400-450 lbft goal in stock L59
08-01-2019, 04:15 PM
#21
Torque is a function of CID and cylinder pressure.
That's IT. To get more torque, you have to increase one or the other, or both.
Cyl pressure is a function of compression, and how full of fuel/air mixture you can pack it in there.
In the real world, N/A, on real-world pump gas you can buy at real-world gas stations down the street, driving in real-world conditions such as summer heat and winter cold, using real-world parts you can buy at real-world parts stores of various sorts, it's REAL HARD to exceed about 1¼ real-world ft-lbs per CI at the engine's peak. For a 5.3 that's around 400 ft-lbs. The factory's ratings for those is close to that, as might be expected; but can be improved by better exhaust (less contamination of the incoming A/F charge), higher compression, and attention to detail like making sure ALL 8 cyls have EXACTLY the same compression and flow. Obviously if you raise the compression very much, you have to be concerned about cooling, tuning, fuel quality, and various other things, that aren't compatible with your typical daily driver. The motor gets AWHOLEHELLUVALOT more finicky about EVERYTHING.
A cam swap will move the RPM that the torque peak occurs at, up or down; but the actual peak torque value won't change much.
As said by all these others, some form of The Force is the only way to overcome this limitation. And of course even that comes with a price; not just the cost of acquisition, but also, poorer fuel mileage, some degree of finicky behavior as described above, and so on.
Your best friend if you want more torque is CID.
That's IT. To get more torque, you have to increase one or the other, or both.
Cyl pressure is a function of compression, and how full of fuel/air mixture you can pack it in there.
In the real world, N/A, on real-world pump gas you can buy at real-world gas stations down the street, driving in real-world conditions such as summer heat and winter cold, using real-world parts you can buy at real-world parts stores of various sorts, it's REAL HARD to exceed about 1¼ real-world ft-lbs per CI at the engine's peak. For a 5.3 that's around 400 ft-lbs. The factory's ratings for those is close to that, as might be expected; but can be improved by better exhaust (less contamination of the incoming A/F charge), higher compression, and attention to detail like making sure ALL 8 cyls have EXACTLY the same compression and flow. Obviously if you raise the compression very much, you have to be concerned about cooling, tuning, fuel quality, and various other things, that aren't compatible with your typical daily driver. The motor gets AWHOLEHELLUVALOT more finicky about EVERYTHING.
A cam swap will move the RPM that the torque peak occurs at, up or down; but the actual peak torque value won't change much.
As said by all these others, some form of The Force is the only way to overcome this limitation. And of course even that comes with a price; not just the cost of acquisition, but also, poorer fuel mileage, some degree of finicky behavior as described above, and so on.
Your best friend if you want more torque is CID.
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Pender1 (08-01-2019)
08-01-2019, 04:18 PM
#22
12 Second Club
How big is your CNC machine? With the L59, you can bore the cylinders out to 3.898, and build it as a 5.7L. Put some flat-top pistons in there, port the heads, add a "truck cam", and see what it does.
08-01-2019, 06:54 PM
#23
Big enough for heads, not big enough for blocks. I do know a guy though. I hadn't thought about boring it out to be honest, I'll have to ponder on that one. Just out of curiosity, how big can you go on that block before problems start popping up?
08-01-2019, 06:57 PM
#24
It has and absolute garbage 305ci out of another truck I wrecked. It sucked before I put it in this one, but it kept me on the road. Most of this things life will just be a weekend beater, but it's going to do some moderate rock crawling and a lot of camping.
08-01-2019, 07:02 PM
#25
Torque is a function of CID and cylinder pressure.
That's IT. To get more torque, you have to increase one or the other, or both.
Cyl pressure is a function of compression, and how full of fuel/air mixture you can pack it in there.
In the real world, N/A, on real-world pump gas you can buy at real-world gas stations down the street, driving in real-world conditions such as summer heat and winter cold, using real-world parts you can buy at real-world parts stores of various sorts, it's REAL HARD to exceed about 1¼ real-world ft-lbs per CI at the engine's peak. For a 5.3 that's around 400 ft-lbs. The factory's ratings for those is close to that, as might be expected; but can be improved by better exhaust (less contamination of the incoming A/F charge), higher compression, and attention to detail like making sure ALL 8 cyls have EXACTLY the same compression and flow. Obviously if you raise the compression very much, you have to be concerned about cooling, tuning, fuel quality, and various other things, that aren't compatible with your typical daily driver. The motor gets AWHOLEHELLUVALOT more finicky about EVERYTHING.
A cam swap will move the RPM that the torque peak occurs at, up or down; but the actual peak torque value won't change much.
As said by all these others, some form of The Force is the only way to overcome this limitation. And of course even that comes with a price; not just the cost of acquisition, but also, poorer fuel mileage, some degree of finicky behavior as described above, and so on.
Your best friend if you want more torque is CID.
That's IT. To get more torque, you have to increase one or the other, or both.
Cyl pressure is a function of compression, and how full of fuel/air mixture you can pack it in there.
