KSA Aaron

After getting minimal feedback in the other forum, I thought I would ask over here....


LS2 / MN6 application with APS TT system.


Replacing my engine, and since I am rebuilding will upgrade a bit. Here is the plan thus far:
- fully forged rotating assy
- coated pistons
- bronze bushed lifters
- shortblock is rated to 1000hp
- LS3 CNC heads
- LS3 intake with LS2 TB
- BTR custom cam (it will be close to a Stage 3 turbo cam)
- ID1000 injectors
- 10.7:1 SCR (factory 10.9:1)
- upgraded fuel pump
- staying with the current APS TT kit
- methanol injection


The shortblock comes in one of two sizes 393cid or 427cid (same price, either variant).


Either way, the HP will be similar, as I recognize the APS turbo kit (airflow) is the limiting factor. I have no plans to build it to 1000WHP in the future. It will likely stay at ~700-750WHP for the remainder.


Which size would you build, and why?

Unreal

What block? What bore? What stroke?

KSA Aaron

Same components / price for either combo.


393 cid --> 4.125" bore x 3.62" stroke
427 cid --> 4.125" bore x 4.00" stroke


LS2 block




Thoughts?

Unreal

How are you getting to a 4.125 bore?

Either will work if sleeves/etc are up to it. 427 will spool quicker and probably be a funner street car. If price is same, for a 700-800rwhp I would do the cubes.

KSA Aaron

ERL Superdeck based on LS2

KSA Aaron

Would you be concerned with heat? I will likely upgrade the radiator at the same time.


Obviously, the APS turbos will be the limitation on the combination.

Unreal

FI on a vette, heat is ALWAYS a concern.

KSA Aaron

I think the question was more based around the heat generated from the 427 vs the 393. Should I expect the heat to be considerably more than the 6.0L that I am removing (would run 220-228°F coolant temp during TX Summer)?


My basic understanding on this topic surround thermodynamics. Heat is a function of work delivered over time. As the work delivered over time (HP) will be similar between both options, my thought would be that the heat needing to be removed would be similar for either option.


So from any perspective, is there a compelling reason to select one size option over the other?


Strengths listed:
Build boost earlier - 427
TQ will come in earlier - 427
Greater amount of TQ - 427
More fun as a street car - 427
Slightly less fuel consumption - 393

Unreal

Peak torque probably won't change
Depending on parts, 393 maybe "stronger" but at your level that isn't an issue.

No a 427 be any different heat wise than a 393. The radiator/fmic/cooling system will determine that. Any difference will be soooo small it won't be noticeable.

playtoy

The shorter stroke of the 393 will help with longevity. The 4" stroke will tend to wear the bottoms of the cylinders in an egg shape over time which will lead to excessive blow by. I currently have an 427 LS2, Dayton sleeves, 4.125 bore and 4.000 stroke. After about 15,000 miles I pulled the motor to be refreshed and found all of my cylinders were egg shaped at the bottom. Have a couple of friends that have experienced the same thing with strokers in an LS. As far as temps go my car runs about 190-220 in the summer time in Houston depending on how I'm driving it. I have a Dewitt's radiator and dual spall fans running off of the factory fan controller, 80/20 mix (distilled/Dexcool)with water wetter. If you don't have an oil cooler you will need one of those also.

slow ride

What turbos on the APS kit, stock c6z gt35's or upgraded? I think a nice forged rod/piston stock crank ls2 would have been fine with the APS kit. Longevity build the stock stroke engine and make some more peak power and still plenty of torque, for all out spool and torque do the 427.

Unreal

Those sleeve should be longer and account for the longer stroke.

neverstop

if you're only looking for 750whp then ERL superdeck is insane overkill and waste of money imo. Forged pistons/rods and stock crank in ls2 will work fine for that. My old setup was 750whp-ish on stock ls2 block with forged pistons/rods/crank for a long time and only died because of bunk local tuner messing something up.

for this setup I would just put forged pistons/rods in the stock block and crank and call it a day for 1/4 the cost. spend the other money on other stuff, like trip to hawaii, or bigger turbos, better tires, etc.

if you're intent on using the ERL then it should have longer sleeves and I would also recommend 427ci. If you plan on doing big 1k+ hp later on though I would go with shorter stroke for more strength, although when I look at all the huge power builds I have seen they all seem to be 427ci so it probably doesn't really make much difference either way.

Unreal

Agreed
For <800 just do forged rods/pistons and stock block and crank.

playtoy

All of the Darton sleeves for LS 2/3/7 are 5.800". If you want longer you have to have a custom set built. If they were any longer I would think you would start to have clearance issues with the crank and rods.

KSA Aaron

I live in the Houston area, so I will see similar hot temperatures. I am currently in Saudi Arabia, so everything is being coordinated by my son who also has a couple of vettes.


The current combo (basically stock LS2 with APS kit) ran great for years and then I lost some compression in #7. Car still runs quite well, just have a CEL due to #7 cylinder.


The current plan is to pull the drivers head over Christmas with a replacement piston/rod assy ready to be installed. A spare, low mile LS2 block has been shipped to ERL for conversion. I would like to build this car to be super reliable and back to the fun level that it was previously. I don't want to build into a MONSTER, but still want this car to be fun when I drive it.


Thanks for all of the feedback! It is really appreciated!

WHITE_SHARK

In performance world, the super reliability thing is not exists however the right setup will make it close with the correct parts + right TUNE.

At the power level you mentioned 700-750rhp, any block should be do fine, Any CR you mentioned will be fine, Any cubes will be fine, my only top concerns will be the tuner + the fuel system

gnx7

Save your money and just run a stock block like everyone is saying at that power level. A stock crank below 1000rwhp with forged rods/pistons should be reliable for years of racing.
Even with a forged crank the shorter stroke will be better or you will see backpressure issues running small turbos.

I made 1400hp with a stock cast crank, Compstar rods, Wiseco pistons for years and easily 200 passes with most of them being 1/2 mile before I broke the crank.

ARP head studs, LS9 gaskets, turbo cam, quality lifters, rebuilt trunion bearings in the rocker arms and you are done. There are plenty of quality machine shops in the Houston area that can build this for you. Save the money on shipping and put it into better quailty lifters. At 800rwhp you aren't really even pushing it that hard. Maybe opt for aftermarket thick deck heads.... LSA heads (better casting) would work too for budget purposes and have the ports cleaned up.