Ways to increase the efficiency of a GM 5.3L
 

Hi all, I wanted to stop by and ask about ways to increase the fuel efficiency of a GM 5.3L v8. My old 5.7L 350 is worn out, and I want to replace it with a more modern, better engine. It will be going in a 1987 Chevy Silverado.

I don't really trust junkyard engines, so I'm going to have a reputable engine builder put the 5.3L together for me. So why not have him use parts that increase efficiency? Here's my rough list of things that may increase the fuel economy of the 5.3L engine.


1. Lighter connecting rods
2. Better roller rockers Aluminum
3. Lighter crankshaft? Aluminum
4. Good oil cooler with thermostat
5. Good trans cooler too, also with thermostat
6. Electric water pump
7. Electric fans
8. Electric power steering?
9. More efficient alternator
10. High flow oil pump with bigger better filtration system
11. Canceled - Bad idea.
12. Lighter better flywheel?
13. Aluminum or carbon fiber driveshaft
14. Long tube headers and good exhaust system
15. Floating pin pistons
16. Internally balanced. The crank itself is balanced, and does not need a harmonic balancer or balanced flywheel? Seems like less rotating mass if no harmonic balancer
17. Cancelled - bad idea
18. Better pistons and rings somehow?
19. The usual heads, cam, and intake upgrade - if this can increase efficiency
20. A "tune" for fuel economy
21. E3 spark plugs
22. Upgraded ignition system?

I tried posting this earlier, but I think it glitched and didn't post my thread. Hopefully two threads don't appear.

Windage tray, else dry sump.

Thanks! Wasn't sure if they came with that from the factory or not. I'll add it to my master list. I'm hoping I can manage to squeeze out 5 more MPG just from modding the engine itself.

Also the ones with question marks are things I'm not sure of. In case anyone wants to chime in with info on whether or not that item could increase fuel economy. For instance, I'm not sure if there are any lighter pistons that would increase efficiency. One would think that forged pistons pack more material into a smaller package. Thus increasing the density, and increasing the weight.

How do we know what #11 and #17 are?

Also ported and polished heads with three-angle valve grind.

Those two were just bad ideas and stuff I don't want to do, like over inflating the tires in an attempt to squeeze out more. Stuff I'm really not all that comfortable with.

As for the cylinder head thing, that's something I haven't really been able to work out well. You can port and polish, but where is the stopping point? There must be a sweet spot somewhere, and if you go over that, now you have to spray more fuel.

But there comes a point where you increased power by doing that, and thus you might have increased efficiency somewhat.

I don't remember having ever seen aluminium crankshafts. Since it's way softer than both forged steel or cast iron, most likely it won't be up to the task.

That would outperform anything else on that list.

1. 2. 3. and 12.

Aluminum parts that are under high stress will not last long. I'd forget about aluminum cranks, connecting rods and rockers unless you're ok with replacing that sort of stuff every year or so.

You could do titanium rods, but not worth it in my opinion. Those need to be very well designed and treated so as to prevent galling.

In the end, I don't think 1. 2. or 3. would be worth lightening unless you're trying to make a high revving racing engine. But for fuel mileage you won't notice a difference IMO.

You're best bet is a lighter flywheel, which is what you'd want to do before trying to lighten anything else of the rotating assembly. But whether a lighter flywheel will help or not depends on one thing: are you going to be accelerating and decelrating a lot? A heavy flywheel won't noticeably hurt fuel mileage if you're just going to get on the highway and cruise. But around town a heavier flywheel takes more energy to spin up and then releases more energy spinning back down.

4. 5. 6. 7.

These are great ideas!

8.

Have you seen the thread where someone took an A/C pump clutch and put it on his power steering pump? That way the power steering could be turned on and off as needed.

9.

Nice idea.

10.

How is this going to help fuel mileage? I'd say just change your oil regularly (every 3,000 miles or 3 months for your engine) and use a good filter and good oil.

14.

I saw an interesting idea for unequal length headers for a crossplane V8. There are also 2 into 2 headers that accomplish a similar idea. I wonder if you could make them long enough (depending on your RPM goal) to connect the two end cylinders of one bank with the two middle cylinders of the other bank to create 180° firing order manifolds...

The problem with a crossplane is you have firing interavals of 270° 180° 90° 180° on each side. That 90° space between the two cylinders means you have one cylinder starting it's exhaust cycle while another is still in it's exhaust cycle on the same exhaust manifold. That means more back pressure for those cylinders.

Or you could try to convert to a flatplane crank and have all 180° firings on one side, but then you'd have a secondary imbalance.

16.

This is a great idea. Dynamically ballancing with the pistons and rods is best. A crossplane crank cancels out primary imbalance of the pistons by means of counterweights.

18.

Hypereutectic pistons hands down! These are lightweight and expand less than any other aluminum piston letting you build with tighter piston to cylinder tolerances, so less blowby and less friction. They are also less conductive to heat so they keep more of your heat in the engine, kind of like with ceramic coatings.

