Well isn't that just what we are doing Brother. We are now going to 7 to 8k this still shows the Potential difference correct. So engines are free now? You may as well add cost to be Honest with oneself to know what your getting into. Potential Difference in cost doesn't hurt or does it? Just Chattering Hammer but the numbers are what I'm looking for.

 

Add cost so you can price out an engine that you'll
Never build?

 

To know something is Half the battle. Is it better to know or think you may know something. I like knowing something as does everyone(because we think we know the outcome of this thread). It's just typing and adding is nothing too hard. I don't have a load so I have time.

 

That's why op asked which configuration would have more hp potential. He already said he knows the 406 will cost more

 

I understand Hammer. You got me laughing this morning your always turned up. LOL!

 

The OP asked if you would rather have a big bore 3.75" stroke 406 or a 4" stroke 408.

If asked that question I take the big bore every time for a long list of reasons.

With a sleeved block - For my 2800 pound traction limited car I'd rather have a 394" vs a 434 even if it limited total power output. The 406 is an interesting option with a 3.75" stroke instead of a 3.622".

For a heavier car, car with more traction, or a 100% drag build yes I would want more cubes. Mechanically a 4" stroke can be done without any sweat and will easily rev to 7500+ with a good top end which is I think why Patron has derailed this thread so hard lol.

Me personally I would not put a 4" stroke in a stock block for a street car again after building my 402 LS2 unless it is very heavily favoring performance over everything else.

 

Yeap! Not trying to derail it just on the side of the the 408 as All or most are on the side of the bigger bore 406. You have more people that are with the 406 ....I gotta stand my ground for the 408 guy's. LOL!

 

Spank 13. You said u wouldnt stroke a stock block with a 4" crank. Why not?

 

Because of builders who don't know what there doing when purchasing and setting up Rings and piston also for finishing the bores. Oil burners or wasters. We are Way past this. Also because that's what SAM stated. Wonder why all the properly built 4 inch crank don't say this. The cylinder sleeves are a little short but if Done Correctly does not represent or present a problem. Done correctly is the key word.


Oh Spanks did you get the PM with the simple 402 in a 2800 lbs car running 9's the first time out. LOL!

 

Depends what block you use too. The iron 4" bore blocks supposedly have even shorter sleeves than the aluminum

 

True Hammer, but still presents no problem for any Good Ls engine builder with either. I've Heard and Read Eric say this: HKE. KCS builds engines would you think he's trying to build a oil burner aka .250 added to a 4 incher. We've come past this old train of thought. Newer piston designs kill this notion. Then we'll hear about piston speeds. There's a guy here with well over 50k miles on a 408 iron block.

 

Hi Patron, OK DONE, Both with the Super Vick as it is only fair.
The other items Momo/FRH as requested (266/270 .750" 110 C/L )

Momo with better head/short stroke 406.
Torque at 6000 RPM = 597
HP at 7500 RPM = 786
CFM = 7500 RPM of 992

FRH with less head/long stroke 408.
Torque at 6000 RPM = 604
HP at 7500 RPM = 793
CFM = 7500 RPM of 1001

Piston Speed at 7500 with 4.00" = 5000, a Maximum Safe Speed for Drag Racing ???

Lance

 

I never said they couldn't run lol I know they can. I have one. I'm expressing my personal experience and not pulling up other people's results from the forum. My engine makes WAY more power everywhere as a 402 than it would as a stock displacement LS2. It also burns more oil than stock due to the wrist pin in the oil ring, increased windage, and piston rock at the bottom of the bore. You never forget there's a 4" arm in the car...the power delivery is rougher than any LS engine I've ever driven including my solid mounted LS3. There is a lot more mass swinging around in the bottom end than stock, and it is swinging around a lot further than stock.

I don't doubt that piston design has improved since I bought my rotating assembly with diamond pistons in 2011, but the wrist pin in the oil ring and more windage will increase oil consumption compared to a stock bottom end.

