Building an Engine for Mileage Input

[dqami]

Hi guys,

 

newbie here. I'm looking to buy a pre '75 pickup so I don't have to worry about smog here in Cali. I was wondering what would be a good setup for building an engine for high gas mileage (30 mpg+) and performance for little $. I will assume a 5 speed tranny would be a minimum.

 

I've really been enjoying reading this forum. I've had a 620 KC, 720 KC, a 521, and a 510 in the past and look to come full circle now.

[Bleach]

mileage and performance don't mix. You have to focus on one.

 

My suggestion is an engine swap. Small displacement, and efficent factory fuel injection. Its hard to find that in RWD form though. I had thought if I did the same I would find a CA16DE from a 1986 Pulsar. Those engines can be mounted to the RWD transmission from a 200SX (CA20e).

 

You can drive it and track your milage. Then swap to a 4.11 diff and see if that improves your overall economy.

Your acceleration will likely still beat out a stock L20b.

[dqami]

I should be more specific since 'performance' is a relative thing. I want enough power to get up steep hills or pull a load w/o the engine straining. Not looking for drag performance.

 

I was reading where someone put a 210 head on an L block for mileage but couldn't get any more info when i did a search. If anyone knows more about this swap, I'd like to hear about it.

[420n620]

if you do need a 210 head, I might be willing to sell it, just not to sure of as yet. where you located at.

[datsunaholic]

Here's what I have:

 

In my '76 Rustbucket I have an L18 with a U67 (L20B) head, Weber 32/36 carb jetted for a 1.4L B210, tall carb adaptor, and a '82 280ZX 5-speed. I have the front end dropped onto the bump stops to reduce drag (tail end is unchanged so I can still carry a load of engines and whatnot in the back). I get 30-35MPG, 32MPG is my normal, commuting average, and that's carrying a couple hundred lbs of extraneous crap in the bed (I really should clean it out, I have 2 flywheels, 2 spare tires, and a wagon hatch back there).

I don't have any major extra electrical loads- no amplifier (heck, all it has is the original AM radio), original 35Amp alternator, radiator fan is clutched, etc. Just the fuel pump and electronic ignition. No A/C, no air pump. This is pure function, creature comforts don't exist on this truck.

 

 

On the freeway it's fine but I can't out accelerate anything. It'll do 70+ no problem once it gets up to speed. 1st gear takeoffs are sloooow... that's because of the 280ZX close-ratio 1st gear. But in 5th it just ticks along at freeway speeds, well under 3000 RPM.

 

 

I would think a 210 head, with its tiny valves and ports, would be worse for mileage because to make any power it would have to run rich to make up for the lack of air. And it would be starving at high RPMs.

[Bleach]

in theory the smaller vales and ports in a head would improve velocity and torque.

Its hard to say what the new ideal rpms would be tough. If it improves power in the 1000-3000rpm range vs the U67 head then your gas milage should improve if you cruise in that rpm range.

30+ mpg is great.

 

The 210 head came on the L16. I dont' think you'll get gas milage improvements by putting that same head on a larger engine. Stick to the smaller engine if gas is a concern. Leaning the carb out will help low to mid rpm power and it'll run out of power at higher rpms where you seldom go if you're driving easy.

[ggzilla]

Here's how Nissan created the 50 mpg (yes, 50!) Datsun 210 way back in 1980:

 

* Large engine (they used A14, not the optional A12A)

* Large valve head

* Smallest port head

* overdrive 5-speed

* 1.5" exhaust (same as all other A14s)

 

Presumably the camshaft was lower RPM that other A14s. The carb was smallish, but not smaller than others.

 

With EFI you could easily beat that ... but I can't think of an RWD Nissan engine smaller than 2.0 liters.

[Bleach]

well, smaller than 2.0 liters is the CA18DE and CA16DE. That's why I suggested the 1.6L CA16DE. They are FWD and can be fitted RWD easily.

[dqami]

Hey Datsunholic, that sounds pretty good for mileage and will probably be the setup I'll go towards. Is there any benefit to putting the L18 or L20 head on the L16 and will the L series engines fit on a 520 or only from the 521 and up?

