carburetor small block Chevy 350 fuel mileage....

[hermitjohn]

The 1973 version I owned in a pickup never impressed me with power or its lousy hiway fuel economy (8mpg).  Forever colored my opinion of that engine though I know it was improved in 80s when it became the GM corporate V8 and most of the other division V8s quietly faded away.

Now I had a 71 Buick with that division's 350 which was long stroke in a 4000 pound car.  It got 22mpg on long trip.  I always gave credit to it being a long stroke engine whereas the chevy and most other make V8s were short stroke.  But have been reading about small block chevies online and wondering if the real difference was that the Buick engine was a pre-pollution era engine.  It wasnt detuned to meet arbitrary pollution requirements.  73 and 74 were particularly nasty years for this, just before catalytic converters entered picture in 75, letting car companies tune for bit more power and mileage.  Not pre-pollution era power and mileage, but better than the detuned cars.

I ran across this post:

To be honest if you rebuild the motor to almost orgional specs and drive the car easy you will get pretty good gas mileage out of old technology. I rebuilt the motor on my 63 impala with a 327 back in 82. The motor was built to 300HP specs. I have a 600 CFM holley carb and only 2 years ago converted the ignition to pertronix from points. Also I see another post in regards to small valves, this car has the 2.02 fuelie heads on it. The car has a M20 4 speed and 3.36 rears. I have over 150,000 miles on this motor since I rebuilt it. This car wieghs with me in it almost 4,000lb. When the care is driven easy not stomping on the pedal the car will get 15-16 miles around town and on the highway she will gets between 21-22 miles cruising at 70-75 mph. One time on a trip from NY to Rhode Island with 3 passangers the car got 23 1/2 miles to the gallon. Also I take this car to the track from time to time. While by no means a fast car, it still runs in the high 14's. To sum up what I am saying is that if you don't go crazy on the rebuild and drive it with some common sense you will get a great return on mileage. As for fuel injection and the overdrive transmissions while there is something to be had out of that there is the cost factor, is it going to bring you that much in return of mileage to pay for itself in the next 5-10 years.
Another example of good mileage out of stock equipment is a own another boat a 59 ford galaxie with a 292 and a 2 speed automatic all stock and it gets even better mileage around town no less than 16, while highway is about the same.

 

This quote is from a thread here: www.hotrodders.com/forum/67-camaro-327-rebuild-gas-mileage-help-137498-2.html by some poster named cowbay.

A 327 is close enough in size to a 350 to make me wonder a bit.  Now most "hotrodders" seem focussed on most horse power at like 6000rpm.  What makes a race car doesnt make for economy in car driven on street that never tops 3000rpm in its lifetime.  In street car its all about most low end torque, top end horsepower is irrelevant.  Least not by any mature driver unless he is racing on the track on weekends in same car.  So if you have crazy loping cam and way oversized carb, and numerically high rear axle, you would be truly lucky to get 10mpg.  And betting it wouldnt be much fun to drive on street either.  A cam and carb and exhaust sized for high rpm driving, dont have lot torque at low rpm.

I am just curious what various people on here got for fuel mileage with small block chevies over the years.  I have heard when they were first introduced in early 50s, in like 3500 pound car with manual transmission and an over drive the 265 could get honest 25mpg driven conservatively.  I had a worn out '67 pickup with a 283 and three speed manual that got around 15mpg, but it wasnt geared for economy and like say was pretty worn out.  Very reliable though, engine so loose, it would easily start at minus 30F without being plugged in.  Then that '73 pickup with the 350 that got 8mpg.  Nothing at all pleasant about driving it.  When it finally threw a rod, I replaced it with a pre pollution Buick 350 and mileage miraculously doubled to 16mpg.  Same automatic transmission, even same 2bbl carb.  Again at time I thought it was all because the Buick was a long stroke engine, but maybe more that it was a pre pollution engine.

