TGriz

iTrader: (3)

Hello All,
I am new to the forums here but have been posting on the FSC and LS1 truck forums for a while.
I hope I put this in the right section of the forums.

This is a x-post from my thread on the LS1 Truck forums. This seems to be the place to talk about LS based motors so I figured I would post it here and get some different takes on my question. If this is in the wrong section please tell me so I can delete it and move it to the correct one.

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I am building a LM7 (5.3) motor into a 383. I know this kind of build has been done before but I am having trouble finding information on the build. I will be using an ls6 cam and some 243 heads. The motor will be N/A, no boost or spray. The question I have is what kind of upgrades would the fuel system need to support this kind of build?

The vehicle that this is going in would be an 03 GMC sierra with the LM7 (5.3) and as of now everything on the motor and fuel system is stock OE.

Thanks,
Ty

Fbodyjunkie06

iTrader: (10)

Not too sure of your question but, I'd look into a little bit bigger cam that the stock Ls6 cam there are plenty of them out there that will still pass smog and be a better performer. Like a 224/224 581/581 114 or 220/220 566/566 114.

TGriz

iTrader: (3)

Well the truck is my daily driver and I tow with it so I figured I would go with a moderate cam instead of something crazy. I still want something resembling fuel economy. haha

00MaroonZ28

iTrader: (3)

just do a 6.0L swap. It'll be a lot cheaper than machining and stroking your LM7 block.

TGriz

iTrader: (3)

too late for that. haha. the build as already begun!

SOMbitch

iTrader: (8)

I agree on the cam. There are a lot better cams for your needs. Find Predator-z or Patrick G on here and have a custom speced

As for the fueling since this is a mild build allyou will need are some LS1 26lb. or 28.5lb. injectors and they are cheap in the classifieds...

TGriz

iTrader: (3)

So you think like a TR220 cam would do the trick? How does one of those compare to the LS6 cam? And would those 28.5# injectors be enough to power this set up with an LS6 cam or one bigger?

TGriz

iTrader: (3)

I have decided to run my ls6 cam with a little custom grind to make it a 212/218 duration. I was looking into some LS6 injectors which are supposed to be 28.5 # injectors which seemed to make sense for this build since its using the LS6 heads and basically an LS6 cam. Anyone have any input on this? and the stock injectors are supposed to be 24# injectors, is this at 3 or 4 bar?

1nasty86

iTrader: (63)

what kind of rotating assembly did you go with? i have a lm7 and thinking ab going to a 383. how did boring it from 96mm to 99mm go?

Bader-X

iTrader: (2)

98 camaro injectors are also 28 lb/h and cheap used

if ls6 cam pick the 550 lif one 02 and later

TGriz

iTrader: (3)

I have not actually begun the bottom end build yet. I just picked up the block yesterday. As soon as I decide on the rotating asy and get it all buttoned up I will let you know how it goes.

TGriz

iTrader: (3)

I made sure the LS6 cam I got was the 02 and later (5308) one. all these 28# inectors, are those 28 lbs at 3 or 4 bar? And does anyone know if the stock 5.3 injectors are 24# at 3 or 4 bar?

Thanks!

TGriz

iTrader: (3)

ttt.

Well I am getting ready to make the final decision on which pistons I am going with in the stroker kit. Which compression ratio should I be shooting for on this motor? Stock compression ratio is about 10:1. What should I be shooting for on this motor?

Build Spec:
LM7 5.3 bored and stroked to 383ci
243 LS2 heads
LS6 Cam (405hp version)

using a Walboro 255lph and racetronix 38lb/hr @43.5 PSI & 44lb/hr @ 58 PSI injectors for fuel system upgrades.

Going in a 5000lb truck.
I want to run pump gas. preferably 87 octane, but I would go with 92 octane if the benefits were there.

Also would the stock 78mm throttle body be sufficient to supply airflow to this type of motor? Its the stock throttle body on my truck which is a drive by wire design (no throttle cable).

If I was to go with a bigger throttle body which one would you go with and would it need a different intake manifold?

Thanks for all the help guys!

TGriz

iTrader: (3)

I need a suggestion on a converter for my build.

I ended up deciding on a TR220/220-114 cam.

I have a TB stall available for a decent price. Is this enough stall for this type of cam in this cubic inch of motor? i think its in the 2000-2400 range.
maybe a 3000 stall? or no stall at all?

what do you guys think?

jevonniespapi

You fire this motor up yet!?

xdanny510x

if ur gonna tow dont go with a big stall.. i was recommend on my lsx 4** silverado not to tow but i dont know if he was pulling my chain

TGriz

iTrader: (3)

Yup its in and running. Got 850 miles on it.

My final build consisted of:

5.3 Iron block Bored to 3.905
Mahle Pistons
Eagle 4in stroke crank
Eagle rods w/ ARP bolts
Cloyes Double Roller Hex Adjust
Mellings m295
243 heads with comp 918 springs
TR220 -114 (220/220 .556/.556 114)
TBSS intake 90mm running with a DR.X Link

It runs strong, but it still needs to be dyno tuned. I am gonna pick up some LTs and throw those on before the dyno.

But I am thinking I want a bigger cam...
What do you guys think for a 5500 lb 4wd truck that tows a little bit?

maybe a TR230/236? TR224? TSP 228? Custom Spec'd?


Ty.

jevonniespapi

Sounds like a great build!
Question:
How much did the machining run you?

TGriz

iTrader: (3)

too much. lol. should have done a 408, would have been cheaper. I paid $2k in labor for everything. That included boring 120 over, working the 243 heads, and assembly from intake to oil pan.

TGriz

iTrader: (3)

Well I have an update after putting 1500 miles on it.

The new engine runs good. But it seems to lack some of the low end grunt that I want. It takes a bit of RPM and throttle to get it moving. And seems to always need a lot of throttle to keep it moving up hills. It seems that it sometimes has trouble getting into OD while cruising. Is this a product of my cam, torque converter, gears, maybe all three? It is fast from 3k RPM and up.

5500 lb ECSB truck
4wd
32 or 33in tall tires on 18 wheels
383 cubic inch
3.73 gears
220/220 .556/.556 114lsa
4L60E running a shift kit & Trailblazer I-6 Torque Converter
3.73 gears


what do you guys think?


p.s. - i am getting LTs and my final tune on the dyno soon. we will see how it turns out after that i guess.