Who has some real world numbers from a 4x4 with 33"/35" tires and a 440 with 400+ HP. What could a fellow expect the mileage to be on a motor of this caliber?

probably around 6-8mpg would be my guess.

Back in the early 80's, I had a '75 Ramcharger with a stock 440, 3.55 gears and 33" tires. That thing got 8 MPG whether it was towing or not towing.... Certainly was no rocket but it had nice torque. With a little more horsepower as you have mentioned and some compression, I still doubt you'd ever get over 10 MPG.

My old 86 W250 with a 440, 4 spd, 285/75/16s and 4.10s got terrible mileage. Less than 8 mpg in most cases. However, I never expected it to get very good with a 850 double pumper on it. I didn't care what it got, just as long as it ran good. If you want mileage, you need to go diesel.

i have a 78 3/4 ton with a 440 that gets around 6,it has a loose converter,4.10's and 35"tires,i use an 800 holley,10.0 to 1,nice cam ported heads,prolly makes 450-475 horse maybe.

Almost all 4wds with 3spd autos no matter what motor got 10 or less that I've seen.
I had a 400/727 3.23 295/50s and got 11.4 when driving easy and 4.6 when getting on it and it was a very mild motor. Don't plan for more than 10mph. Plus its a truck with a flat nose

10 on a good day-78 400 runs 11 with a tailwind,8 usually

My 93 Ramcharger with the rebuilt mild 440 was getting 8-10 mpg on average.

This was with a 727, 34" tires, 4.10 gears. 95% highway use. Never drove it over 60mph.

It now waiting for the remainder of a 518 OD swap.

Sounds like 7 to 8 is a pretty average number. Thanks everyone.

all though not a 4x4,my 88-440/727/3.91sg with 29x15x15 M/Ts got a flat 10 mpg.

swaped in 3.23 with a new q-jet/performer RPM intake and picked it up to 13 mpg.

hoping a 2.76 gear will net me a couple more for 15-16 mpg. then I could drive to the next town over for more gas.

I gave up on mpg in a 4x4 muself.

My "truck" (motorhome) .... was getting 12 or so ....with a TQ and Streetmaster intake(way better UPgrade from the OEM garbage) .... but later on - with a new-tech cam, head work, exh work, going from a 4.56 to a 3.73 gear and more compression(flat top pistons) it will get 16 ....and I have been challenged on that .... two people have bet me it can not be done .... so I have two bets - a total of 3500$ !

NO real trick there cf ... just keeping the MPH around 60(the MH is a pretty AERO piece) ..... and putting on a better fuel delivery combo .... that being a TQ and a StreetMaster intake. THEN playing with the metering rods

Now my 16 mpg mark is NOT going to be an average of say a trip from MI to FL ... it will be with a measured 1 gallon container ...and will be run on-the-flat.

HONESTLY .... I think that it will be closer to 18

...with the new cam, compression, SP2P intake and the gear change.

I dont see a big camper getting 16-18 if the trucks with a 318-360 barely pull that with 3.23grs. Good luck

My 78,000 mile 74' Ramcharger with the unmolested 440, fulltime 4 wheeldrive gets 9mpg. The only time I've checked it is during the cold weather. I've had a tough time not modifying the motor, I know I can make it better.Dave

Is this worthy of additional chat ?

My 1980 W150 shortbox had a 440 auto w/3.73 gears and 35" tires got 8 mpg & 1985 W350 440-4speed w/4.10s and 235/85R16's gets about 8

What are the driving conditions?

8 mpg ? ... only a from the least coast of Florida could continue dealing with those conditions!

I am up for it. But, you already know what I am up to. Was it 440 or 413 you were running to get 12mpg? That is pretty impressive for an RV.

My 413 heads are going to the machine shop tomorrow to get cleaned, magged, and shaved. Then it will be time to get after the chambers with some roloc grinding discs.