[Cabin Fever]

1970 2WD Pickup with 3.42 rear end: about 15 mpg highway

1985 2WD Suburban with 3.08 rear end: 18 to 20 mpg on highway

1999 4WD Pickup with 3.42 rear end: 15-16 mpg highway (this was the last year Chevy put the 350 in a pickup)

Current vehicle in a 2008 4WD crew cab with the 5.3L V8 and 3.42 rear end. It automatically calculates mpg. With 100K on the truck, the average is 18.3 mpg both city and highway combined.

[hermitjohn]

Thanks. I got into this as a thought problem cause the much smaller V6s in Ranger/S10/Dakota frankly dont do much better than 18mpg on a good day. And they are computer controlled up the wahzoo. You'd think with all the complex control freak computer technology they should have hiway mileage in the 30s not the teens! So that guy I quoted saying he gets better mileage with simple carb V8 in similar weight vehicle (yea still not sure when compact pickups got to be 4000+ pound), makes you scratch your head. I knew that old pre pollution Buick 350 could do it (good luck finding one of those), didnt know a Chevy 350 could. By way that old Buick LeSabre had 3.08 rear in it and bit more torque down low because of its long stroke, but otherwise... I mean I had to seriously concentrate to keep speed down, it was very easy to look down and be going way too fast. Never got a ticket, though only pure luck. Still it was burdened with TH350. Guy in the quote had four speed muncie. Back in days before automatic overdrives or even lockup torque converters, it made lot difference.

Anyway made me wonder best mileage one could get with one of those Hecho En Mexico small block 350s they sell brand new as replacement crate engine for $1500.... If one was tuning it for maximum low end torque and fuel mileage rather than mild hotrod engine. They are basically 70s era version of the 350 with the pollution heads, but slightly better cam. From reading think there are more efficient cams for low end torque though maybe not significantly so??? Be nice to have cam that puts all torque at low rpm and is all done by 3000rpm. Also means you can use small 2bbl and small runner intake like used on old 265/283. You dont some big honkin carb or high flow intake, to go 3000rpm. You just arent flowing that much air through the engine. And you simply dont need to go over 3000rpm with large OHV street engine.

[hermitjohn]

Yes noticed you can get an adjustable timing chain set for a SBC. No gouging a new groove in timing gear with a file and hacksaw. You advance valve timing three or four degrees, and it can improve low end torque quite a bit. But you really need to properly degree the engine to do this. That is nice thing about SBC, its not a particularly great engine, just that its traditionally a popular engine so aftermarket parts are abundant and cheap. Lot easier to modify. I suspect at least first generation SBC will even fade away soon enough. Time marches on. And younger generation are convinced carburetors are old and evil and the cause of all ills.

[hermitjohn]

Found another 350 mileage post:

'72 Nova, 3.08's, 4-speed, 350, 8.5:1, OEM Q-jet, L-82 camshaft pn3896962, points ignition w/40* mechanical advance @ ~2500rpm + 15* vacuum advance, factory dual exhaust, pretty much stock ride height, 235-60-14 radials w/~36psi.

Years ago when the motor was fairly fresh, it got a best of 23.25mpg (highway), but would consistently get 21 or 22 if I kept my foot out of the gas. Around town, more like 15-16.

This quote from a jimfulco from www.hotrodders.com/forum/making-chevy-350-v8-more-fuel-efficient-119904.html

Is interesting both that the two high mileage cars both the 327 with 3.36 gears and the 350 with 3.08 gears had four speed manual transmission and .... and both nearly stock pre-pollution era cars, not modified to any great extent. Though think '72 Nova more like 3300 pound so lighter weight car though it had 14inch tires instead of 15inch so effective axle ratio very similar.

