Lm7 5.3l Build

Toadz · September 23, 2009

I've done a little searching but didn't find what I wanted. I wanted to start acquiring parts for a build I plan on doing next summer when I return home from college. I figure I can use this time to do some research and find the best deals.

What I'm wondering is, is it possible to build an LM7 to produce it's peak TQ in the lower RPM range like the Gen II V8's did? I rarely hit 4K RPM while driving and I don't see the practicality in a higher stall as gas mileage is surely to suffer from increased RPM. I'm talking about in the 1000-4000 RPM range. Are there cams, intakes, heads, etc. that would lower the peak? I want the truck to perform like a truck, not a sports car. Torque is obviously the main goal here.

WilliamBos · September 23, 2009

I've done a little searching but didn't find what I wanted. I wanted to start acquiring parts for a build I plan on doing next summer when I return home from college. I figure I can use this time to do some research and find the best deals.
What I'm wondering is, is it possible to build an LM7 to produce it's peak TQ in the lower RPM range like the Gen II V8's did? I rarely hit 4K RPM while driving and I don't see the practicality in a higher stall as gas mileage is surely to suffer from increased RPM. I'm talking about in the 1000-4000 RPM range. Are there cams, intakes, heads, etc. that would lower the peak? I want the truck to perform like a truck, not a sports car. Torque is obviously the main goal here.

The mileage of the LS engines is better than any of the old V8's they replaced. Driving around at peak torque all the time probably decreases mileage.

I would like to hear what others have to say about this too. Stroking is an option.

WilliamBos · September 23, 2009

I've done a little searching but didn't find what I wanted. I wanted to start acquiring parts for a build I plan on doing next summer when I return home from college. I figure I can use this time to do some research and find the best deals.
What I'm wondering is, is it possible to build an LM7 to produce it's peak TQ in the lower RPM range like the Gen II V8's did? I rarely hit 4K RPM while driving and I don't see the practicality in a higher stall as gas mileage is surely to suffer from increased RPM. I'm talking about in the 1000-4000 RPM range. Are there cams, intakes, heads, etc. that would lower the peak? I want the truck to perform like a truck, not a sports car. Torque is obviously the main goal here.

The mileage of the LS engines is better than any of the old V8's they replaced. Driving around at peak torque all the time probably decreases mileage.

I would like to hear what others have to say about this too. Stroking is an option.

Toadz · September 23, 2009

Driving around in peak torque wouldn't decrease mileage, it would actually increase gas mileage because the engine will not have to work as hard. The LS series engines have better gas mileage because of the increase in efficiency.

I would prefer not to change the bore or stroke, although building a stroker would be fun.

Toadz · September 24, 2009

Any other input?

66nova · September 24, 2009

Any other input?

What are your goals? Do you have a certain amount of torque in mind?

You have a very capable starting point and these motors are capable of a lot of torque, but you are dealing with relatively low Cubic Inches. That is going be your biggest factor inhibiting torque.

With only 327ish cubic inches you are not going to build a torque monster, but with the right cam you can certainly have a stout motor.

Have you considered Forced induction?

I would call a few cam companies with you goals and have them give you some cam recommendations. Not know your goals it is hard to get too specific and even if it is feasible.

If I were going about this, I would either be looking at a super charger or finding a 6.0 to start a build on.

Toadz · September 26, 2009

What are your goals? Do you have a certain amount of torque in mind?

You have a very capable starting point and these motors are capable of a lot of torque, but you are dealing with relatively low Cubic Inches. That is going be your biggest factor inhibiting torque.

With only 327ish cubic inches you are not going to build a torque monster, but with the right cam you can certainly have a stout motor.

Have you considered Forced induction?

I would call a few cam companies with you goals and have them give you some cam recommendations. Not knowing your goals it is hard to get too specific and even if it is feasible.

If I were going about this, I would either be looking at a super charger or finding a 6.0 to start a build on.

I do not have any specific goal for TQ. I am simply looking to move the powerband lower in the RPM range for that truck feel and better towing. I believe they are 325CI but these engines are a far cry from the V8's of yesteryear so I think lack of cubic inches can be made up for. Forced induction and/or a 6.0 is not reasonable to me for my truck. If I were thinking about a swap it would be for a 4BT Cummins. I guess I am asking if there are cams, heads, and intakes that would move the powerband lower with improved TQ. I did not buy a truck to perform like a race car. I would be happy with 325 ft-lbs of RWTQ if it hit low.

WilliamBos · September 26, 2009

I believe they are 325CI but these engines are a far cry from the V8's of yesteryear

There is not a 5.7L on the planet that I would ever trade for my 5.3L for. But if you could give me the awe inspiring torque of a 455 Olds, I would be happy!!

66nova · September 26, 2009

What are your goals? Do you have a certain amount of torque in mind?