I am thinking about just doing a basic clean up of casting flash and overhangs between the port and exhaust valves. There is a BIG overhang in the runner just behind the bottom of the pressed in exhaust seat. I wonder if there would be any mileage gain from a 3 or 5 angle valve job on the intake side? Exhaust I think I want to keep the nice fat seat contact width for cooling.

It will be a while before I have any numbers with the new engine, but will get baseline gas mileage numbers with the old one this summer.

Anyone have any experience with a do it yourself ceramic coating for piston tops?

The biggest thing you can do to help a 440 is slow down the RPM either by reducing speed or gearing higher and locking the converter, higher gears don't do much if you just slip the converter more. If your building a motor than run as much compression as you can get away with, enough compression to require premium fuel helps MPG enough to cover the extra cost in fuel, any tricks to permit more compression helps also like a source of fresh not underhood air, air gap style intake with no crossover, tight quench with closed chamber heads, fully radiused and polished exhaust valves, sodium filled if you can find them, ceramic coated exhaust under the hood retard cam timing a few degrees. An 850 thermoquad (800 gets into the secondaries too much even cruising) done by someone who really knows how to tune it will do better than a holley. Very little if any cam overlap and as much lift as possible heck some 1.7 rockers on a stock cam would work great. Well tuned spark timing (they like a lot 20 idle, 40WOT 50 or more cruise). Run a 3 angle valve job on the intake to break up fuel droplets.

I know I will get flack from old timers on this but I used to always try to run smallest ports I could find for my MPG motors but eventually found out it didn't help in reality and just killed any chance of getting a few RPM out of a motor (probably the only reason they ever APPEAR to help is you CAN'T turn any RPM), actually the opposite as I have hemi heads that flow 330CFM on my 2011 ram and it can get 20 on the highway empty. I would even run a maxwedge port on that and the longest runner, matching intake manifold I could find.

Some good ideas but just a couple points.

Gearing higher in my rv build will be done with gear vendors od. I am not so sure about using a lockup converter for heavy RV or something that is towing heavy loads. I have not been able to locate a gas unit with more than a single clutch. There are modern converters being built now that stall at 1100-1200 rpm behind a 440. I think that is a better choice in terms of durability.

I am building a 440 six pack pistons near zero deck, 413 closed chamber heads with sodium valves from ma mopar. Will work out to right at 9 to 1. At least 2 points better than from the factory. Not sure what gas prices are in your area, but 93 premium here is about 70 cents higher that regular 87 at about 2.20 a gallon. When stuff was only 20 cents a gallon more, I could see making up the difference in cost. I don't see any way to make up a 30% higher fuel cost though.

Agreed on the 850 thermoquad to try to run on the primaries as much as possible. All big block intakes are "air gap" design. Maybe I should fit a tunnel ram under the doghouse? I will get the thermoquad dialed in using a wide band O2 sensor. I think I am going to put a bung in each header tube to be able to measure what individual cylinders are doing. Might be time to play with some epoxy and popsicle sticks. I know I can't get it perfect, but can at least prevent a too lean condition in one or more of the cylinders. I am going to send the headers to get jet hot coated after fitting and welding the bungs.


On a carb build, wouldn't oversized ports make for lazy flow, poorer mix, increased chance for detonation, and less throttle response? The 413 heads have small block sized ports- intake is a little taller than the intake port on a EQ head I have, and small 1.88 / 1.50 valves. Your hemi with multiport injection is an entirely different animal.

I'll be running a modern profile cam Mike Jones designed just for the 440 motorhome engines. 112 centerline, duration at 202. but .455 lift with 1.5 ratio and only 40 degrees overlap at the seat, and -19 at .050. Just my two cents, but I would rather spend the money on the cam than the rockers.

Dual snorkel cold air, polishing piston tops, chambers, and valves will be done. Heat is the enemy running a big block in an RV. Plan to run some electric fans, a triple flow radiator, and aluminum intake with the crossover blocked to try to keep it cool.