[hermitjohn]

Its a bit like pulling teeth to get good info on setting 350 up for economy, not high end horsepower. There are some wannabe hotrodders that resent any serious discussion of setting up a 350 for gas mileage ( attitude of just buy a prius if you want economy...). Guess there are some people anymore that get seriously offended by anything done differently than they would do things. I dont get it, if somebody wants a race engine, great, go for it. Jeesh... but dont rain on those that dont want a race engine.... or a Prius! Not sure how they expect one to get sheet plywood in that Prius they recommend...

One can buy an exact reproduction of the 300hp 327 cam that keeps popping up as cam in SBC that get good mileage. Or there are other not too radical aftermarket recommended cams for the stock Hecho En Mexico 350. Nobody particularly likes the cam that comes with it. Its relatively low compression engine which makes lot difference apparently. One guy said if you want to keep warranty and not replace the cam that comes with the engine (this voids the warranty), to just advance the stock cam 4 degrees with an adjustable timing chain set. Course you only get the warranty if you put it in GM vehicle that originally offered a 350, so if this is not the case, then doesnt matter.

Ran across one guy claiming 20-25mpg hiway in a 1974 C10 with a TH350. I am bit dubious on that claim. Rare minority if he actually gets that without slipstreaming a semi and also significant tail wind at same time. But he did say he originally had built the engine with huge Holley and racing cam. It sucked gas. Said he got married and it became a daily driver and he needed economy. Tried several cams, finally went to the 300hp 327 reproduction stock cam (the one people keep mentioning gives good economy) and a stock Quadrajet off a 305 so runs just bit on lean side. Also changed rear axle to 3.55 gears so engine didnt have to work as hard moving from a stop. This actually helped mileage compared to taller gears that were in it. This is a pickup with apparently larger than stock tires, so similar to a stock vehicle with maybe 3.27 gears I suppose. Anyway the details gives his story some believability though even 20mpg in a full size pickup with a 350 and a three speed automatic is somewhat of a too good to be true kind of story.

I am still wondering how this pre-pollution GM cam would compare to one like Sum-1100 meant for max low end torque... Guessing the mild Summit cam would be better for vehicle with overdrive that keeps rpm low. Otherwise maybe the 300hp 327 cam better for non-overdrive where engine will have to run higher rpm for hiway speeds, still shouldnt have to go over 3000 rpm. Be interesting to run both and see which did better for economy. You never see that kind comparison done, just see what some dyno shows for max horsepower at 6000rpm.... Meaningless on the street. No sane person wraps engine up like that on street unless its some motorcycle engine meant to run that kind rpms in order to have any power. And if he does, he wont do it more than few times or he will blow the engine. Engine has to be built special for that kind of abuse.

[lilith]

First, Great topic! A little rough about bashing the circle trackers and hotrodders, but I've taken harder hits coming for the checker flag and rubbing is racing right?
To my knowlege, there isn't really a stock 350sbc out there that can claim close to 20mpg pre tbi. The great thing about the sbc/gm motors is that a majority of components are readily available and interchangable! For like the last few decades! And with a little drilling of the intake manifold, some good porting, and a bit of silicone gasket maker, thoes tbi heads flow great under a Holley 4412 - imporoving our fuel useage on the track by over half (and still won races and a championship).
To answer the Chevy/Buick riddle, it wasn't the longer stroke that have the Buick better gas mileage. It is the surface area of the piston. Buick 350 has a slightly smaller bore in the cylinder, thus a lighter piston, same combustion chamber and cubic inch, same friction on the rings, same (comparable) power output, less mass to move resulting in better use of the fuel supplied. The longer stroke is how they achieve the same displacement in the cylinder with a smaller diameter piston.
There are hundreds of ways to decrease your spinning mass all the way through your build, engine to tires, and this is one step in getting better fuel mileage. Us racers and hotrodders May be out to achieve power and speed without paying much attn to gas mileage, but asking the right questions like how to reduce spinning mass will get you pointed in a good direction. Many of our builds will run fantastic at low speeds and rpms with the right timing and cam. Hell, my mom drove her worn out 2.3 Ford race motor back and forth to work at 30+mpg after we changed the head, cam, & carb and dropped it in her daily driver ... For the next 4 years.