Thanks for everyones input.

[datsunaholic]

1973 L16s had the same head as the '74 L18, which breathes better. I wouldn't run a L16 for economy in a truck, though- it's power range is higher up in RPMs, so running a big overdrive to get the RPMs down won't help at all, as you may end up downshifting all the time. My Mom's '73 got a whopping 18MPG with that L16, though having a 4-speed and 4.88 rear gears is part of the reason. I only run the L18 because that was what was in the truck when I acquired it- the 5-speed went in because I had to change the clutch so why put a 4-speed back in- gas mileage was a bonus and I just ran with that when I added the Weber. It got maybe 22-24MPG before all the changes, but hard to tell as it was unreliable before the Weber and EI ignition. It may be possible to get 30+ out of an L20B because it has more low-end torque. I get 25MPG with my 4X4, and it has a smog-head 1980 L20B and a Weber (and a truck 5-speed). However, the 4X4 didn't have big differences from the 4-speed/Hitachi days. Highway mileage improved, but city mileage suffered.

 

I've seen L-series engines in a 520, but it's not a bolt-in swap. The frame mount locations on the L520/L521 (through '69) wasn't the same as the PL521 ('70+), so some welding is required. Plus the 520 nose is shorter.

[datsunfish]

I have a mileage setup on my 620. It is the 210 head on a l18 block. I run a pertronix with ngk plugs. a weber dfav using all the smallest jets I had around. Sorry no specifics there. Dogleg 5 speed and a 436 rear(or whatever the one is between the 411 & 488).Its a bit slow but not too bad.

I do believe the 210 head creates better mileage since you need far less accelerator pedal for a normal take off. Also a smaller cam. It also hauls a lot of weight without having to lay into it.Basically I have it were I can dial it in by the smell of the exhaust. If it smells rich just a little turn of the carb screw and it smells like normal exhaust. Which leads me to believe it is jetted perfect for the application.

I also have a long tube header with 2 1/4" exhaust ran into a 2" normal can type muffler. It would probably be even better in the low end if it was 1 7/8".

I get 30 mpg easy and that is with about 450 lbs in the back. Longblock z24 and tons of other crap I just started cleaning out. And a canopy missing the front wall that surely created wind resistance.

I recently learned that the 210 head has a smaller cc size than all the others so this would create a higher comp ratio on the l18.

I like it.:cool:

[racerx]

Yep mileage and performance don't mix, like water and oil..even our L16 with a 32/36 weber, lucky to get 25 mpg...if anyone else tells you otherwise they are stretching it. I've had 4 Datsuns 2 wagons and 2 510s and always tuned rigth and no major mods...most I got was like 25 mpg. Carbs are not fuel efficient like fuel injections. It don't matter much if tune it right you can only do so much with carb set-ups.

 

Remember back in the 70's if cars got 25 mpg you were king! for ful efficiency. Today the norm is like 32 mpg and even 48 mpg with the Prius. So be honest with your self, do you want performance or MPG. If you want to save gas buy a moped, you wll get easy 65 mpg.

[datzenmike]

Another big thing that limits mileage is weight. Gas only contains a finite amount of energy. That energy won't move a 620 as far as a 510 (all things equal but weight) Most of it goes into getting up to speed, only to loose it at the next lights. That's why highway mileage is better even though you are pushing against more air resistance. It takes 4 times as much energy to only double your speed.

[OL YELLER]

73 620....L16 w/w53 head, actually no other mods, except for the "hardbody" rearend from an "89 Nissan ..(no i don't know the particulars, as the swap was made by Cal mini Truck in pomona)...but anyway back to the real reason for my long winded answer/text.....I drive this truck everyday (4 days a week) 90 miles round trip each day, and my mileage is a very honest 32 MPG. No Bullshit, no crap, REAL WORLD...I keep the oil changed regularly, air filter too, the Hitachi is top notch, It does have a EI dizzy ('79 matchbox).. Oh and even though I am a "granpa" and "old Man", I do not drive below the speed limit to get that mileage, I use the fast or second lane always, my commute is freeway and not without many tie ups on my way home each night (Datsun Dreamer can tell ya the 60 freeway is no fun at 2:30 p.m. weekdays, huh Jason?)...just my usual 2 cents guys, sorry for the rant...