I say NAY to the blocked crossover WITH the 413 heads.

And YEA to water injection

I used to try to run the 302 casting high swirl heads on my MPG small blocks, but then one time tried the 308 milled to closed on a zero deck 318 motor and MPG jumped up quite a bit, on another 440 for a friend we swapped on some eddelbrocks in place of the 516 and mpg jumped up. A third was a 99 durango (I know EFI...) we put on a set of RT heads and his 5.9 and mpg jumped up a lot so I gave up on the small port theory (since then I have found the magnum is way happier and efficent with big ports especially in the pushrod pinch RT RHS Eddy...). I think when the piston starts sucking through a very small well designed valve curtain area (sharp valve edges, no shrouding...) the fuel is va-poo-rized and atomized as it's sucked through there very fast then as well as the high vacuum lowers boiling point of the hydrocarbons so what's happening in the port is not that important as long as it's not a flow restriction. I used to argue with my grandpa for years about how he was wrong because of port velocity when he would tell me they would maximum port a cylinder head and get much better MPG (1970s), till I started trying it myself after he was gone and found out the old man wasn't so dumb after all. I think it's one of those things that is great in theory but not reality. The only thing it (very small ports) really does is act like a governor. Use the cam timing and compression to keep vacuum very high instead of a restricted port size.

Heck even a 906, 452, 915 BB head is barely if any any better than a magnum or X head. Those 413 motor home heads are way too small.

I would seriously get a lock up converter, especially if you make a very high tq motor in a motor home with a gear vendor, non lock up is gonna generate a TON of heat in the trans and lose a lot of efficiency, then you also don't have to compromise on the stall speed you need to get that big rig moving. They are not un-reliable, I have re-built hundreds of those trannys (727, 904, a-500, 518 and REs) with lock-up and never seen any big issues caused by lock up.

As for compression, you could easily add another point maybe two if you get everything else just right with premium fuel. It seriously helps MPG, TQ, HP... I did a 318 with flat tops and magnum heads milled .030 and .029 piston to head clearance and it helped that little motor dramatically in every way (99 1/2 ton long bed ex cab with a slide in camper). That was the only mod, even put the cam, old rings and bearings back in after zero decking the block to get a true comparison.

HRD .. remember... this combo is nearly 10,000 lbs and is as AERO as a barn door

HRD I am going to build a high compression 11 to 1 340 for my challenger, but I am not comfortable building something with compression on the ragged edge for an 27 foot rv that I will be towing a car through the mountains. I am building it to run on cheap swill, with a backup plan to run premium if required at times. If it wasn't for the sodium valves, quench, and center located spark plug in the heads am not sure I would even push it to 9 to 1.

Reliable no trouble service is first goal, then followed by mileage and increased torque. Full time premium costs just don't add up to savings at any rate. Bumping compression a point or even two from 9 to 10 or 11 to one is not going to net 30% increase in fuel mileage, but it will cost 30% more (minus whatever increased efficiency realized is) at the pump.

Those 413 heads flowed enough to make 445 ft lbs at 2000 rpm in factory trim. That with a compression ratio that in reality is less than 7 to 1. You may very well be correct about the ports, but I am going to find out what this combo is capable of doing. No comparison between the 413 water pump and cooling capacity and the regular 440 stuff.

With your 318 you mentioned, any idea what compression ratio you wound up at with those mods? Guessing it was at 11 to 1 with the block decked and heads cut that much.

I don't know if I have the exact number saved anywhere but yes I think it was around 11 to 1, still didn't ping audibly on 87 octane pulling a 65 dart on an open trailer up those big passes coming out of LA in the heat. Premium wasn't even needed in that thing. Ultra tight quench really works to keep down knock. I would liked to have pushed it higher but you can't mill a magnum any more than that without getting into the intake valve seat.