[hermitjohn]

I personally havent seen any V8 except those pre-pollution Buick 350s top 20mpg. The pollution era Buick 350 was more like 12 to 14mpg. So thats not answered by piston size. They used a less efficient cam and played with timing and lower compression in 70s.  Buick 350 ended along with the 70s.  Also did find multiple mentions of late 60s SBC327 topping 20mpg in cars, especially the manual transmission ones.  So thinking there isnt that much difference except cam and most likely the 327 came from factory with higher compression.  Compression lowered in 70s to meet pollution requirements.

Another rather amazing V8 was the AMC 360. I owned two of the 70s era big Jeep Wagoneer/Cherokee with that engine. One got 16mpg and the other 14mpg, but this is with FULL TIME 4wd. Had another older one with that Buick 350 (when Kaiser owned Jeep) and it was part time 4wd but didnt get any better mileage. Course I dont remember axle ratios and all. No doubt the older one had more aggressive axle ratio as fuel mileage wasnt as important in 60s.

Anyway maybe some day be forced to try out theories in practice as SBC might be only carb engine available. Already the only factory new carb street engine available. After dismal fuel mileage in 1994 Ranger I bought with computerized 4.0L V6, a carb V8 properly tuned couldnt be any worse.

[hermitjohn]

It still bugs me the fuel mileage of V6 in Ranger, even after I have it livable, basically 12mpg city and 16mpg highway. Reasonable for a 4200 pound vehicle. Its the heaviest of Rangers cause it came from factory with extended cab and 4wd. Previous owner had made it 2wd but left the heavy front axle.

The old carb V8s got this kind mileage and sometimes better. Plus lot more power. Course the OHV 4.0L V6 when treated well, can go 400k+ miles before a rebuild. Thats its big claim to fame and one that deserves lot respect. Few of the old carb V8s made it to 200k.

Anyway reading more about Buick 350 this morning. Surprisingly the 70-72 version had a relatively aggressive cam as standard. All of them not just some high performance models. the 66-69 cam less agressive and lower fuel mileage, though early high performance versions did have higher performance cam. The pollution cams by late 70s were tiny with much worse fuel mileage, made specifically for best emissions. But it gets more interesting, the original pre-pollution Buick cams had unusual lobe curve compared to most engines. And the heads had unique design. This wasnt just a variation on SBC technology. Their downside, oiling system left lot to be desired, though this pretty well fixed by late 70s just before it was discontinued. The early Buick 350 tended to self destruct by around 90k miles unless you replaced bearings and redid the oil pump before this occurred. I had enough experience with them to have figured this out personally. Actually best of the GM V8s for durability and reliability was the Oldsmobile rocket V8s, even the early ones. Lasted forever with some care, had high nickel content in castings and good oiling system, but got Chevy small block kind of mileage.

No you cant get a reproduction of that 70 to 72 Buick cam unless you hire it custom ground. Assuming your cam grinding person can get exact specs. Closest is the Federal Mogul replacement cam that is probably more like the 300hp SBC cam from late 60s.

Speaking of that you can get reproductions of that 300hp SBC cam for first generation SBC, but the Summit 1101 cam is so darn close to those specs and so much cheaper, that would be the way to go.

This is still rather interesting to me and kinda like to experiment. But seriously no more than I drive anymore, fuel mileage, long as its at least in double digits, isnt that important. Nor is power. So spending money to tinker on such not that useful. Be just for amusement. Though I still think you should be able to have either power or fuel mileage. Mediocre power along with sucky fuel mileage and very complex engine management you cant tune yourself, not great option. That old 71 Buick I had makes Ranger seem like a slug, plus it got better mileage. Can only imagine what that Buick would got with a manual overdrive transmission. Big old boat of a car, so great on long hiway drives but kinda sucked in town trying to park it. Hard to believe it was same weight as the Ranger.

