Ways to increase the efficiency of a GM 5.3L

[freebeard]

Nobody seems to know, maybe something like ten posts?

You can obfuscate the URL, like http***ecomodder.com.

[Solarpowered]

Originally Posted by freebeard

Nobody seems to know, maybe something like ten posts?

You can obfuscate the URL, like http***ecomodder.com.

It says you have to have 15 posts or greater. And it seems to catch on to attempts to circumvent it. So I'll just tell you that the site is eco tech alternators dot calm. All one word of course, and fix the last two words to be correct. Please post a link for me, thanks!

Anyway here's what an actual engine builder had to say about an econo-5.3L:

I will give you some realistic tips on building a Gen III/IV 5.3 for strong fuel efficiency in your older Silverado. This will assume you don't do much towing, or that you are not filling the bed up with 3000 pounds of stuff. I will keep in mind you have a 2.73 gear, and assume you have a 235/75 15 tire, which is 29 inches in diameter. This is for a proper build, that covers the engine top to bottom.

You need to maximize torque, minimize friction and pumping losses, and consider thermal management.

Starting with a good 5.3 core, if you have the option of an aluminum block, it will save you 150 pounds, maybe more, over the stock 1987 drivetrain. The weight savings helps your fuel efficiency goals. But, since iron blocks are most common, that will do for this.

The Gen III and IV blocks have some form of bay to bay breathing in the crankcase. I have seen bored holes and cast in windows of various shapes. You can improve on this by detailing the crankcase. Softening sharp edges, putting a radius on the lower edge of the bores, basically what a lot of people do when they port heads. There is quite a bit of air moving down there, and this could help reduce pumping losses by a percent or two.

You should use a flat top piston, and deck the block for zero deck clearance. An OEM replacement hypereutectic flat top piston for the 4.8/5.3 is perfect. The pistons should be installed at .0015-.002 piston to wall clearance, which is a lot for a hypereutectic but will minimize skirt friction. Set the ring gaps appropriately, along with all other clearances on the bottom end. Make certain the cam bearings are good.

Do not port your heads. Assuming you have a 706 head, do a proper valve job. Do put a back cut on the intake valve. The exhaust valve seat cut should be about .010-.015 lower than the intake. The exhaust valve margin should have a radius (Ferrea has this), the intake should have a sharp chamfer. Make sure the guides are all good and the stem to guide clearance is perfect. This is often overlooked! Deck the heads to get approximately 59-60 cc chambers.

You will need a Cometic head gasket with a 3.91 bore, that is .036 thick. This gasket, with a 60 cc chamber on a zero decked block with .020 over flat tops will give you right at 11:1 compression. This is a significant increase, and will give gains to torque as well as fuel efficiency.

For a cam, you want a 114 degree lobe separation angle on a 5.3 with 706 heads. Considering your goals, and your vehicle gearing, you want about 30 degrees of overlap. This will give you 258 degrees of duration @ .006 tappet rise. This is a very short cam. Cylinder pressure will be high, therefore torque will be good. It should be installed on a 112-113 intake centerline. A good lobe with these specs will get you approximately 200-204 degrees @ .050. With the 11:1 compression, this cam will put your dynamic compression at 9:1.

This cam will not need much valve spring. Good OEM springs will work here, and keep friction down because they are not very stiff. LS7 lifters will work perfectly, as will stock rocker arms. Use the appropriate length pushrod. The OEM LS2 style timing chain is very good, and if possible run one that isn't too tight. Do run a chain damper. A standard volume oil pump, with a lower pressure relief valve spring, will be perfect.

The stock truck intake makes good torque where you want it. Ideally, you want headers with 1 1/2 inch primary tubes as long as possible. Such headers probably don't exist. Most companies sell 1 3/4 or 1 7/8 inch headers. Those are way too big, it seems bigger is better syndrome has infected header choices. If you can't get 1 1/2 inch primaries, 1 5/8 would be a reasonable compromise. You will have to talk to some header companies and see. I think you should run a full 2 1/4 dual exhaust system with real mufflers, like large case Dynomax or Magnaflow.