My current daily driver is a 4 door 4wd ram with 6.4 SRT8 short block with eagle heads, that has very high compression also around 11.5 I think and not very tight quench but does need premium and gets 20mpg doing 75 on the highway. Right now I am building a 6.4 SRT8 long block with 5.7 eagle cam for my 2011 ram 2500, I am going to zero deck the pistons to bump compression, (already milled the heads .020 to get closer to the eagle chamber size) and quench on this one, and am running the BGE head this time (same ports as SRT8 butt with faster heat conducting aluminum alloy and sodium ex valves) this truck will replace the current 1500 and I expect nearly the same MPG.

Couple of questions for you sir. If port size has so little to do with mileage and driveability in a carb application, then why do larger port single plane intakes kill the bottom end on street motors? Again only talking carb motors here.

Also, based upon your experience would there be a difference in running .030 v/s .040 quench in my engine? I guess it would depend upon how much more piston rock my 4.35 bore short block has if I can get by with that little.

This is impossible to believe.

Why would you not block the heat crossover? Cooler intake charge is more detonation resistant right?

If you have very low compression and no chance of detonation or vapor lock then sure, leave the heat crossover, it will vaporize the fuel better. On the other hand if you are trying to get maximum efficency through very high compression then block it or it will increase the chance of detonation.

Water injection does nothing but slow the combustion process like EGR does, unless you are running into detonation don't waste your time, it will hurt MPG. Al Gore would be happy if you do as it reduces NOx emissions by reducing combustion temps. It will like more spark lead (negative work done against the rising piston) and it will also mean less molecules burned before the exhaust valve opens and further combustion of those molecules already in there will not produce any power, you want to burn as many of the fuel molecules in the chamber as possible before the ex valve opens for peak efficiency.

I would not have believed a complete stranger on the internet either so I experimented, first I had the block squared and zero decked and I re-assembled with stock heads and head gaskets, then pulled em off and ran .039 head gaskets still no sign of detonation, then the last time I pulled em I milled them till we were getting into the intake valve seat and put in the .028 head gaskets at the same time. Milling the heads I think it was around .030 made a much larger squish pad and the thin head gaskets made the really tight squish distance to maximize combustion mixing. The biggest improvement came with the combo of square decking and the .039 gaskets but I would do it all if I did another of those and probably will be doing another in a 92 dakota very soon.

Feel free to replicate my experiment and report back, my feelings won't be hurt.

I almost forgot, somewhere along the way I added a set of ford 4 hole yellow injectors after the initial square decking build when one of the stock injectors took a dump but I don't remember witch head gasket swap operation they were before or after.

I think those big single planes kill TQ more because of port length being very short and the fact they are usually on engines with very big cams, the ports on my 392 in my ram are humongous but it has loads of TQ down low.

My take ?...on the 413 industrial head WITH COOLANT HEAT ....leave it open. It’s not nearly the huge heat of the exhaust crossover

SORRY .. but water injection works ... I used it on a duallie tow rig with windshield washer fluid - it worked

Windshield washer fluid is alcohol so of course it would help. Also if you got a heat crossover baking the intake air it probably was burning the fuel in the chamber way too fast so slowing it down with alcohol probably helped keep it out of detonation. Remember not all detonation is audible.

Had to use the solvent because of the ARCTIC TEMPS !

Never was able to try it on a new build ... would have larryLOVEit to do that !

The combo I used it on was a worn out 400 with ZERO QUENCH

I should say that ole oGO is going balls out on the project

I am going to respectfully decline Doc. I am thinking worst case scenario, the engine runs hot, coolant in the intake gets fuel temps way up in the carb. Don't need gas percolating while I am trying to restart on the side of the road. May give up a little mileage that way, I don't know.. I'll be driving in warm weather and it won't take long for the engine to get to temp even without the extra heat.

