[Ifitaintbroke]

Alright guys, you're in for a good one. So the joke goes, this guy has a 9000lb truck with a 460 in it, that he intends to pull a 10,000lb trailer with... and he's trying to build it for fuel economy! What an idiot!

Oh wait, that's me.



Ok. So here goes... 1986 f250, 460 (d9 block and d3 heads) desmogged, zf5 swap, 4x4, 3.55's, offy dual port, original holly 4180 carb (painstakingly rebuilt and modified), edelbrock double roller timing chain, duraspark dizzy controlled by a gm 4 pin module.

So for the question...I am considering taking my motor out and making some modifications. The transmission is already out, so pulling the motor isn't a huge deal. Here's what I'm thinking, would it be worthwhile to swap in a set of flat top pistons and have the block decked to increase compression? Setting the chain to straight up? Also, I would really like a hydraulic roller cam, but I doubt if anyone makes one mild enough for this build. My absolute bottom line is fuel economy. Any thoughts?

 

[5speed65]

I think maximizing your hp for 87 octane is the best bet

 

[Ifitaintbroke]

Could you explain further? I'm fairly knowledgeable on general engine construction, but not so much on how specific modifications directly affect performance. That's the main reason I started this thread.

 

[PSIG]

I'd analyze your needs and best options first. Perhaps this is a fight better done with a different combination? But in-general, more tranny speeds, EFI and ignition - all electronic control to milk every drop of fuel. Each of those maintain the engine in the optimum rpm range, fuel and timing for peak economy. Then, learn how to tune for economy, so you know how to tweak it while going from A to B and back, running light, towing heavy, etc. Productive use of time on the road.

 

[5speed65]

Could you explain further? I'm fairly knowledgeable on general engine construction, but not so much on how specific modifications directly affect performance. That's the main reason I started this thread.

Ported heads
Small voodoo cam
Preformer intake
Sniper
5 or 6 speed trans
small tires
Should all help

 

[Ifitaintbroke]

Thanks for the replies guys, first of all. I kind of hope this turns into one of those big threads where the whole forum chimes in with what ever experience they have.

Some more specifics though. I have already done a fair amount of small detail kind of things to help with fuel economy, but I am one of those people who can never leave well enough alone. I have already begun swapping out Ye Olde T-19 for the ZF-5. Smog equipment is completely removed, and I just recently finished what I hope to be my final carburetor choice. The carb is a factory holley like what originally would have come on the truck. The 4180 is unique in that it has annular booster on the primary side. This is definitely the most in depth build I have done on a carb. Throttle shafts have been bushed, timed vacuum port converted to manifold, automatic choke converted to manual, etc. It will be sitting on top of an Offenhauser dual port manifold.

Anyway, the main question I have is whether increasing compression will give better fuel economy. Currently, I have d3ve-a2a heads(who doesn't?), and the deep dish pistons. I believe I heard somewhere that these pistons have a 25cc dish. Combined with a 0.040 head gasket and 0.040 deck height, that works out to about 7.9:1 static compression. With no other modifications than installing flat top pistons I can get to about 9:1, with -12cc dome pistons, about 10:1. What I am asking is, how much difference will that make in real world driving? I know that theoretically high compression equals higher efficiency, but I'm not going to tear my motor down for a 0.1% increase. I also don't really want to have to run a specific octane fuel either. Any thoughts?

 

[PSIG]

I think maximizing your hp for 87 octane is the best bet

Could you explain further?

His point about octane is the cost vs benefit. In a general sense and based on many factors, an increase in the compression by 1 will net a max of 1 to 7%, while the increase in cost for regular vs premium pump gas is ~11 to 14%. You may pay more to get the higher compression performance (or to avoid knock) than it's worth.

To tag onto this, your effective compression (running) varies in operation, and your cam timing is most responsible for that compression profile. Your choice of cam will be critical for peak efficiency. Always choose your fuel first. Some choose compression ratio for the build, then a cam that works with it. Others choose the best cam profile, then build to work with that cam and fuel. The 2nd option is preferable.