You have a very capable starting point and these motors are capable of a lot of torque, but you are dealing with relatively low Cubic Inches. That is going be your biggest factor inhibiting torque.

With only 327ish cubic inches you are not going to build a torque monster, but with the right cam you can certainly have a stout motor.

Have you considered Forced induction?

I would call a few cam companies with you goals and have them give you some cam recommendations. Not knowing your goals it is hard to get too specific and even if it is feasible.

If I were going about this, I would either be looking at a super charger or finding a 6.0 to start a build on.

I do not have any specific goal for TQ. I am simply looking to move the powerband lower in the RPM range for that truck feel and better towing. I believe they are 325CI but these engines are a far cry from the V8's of yesteryear so I think lack of cubic inches can be made up for. Forced induction and/or a 6.0 is not reasonable to me for my truck. If I were thinking about a swap it would be for a 4BT Cummins. I guess I am asking if there are cams, heads, and intakes that would move the powerband lower with improved TQ. I did not buy a truck to perform like a race car. I would be happy with 325 ft-lbs of RWTQ if it hit low.

You are correct. LS based motors are a far cry from their predecessors. They can make massive Horse Power, but the 5.3 has never been considered a torque monster. Im sorry, but the old adage "no replacement for displacement" still holds true today. There is a reason GM makes the 6.0 the base motor in the HD trucks. With that being said I think your goals are not unreasonable as long as you don't expect those numbers at 1200rpm.

I would call a couple cam company's tell them what you want and get a custom tune to match the cam. I think you will be amazed at the outcome. If you are going to get into aftermarket heads you are going to spend about as much as you would with a 6.0 swap.

ken1mod · September 27, 2009

Gentlemen,

I had a cam wear out in a 454. The Speed shop that sold crane suggested an "rv" cam. I opted instead for a low lift, short duration "economy" cam. The salesman laughed.

Wow! The low end torque was amazing and this truck pulled 20000 lb trailers for a living. The point is that the engine made more driveable torque and power. I know it lost some at 5000 rpm but the gain at 2000 was real. It felt more like a diesel. I also gained significant fuel mileage.

Ken

Toadz · September 27, 2009

There is not a 5.7L on the planet that I would ever trade for my 5.3L for. But if you could give me the awe inspiring torque of a 455 Olds, I would be happy!!

Those 455's were awesome. An ex-gf's dad had an Oldsmobile Riviera with the 455 and some other car with the same engine. Even though they drove like boats they had amazing torque.

You are correct. LS based motors are a far cry from their predecessors. They can make massive Horse Power, but the 5.3 has never been considered a torque monster. Im sorry, but the old adage "no replacement for displacement" still holds true today. There is a reason GM makes the 6.0 the base motor in the HD trucks. With that being said I think your goals are not unreasonable as long as you don't expect those numbers at 1200rpm.

I would call a couple cam company's tell them what you want and get a custom tune to match the cam. I think you will be amazed at the outcome. If you are going to get into aftermarket heads you are going to spend about as much as you would with a 6.0 swap.

I might look into dropping in LS1 pistons and rods to bump up the CI when I do my build, so hopefully this will help compensate. I realize I don't have a HD truck but I still find it pathetic how little low-end power there is in these trucks. They perform like cars which is not what I want out of this engine. I may stick with the stock heads and port them. Any preferred cam company to contact? I always hear good things about Comp Cams.

Gentlemen,

I had a cam wear out in a 454. The Speed shop that sold crane suggested an "rv" cam. I opted instead for a low lift, short duration "economy" cam. The salesman laughed.

Wow! The low end torque was amazing and this truck pulled 20000 lb trailers for a living. The point is that the engine made more driveable torque and power. I know it lost some at 5000 rpm but the gain at 2000 was real. It felt more like a diesel. I also gained significant fuel mileage.

Ken

This is exactly the type of cam I'm looking for.

66nova · September 28, 2009

I might look into dropping in LS1 pistons and rods to bump up the CI when I do my build, so hopefully this will help compensate. I realize I don't have a HD truck but I still find it pathetic how little low-end power there is in these trucks. They perform like cars which is not what I want out of this engine. I may stick with the stock heads and port them. Any preferred cam company to contact? I always hear good things about Comp Cams.

Compression will definitely help. I just don't know off the top of my head how much compression your truck currently has. If you are going to have your heads worked, make sure you trust your head guy. They open them up too much and you will lose low rpm velocity. Then you will have a head that would be great on a car. I would just want them cleaned up a bit and NOT polished.

Comp is a great cam company. I have also had good luck with Bullet custom ground cams. Comp has a line of truck cams that would probably work great.