You will need a fuel system that can maintain pressure at, or just above, the max fuel pressure recommended for your injectors. This will better atomize the fuel. You need a very efficient cooling system, and will want coolant temps around 200 to 220 degrees F. Not less. This may require a cooling system pressure over 16 psi. Give this careful thought, you don't want the engine too cool, yet you have a high compression ratio and cylinder pressure is significant.

I assume you will probably use the 4L60 trans, which is fine. This should be tuned to have a lean idle and part throttle cruise. You will need to find a tuner that knows a 13:1 air fuel ratio is not lean. At idle, you might want afr of 15-15.5:1 or so, and as lean as you can stand at steady state part throttle cruise.

Some other things can help, like a smaller, lighter, low stall torque converter, running 36-42 psi in the tires, an aluminum drive shaft, and an electric cooling system fan.

These details add up significantly. This type of build is unconventional for many people. Careful attention must be paid to tune, cooling, and engine assembly. If anything changes, I would probably suggest some different cam specs. For example, a 243/799 head would be a different cam. You might also consider your driving habits.

The same concepts of this build can be applied to many engines, including your old 350. Some people might prefer to build a 312 cubic inch Gen III engine from a 4.8 for max fuel efficiency. But, that's a separate conversation.

[Isaac Zachary]

Originally Posted by Solarpowered

It says you have to have 15 posts or greater. And it seems to catch on to attempts to circumvent it. So I'll just tell you that the site is eco tech alternators dot calm. All one word of course, and fix the last two words to be correct. Please post a link for me, thanks!

Anyway here's what an actual engine builder had to say about an econo-5.3L:

I will give you some realistic tips on building a Gen III/IV 5.3 for strong fuel efficiency in your older Silverado. This will assume you don't do much towing, or that you are not filling the bed up with 3000 pounds of stuff. I will keep in mind you have a 2.73 gear, and assume you have a 235/75 15 tire, which is 29 inches in diameter. This is for a proper build, that covers the engine top to bottom.

You need to maximize torque, minimize friction and pumping losses, and consider thermal management.

Starting with a good 5.3 core, if you have the option of an aluminum block, it will save you 150 pounds, maybe more, over the stock 1987 drivetrain. The weight savings helps your fuel efficiency goals. But, since iron blocks are most common, that will do for this.

The Gen III and IV blocks have some form of bay to bay breathing in the crankcase. I have seen bored holes and cast in windows of various shapes. You can improve on this by detailing the crankcase. Softening sharp edges, putting a radius on the lower edge of the bores, basically what a lot of people do when they port heads. There is quite a bit of air moving down there, and this could help reduce pumping losses by a percent or two.

You should use a flat top piston, and deck the block for zero deck clearance. An OEM replacement hypereutectic flat top piston for the 4.8/5.3 is perfect. The pistons should be installed at .0015-.002 piston to wall clearance, which is a lot for a hypereutectic but will minimize skirt friction. Set the ring gaps appropriately, along with all other clearances on the bottom end. Make certain the cam bearings are good.

Do not port your heads. Assuming you have a 706 head, do a proper valve job. Do put a back cut on the intake valve. The exhaust valve seat cut should be about .010-.015 lower than the intake. The exhaust valve margin should have a radius (Ferrea has this), the intake should have a sharp chamfer. Make sure the guides are all good and the stem to guide clearance is perfect. This is often overlooked! Deck the heads to get approximately 59-60 cc chambers.

You will need a Cometic head gasket with a 3.91 bore, that is .036 thick. This gasket, with a 60 cc chamber on a zero decked block with .020 over flat tops will give you right at 11:1 compression. This is a significant increase, and will give gains to torque as well as fuel efficiency.