Smog equipment is completely removed

Unfortunately, most tuning you read about is for power racing and street performance, e.g., 1/4-mile or lap times, not economy performance. It is a different scientific approach. Know that some "emissions" equipment actually helps with economy, and often power as well. The EGR is a good example, often thrown-in with "smog" equipment, that can add noticeable performance (economy is a performance) in areas such as cruise. Don't throw it all away until you know what hurts and what helps, or what you can use.

 

[The Mad Porter]

We frequently build engines for applications like this with 466 EFI combos getting into the 13's unloaded with OEM EFI. Working on even better with tuning via the tweecer F3 piggyback.

We've seen a couple of instances where our 425 hp 87 octane carbureted work combo with an eddy 1411 into the 13 unloaded.

Expecting a less than 8 to 1 460 with straight up timing and an optimized ignition curve to lug around 20k lbs at anything close to reasonable fuel economy with a 4180 carb is not reasonable. 5 to 8 mpg would be reasonable.

This type of application demands high throttled torque and the ability to make that torque at or near stoich while using MBT timing for reasonable fuel economy. Think godzilla 7.3. which will return 8 to 10 heavily loaded and 12 to 14 unloaded at 7 to 8 k lbs.

The 4180 is a good carburetor but can not move enough air and still keep AF at stoich at 70 mph highway cruise at 19 to 20k GVW.

Tight quench and static c/r with iron heads of about 8.8 to 1 with short cam timing and good lift, back cut valves for cylinder filling will all help to optimize for work duty. High intake runner velocity is key as well.

Our solution if budget is tight is to optimize the combination with the pistons out about .005". High 8's static and about 207 to 213 intake duration keeping intake closing @.050" to about 32 abdc.
Limited to no intake manifold cross over heat.
Free breathing exhaust with headers and a SINGLE 3 inch exhaust will make the most throttled torque and peak torque under 460 hp.
I have an old torker 1 intake with very small intake port cross section. This is an application where I'd try it.
Not a big fan of the offy dual port as it works better with the carb on backward lol.

IMO you need a bigger engine that will offer the needed torque while throttled rather than at or near WOT.

Check this designed to WORK telephone yanker out:

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Shorter cam timing or advancing the cam will concentrate the peaks even lower for 4.10's and OD.

The ability to tune the AF and timing for MBT in the cruise areas of your maps is the key to good fuel economy. A holley sniper is a good fit here.

Sometimes the larger engine will get better economy under the narrow conditions you outline.







Scotty J. "AKA" The "Mad Porter"
"EMC 2006" 3rd place finisher
Ported BBF iron head specialist & Aluminum heads from all sources.
Custom ground cams
See our products in the Vendor for sale section
Customized crate engines
ParklandAutoMachine.com
R-H-P.biz
"Parkland Performance Auto Machine" Formerly RHP
(253)-988-6648
Parkland Auto Machine

 

[The Mad Porter]

His point about octane is the cost vs benefit. In a general sense and based on many factors, an increase in the compression by 1 will net a max of 1 to 7%, while the increase in cost for regular vs premium pump gas is ~11 to 14%. You may pay more to get the higher compression performance (or to avoid knock) than it's worth.

To tag onto this, your effective compression (running) varies in operation, and your cam timing is most responsible for that compression profile. Your choice of cam will be critical for peak efficiency. Always choose your fuel first. Some choose compression ratio for the build, then a cam that works with it. Others choose the best cam profile, then build to work with that cam and fuel. The 2nd option is preferable.

Unfortunately, most tuning you read about is for power racing and street performance, e.g., 1/4-mile or lap times, not economy performance. It is a different scientific approach. Know that some "emissions" equipment actually helps with economy, and often power as well. The EGR is a good example, often thrown-in with "smog" equipment, that can add noticeable performance (economy is a performance) in areas such as cruise. Don't throw it all away until you know what hurts and what helps, or what you can use.

I've tried both with and with our EGR on my 1997 F250 HD. The fuel economy difference is in the 1/10's with poor throttle response with EGR.

In my OEM TAG0 calibration there is NO EGR timing bump relative to EGR position sensor nor is there any closed loop MPG timing or AF.
MPG mode set to open loop in the oem calibration which is off.

I've been adding timing in the cruise area of the timing map with significantly better throttle response both off idle and transitionally.
Mileage is improved and manifold vacuum increases when doing X amount of work.
So far 4* at cruise and I've added 1* in the area of the map where the engine lugs after convertor lock in 3rd gear of the E4OD. Going to add 1 more degree there at 25 to 27 MAP between 1200 and 1500 rpm.