[banzai510(hainz)]

my 521 gets about 22mpg

i drive slow now and try not to use the 2nd barrel

 

32 mpg is good

that rear end swap must be the ticket and maybe a stock carb.

[dqami]

Hey Ol Yeller,

 

that's pretty good mileage from an L16, especially driving in stop & go on the 60. Is that running a 5 speed w/ the different rearend?

 

I picked up a 71 521 that has an L16, 4 speed, weber 32, and a cherrybomb exhaust. Running the stock dizzy but has a CDI unit hooked up. Runs good but on the freeway, it's really buzzing at 65 mph. I'm sure the glasspack doesn't help. Definitely needs a 5 speed or higher rear end gears. Maybe I'll check where you got your rearend done and see what they say.

[racerx]

32 miles per gallon seems kinda high..

 

here check this out...and as you see the ones that get mid 30s' are hybrids!

 

 

http://consumerist.com/consumer/cars/top-10-most-fuel-efficient-cars-311974.php

[SHADY280]

mike brings up a very good point with weight. also look into the tire size, running stock width, and maybe a taller tire will yeild a better mpg. also keeping them at the manufater's max reccomended pressure will help lots, ive seen ppl losing nearly 3mpg just from improperly inflated tires. now as for my z car, i get 23mpg, and i have 255 width tires on, stock is 195. that cant help much. i have stock fi maxed out for fuel input and 10.8:1 cr. if you really want mileage, run megasquirt fuel compter and can tune it for exactly what the engine requires. you may want to spend the money and buy a wide band o2 sensor to tune it perfectly during your personal cruise speed

[datsunaholic]

32 miles per gallon seems kinda high..

 

here check this out...and as you see the ones that get mid 30s' are hybrids!

 

 

http://consumerist.com/consumer/cars/top-10-most-fuel-efficient-cars-311974.php

 

Today's cars weigh a LOT more than our 1970s Datsuns though. My King Cab has a curb weight of 2650 lbs. A 2007 Prius weighs 2890 lbs... OK, that's only 240lbs more, but it is more, and my truck is several feet longer. It's all those "Must Haves" that modern cars have- A/C, power windows, power locks, comfy seats... and the safety equipment- Air Bags, shock-absorbing bumpers, reinforced doors, soundproofing, etc. All adds up. With todays materials you could easily build a 1500 lb 5-seat car the size of a Corolla, powered by a 1000cc engine that could run at freeway speeds with ease. But it'd never meet NHTSA crash requirements, and it wouldn't be particularly comfortable OR quiet. Remember the ORIGINAL Geo Metro? Folks really did get 50 MPG out of them- I know someone who still has his, keeps it well maintained (which is critical with those 1.0L 3-cyls) and he still gets that. But when the 2nd Gen Metros came out, the mileage was in the low 40s, and by the time the line ceased they were high 30s at best. Why? They got bigger and heavier. In the roaring 90s, 1997-1999 when gas prices dropped BELOW $1.00/gallon HERE, in the land of the highest gas taxes in the nation, even Joe Schmo who flipped Burgers at McD's could afford to gas up the Chevy Suburban Subdivision. It became a matter of personal pride how many cupholders your SUV had. I went to the 1999 Seattle Auto show where they had a 2000 Ford Excursion... 10 cupholders (it had 9 seats). I guess that's not as ridiculous as the 7-passenger Honda Odyssey with 15 cupholders, but still... Anyway, gas mileage standards went out the window.

 

I really do get 32MPG out of that old rusty heap. I work 50 miles from home- commute ALONE is 100 miles a day, and I don't just commute- I go to the store, the bank, the drive-thru, the post office, all on weekdays too. I fill the tank every other commuting day so that I don't push the issue, but I HAVE gotten 3 days commuting on a tank and still didn't get 11 gallons in it. Normally I put between 6.5-8 gallons, after having run between 210-260 miles. But as I've said before, I'm running a 32/36 VERY lean- it's jetted for a 1.4L B210, and I'm running a L18. It's right on the verge of pinging all the time.