I don't know HRD. I have tried torker intakes on two small blocks street engines before I knew better. Wound up being a horrible mismatch of parts and absolutely killed any bottom end. I have also put 360 heads on a smog dog 318 with similar results. I am just skeptical based on these past experiences. I have used a street dominator before with a little cam and headers and had much better luck, I suspect because it has a lot smaller runner volume than the torker. I am going to give my frankenmotor a try with the 413 heads and see what i can do. I am going to estimate 500 ft tlbs of torque from 2000 or a little higher to a little more than 4000 rpm- exactly the range where I will be using the engine. I don't see the need to spin the engine up any higher, as that torque is higher than the first couple cummins models in dodge trucks put out.

As far as the high compression build, I have followed your posts through the years since you did the mileage experiments with your old a body barracuda. If you say you ran 11 to one I am sure you did. Magnum combustion chamber is a much better layout than my 413 cylinder heads though. I am going to try to run compression up on my 340 build with some closed chamber heads- either EQ or Eddies I have not decided.

In your mileage experiments did you ever test out any type of anti reversion chamber or muffler, or try to tune header/collecter length to achieve some type of anti reversion?

The 318 with 360 heads absolutely kills compression, that's where the low end TQ goes, depending on what head gaskets you use (cheap rebuild kits are usually .054) and if you use pistons with 4 valve reliefs like most cheap replacements it is very easy to end up in the 6ish compression ratio. You need to run a 360 head milled to closed chamber and then you might as well go magnum with ports the same size as a 360 and already a good closed chamber design.

The torker was a terrible design no matter what motor you put it on, sharp angles turning into the ports causing fuel to drop out and no air gap to keep things cool.

No on the anti reversion mufflers, I don't think it would be hard to make some up (tesla valve maybe?) but I kind of doubt it's effectiveness unless you had a cam with too much overlap or something. My theory on it would be that if your exhaust flows good enough there won't be any significant reversion going on, maybe I need to try to build one for the 92 dakota.

It's not hard to make more tq than an old 12 valve, I Never could figure out why they were so popular for towing (at least in stock form), the 6.4 in my 2011 ram 1500 would destroy my old 93 12 valve in a towing contest, I just towed another 2011 1500 ram on an open trailer on a 200 mile trip and got 14.5 MPG passing 18 wheelers on a couple big passes. I did like running used oil and transmission fluid for fuel in the old cummins though, it was fun filling it with an endless supply of used oil at the honda dealer I was working at.

6.4 truck motor is a beast for sure. I wonder is there a way to use the 6.4 sodium exhaust valve in a small block magnum head?

The one in my half ton is actually an SRT8 not the BGE and the heads were milled down to eagle size 65CC (I think I ended up around 11.5 compression) and a little touch of porting.

I am trying to decide exactly what to do with my 6.4 I am building for my 2011 ram 2500 I just bought (locked up 5.7). I think I want to run either the BGE MDS cam or stock 5.7 MDS cam this time to trade a little top end witch there is no shortage of for a little more low end TQ. I have a complete BGE engine and a spare set of SRT pistons, injectors and cam to convert it so I just need to finger out what compression and cam combo I want to run (can't afford a custom or any aftermarket cam really), how much cylinder pressure do I dare run (SRT8 in current 1500 ram runs around 210-220 PSI? I am currently thinking BGE pistons zero decked (about .020 down right now) mill heads .020 and run .030 head gaskets and I should be just under or at 11 to 1 then run the 5.7 cam, SRT8 injectors and a 90 MM throttle body, that should work real good with the 5.7 stock tune but add a butt load of TQ down low. Im trying to think of it more as a bored and stroked 5.7 instead of an SRT or BGE engine. There is even a small part of me in the back of my head saying run the eagle heads for easy compression and higher velocity but the BGEs I have do use a better metal to conduct away and spread out the heat better, sodium filled ex valves and an even better chamber shape... I think the SRT pistons and smaller cam would just be too much cylinder pressure but maybe it could take it??? Honestly I always get scared when building a really high compression motor because it is a pain to go back in and lower it if needed.

I sure wish e-85 was readily available here I would zero deck it with the SRT pistons, mill the eagle heads .030 and run the 5.7 cam and really make some cylinder pressure.