[hermitjohn]

I had gotten into a discussion with a guy determined to get 20mpg out of carb engine in his 70s C10. He tried a crate 350, a junkyard 305, and a crate 4.3L. All with TH350 with no lockup and no overdrive. Rear was like 2.73? Seems way tall for working truck but whatever.

Said he got 16 to 17mpg out of all them. He didnt change cam or recurve distributor so stock Chevy pollution cam. With the 4.3L he did hit 19mpg couple times. This is an adult person driving sanely looking for good gas mileage.

This has gotten me very curious if I could tune a full size half ton with carb V8 engine to get better mileage than my 4.0L Ranger. To refresh memories, after repairing plastic air tube between maf and throttle body, it gets around 12 city and 16 hiway with manual transmission. Weighs 4200 pound, as much as traditional half ton, but narrower profile.

Not really needing another vehicle, remembered the old 1976 Dodge D100 with 318-V8 that I bought cheap at auction in 90s, drove couple years until automatic started slipping, and parked it out back. The engine best I remembered was still good. But its set 20+years.

Looked it over and body is ugly with peeling green paint the previous owner must put on with a paint brush. But its solid, no obvious rust. I pulled sparkplugs and put ATF in cylinders. It turned with socket on crank, didnt put up any fight. Pulled valve cover and its a remarkably clean engine, no sludge. Odometer says 34k, but assume thats 134k.

I do remember the best mileage it got was 13mpg. Nothing unusual for V8 pickup, especially carb engine. Did lot googling and about best any did with a carb 318 was 15 to 16mpg. Nearly all with automatic. The one 3spd manual version (three on the tree) I ran across claimed he regularly hit 20mpg. But he was only one. Another said when Chrysler lean burn system on his still worked he too would hit 20 occasionally. Nobody liked that lean burn system... The 318 was burdened with a pollution cam, and a Carter BBD carb nobody particularly liked. No doubt a screwed up distributor advance curve. This generation vehicle and still today were first and foremost trying to meet pollution standards above all else.

Anyway I have an old Dodge granny four speed transmission bought cheap long ago for this truck, I intend to put into it now. I really, really hate an automatic in a work truck. Want an automatic, buy a car, though for most people anymore their pickup is their car, just a sedan missing its trunk lid. And found interestingly that the 360 from same era had a pretty efficient factory stock cam. No idea why the difference in cams between stock 318 and 360, but its 203/203 at 050 cam, single pattern, and big upgrade for the 318. I found new one on ebay, seller said he got it at estate auction. Got it $40 shipped. Have to buy set lifters and new timing chain to go with it, just on general principles. I might slightly prefer a dual pattern after market cam but one I want isnt that different and whole lot more expensive for the Dodge engine version. Remember that Chevy cam I mentioned in prior post, its 194/204 at 050, and was considered most fuel efficient cam for street SBC. By way Ford used very similar cam in mid 80s 302 on the Crown Vic. They were 3700 pound car and got low to mid 20s gas mileage on hiway with 3.08 rear. They had just transitioned to throttle body injection so had some freedom to choose a more fuel efficient cam for couple years in there. The last 302 used as optional engine in Explorers in late 90s, though roller cam, was similar profile.


www.vinny.us/archives/298  Link to blog by guy that had 1984 Crown Vic with TBI and that good factory cam.  No doubt this would be the 3.08 rear.  There was optional 3.55 rear for towing, mileage topped around 19mpg set up that way.  Interesting thing, this guy converted from TBI to 2bbl non electronic carb from 70s due to age and cost of parts for the TBI.  Used a HEI Chinese aftermarket distributor and got rid of computer.  Doing so also got rid of the overdrive on his AOD transmission.  Still got 22 to 24mpg highway.  