 

Back in the early-mid 90s I routinely got 35MPG out of my '78 510 hatchback, and that was hauling around 100lbs of dead A/C systems under the hood and a disconnected air pump. Hitachi carb, and a stock dogleg. Heck, the bugger passed emissions with the smog pump belt off- when the compressor seized in 1994 it still had to go through smog biannually. That was documented- I tracked every fill up. I was commuting the 60+ miles from Seattle to Bremerton, on basically wide-open freeways. It's doable. But I couldn't coax 20MPG out of my Mom's '73 620 on those same trips.

[datsunfish]

I really dont give a shit what other folks think. I dont make up random facts about my vehicles. My L18 with 210 head DOES!!! get 30+ mpg even with alot of excess weight in it. The low end power is far more noticeable than before. I can maintain speed up hills in 5th gear without having to open the secondary. The less you actuate the accelerator pump the less fuel dumped in. I took off the carb yesturday to swap out for a dgv so I could use the dfav for my vw and the intake was super clean. They almost always seem to be black or varnished. I will do an actual mileage to fuel reading when I get back to daily driving it.

Datsunaholic makes great points. I have talked to some other pro auto techs and they agree that if we could use todays technology with yesturdays manufacturing standards we would have super high mpg with waaaaay better power output. Emissions and safety standards reduce mpg and add extra weight.

[racerx]

I don't think nobody is accusing you of lying...I've had a lot of 4 cylinder cars: Honda CRX 85', Datsun B210, 2 Datsun wagons, 2 Datsun 510s, 73 and 76 Capri, 73 240Z, dodge colt vista wagon, and 75 Celica and the best MPG was the Honda CRX. I got like 38 miles per gallon. The Datsuns I was lucky to get 25 miles per gallon, specially with the 32.36 weber. I actually think that the stock carb was better gas mileage but not performance. All of these cars, I've disconnected the AC and smog and a couple I practically stripped the inside and I kept them tuned, still nothing better than the CRX.

[ggzilla]

1990 Honda Civic Hf: 58 mpg

1980 Datsun 210 mpg: 50 mpg

 

It is possible. Why aren't people asking for cars like this now?

[datsunfish]

If I am right(which I may not be) I think the reason jap cars and trucks actually got popular in the US in the late 60s through the 70s was there was a gas crisis back then. Right?

It is mostly a fluke I found this mileage in my 620. I went with what I had to keep her going and it worked out good. Also something I havnt heard of anyone else doing.

The dgv is "supposed" to get better mileage than the stock hitachi. It has larger power potential and smoother throttle response so you dont have to pump as much fuel to acheive the same actual speed. I personally like a nice hitachi on a l20b. Rips about the same as a dgv but a weber is easy to R%I and work on in the vehicle. Just cut the secondary spring down. I also made a mechanical linkage once that worked great but I lost it.

[Duke]

1990 Honda Civic Hf: 58 mpg

1980 Datsun 210 mpg: 50 mpg

 

It is possible. Why aren't people asking for cars like this now?

 

Because people want their cars to have all the modern features a.k.a. power windows, locks, seats, etc, etc...all of which add up to more weight. I can only think of a few new cars that weigh in at around the 2000lb mark (Lotus Elise/Exige...not sure what else) and those are performance cars!

 

IMO, the vast majority of new cars are overweight bloated pieces of shit!

 

Back to the original topic, I would agree with Bleach in that a motor swap is most likely your best bet. EFI will help a lot in terms of fuel economy.

 

Another thing to consider when thinking fuel economy is aerodynamics...something our cars/trucks just plain suck at.

[rbastedo]

Interesting read - giving me some ideas for sure.

 

Today I filled up - somehow it just works out I have to do that once a week.

I commute & I drive it for pleasure and for trips to the store etc.

 

This morning - 6.6 gallons.

 

I really have to rebuild that carb, it's pretty nasty - I know I could be getting more out of it.

 

:)