I am a firm believer that most any factory engineered engine can easily take another half or even full point of compression (some even more!) but they are compromised to minimize NOX and warranty claims from people using the wrong grade fuel.

So I just got to thinking about my current combo, I ran the numbers through KBs compression ratio calculator, the 392 in my ram right now is 12 to 1 with a 6.4 SRT8 cam, if I so much as think about running anything less than premium the knock sensors start getting a little activity but nothing audible. I think I am gonna shoot for 11 to 1 with a 5.7 cam in the new 392 for the 3/4 ton, basically an SRT8 with a smaller cam.

HRD do you work at a dealership? Judging by your posts you have always seemed to have a bunch of factory mopar stuff on hand for builds

Maybe you could start a thread on your hemi build. Like you, I can't just do a simple build and I try to make something better than the factory did.

I would be interested in reading more about your hemi build. Hemi stuff is finally old enough now and reaching my price point- cheap, plus the price of a tow bill to get it home.

I used to work at a dealer years ago, I run my own repair shop now butt just knd of ended up a dodge specialist after that first dodge job. High efficiency stuff has always interested me, not just MPG but decent MPG with some power also. I started onto the high compression kick when my dad bought a new geo metro and it would get 50mpg and had 210 PSI cranking pressure and ran best on low grade fuel, I just had to know why we couldn't do that in more hot rod type stuff.

If anyone has a set of old 413 MH head bolts and push rods I could use them. Any accessory brackets as well for ps pump, alt, ac. Thanks,

Not enough info to quote accurately, but I'd guess somewhere between 5-8.

Once upon a time I had a 440 in a D200 crew cabwith 4.10s and 33" tires that would knock down low-mid teens in town and high teens on the highway. Engine was built not for horsepower but for torque and was all in by 3500 with a redline of no more than 5000. It was a pretty basic build; balanced, almost blueprinted, around 11:1 compression, performer intake, Ebrock carb, small cam, and a lot of thermal barrier and dry lube coating throughout the engine.

The 11:1 worked great where I live at 6500' elevation. It also was a beast pulling over mountain passes in the 10,000' range as well. I could pass traffic with a loaded trailer. However, it was a big problem at lower elevations. A trip to Phoenix once was detonation city and it was drinking octane boost like nobodie's business. I built a replacement for it that was down a couple points on compression and it also was down on mileage and power, but it would live at lower elevations.

In hindsight, methanol injection on the higher squeeze motor would have been a good addition to help with lower elevation issues, but I never got around to it. This engine is still sitting in my garage on a stand. I've been thinking of a larger cam to offset the high compression would be nice, and drop it into something lighter weight than a truck.

With the engine on your stand I would seriously consider retarding the cam a few or 10 degrees to bleed off compression and a little reversion back up the intake will help mix the air and fuel better, lastly it will give the burned air and fuel more time to press down on the piston before the exhaust valve opens and lets the pressure out, this is the expansion ratio and the theory is that this is even more important than the compression ratio, sort of like an atkins cycle engine.

I recently got my wife's 74 Ramcharger running & driving again after sitting for too long.

It's a factory 440 truck and the only mods are an intake off of a 71 440-4speed car, heat crossovers blocked off, double roller timing chain and melling HV oil pump. I'ts got D60/D70 axles with 3.54 gears and 33" tires on aluminum wheels. I've driven it 255 miles now and using the Fuelly App to track everything, I'm getting 6.7mpg average. Currently having to leave the hub's locked as I have not installed the MM 203 Part Time kit yet.

I drive it to Mustang Island / Port Aranas to cruise, eat, drink, get sunburnt and back. going 63mph on the highway I'm turning 2100rpm.

My 86 RC 2wd.....with 446cid with 915 heads that had gotten E-brock size valves and a 518 with 4.10's with 31's....got horrible gas mileage.

I'm about to try it with an OD833....but I'm not holding my breathe for good mileage.