[fordy]

..........This whole discussion makes me wonder if the 5.3 (323 ci.'s) is a kissin' cousin of the 327 ? And , if yes can a fuel injection system off a 5.3 be made to work on a 327 block ? Surely , there are programmable parameters that could be fine tuned to optimize fuel milage on a 327 ! , Just wondering ? , fordy

[hermitjohn]

Jun 11, 2018 21:50:50 GMT fordy said:

..........This whole discussion makes me wonder if the 5.3 (323 ci.'s) is a kissin' cousin of the 327 ? And , if yes can a fuel injection system off a 5.3 be made to work on a 327 block ? Surely , there are programmable parameters that could be fine tuned to optimize fuel milage on a 327 ! , Just wondering ? , fordy

I dont think they are related, meaning parts not interchangable, but I am just not that familiar with engines from this century.

Oh there lot ways to fuel inject a carburetor car.  There is a Holley kit (think its holley) to convert 2bbl Holley carb setup to two injector throttle body setup.  The throttle body just bolts on in place of the carburetor. You can use the vacuum advance distributor like you did with carb or the computer that controls the Holley throttle body can also control distributor advance curve.  You can program your own advance curve.  There also other brand ignition boxes that can do same, starting at $200.  Anyway the Holley setup is nice in that the computer learns as you drive, no having to program it on your own.  Some people like them.  Around $800 for the 2 injector version.  I think lot more for the 4 injector version and be pointless for a street engine.  This is just the kit, dont think it includes high pressure fuel pump and other necessities.

Of course there are other ways if you want port injection.  But fancier you get the more it costs.  Well unless you can adapt junk yard parts.  Injection been around and almost universal for long time now.  There is also the cheaper Megasquirt system, it gives you complete freedom to set things up way you want, but not for faint of heart, its all trial and error, it doesnt automatically tune itself.

If I had a 327 in good shape I would imitate that guy with his 1963 Impala that I mentioned and quoted in an earlier post.  I get strong impression he is telling the truth.  4bbl Rochester Quadrajet carbs by way had good rep for being fuel efficient if you didnt open the secondaries.  I personally like the Ford Autolite 2bbl carbs, think if you dont go overboard with venturi size, they are quite efficient.  Using an adapter I have one of those on my F250 with 300-6.  The Carter 1bbl on that particular engine gave me no end of hassles, odd since I had no problem with the Carter on other 300-6.  The Autolite 2100 just works.  I tried different venturi sizes.  Found for the 300-6, it did best with the 1.02 venturi.  One on there is off a 1959 Ford Fairlane that had 292 Y-block.  I am thinking of trying same carb on the Dodge 318 when I get to where I want to try for gas mileage though I will need an adapter.  The Jeep people that like old Ford carbs for their 258-6 like the one with 1.08 venturi though betting they never tried the 1.02 venturi version. The 1.08 version got so popular with Jeep people, getting hard to find a cheap one.

[hermitjohn]

Here is a link for that Holley 2 injector TBI  conversion system.

www.holley.com/products/fuel_systems/fuel_injection/sniper_efi/sniper_2300_2bbl/parts/550-849

I still dont think its by any means a cure all.  Injection when working well makes cold starts and warm up very pleasant.  But I wouldnt expect any great improvement in fuel mileage, maybe  upto 10% over a well sized and tuned carburetor.  Cam makes lot more difference in fuel mileage than carburetor.  In other words unless you drove the wheels off your car, doubt you would cover cost in fuel savings very soon.

[hermitjohn]

While we are at it with the electronics, if you have carb vehicle and want to keep the carb, but want precise control of distributor advance curve, there are now magic boxes that just do that. Two cheapest I found:

www.cbperformance.com/product-p/2013.htm

Here is long thread discussing this one. www.thesamba.com/vw/forum/viewtopic.php?t=606203&postdays=0&postorder=asc&start=0 Its sold by a air cooled VW parts place, but its a universal ignition control. Works on 4, 6, or 8, except odd fire V6. Oh its $200, cheapest I found.

This one is $300: www.retromotioninnovations.com/ I like software much better on this one. You can download the software and run it before buying anything.

