fish5225

I have decided to put a new stroker in my 03 Denali PU. I am trying to decide between a FI or N/A motor. I live in Colorado so large power loss due to altitude but I can't decide in FI is necessary due to limitations of 4L65 tranny. Can you build a stroker 408 or 420 N/A with 600-700 HP?

Richard@WCCH

iTrader: (3)

You're going to need lots of torque to move the weight, not horsepower. Horsepower comes with higher rpms and that's definitely not what a 4l65 wants to see. IMO a Magnusson will do what you want at high altitude with lower engine speeds. A small cam with ported heads will round out the power curve.

Good luck,

Richard

Steve Bryant

iTrader: (1)

I agree with Richard completely. With the high density altitudes that you have in the Rockies, you need low to mid-range torque more than you need horsepower. The best way to get that is with a Roots supercharger and the best version available on the market in my opinion is the Magnacharger kit that uses the Eaton supercharger. If I were going to buy one, I'd wait until the new TVS 1900 version is available because it is significantly quieter than the current version. The Magnuson kit is extremely complete and well made with excellent instructions.

Also, as Richard mentioned, some properly ported heads with a good valve job and perhaps a small duration cam would be icing on the cake. I wouldn't change the cam though unless you are willing to get some additional tuning.

Steve

fish5225

Thanks guys. That was my seat of the pants guess. I was just hoping to save the additional expense of the new TVS unit. I am currently running a old 112 on my stock setup. It has been flawless for 75k miles. I guess if you want to play you have to pay. Do you guys have any input on the 408 vs the 420 stroker considering the TVS 1900? Will the 420 add torque before I get into the boost? I am still debating the tranny switch to the 4L80 and just going for it, which I assume means the 420 but I really haven't found out how much additional power the 420 adds to the equation.

Steve Bryant

iTrader: (1)

With or without a blower, I don't think that 12 CID is worth considering for the kind of situation that you are talking about. With a 4.030" bore, you get 408 CID with a 4" stroke and 420 CID with a 4.125" stroke (you probably know this). However, I think that the compression height of the piston and the amount of piston skirt sticking out of the bottom of the bore both become much more difficult to manage with durability with a four and an eighth inch stroke. It's just not worth going there with a 9.24" deck height block. If I wanted more displacement and had the funds, I go to a tall deck LSX and I don't think that you need to go there either.

Especially, with a blower, I just consider getting some forged connecting rods and pistons and stay at or near stock displacement. My guess is that one or two PSI of boost will bring your power/torque level up to that of a stroker with all other things being equal. So running the 112 at 6 PSI on a 6.0 L should give you lots of torque/power. The 112 is an excellent blower, just noisy compared to the TVS. I used to be a Detroit Diesel mechanic and they are great engines, but I never really cared for the whine of a Roots blower even then (about thirty-five years ago). I've chosen to build a stroker because of simplicity of mechanical systems and I plan to stay with 87 Octane, but then the elevation of Wichita is 1,400' above sea level.

Steve

fish5225

Thanks steve. I agree and will go with the 408 stroker. I am now debating between the 1900, 2300 and 122hh. Tranny is the weak point, so I need to decide on HP and torque to make ultimate decision. Since I am going with a new block, I may try and go with a 6l80, otherwise I will probably turn down blower and build the 4L65 or just bite the bullet and convert to a 4L80. Certainly a 2300 and a 6l80 would be awesome.

Stoichiometric

iTrader: (10)

The torque produced by a 408 with a TVS 2300 would allow you to stick with a 4 speed trans (4l80). The 6l80 or 6l90 would make the truck potentially quicker and more economical, but the complexity would overcome the need to swap to anything other than the 4l80 in my opinion. I would swap for a 4l80 with a Precision tripple disk converter and keep the go pedal on the floor!

Richard@WCCH

iTrader: (3)

Steve makes excellents points about the probles with the longer than 4.0" strokes. I would think the TVS1900 would suffice in a truck that is not being raced. The efficiency of the new generation of blowers is phenominal. Don't build this engine to run a short time and then break. Back it down a notch and enjoy it for a long time.

Just my couple of cents worth........

Good luck,

Richard

fish5225

Thanks Richard: I agree fully in that I only anticapate running boost below 10lbs. With a completely forged 408 and the LS2 iron block this engine should run a long time with all the power I need when I hammer the gas. I am leaning toward the 2300 based upon Blownchevy's from Magnacharger advice. The IAT's are low, no risk of detonation yet should be able to push 800ft/lbs when up to full boost. I am still researching the tranny. The 4L80 is the easy answer but I really want the new technology of the 6L90 if the hurdles of the PCM can be overcome. I may have to give up the quest but certainly it is only a matter of time till some smart tranny aftershop or GM itself comes up with a fix. They are going to phase out the 4 speeds fairly quickly in our trucks due to gas mileage so lets hope they recognize the aftermarket potential. I have a call into Speartech, has anyone else tried the conversion?