Toadz · September 28, 2009

I might look into dropping in LS1 pistons and rods to bump up the CI when I do my build, so hopefully this will help compensate. I realize I don't have a HD truck but I still find it pathetic how little low-end power there is in these trucks. They perform like cars which is not what I want out of this engine. I may stick with the stock heads and port them. Any preferred cam company to contact? I always hear good things about Comp Cams.

Compression will definitely help. I just don't know off the top of my head how much compression your truck currently has. If you are going to have your heads worked, make sure you trust your head guy. They open them up too much and you will lose low rpm velocity. Then you will have a head that would be great on a car. I would just want them cleaned up a bit and NOT polished.

Comp is a great cam company. I have also had good luck with Bullet custom ground cams. Comp has a line of truck cams that would probably work great.

I believe the trucks have a decent amount of compression compared to the car setups. I think going to LS1 pistons will increase my compression even more. I know compression would help a lot but I would prefer to keep this on 87 octane. I'll be doing the heads myself. I'll just be indexing the intake and exhaust ports, polish the exhaust, and I'll figure out a game plan for the intake when I see them with my own eyes. I know less can be more with porting and I know polishing can actually hurt velocity with the intake. It's best to keep a slightly rough surface to create a layer of slow moving air to improve the velocity of the incoming charge.

I'll check out Comp Cams, it seems they are the way to go.

66nova · September 28, 2009

I might look into dropping in LS1 pistons and rods to bump up the CI when I do my build, so hopefully this will help compensate. I realize I don't have a HD truck but I still find it pathetic how little low-end power there is in these trucks. They perform like cars which is not what I want out of this engine. I may stick with the stock heads and port them. Any preferred cam company to contact? I always hear good things about Comp Cams.

Compression will definitely help. I just don't know off the top of my head how much compression your truck currently has. If you are going to have your heads worked, make sure you trust your head guy. They open them up too much and you will lose low rpm velocity. Then you will have a head that would be great on a car. I would just want them cleaned up a bit and NOT polished.

Comp is a great cam company. I have also had good luck with Bullet custom ground cams. Comp has a line of truck cams that would probably work great.

I believe the trucks have a decent amount of compression compared to the car setups. I think going to LS1 pistons will increase my compression even more. I know compression would help a lot but I would prefer to keep this on 87 octane. I'll be doing the heads myself. I'll just be indexing the intake and exhaust ports, polish the exhaust, and I'll figure out a game plan for the intake when I see them with my own eyes. I know less can be more with porting and I know polishing can actually hurt velocity with the intake. It's best to keep a slightly rough surface to create a layer of slow moving air to improve the velocity of the incoming charge.

I'll check out Comp Cams, it seems they are the way to go.

Talking about octane put a thought in my mind. Do you have a custom tune?

If the answer is no, then let me give you a recommendation. First off, I am not talking about a something like hypertech or superchips, I am talking about a tune from someone like Black Bear Performance , Nelson, or Wheatley.

I highly recommend you contact Justin, with Black Bear Performance and get a custom tune first. A lot of the piss poor driveability these trucks have are due to the factory tune. You will be amazed at the difference a tune makes in not only the power down low and up high, but it is actually available to use.

Plus, if you change cams you are going to need to get a custom tune anyway. Justin has free retunes, so get it tuned now drive it for a bit then once you change cams Justin will retune your computer for free.

I would also consider getting it tuned for higher octane. You will be leaving quite a bit of power on the table sticking with an 87 octane tune. Plus, it only cost about $5 more per tank for 91 or 93.

Toadz · September 28, 2009

Talking about octane put a thought in my mind. Do you have a custom tune?

If the answer is no, then let me give you a recommendation. First off, I am not talking about a something like hypertech or superchips, I am talking about a tune from someone like Black Bear Performance , Nelson, or Wheatley.

I highly recommend you contact Justin, with Black Bear Performance and get a custom tune first. A lot of the piss poor driveability these trucks have are due to the factory tune. You will be amazed at the difference a tune makes in not only the power down low and up high, but it is actually available to use.

Plus, if you change cams you are going to need to get a custom tune anyway. Justin has free retunes, so get it tuned now drive it for a bit then once you change cams Justin will retune your computer for free.

I would also consider getting it tuned for higher octane. You will be leaving quite a bit of power on the table sticking with an 87 octane tune. Plus, it only cost about $5 more per tank for 91 or 93.

I know all about the tunes, I've been over at Full Size Chevy for quite sometime and S10Forum before that. I know that hand held tunes are a huge waste of money for gasoline vehicles.

My truck is in WI, I'm in AZ, so I won't be driving it until next summer when I return home for a month. I will be getting a tune done the same time as the rebuild. I don't think I could justify a 93 tune as that $5 (actually closer to $8 a tank, 30 cents x 26 gallons = $7.80) quickly adds up being a daily driver and I'm not in this for competition, just satisfaction and easier towing.