ZZ4 MPG Challenge

[gchemist]

1500 miles or bust!! My truck will be my daily driver for the next two weeks. I leave Austin on Thursday morning for a short vacation. I'm parking the Jimmy during my trip. The ECM is being sent to www.wait4meperformance.com for reprogramming.
The challenge: estimate the average MPG for my trip. Most of the trip will be at 70 MPH. Cruise RPM 1900-2000.
The average MPG in city driving is 13.5 to 14. Equal to the old stock 305!! Milage goes down a little due to dead stop traffic.

[MylilBowTie]

I voted 16-17 but wouldn't be surprised if it got over that. I know that's what my 350 got on the highway without od.

Are you doing an oil change or tune up before the trip?

[454HO]

So you've got a 700R4 right? Lock up convertor is working? What rear gears do you have? How much weight are you going to be carrying? Some kind of tonneau cover on the bed? Too many variables to guess accurately. And your driving style can influence the numbers dramatically. But I would guess your truck should easily be capable 18+ on the highway.

I had a '87 short bed several years ago with the TBI 350 and 700R4 that regularly got 20+ mpg on the highway. It doesn't matter how much total HP you have. What matters is how efficient the engine and drivetrain are at the cruising RPM.

[gchemist]

Specs:
Z44 350, 1406 Edelbrock, RPM Air Gap Intake, dual snorkel cold air intake, 700R4, 2500 stall lockup converter, 3.08 gears with 255/60R15 wheels, A/C, dual electric fans, and more mods than I can list.
On the first leg, I'll be carring a washer and dryer, a two tires and misc junk. No more than ~350 lbs with tools. On the return trip. Luggage only with the bed completely covered with a tonneau cover.

[boatpuller]

i'm considering the zz 350.just wondering if it's everything you expected it to be? and would you buy that engine again?

[AceX]

I'm sating 18+ due to the 3.08 gearing.

[gchemist]

Originally Posted by boatpuller

i'm considering the zz 350.just wondering if it's everything you expected it to be? and would you buy that engine again?

I would buy another off the shelf or craigslist.
I found mine on craigslist!! $1800 but gave $1900 because the kid helped me load it and unload it. The kid paid $2500 for it from a totalled mid 70's Vette. Until the tack is working, I know performance is still missing. The engine is great for a weekend warrior or even a semi-daily driver. The torque is awsome. The motor has no problems moving the truck. Even in OD at 45 MPH. The engine really needs deeper gears. 3.73 gears are probably the best for the engine. If I did it again, I would opt for the LT1 hot cam with rockers. A few more horses with the same torque curve.

Search youtube for ZZ4 videos. A guy in Europe had one in a Z-car. The car is fast.

[gchemist]

Okay, here is another wrench in the bucket. I connected the cruise control this morning! It works!! I used my dremil tool to make a small hole in the cable bracket. I did not want to take it off. The bracket is bolted to the intake.

I also repaired the windshield washer pump. I had broken off one of the connections. LMC has a kit available. Save me big $$$ from replacing the entire motor.

Temps are in the lower 80's today. Truck ran about 177-179 down the road with the cruise control on.

[gchemist]

I'M BACK!! Wow, what a trip. Rain, wind gusts and sandstorms. A few minor mechanical problems. All easily fixed. Spent $$$ on a new belt pulley, carb clip, 195 thermostat, and fuel pump. I blew the fuel pump while showing off. :biggrin:

I'll post the final MPG results later this week. Let's say if ya voted over 18+ ya got it right!!

[vern350]

congrats on the round trip and impressive MPG!!

[killthewabbit]

Nice!

[piecesparts]

Originally Posted by gchemist

Specs:
Z44 350, 1406 Edelbrock, RPM Air Gap Intake, dual snorkel cold air intake, 700R4, 2500 stall lockup converter, 3.08 gears with 255/60R15 wheels, A/C, dual electric fans, and more mods than I can list.
On the first leg, I'll be carring a washer and dryer, a two tires and misc junk. No more than ~350 lbs with tools. On the return trip. Luggage only with the bed completely covered with a tonneau cover.