With a simple Banks kit and tuning this truck is a completely different animal.
Where it used to hit a brick wall at 3600 rpm and struggle to the 3950 1-2 shift point with oem timing and exhaust it now will pull hard to 4500 rpm where I now have the shift commanded. The ability to hold a hill at 70 mph from 15 to 20 map or 14 to 9" HG vacuum is also improved.

Fuel command is lambda 1 to 1.07

For the OP. Installing and paying attention to a vacuum gauge is a great way to learn how hard your engine is working at any given time.
Over time you see patterns on repeated routes you take. When tuning you can see improvements in reduced loading to get the same work done on the freeway on both flat and graded repeat drive cycles.





Scotty J. "AKA" The "Mad Porter"
"EMC 2006" 3rd place finisher
Ported BBF iron head specialist & Aluminum heads from all sources.
Custom ground cams
See our products in the Vendor for sale section
Customized crate engines
ParklandAutoMachine.com
R-H-P.biz
"Parkland Performance Auto Machine" Formerly RHP
(253)-988-6648
Log into Facebook

 

[Ifitaintbroke]

_

 

[Ifitaintbroke]

I've tried both with and with our EGR on my 1997 F250 HD. The fuel economy difference is in the 1/10's with poor throttle response with EGR.

In my OEM TAG0 calibration there is NO EGR timing bump relative to EGR position sensor nor is there any closed loop MPG timing or AF.
MPG mode set to open loop in the oem calibration which is off.

I've been adding timing in the cruise area of the timing map with significantly better throttle response both off idle and transitionally.
Mileage is improved and manifold vacuum increases when doing X amount of work.
So far 4* at cruise and I've added 1* in the area of the map where the engine lugs after convertor lock in 3rd gear of the E4OD. Going to add 1 more degree there at 25 to 27 MAP between 1200 and 1500 rpm.

With a simple Banks kit and tuning this truck is a completely different animal.
Where it used to hit a brick wall at 3600 rpm and struggle to the 3950 1-2 shift point with oem timing and exhaust it now will pull hard to 4500 rpm where I now have the shift commanded. The ability to hold a hill at 70 mph from 15 to 20 map or 14 to 9" HG vacuum is also improved.

Fuel command is lambda 1 to 1.07

For the OP. Installing and paying attention to a vacuum gauge is a great way to learn how hard your engine is working at any given time.
Over time you see patterns on repeated routes you take. When tuning you can see improvements in reduced loading to get the same work done on the freeway on both flat and graded repeat drive cycles.





Scotty J. "AKA" The "Mad Porter"
"EMC 2006" 3rd place finisher
Ported BBF iron head specialist & Aluminum heads from all sources.
Custom ground cams
See our products in the Vendor for sale section
Customized crate engines
ParklandAutoMachine.com
R-H-P.biz
"Parkland Performance Auto Machine" Formerly RHP
(253)-988-6648
Log into Facebook

So, with a 4.5 stroke scat crank and 0.040 over pistons, I can get to 547ci. What do you think of a scat internally balanced 9000 series cast crank? I also found some 39cc dish pistons. With my other choices, that adds to roughly 8 1/2 on sc. No matter what, I'll be sticking with factory iron heads. Valve train recommendations? I know the stock stuff won't hold up. Also, should I have the block machined for four bolt main caps/ use a girdle? Or should everything hold up fine? What cam specifications should I go with? Remember, I am not an engine builder, so that's why I ask so many questions. Thanks in advance.

 

[PSIG]

Remember, I am not an engine builder, so that's why I ask so many questions.

My suggestion is to review the builds @The Mad Porter linked. They are proven and tested builds, that would make a solid foundation for your purposes.

It was not my intent to derail the thread with smog equipment, but I was just mentioning options and assumptions about some "emissions" stuff.

The use of EGR can be approached different ways, depending on the desired outcome. Two examples are cylinder stuffing at low-MAP cruise to increase effective compression, and suppressing detonation from that increased effective compression. Another approach can be high-output power production using EGR.