Prices go up from there. As I mentioned the Holley TBI system has this ability already built into it. Just saying these magic boxes make a custom advance curve whole lot easier than playing with springs. All require the distributor to be locked and any built in advance system disabled. Watch the video on the retromotion site where they tune in advance curve while driving the car. Better if you have helper manning the laptop I think. But they can do much more accurate advance than you can ever hope to do with at home with a spring kit. If you want to come close without electronics, you will need a shop that has machine for this.

[Jolly]

Owned a 73 Buick with a 350. Even with the pollution stuff it got 17-18 and would chirp the tires going into second gear. But the car that surprised me the most was my 1947 Buick Super with the Straight 8. Car got 20mpg, and would run on 75 octane if you fiddled with the carb (according to the owner's manual). That hunk of steel would run 100mph, with a backseat big enough for four people.

Shame it ate waterpumps.

[hermitjohn]

Those old straight 8 werent most robust critters. Pretty cool engine though and surprise any younger person when you open the hood. Two of best engines from 50s were the Buick nailhead V8s and the Chrysler flat head sixes. That nailhead such good engine they made kits to put it in things like Ford pickup. It wasnt a race engine, but it was truly long lasting one. Other good engines of course. I liked the Hudson 308 flathead six. But not plentiful. Hudson was small company. Still wouldnt mind having a smaller displacement nailhead but think that ship has sailed. Anymore just be an expensive rebuild for no good purpose unless you are restoring a period car. Same with the Hudson. Time passes.

[hermitjohn]

I was trying to remember the size of the Buick straight eight. Apparently came in variety of sizes over the decades from 221 to 345. Dont think I have ever seen 345 straight eight, assume it was in their top of line luxury mobile. Probably very heavy engine way engines were made back then. But guessing by your year and gas mileage, you had the 248.

[Jolly]

It was less than 300, IIRC. This is not my old car, but it looks almost (same bodystyle and color) like it:

[hermitjohn]

Looks like that pic of a 71 LeSabre disappeared above. Here is one that matches color I had. It was a big ole boat, but comfortable out on hiway and as say on long trip, 22mpg.

[Jolly]

Wife had a blue 72. I had several Buicks (Dad worked for Buick dealers in one capacity or another from 1953 to 2010). I had the 47 (my first car, had 46,000 original miles when I got it in 1974), a 73 GS, 66 Wildcat, 68 Riviera, 80 LeSabre, 84 LeSabre, 93 Century, 92 Ultra (supercharged V6) and a 2001 LeSabre. Only the 84 was new.

[hermitjohn]

Frustrating but interesting. Not all in the cam. I ran across replacement stock cam for the Ford OHV 4.0L. One gave the specs. It is 189/206 at 050. This for the manual transmission version and most automatics too by mid to late 90s. When automatics had own cam, it was bit wimpier. Federal emissions, California engines had their own cam and it didnt give specs.

This is in that sweet spot for fuel mileage. Only nobody got great fuel mileage with these. Some OHV 4.0L occasionally break 20mpg with the lighter 2wd 5spd Ranger and Explorer Sport , but even that wasnt common.

There also is no way to know how the ECU is programmed. No doubt its for emissions first and fuel mileage secondary. Ford secret. And wasnt any carb version of this engine that you can actually tune yourself.

Lot other V6s by other manufacturers that didnt do whole lot better put in the heavy mid size SUVs and pickups of 90s and up. Whole lot heavier than the compacts from the 80s. Takes more fuel to push around all the extra weight. Thuogh 4.0L whole lot better engine than its 2.8L and 2.9L ancestors used in first generation RAnger.

