHOLIC

Bore is a limiting factor no doubt. But rpm limit is the largest limiting element !!

Violence.Z06

Nah i dont think rpm is as much of a limit. There is more then enough areas in the motor to free up horsepower. But thats only if we are not talking stock bottom end. On a stock bottom end the way GM has it, it would be REAL hard to pull off. On a not stock bottom end it can be done with not to crazy parts and still be reliable.

LSOHOLIC

I think we are on the same page...lol. Just saying it different.

I'm saying bore is not the ultimate limiting factor, rpm is with the sbe. Full build 346" is capable of 800hp with that bore.....with rpm.

I know I would not want it the other way !! More bore and less rpm....serious losing combo there.

Bore, rpm and intake valve are the critical items that limit hp potential. To say one is less important is crazy.

I spin my sbe to 7600 - 7700 with its current cam. If you break down max piston speed....I'm nearing my comfort zone.

All though there is a max piston speed that seems to be the sweet spot for most hp engines....and I'm missing it by 4000fpm....



Thanks....

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robz

All on the same page with what 's easier. (Built bottom end, high conpression, custom manifold, bigger bore, high rpm, roller cam, dry sump.) I've built 2 motors that support many of those components. One that is capable of 1000fwhp with under 400 cubes.

As I stated in the 1st post I'm saying stock bottom end based on my experience with my setup. Throw in rod bolts for safety. I'm trying to use parts that are readily available and strictly playing a hp game.

My cammed setup with the stock 243 unported heads makes around 525-540 dynojet rwhp by crunching the numbers 10 different ways.

Being conservative let's use 525 rwhp.
+ 10 hp for loss due to 4.10 gears
+ 10 hp using a ported MSD manifold and 102 TB
+ 10 hp for fine tuning (very conservative)
+ 10 hp for lightweight clutch
That's before adding heads.
How much can heads add? 30,40, or more.
The numbers work out IMO.
Probably good for mid-low nines in 1/4.

Violence.Z06

well with no stock bottom end you can change a bunch of stuff. Can change rod journal diameter, can change ring pack setup, piston design, piston weight, valve reliefs. If i would do it i would change a few things.

MAX effort 346 and still reliable ALL MOTOR. I would do a 1.888 rod journal, X style forging pistons, FLAT top pistons with one valve relief style, hi ram style intake with a 4 barrel style throttle body EFI, work on crankcase windage, rotating mass, friction and so on.

i would also run a ls7 style head on the small bore but thats just me.

LSOHOLIC

A built max effort 346" would look like 4.125" bore on 3.25 stroke with 2.16" worth of valve. I would push it to roughly 9500 fpm max piston speed (not rpm) which would dictate my runner size...and all of the important chit no one talks about.....

zeevette

I don't have the engineering background to even understand some of what you guys are sayin', but, to get a 4.125" bore, wouldn't you have to sleeve the block? And if you did, wouldn't it be advantageous to just go for more CI? I can see a short stroke, big bore being a screamer, but can't you go faster with more torque?

LSOHOLIC

I was just humoring the max effort 346 discussion. In short, I was saying if I was to build a "money no object" 346 build, that is the basics in which I would start the build.
4.125"+ bore is reality with ERL, LSX, LS7...etc blocks.

Bore, stroke & rpm will dictate runner dimensions (full depression at max piston speed, which happens to be 74.5* on this particular combo.).

Torque is a product of cubes....but rpm can trump torque when done correctly.
Example;
650 ftlbs @ 4000rpm
VS....
550 ftlbs @ 6500rpm

The latter has more potential to be the quicker combo. It's all about the unit of time. Which combo is doing more work in the given amount of time....

*****EDIT******
just wanted to state something that is important to me.

Cfm = rpm
More rpm = allows more gear
More gear = greater rear wheel torque
More rear wheel torque = greater acceleration
Greater acceleration = quicker ET

Pretty simple stuff.....


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LSOHOLIC

What does everyone feel is the max rpm (mechanical limitation) of a stock bottom '04+ (better wrist pin design) bottom end ??

I'm going to assume rod bolts are on the list of items to be upgraded. But aside from that...all stock rotating components.

Imo, the weak links could be any of the following....
~rod cap
~wrist pin
~wrist pin boss (piston failure)
~reluctor

Here are some basics to help analyze.....
Conrod journal = 2.0995"
Crank main journal = 2.5589
Max piston speed crank angle = 74.64*
Rod ratio = 1.6836
Crank journal overlap = 0.52
2004 and later piston weight = 425 grams
2004 and later conrod & wrist pin weight w/clip = 640 grams

I included weights for G calc's if anyone was interested.....

Here are some max piston speed numbers to evaluate.....
7250rpm = 7173 piston speed
7500rpm = 7420 piston speed
7750rpm = 7668 piston speed
8000rpm = 7915 piston speed
8250rpm = 8162 piston speed
8500rpm = 8410 piston speed
8750rpm = 8657piston speed
9000rpm = 8905 piston speed

FYI, in an ideal situation.....a max piston speed of roughly 9500fpm is what most top teams shoot for.


In order for you to even begin to break down the events below......and shoot for an ideal situation......we must have a target rpm for the short block to build the induction system on.....


Valve overlap------ - TDC
---------------------------- - EVC
Intake pumping
---------------------------- - BDC
Intake ramming
---------------------------- - IVC
Compression
---------------------------- - TDC
Fuel burning & expansion
---------------------------- - EVO
Exhaust blow down
---------------------------- - BDC
Exhaust pumping
---------------------------- - IVO


Thanks.....


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LSOHOLIC

Man...and here I thought you guys wanted to build a max effort stock bottom 346.....lol.

Let's call it 7500 for the max rpm....mainly because of hydro camshaft short comings. Even though it is possible to get more out of it. That rpm should keeps us from using any exotic valve train. Even though in a "max effort" build I would consider that to be mandatory.

Sine the max rpm is decided....we can move on to some fun stuff....

CSA = PI × (.52 × 3.898 × .925) ^ 2) ÷ 4 = .2314 × PI × 3.898 ^ 2 ÷ 4

CSA = 2 × PI × ((VALVE DIA × THROAT % ÷ 100) ^ 2 - VALVE STEM DIA ^ 2) ÷ 4

We can set the throat and intake valve size and run through calc's chasing the elusive 146.0 CFM/in ^2....and more accurately the 133CFM/in^2....



This is only if we are serious about max effort....

Or we could just throw some heads on it crank up the compression and rpm and hope for the best.....



Thanks....


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robz

So, if I don't find the right buyer for my Z I may just do a nice set of ported 243 heads with a Mamofied MSD intake, 102 TB, and the stock Ti exhaust and try and put down a big dyno number for fun.
Or maybe go back to a bolt-on setup and shoot for 9.80's and 137mph.

Violence.Z06

why stick with hyd cam? LLSR would be my go to choice if anything.

LSOHOLIC

Lol...opening up a can a worms .


*****EDIT***** maybe I should have just asked why you'd suggest the LLSR ??



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