For a cam, you want a 114 degree lobe separation angle on a 5.3 with 706 heads. Considering your goals, and your vehicle gearing, you want about 30 degrees of overlap. This will give you 258 degrees of duration @ .006 tappet rise. This is a very short cam. Cylinder pressure will be high, therefore torque will be good. It should be installed on a 112-113 intake centerline. A good lobe with these specs will get you approximately 200-204 degrees @ .050. With the 11:1 compression, this cam will put your dynamic compression at 9:1.

This cam will not need much valve spring. Good OEM springs will work here, and keep friction down because they are not very stiff. LS7 lifters will work perfectly, as will stock rocker arms. Use the appropriate length pushrod. The OEM LS2 style timing chain is very good, and if possible run one that isn't too tight. Do run a chain damper. A standard volume oil pump, with a lower pressure relief valve spring, will be perfect.

The stock truck intake makes good torque where you want it. Ideally, you want headers with 1 1/2 inch primary tubes as long as possible. Such headers probably don't exist. Most companies sell 1 3/4 or 1 7/8 inch headers. Those are way too big, it seems bigger is better syndrome has infected header choices. If you can't get 1 1/2 inch primaries, 1 5/8 would be a reasonable compromise. You will have to talk to some header companies and see. I think you should run a full 2 1/4 dual exhaust system with real mufflers, like large case Dynomax or Magnaflow.

You will need a fuel system that can maintain pressure at, or just above, the max fuel pressure recommended for your injectors. This will better atomize the fuel. You need a very efficient cooling system, and will want coolant temps around 200 to 220 degrees F. Not less. This may require a cooling system pressure over 16 psi. Give this careful thought, you don't want the engine too cool, yet you have a high compression ratio and cylinder pressure is significant.

I assume you will probably use the 4L60 trans, which is fine. This should be tuned to have a lean idle and part throttle cruise. You will need to find a tuner that knows a 13:1 air fuel ratio is not lean. At idle, you might want afr of 15-15.5:1 or so, and as lean as you can stand at steady state part throttle cruise.

Some other things can help, like a smaller, lighter, low stall torque converter, running 36-42 psi in the tires, an aluminum drive shaft, and an electric cooling system fan.

These details add up significantly. This type of build is unconventional for many people. Careful attention must be paid to tune, cooling, and engine assembly. If anything changes, I would probably suggest some different cam specs. For example, a 243/799 head would be a different cam. You might also consider your driving habits.

The same concepts of this build can be applied to many engines, including your old 350. Some people might prefer to build a 312 cubic inch Gen III engine from a 4.8 for max fuel efficiency. But, that's a separate conversation.

I agree with everything there he says. A lot of that seems like a dead given to do. I'm no expert on valve timing though, so I'd take his word for it. I also have zero experience with aluminum driveshafts, but if he recommends it, then they must be ok.

https://www.ecotechalternators.com/

[freebeard]

Your halfway to the sixteenth post.

Radius the exhaust valve and chamfer the intake is really getting into the weeds, but given the outflow and inflow it might make sense.

[Solarpowered]

Well I figured an engine builder would get into the weeds some. And would know all the little tricks the layperson wouldn't, when it comes to the engine itself. He said lower rotational mass isn't worth enough to go chasing it down, and to focus efforts elsewhere. Because you'd spend $3,500 or more just the gain 0.3% fuel economy. Not even a full 1%

Still be fun for me to try if money was no object, but that ain't the case so yeah I'll just do what he says.

[Isaac Zachary]

Originally Posted by Solarpowered

Well I figured an engine builder would get into the weeds some. And would know all the little tricks the layperson wouldn't, when it comes to the engine itself. He said lower rotational mass isn't worth enough to go chasing it down, and to focus efforts elsewhere. Because you'd spend $3,500 or more just the gain 0.3% fuel economy. Not even a full 1%

Still be fun for me to try if money was no object, but that ain't the case so yeah I'll just do what he says.

