Doobie

iTrader: (2)

I agree with sharpshooter. LT's will lower his boost level a little bit but the added efficiency will make up for that. The final results would be interesting to see on a BB.

Whippled 496

iTrader: (4)

You guys have some valid idea's and opinions and i appreciate it! I DO like the idea of a set of LTs and realize that it will probably bring my boost down to the 5psi range. I cant help but think though.....how much RWHP can 5 or so PSI actually be giving me on my truck? I mean if you assume a consistant 6lbs of boost, that equates to roughly 25rwhp per pound. I went from about 260rwhp to over 412rwhp and that measurement was before the exhaust and injector upgrade. That seems like an awful lot considering it must be closer to 35 crank HP per pound before the allison tranny and 14" rear has its way with things. My truck weighs 7050lbs give or take a few pounds depending on whats in it at the time....so for it to be running mid to low 13's on 6psi is still really nuts in my opinion.

I hear you Y2K.....13's N/A does not sound doable without F/I. I have found that comparing vehicles though does not work all the time. Even when they are the same weight and close to the same HP levels....there are always underlying factors that cant be accounted for that come into play. The numbers from your 502 sound very close to what Raylar is promising with thier setup. They are not however taking a few other bolt on's I have into consideration.

Sharpshooters idea sounds pretty solid....maybe I will see how Santa treats me this year and see what i have left over after Christmas. Whats a conservative estimate for HP increase with a set of LT's? 25-35rwhp? Does 140rwhp from a set of heads, cam, intake, and LT's sound like a lot? That sounded like a lot to expect from that kit.....but i dont know.

Here is a shot of the StainlessWorks 8.1L LT's. They are 2"x3"...

STAINLESS WORKS 8.1L LT's

TrickTurbo

iTrader: (12)

Can you just throw the new stuff on and keep the blower.?
Or is just time to say I been there done that now lets do something else.?
Good luck with what ever you deside.

sharpshooter

iTrader: (10)

those headers look nice!

Mangled03gmc

iTrader: (95)

I say, ditch the whip, put a procharger or a turbo on it.. Or try and find a marine 8.1 engine. They come with a forged crank ect, also a aluminum intake(not sure yours is)?
Either way, your truck is still a beast, best of luck


John

Breeze

iTrader: (16)

You know I actually agree with him for a change also. Good one Russ. JFWY.

XLR8NSS

iTrader: (4)

sharpshooter

iTrader: (10)

gee thanks guys, I think

hog

GM did release the MP3 8100 marine engine. It produced 525+ hp and 560+ lb/ft torque.
It came with iron 8.1l heads with a weirdo part nuimber assigned to them as they were ported by soemone for GM. i remeber trying to get info on the ehads, but my searches came up empty. The heads were 1 number diffrent from the normal 8.1 heads.

As far as worrying about boost numbers. If you are pushing 6psi now, then you drop down to 4 or 5psi, you are still going to be making more power. Boost is a measre of restriction, taking away the restriction will make boost go down, but power WILL go up.

I remember the guys running 9 psi Vortech blower kits on Vortec 350 trucks. With the stock headpipes and cats they were seeing 8 psi of backpressure in the exhaust. WAYYY too much. A set of LT headers, larger headpipes and dual 3" cats brought the exhaust backpressure down to 2-3 psi, much better, and there power went WAY up.
There are a lot of reasons to not worry about boost numbers and concentrate of power output.

The ideology of so many hp per # of boost needs to be cast aside. If you go from 6psi, down to 4-5 with exhaust restrictions gone, your power will be up substantially. We are talking about feeding a 496 cubic inch engine. Losing a pound due to improved breathing will net big power/torque IMO.

Throw the beast on a dyno and do a pull, then pull the exhaust, boost will go down, power will go up, I'd bet the farm on it. Perhaps gaining so much better breathing, that retuning might be necessary to keep the a/f within safe limits.

If you are contemplating the NA setup, why not try a set of LT headers on your current setup? They can be used on the NA setup as well.
I'm not sure if you are running the stock dual 3" exhaust or not, but remember that that exhaust was desined and used on both the 8.1 and the 6.0l engines.
Both have dual 3" pipes that converge into a single muffler with dual outlets into a y. On the 6.0 one of teh exit pipes from teh muffler is a dummy, no exhaust flows through it. On the 8.1, the same muffler is used, but BOTH exits flow exhaust. This gives the 6.0 some back pressure that wouldnt be there if both muffler exits were functioal.

Seeing that everything muffler forward is the same between the 6.0 and 8.1, we might surmise that the dual 3" pipes are slightly too big for a 6.0 and slightly to small for an 8.1. May we go so far as to say WAY to small for a blown 8.1.
I am not familiar with your current exhaust setup, but from this thread its fair to say you arent running LT headers. If you are running the stock cats, and stock dual 3" tubing there may be some gains to be had with in teh exuats department. I will add that if youa re running the stock manifolds, there will be a sunstantial improvement in running LT headers, and a higher flowing exhaust.
You may want to pull an O2 sensor and screw in a pipe that attaches to a low pressure gauge(0-15psi) and see exatly what kind of exhaust backpressure you are seeing.
I apologize for my ignorance in your existing setup. If you are indeed running a shorty header/high flow-dual cat/muffler setup, exhaust may not give you as dramatic results as I have inspired above.

If this were my truck, and I really wanted "the best" I would run, at least dual 3 1/2" cats, dual 3 1/2" pipes into dual 3 1/2" mufflers, with some sort of LT headers with 2"+ primary and 3 1/2" or greater collectors. If the tubing that will be used for the exhaust is to be crimp bent, I may look into a dual 4" exhaust. I know it sounds crazy, but we are talking about a boosted 496 cubic inch engine. 496 cubes used to only be had by taking a 454 and stroking it, and dual 3" exhaust are comsidered by many, the norm on a high performance naturally aspirated 454 cube engine.

My thinking of such large exhaust diameters has been influenced by my trip yesterday to the local GM dealership, where I found some Duramax cab and chassis trucks, whose single exhausts were SO big, that when I put my hands around them, my thumbs and fingers were no-wheres close to touching. And that was on a truck rated at 330 hp@3000rpm and 620 lb/ft of torque at 1600rpm using a turboed 6.6L engine. You have a supercharged 8.1L engine that will spin over well above those rpm numbers.

The Raylar stuff is really nice, it will also need a large exhaust to function properly.

Take care

peace
Hog

BADMOFO

Hey Jim have you heard about that place on Mt. Road called "Mandrel Bends"? I heard that they do up to 4" exhaust, and from what I understand it's priced "resonably".