LM7 vs L33
 

So I was wondering if you guys could help me with the differences between the two engines besides ones aluminum and the other iron. I have a 2000 silverado 1500 with the 5.3 in it and added some headers just recently. I have about 160K on the engine and was thinking to maybe rebuild one on the side. If I'm gunna do that I may as well upgrade a little. Not looking to make a shit ton of hp but I do like the sound of moving up from 260 to 310. I know it's probably gunna have a different cam and the heads are different too but what numbers are the heads and cam and what else is involved?

Also the guys who have a stock L33, how do you like it?

Oh btw my truck is lifted with 35" tires and 4.56 gears. It's a 2wd as well.

the lm7 you can get worked 243 heads or 706 i know the 243's flow better im running worked 706 heads and love em...

What are the differences between the two heads? The 243 and 706?

What motors do each come off of?

The L33 was an aluminum block version of the LM7, and was referred to as the Vortec 5300 HO in marketing materials. Power increased by 15 hp (11 kW), to 310 hp (230 kW), over the LM7, and torque was unchanged. It was only available on extended cab 4WD pickup trucks.


Casting Number 243
Head: 2001 LS6 5.7 Liter Passenger Car
Material: Aluminimum
Part Number:
12564243
Combustion Chamber Volume: 64.45cc
Compression Ratio: 10.5:1
Intake Port Volume: 210cc
Exhaust Port Volume: 75cc
Intake Valve Diameter: 2.00 inches
Exhaust Valve Diameter: 1.55 inches

Stock Head Flow Numbers
Chamber 64.45 cc-------0.100---0.200--0.300--0.400---0.500---0.550---0.600
Intake 210 cc------------62------126----184----224-----251----256----257
Exhaust 75 cc------------57------108----143----163-----176----180----183




Casting Number 706 and 862
Head: 1999+ 4.8L / 5.3 Liter Truck
Material: Aluminimum
Part Number:
12559862
12561706
Combustion Chamber Volume: 61.15cc
Compression Ratio: 9.5:1
Intake Port Volume: 200cc
Exhaust Port Volume: 70cc
Intake Valve Diameter: 1.89 inches
Exhaust Valve Diameter: 1.55 inches

Stock Head Flow Numbers
Chamber 61.15 cc----0.100--0.200--0.300-- 0.400--0.500---0.550---0.600
Intake 200 cc----------63 ---128----179-----210----218----221-----226
Exhaust 70 cc----------54 -- 93 ----121----145-----163----168----174



Hope this is what ur wanting to know ;)

Ok, if building a engine on the side whyyyyyyy another 5.3?

Don't forget the L33 uses Flat top pistons from the 4.8 rather then the -8cc Dish pistons found in the standard LM7.

Ok so they use the ls1 heads? Are the bores the same size? I herd here isn't much room for bigger valves. What about the cams? Do they use the 2001 ls1 Camaro cam?

As far as building a motor on the side and keeping it a 5.3L is because I really dot want to put a 6.0 in there because I'm not looking to go crazy with HP. Just a little extra, seeing as its all pretty much stock parts for the L33 I figured the gas mileage wouldn't be terrible. This is my DD and I'm tryin to keep it mild not wild.

Basically if I'm gunna build a motor on the side and a trans as well then just swap everything out and maybe use my old power train in another project down the road haha maybe put it in an old mustang to piss off some ford guys lol.

The 5.7 I built for my truck gets better mpg than the 4.8 it replaced.

with my motor stock besides K&N drop in and blowmasters dumped, 4.56s and 37"s it moved alright. I would beat stock similar trucks all the time
block, heads, pistons and cam I do believe are the differences

The L33 uses the the flat top pistons from the 4.8 giving it ~9.9:1 compression on the same 3.78" bore. The cam has slightly more lift albeit with the same duration and also came with 243/799 heads. They also had floating rods vs the press fit pin rods in the LM7. You already knew of the aluminum vs iron block difference. Other than that, it's about it.

I bought a used L33 for $500 and sold off the rotating assembly, cam, heads and still pocketed the block and ~250 bucks toward a newer rotating assembly. They make good power and respond a bit better to a cam change thanks to the better design of the heads. If you have the heads off, have a valve job done and do a cam swap. That will net you ~50 hp or so which would probably make you happy from the sounds of it.