In the real world, N/A, on real-world pump gas you can buy at real-world gas stations down the street, driving in real-world conditions such as summer heat and winter cold, using real-world parts you can buy at real-world parts stores of various sorts, it's REAL HARD to exceed about 1¼ real-world ft-lbs per CI at the engine's peak. For a 5.3 that's around 400 ft-lbs. The factory's ratings for those is close to that, as might be expected; but can be improved by better exhaust (less contamination of the incoming A/F charge), higher compression, and attention to detail like making sure ALL 8 cyls have EXACTLY the same compression and flow. Obviously if you raise the compression very much, you have to be concerned about cooling, tuning, fuel quality, and various other things, that aren't compatible with your typical daily driver. The motor gets AWHOLEHELLUVALOT more finicky about EVERYTHING.
A cam swap will move the RPM that the torque peak occurs at, up or down; but the actual peak torque value won't change much.
As said by all these others, some form of The Force is the only way to overcome this limitation. And of course even that comes with a price; not just the cost of acquisition, but also, poorer fuel mileage, some degree of finicky behavior as described above, and so on.
Your best friend if you want more torque is CID.
08-01-2019, 10:15 PM
#27
12 Second Club
There are plenty of articles talking about boring the LM7/L59 out to a 5.7L. There are even companies that sell LM7s bored to 5.7L. It's best to ultrasonic check the cylinder walls before boring. That will give you an idea of how big you can bore it. If you can bore it to 3.905", you can get about an 11:1 compression ratio with your heads and flat-top pistons. That's about equivalent to an LS1 with milled 243 heads. I think 450 ft lbs at the crank is very possible with that set-up.
My LS1 has a very conservative heads/cam combo, and I get 362 ft lbs to the wheels. Guestimating 20% loss through the drive train puts me at 434 ft lbs at the crank. I was building for a boosted application, so my N/A numbers are a bit low. My cam is also a little bigger than the truck cams. The truck cams might make a little more torque down low. My intake also isn't the best for low-end torque.
It sounds like you have the equipment to do this job yourself. If you can find a set of 2" intake valves, you might want to machine your heads for them while you're at it. The 706 heads have smaller valves.
My LS1 has a very conservative heads/cam combo, and I get 362 ft lbs to the wheels. Guestimating 20% loss through the drive train puts me at 434 ft lbs at the crank. I was building for a boosted application, so my N/A numbers are a bit low. My cam is also a little bigger than the truck cams. The truck cams might make a little more torque down low. My intake also isn't the best for low-end torque.
It sounds like you have the equipment to do this job yourself. If you can find a set of 2" intake valves, you might want to machine your heads for them while you're at it. The 706 heads have smaller valves.
08-12-2019, 01:13 PM
#28
10 Second Club
iTrader: (8)
I'll tell ya what we did to my uncles 03 5.3 rcsb that resulted in a nice improvement. His had a cracked head (706)and was using antifreeze. So i found a set of 243s and had them milled to the 61cc chamber as to not loose any compression. Installed those with a cheapy set of ebay headers with a ory that connected to the oe exhaust. Put new ls6 valve springs on them with a set of 1.9 roller rockers from speed master. The only tuning i did was reduce the tm because the added tq really made it fall over on shifts and threw it's timing of the tm off....was just bad.
With those being the only changes the truck is just better. Gets better mpg's. Some hills it would go up before it would unlock the converter now it just chugs up locked.....so low rpm was very much improved and what a truck needs.
At the track it went from a 15.7 to a 15.4 or 15.3....i forget. It picked up like 4 mph to. The changes did really expose the restriction of the stock exhaust tho. It seems to really need a catback now. Other than the mods mentioned the truck is stock.
With those being the only changes the truck is just better. Gets better mpg's. Some hills it would go up before it would unlock the converter now it just chugs up locked.....so low rpm was very much improved and what a truck needs.
At the track it went from a 15.7 to a 15.4 or 15.3....i forget. It picked up like 4 mph to. The changes did really expose the restriction of the stock exhaust tho. It seems to really need a catback now. Other than the mods mentioned the truck is stock.
08-13-2019, 09:01 AM
#29
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If you go full on max effort, 400-410 ft lbs peak RW torque is the best you can do. At stock cubes 323. I seen several cars use hio recipe above with rockers, intake, headers and get great torque. So it is a great way to get there without needing rpm. One was a ls3 that cleared 470 lbs RW tq
I would also look into the cam motion drop in truck cams or a btr truck cam. Great valve events to help build torque. I would still do the rockers even with those cams. Maybe go to psi1511 springs.
I would also look into the cam motion drop in truck cams or a btr truck cam. Great valve events to help build torque. I would still do the rockers even with those cams. Maybe go to psi1511 springs.
08-13-2019, 11:56 AM
#30
10 Second Club
iTrader: (8)
Yea those drop in truck cams seem to work pretty well.
Another thing op......gear gear gear. Some of those old k5's only had 3.08 gears. That's what my 86 k5 had. I eventually put 4.10s in it but always wished i had put more gear in it with the 35s i had on it. My 03 2500hd 6.0 has 4.10s. I wish it had 4.56s or 4.88s and it only has a 33" tire on it. Gear will/can multiply your tq pretty good.
Another thing op......gear gear gear. Some of those old k5's only had 3.08 gears. That's what my 86 k5 had. I eventually put 4.10s in it but always wished i had put more gear in it with the 35s i had on it. My 03 2500hd 6.0 has 4.10s. I wish it had 4.56s or 4.88s and it only has a 33" tire on it. Gear will/can multiply your tq pretty good.