I'd go with good cast iron rings too for best wear.

20.

Man! There is so much you can do tuning, I'm going to have to get back to you on that! Tuning is where it's at!

Dont forget a block girdle when doing boring. I slao prefer perfect circle or no gap rings and spending time matching fits to mating parts.

Three angle valve grind is pretty straightforward. Porting and polishing is a black art, at least it was in the mid-1950s.. Rough finish in some areas prefered.

Today we have extrude honing.

It's not just the weight. It's mainly the clearances. Forged pistons are stronger (good for racing applications) but expand more. Therefore you need greater clearances, therefore the pistons rock and slap more, therefore you get more friction and wear.

Here's an example:

https://www.youtube.com/watch?v=rN2ND_FPnUA

Intakes are more about keeping the fuel atomized. Rough can be better because of that.

Usually your best bet is getting OEM stock heads and getting the valve seats cut right. The company that build the original engine probably did more testing and research than any aftermarket company. If you want great atomization you need to do a lot of work. Wetflow is a lot of trial and error, something probably not worth the extra 5mpg.

https://www.youtube.com/watch?v=f8XG9T8v-ng&t=7s

https://www.youtube.com/watch?v=BFypM7ADAA0

https://www.youtube.com/watch?v=lcxp9ufC1DY&t=5s

Simple Aerodynamic mods would out preform that entire list.
No aluminum crank shaft, not even single cylinder engines use aluminum crankshafts.
The 5.3L connecting rods are already as light as they can be. After market will tend to go heavier and stonger.
The 5.3 manifold is already very well flowing. The only way you might be able to improve on it noticeably is go with ridiculously long tube headers optimized for cruise RPM, which means they will end up being like 8 foot long primaries.

Exactly! Unless this is used at low speeds only.

One note about intake flow, unless it's a diesel, your greatest restriction is the throttle. Unless you remove the throttle or at least drive around with it wide open, there's no point in reducing intake restriction and increasing flow. Your best bet is an intake that keeps the fuel atomized, and that's all that really matters.

With number 13 I'd have to ask at what point would it be better to just get a different truck? I mean, it's one thing to tune the carb and advance the timing. It's another to pour thousands or tens of thousands into an old truck.

With number 16, a good balance will never completely remove all imbalances in a crossplane V8. But it may be good enough to not need a harmonic balancer.

And if you managed to lower the total rotational mass of the engine by 10%, well that's 10% less power needed to start that push, every cycle. So ideally the computer would detect this and spray less fuel. There's all manner of varying opinions here, but all these 1 and 2% increases add up. In the end, if you were able to squeeze out a 25% gain in fuel efficiency from the engine, I'd call that a big win. Even if it were quite expensive, if you're going to drive that vehicle for a very long time (and many of us are) then it will still be worth it. You'll eventually reach the point where the fuel savings have paid for the cost of the changes, and everything after that would be money saved.

As for the aluminum or carbon driveshaft, it sounds like you may be thinking they're more expensive than they actually are. An aluminum driveshaft is an excellent upgrade to any old vehicle with a cult following, like the 73-87 "Squarebody" chevy trucks.

And to reply to several posts at once, yes of course aerodynamics, tire pressure, the driver's foot pressure, etc ad infinitum are also important. I kinda took that as a given.

The rotational mass or inertia is only part of the total inertial mass. So if you lower the rotational inertia by 10%, but rotational inetia is only, say, 20% of total inertia, then you only saved 1%.

The drive shaft also doesn't have a lot of inertia, even if it has a lot of mass. That's because 1. it usually spins slower than the engine, at least when starting out and 2. its mass has a small diameter, not a large one like the flywheel or the wheels.

I could be wrong, but I read somewhere that around 80% of the rotational inertia is in the flywheel. That's why you usually start there before reducing other things.

Aluminum also doesn't fatigue well.

But yes, every little thing adds up. However, there are things that may help only a fraction of a percent, and other things that would be better to put that money towards and get you more percents. Tuning each cylinder for fuel and spark would be one of those things.

No wonder some newer engines are either getting rid of the throttle at all, or only keeping it as a quick vacuum provision for brake boosters. And since most throttle-bodies are electronic nowadays, sometimes it's possible to have a remap allowing the throttle to stay wide-open at a broader RPM band.

Sure, and I'd like to know what that list is. You said aluminum flywheel. I have heard somewhere that they do "wear out" and need to be replaced eventually. But what about that harder aluminum? Maybe not cost effective in this case. All the racing guys seem to love aluminum driveshafts. So it would at least be good for a bit of power, if not actual fuel economy gains.

Back to this list of proven mileage increasers, maybe low rolling resistance tires should be considered. You'd just wait until your tires were worn out and had to be replaced anyway.

Is there a master list for typical internal combustion engines somewhere on this forum? Seems like there would be something like that by now.

I did find more efficient alternators:

Well I can't post a link.

I didn't say aluminum flywheel. I take it this is a stick shift?