At least the 4.0L has some low end torque. Its similar feel to smaller plain vanilla carb straight six from earlier eras. The 2.8L, which I have lot experience with, sucked as pickup engine. Euro engine that was really designed to make power at higher rpms, though in Ranger they put in a cam that didnt let it rev very much so it just truly wimpy with extremely bad fuel mileage. No matter what I did never got over 13 to 14mpg and struggle maintaining 40mph on small hills. Didnt change out cam as the only aftermarket cams for it were pretty aggressive plus they were very expensive. Doubt mileage would have improved, but might at least had more power.

[Jolly]

Anyway you can change out to an aftermarket manifold and go to a carb?

[hermitjohn]

Jun 17, 2018 12:36:59 GMT Jolly said:

Anyway you can change out to an aftermarket manifold and go to a carb?

Nope, there was no aftermarket manifold for the OHV 4.0L and no carb version.  It never had a distributor. And it was only used for ten years and only in Explorer or optional engine in Ranger.  They Explorer/Ranger went to the SOHC 4.0L in 2000s. They also used it in some Mustangs for few years.  It got slightly better mileage, but had the stupidest most expensive complicated timing chain setup I have ever seen.  Two timing chains, one on front of engine, one on rear.  You had to pull the engine to replace rear chain and it was EXPENSIVE just for the parts if you did it right and replaced everything.  Replacing the chains is required about every 100k miles.  The block is still about same as the OHV engine and holds up well.  The OHV 4.0L had traditional OHV type timing chain and you didnt replace it until you rebuilt the engine.  Unlike every other OHV engine I have ever seen, it just didnt stretch or wear out.  Was cheap to replace if you ever did replace it.

Thing is you could put a 302 in there and get at least same mpg and had lot more power.  All 302 could be converted to carb.  The only claim to fame with the OHV 4.0L is that with regular maintenance and no abuse, it could last 400k+ miles before a rebuild.  That deserves a LOT of respect in my book. In that same 400k miles you probably replaced the light duty 5spd twice or the automatic four or five times.  When you see a OHV 4.0L with super high mileage it nearly always was in vehicle with the 5spd.  Those automatics were pricey and lot of rebuilds didnt hold up very well.  On internet only found one other person adapting an old granny four speed into it like I did.  He had machine shop and custom made his own bellhousing out of some heavy steel pipe. I used light duty bellhousing from 80s Mitsubishi transmission Ford used some in first generation Ranger/BroncoII with 2.8/2.9 Cologne engine. You just dont easily break one of those granny four speed trannies.  It should last as long as the engine lasts if not longer.  The weak point is that light duty bellhousing I used. There was also at one time an aftermarket kit to put a heavy duty older GM automatic into it.

I keep thinking the OHV 4.0L gets poor mileage but its not that bad when you consider the weight of Explorer and second generation Ranger.  They are bloated and many weigh near what full size predecessors weighed.  My Ranger is 4200 pound, this is what a full size V8 half ton pickup weighed in 60s, 70s, and 80s.   I was kinda shocked when I found this out.  The 4.0L in a 2wd Ranger with single cab and short bed that weighs 1000 pounds less should get 20mpg or slightly better.  

[hermitjohn]

I do think I could rig a OHV 4.0L to where it could run without a computer. But it would be desperation type thing and I doubt very efficient. Homemade intake manifolds tend not to be very efficient.

And thats why I am puttering with the 1976 Dodge, though heat probably postpone that until cooler weather. But its already got a V8 with a carburetor and I remember it never getting better than 13mpg though it ran fine until automatic transmission started slipping. Anyway its perfect to experiment with. See if I can get mileage above the 16mpg I get on hiway in the Ranger. Should be doable to get at least 16mpg, might do that just with the manual transmission I am putting in it, though whether I can hit 20mpg, not sure. I only ran across one serious person on Mopar board that claimed he regularly got 20mpg with a carb 318 in pickup. He also only person with a three speed manual, so though I still find it hard to believe, its not outside realm of possibility. I have seen darn few 70s and 80s Dodge pickups with a manual transmission and a 318. Most with manual had the slant six, which I surely would rather had. But people kept those and drove wheels off them...