Exactly! When I rebuilt the 1972 Super Beetle engine I spent a lot of money on a few things to improve efficiency that I wished I hadn't afterwards. I got a solid 30mpg during the break-in period. But some of the things I spent a lot of money on didn't really seem to help in the end. Namely, a much larger oil cooler and modified cooling shroud, a plate with holes in it to put under the carburator, "1974" double heat risers to the intake manifold instead of the common single heat riser, and a weighted pulley wheel with the intent of taking some weight off the flywheel.

What did seem to make a noticeable difference was installing an O2 sensor in the exhaust and being able to adjust the carb to get leaner air-fuel ratios at low loads while not going lean at high loads (this actually made the engine run cooler, not hotter like some claim). I also increased the compression ratio to 10.0 (yes! in an air-cooled engine!). I took some builder's recommendations on what cam grind to get, and got one that was both claimed to be better for fuel economy, throttle response and would work with the 10.0CR. I also make the engine have a small quench. I installed hypereutectic pistons.

But the biggest difference was getting the timing down. I ended up buying an electronic programmable distributor I could hooke up to a computer and have an entire load/RPM map. There were areas I could hit 50° advanced and see improvement.

I look back and laugh. A 10.0CR lean running 50° ignition advanced air cooled engine that never pinged or knocked, the complete opposite of what most laymen people would recommend. But I got these ideas from actual builders who knew what they were talking about. The only problem was that then the engine ran a too cool even with a stock thermostat and an added oil thermostat.

[freebeard]

Originally Posted by Solarpowered

He said lower rotational mass isn't worth enough to go chasing it down, and to focus efforts elsewhere.

This comports with John Karcey, the OG Mileage Motor builder. He went with a stock flywheel and 50lb Jaguar crankshaft pulley. On my build, I just added a Gene Berg 8lb pulley and a Type IV oil cooler in the stock location.

It's been sitting on the bench for years. Now that I'm past my EV conversion phase, I think it will go in the Superbeetle instead of rebuilding the stock (130,000 mile) motor.

[cRiPpLe_rOoStEr]

Originally Posted by Isaac Zachary

I also increased the compression ratio to 10.0 (yes! in an air-cooled engine!)

A guy from Bahia who used to own a buggy told me 14.0 was the limit for a VW air-cooled block.

[Isaac Zachary]

Originally Posted by Solarpowered

Well I figured an engine builder would get into the weeds some. And would know all the little tricks the layperson wouldn't, when it comes to the engine itself. He said lower rotational mass isn't worth enough to go chasing it down, and to focus efforts elsewhere. Because you'd spend $3,500 or more just the gain 0.3% fuel economy. Not even a full 1%

Still be fun for me to try if money was no object, but that ain't the case so yeah I'll just do what he says.

That's what I was trying to say. Rotational mass is a certain percent of total mass, and it's only a loss every time you brake (because using a bit more fuel to spin it up isn't a loss as it's stored energy that can let your vehicle either coast longer or help it up a hill). But braking is only a certain percentage of your driving. So say rotational inertial mass is 20% of total inertial mass, and you reduce it 5%, but you are braking and losing 30% of your energy throug braking, then even at those extremes you'd be gaining only 0.3% efficiency... Not great really.

You're better off slowing down earlier, as you get the same effect.

Originally Posted by freebeard

This comports with John Karcey, the OG Mileage Motor builder. He went with a stock flywheel and 50lb Jaguar crankshaft pulley. On my build, I just added a Gene Berg 8lb pulley and a Type IV oil cooler in the stock location.

It's been sitting on the bench for years. Now that I'm past my EV conversion phase, I think it will go in the Superbeetle instead of rebuilding the stock (130,000 mile) motor.

I put a Type IV cooler on mine, but even by drilling and blocking passage ways so I could install an oil thermsostat, it still ran too cool.

I also put on a generic brand (Bugpack??) weighted crankshaft pulley. It ran very smoothly, but I'm not sure if the weighted crankshaft was all that necessary. ??

[freebeard]

I tried a CB Performance Magnaspark ignition. Now the Magnaspark II

After a year It was corroded from ozone or something, sent back to the factory for a refurb ($$$) and it didn't help it. Went back to 009 with Hall effect sensor.