In the economy case, the increase in effective compression does not result in a large gain in efficiency, however, the combination of that—and assuming the engine and fuel are built to operate on the ragged-edge of chosen octane—suppression of the typically resulting detonation. It isn't adding timing that helps, as that is assumed to be correctly aligned at the peak-cylinder pressure point for peak efficiency already. So, instead it allows exceeding the max efficiency established with more compression without de-tuning using retard to counter det from the chosen fuel's octane, while maintaining the gains toward pumping losses (the largest gains in economy tuning).

When approaching tuning for high-power, the additional octane of CO can allow much higher cylinder pressure, effectively making an octane factory from the engine. The fuel tuning is important at this stage, producing much more CO, as CO is a high-octane fuel. This contributes to the fuel load, while also working to suppress detonation. Research by the likes of Smokey Yunick and OEMs such as Volvo have produced incredibly powerful turbo engines running on 70% or more EGR.

TL;DR - Just leaning and throwing-in EGR on an engine not optimized will show small gains beyond pumping efficiency. The coordination of the build to bleeding edge, cylinder stuffing and detonation suppression combine to show useful gains beyond normal limits. Not a flavor for everyone or every purpose, but another small tool in the quest for efficiency. Lean alone does not mean more efficiency, as it still takes X amount of energy to get from A to B. It's about efficiency and reducing losses. Start with more conventional economy tuning (very lean-burn with timing correction to MBT) for pumping gains, and go from there. We now return you to your regularly-scheduled programming.

 

[Ifitaintbroke]

My suggestion is to review the builds @The Mad Porter linked. They are proven and tested builds, that would make a solid foundation for your purposes

That's what I intend to do. My feeling got a little hurt when he told me the truth about my ugly iron heads. I have some affection for them, they've been through a lot. Trying to get a running total on the build. I'll be doing the assembly myself, and, since I work at a parts store, the machinist I use is cutting me a good deal on the work. But prices first. Might be eating ramen noodles for a while.

 

[Mike R]

That's what I intend to do. My feeling got a little hurt when he told me the truth about my ugly iron heads. I have some affection for them, they've been through a lot. Trying to get a running total on the build. I'll be doing the assembly myself, and, since I work at a parts store, the machinist I use is cutting me a good deal on the work. But prices first. Might be eating ramen noodles for a while.

Hamburger Helper without the hamburger is pretty tasty too

 

[The Mad Porter]

That's what I intend to do. My feeling got a little hurt when he told me the truth about my ugly iron heads. I have some affection for them, they've been through a lot. Trying to get a running total on the build. I'll be doing the assembly myself, and, since I work at a parts store, the machinist I use is cutting me a good deal on the work. But prices first. Might be eating ramen noodles for a while.

I've always been a proponent for the use of iron heads and they can certainly be used here as well.
Simply drawing a comparison between the results to be expects for non ported, budget ported like we do and the AFR heads on both a 460 inch combo and a stroker.





Scotty J. "AKA" The "Mad Porter"
"EMC 2006" 3rd place finisher
Ported BBF iron head specialist & Aluminum heads from all sources.
Custom ground cams
See our products in the Vendor for sale section
Customized crate engines
ParklandAutoMachine.com
R-H-P.biz
"Parkland Performance Auto Machine" Formerly RHP
(253)-988-6648
Parkland Auto Machine

 

[Ifitaintbroke]

I've always been a proponent for the use of iron heads and they can certainly be used here as well.
Simply drawing a comparison between the results to be expects for non ported, budget ported like we do and the AFR heads on both a 460 inch combo and a stroker.





Scotty J. "AKA" The "Mad Porter"
"EMC 2006" 3rd place finisher
Ported BBF iron head specialist & Aluminum heads from all sources.
Custom ground cams
See our products in the Vendor for sale section
Customized crate engines
ParklandAutoMachine.com
R-H-P.biz
"Parkland Performance Auto Machine" Formerly RHP
(253)-988-6648
Parkland Auto Machine

I understand. Some more questions. If I were to build a motor based off your plans, do you think the ZF would hold up? If I remember right, they are rated at 420 ft-lbs of torque, so this engine would be well above that. Another thing, all things considered, my best option with this truck is going to be to optimize it for pulling the trailer because it really won't be used for much else.