At any rate aluminum does wear down from fatigue in something that's constantly getting "bent" back and forth. For surface wear there are ways to extend it's life if it's something like a flywheel that's not going to be flexing back and forth due to it's shape. Nikasil coatings come to mind.

One thing to keep in mind, and what I'm trying to say, is that racing guys will use aluminum, but they're not after longevity. Some races you rebuild the engine and replace important parts after every few races, or even after every race. Aluminum does last a long time for some parts, like pistons. But I'd be weary about things like a drive shaft.

Low rolling resistance tires are a good idea for fuel mileage.

Yes, but maybe not as in depth as you want. The 65+ Efficiency Mods button up at the top of the page is that list.

Cool! I think you have to be on the forum for a certain amount of time to get the privledge to post links.

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.

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/

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.

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.

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.

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

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.

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. ??

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.

I had a digital Magnaspark. I'm not sure they still sell it, but they still sell the Black Box that does basically the same. I wish now I would have stuck with a 009 and just added the box somewhere. I could get a stock fuel pump on with that wide Magnaspark distributor, nor did it look stock with the rest of the engine (like the Oil Bath air filter).

I wonder if it would be possible for someone to design a "Rolex" precision vacuum/mechanical distributor that's just as accurate as anything digital (with the exception of knock detection).

Not a distributor properly said, but some guys in Argentina did some makeshift capacitive-discharge ignitions which worked like that. Plus side is it was better than a distributor when it comes to weatherproofing.

If you do waste spark on an aircooled, you need 2 crank triggers and use the distributor to steer the spark or you could use 2 systems and get that style of precision sans the distributor

One thing worth mentioning as it could (???) pertain to any old two overhead valve engine would be adding a second sparkplug per cylinder. I don't know if or how you would do that on a small block Chevy, but it would increase flame speed and therefore efficiency.

This is something that has been done on Type 1 VW engines with good success.

Reading through this thread, I'm largely in agreement with Isaac Zachary - reducing rotating mass is going to have a negligible effect on economy. As long as you manage that inertia productively, it isn't a loss.

The areas where you'll see gains are in reducing parasitic losses, and to some extent, things that increase thermal efficiency. Some tricks modern engines use, in no particular order:
-Elimination of belt drive items (e.g. fan), electric power steering
-Variable displacement oil pumps
-Variable displacement water pumps
-Higher compression
-Low friction coatings
-Low tension piston rings
-Atkinson cycle
-Reduced displacement

Maybe you can get away with a highly efficient V6 that makes similar torque/power to an older V8?

Isn't there also an inline 4 cylinder that would work? (or you could take all the pistons out of one bank on a V8?)

I'd be concerned about the 4's torque - it would require a different rear-end, and likely there isn't a 4 that bolts up to the existing transmission. A modern 6 can out-torque an older V8. But, it's certainly worth considering. A 4 is far more efficient than a V6.

I'd be concerned that a V8 with a bank removed (or even just two cylinders at the end) would have terrible balance and would vibrate a lot.

I actually have some experience with extrude honing, and it's got nothing on plain old hand porting. Extrude honing is a very expensive service and the process doesn't remove a lot of material. Forcing a media thru a port/runner is not going to re-shape the port/runner for better average flow as if you were hand porting it. The media removes more material in areas of high flow better than areas of low flow which is not effective when compared to hand porting. At best, extrude honing can save a bit of time for the hand porter. But he's still going to have to go back in and get everything that extrude honing missed, which will be quite a lot.

I think there are two things to consider.

1. What is the intended purpose of the vehicle (not everything needs a lot of power and torque)
2. What is possible with a 4 cylinder? There are 3 cylinder engines now with over 300hp (I think there's one with 600hp IIRC). I'm sure getting 150 or 200hp out of a 4 cylinder is perfectly possible. But could you get that and better fuel mileage and not cost a lot?

The V8 to 4 cylinder idea would require a lot of work, that's for sure. For one you couldn't use a crossplane crank, you'd have to use a flatplane crank. And yes, even then the thing would not be balanced for only 4 cylinders.

And there's no need to port. Just as was said that you want small (but long) exhaust primaries, you want small (but long, if possible) intake runners. The same with exhaust and intake ports.

Intakes and exhausts are not an "open it up and you get better flow" type system, although the majority of people seem to think so. Air, fuel and exhaust are constantly speeding up and then being forced to stop. This creates pressure waves (harmonics) that bounce back down the runners to the plenum and then come back. If things are way off, including too big, you actually get less flow in and out of the engine. The lower the RPM target, the longer and narrower the intake and exhaust should be.

Nice smooth intake ports can also lead to more fuel condensating and accumulating on the port walls. A rough surface should, in theory, help keep more fuel in the air.

It seems a lot of folks think even the classic 7.3:1 is too much, and will lower the CR down to 6.5:1 or around there. Then they also enrich the snot out of the carburetor and run very low advancing distributors like the 009 (no load advance) as if they're trying to keep the engine from blowing up or melting down.