The drag results you're pulling up have no relevance to what I'm talking about. My car is a street car first. It is a 2800 pound tin can '94 rx7 with a t56 magnum, ohlin suspension, and either 200tw or 100tw R-comp road race tires. My cam has 0* overlap at .050 and is very docile at idle. It isn't a drag car, but on R888's with a soft launch I went 11.40@130 mph in the middle of summer. I put the 4" arm in my engine on the rebuild for the exact reason you're arguing - it is kind of dumb not to as the money is essentially the same. There are just some drawbacks to it and for me personally I'd give up some power down low for more of a sports car power curve that encourages you to run it out and for more of an OEM level of refinement.

If it was a drag race car I'd take the cubes any day. If someone was offering to gift me one of two engines - a 406 with a big bore or a 408 with a longer stroke I'd take the 406 every day. I would love for my engine to suddenly turn into a .030 over LS3 instead of a stroked LS2...suits my needs and goals much better.

All I'm saying is if the choice was 406 vs 440 you'd have to consider a few things. You can't just say everyone always 100% of the time should take the 440 and you'd be wasting money if you didn't...
____________________

Also - since the beginning - I've understood the question to be all things equal which will run better the 406 or 408. Your simulations are not all things equal.

 

Thank you So very much. Something I already know as the formula is Correct. RPM x Tq = Hp. That Simple. I fill like Ty: I just can't hold all this! I can wait till mines done. Also the Cubic inch displacement is to close.


Lance to your question of is 5000 to much piston speed *PS* I wonder how others fill. And not some exotic builds some are going 7800 to 8k with no worries. Heck John B's engine rev's to what rpm. This represents the Non ordinary build which adds to cost. I like more rpm myself as I have ordinary cars. I'm on the far end of the spectrum in terms of what I like.

 

Spanks I understand what your saying. My thinking is as such a number wanted is a obtainable # just add Cubic inches and problem solved. Bigger bore and stroke to a certain point, with less RPM to make the shorter strokes same Hp and Tq.

 

Hi Spanks, the GM OEM LS-7 has NO Rail support ! (4.00" crankshaft)

Piston Advancement ??? = JUST better engineering.

The Vibration = Poor Balance Job.
I "OVER" Balance by 1% to 2% as common !
What is your Target Wheel, crankshaft, tooth count ?

Patron = NO for formula.

RPM x Torque DIVIDED by 5252 = HP

Lance

 

My 403" LS2 with Dart Pro1 LS3 heads also makes way more power than my LQ9 with LS2 heads ever dreamed. However, mine is as smooth as you could imagine. I don't have any oil consumption problems, but the windage is much greater. I had to install -10 fittings in my valve covers and install a catch can for this reason. I have to say though that I turn my 403 500 more RPMs than I did the LQ9.

I have a Callies Compstar rotating assembly with CP bullet pistons. I am very pleased with the setup.

 

Momo is a steering wheel, or Aftermarket rims.

Tony MAMO is a Cylinder Head Designer.

In the interest of accuracy.

 

I don't think my rotating assembly is out of balance it was match balanced before assembly. I can rev it up in neutral slowly all the way to redline and it doesn't vibrate. Power delivery on the other hand I feel like a lot more goes into the chassis than I'm used to. Some just tell me it is a big engine small car issue but I'm not really accepting that.

I have a stock pcv setup on my car sucking into the intake. Not the most room in my engine bay for a catch can setup. I might look into improving that on my next round of mods (if I ever get my cylinder heads).

 

The LS7 has a shorter rod and the wrist pin does not impinge on the ring land.

It also has piston sleeve extensions that help support the piston at BDC.

My crank is a 24x reluctor as it was a GTO based LS2. What does that matter?

Crank pistons and rods were match balanced by Livernois. I have an ATI balancer. Engine is smooth in neutral up to redline - I just feel it imparts a lot of vibration into the chassis under load.