I am betting on a 13 MPG (at best) run for you on the highway. I have an 84 SWB with a 383 stroker motor, 700R4 (without the lockup converter) with 3.73 gears, 295/50/15 (26.5" tall) tires, headers, dual exhaust, Edelbrock AVS carb, Edelbrock Performer RPM intake, K&N air filter, long tube headers, 2400 stall converter (due to the Comp Cam that I run), electric fans and a hard tonneau cover. I can run around 2500 RPM at 70 MPH and get 15 MPG and running the cruise module.

You are running a 3.08 gear with a 28" tall tire that will hurt you on hills and acceleration and maybe your engine will have to work a little more to overcome the OD when you are hauling weight. Your RPMs will be around 1900 or lower at highway speeds of 70 MPH and that sounds good, but it is just a little too low for efficiency in this motor with a carb. My son's 86 SWB truck was running a replacement GM 350 motor, Edelbrock 1406, Edelbrock Performer RPM, Crane Cam, headers, dual exhaust, 700 R4 (without the lockup converter), 295/50/15 tires and the 3.08 gears- he got around 12 MPG until we finally put in a set of 3.73 gears to get the RPMs up to allow for driving without lugging the engine. His mileage increased to 14 MPG and the truck has a lot of pull now. These trucks are bricks to be pushed around and they are heavy by comparison to the later models.

I have driven my truck all over the country on many long trips and the mileage has been repeatable with the equipment that I have. So I would be surprised if you get much more than what I predicted. I can be surprised, but I spent a lot of time working on the different combos to get what I am seeing for mileage.

[454HO]

Originally Posted by gchemist

I'll post the final MPG results later this week. Let's say if ya voted over 18+ ya got it right!!

Woo Hoo

Sounds like you had a pretty good trip. Are you coming to Houston Sunday for the swap meet?

[Pyrotechnic]

With the roller cam and smallish runner heads I could see this motor being efficient at lower RPM's. The 3.08 gears sound awful, but with those low profile tires they probably arent as bad as they would be with 28" plus tires. If he was cruising it at about 65 MPH, which seems to be the peak efficiency point for these bricks, then he should have been able to do about 17-18 MPG provided the carb is optimally tuned.

[daman02]

my mild 350 with vortec heads, 670 street avenger carb, 2500 stall, and 3.42 gets about 15-16 on interstate at about 70-75 mph.

[gchemist]

The thermostat changed MPG. The 180 was way too cool for the Texas Panhandle weather. Temps ranged as low as 138-158. I had to slow down to heat up the engine. The new thermostat kept the engine from 188-194. The average temps were 193-194.

[Thumpin455]

Not bad at all. Yep an engine running too cold can use more gas, sure it will make a bit more power in some cases, but at a price.

[gchemist]

Finally after four weeks of travel time between vehicles here are the results. I need two tanks to find new MPG on the 195 thermostat for city driving.

Starting milage: 73650
Ending milage: 74918
Total miles traveled: 1268
Fillups 5
1. 239.6 miles/15.158 gal/$53.95 = 15.81 MPG 180 thermostat
2. 233.4 miles/15.217 gal/$57.20 = 15.34 MPG 180 thermostat
3. 283.2 miles/15.296 gal/$57.20 = 18.51 MPG 195 thermostat
4. 226.8 miles/15.681 gal/$58.00 = 14.46 MPG 195 thermostat/leaking fuel pump
5. 285.3 miles/15.213 gal/$59.00 = 18.75 MPG 195 thermostat
Cruise control set at 70 MPH.
Currently running in the city. 180 thermostat MPG was 13-14. I expect it to go up a little with the 195 thermostat. If it does increase to at least 15 MPG, then I'm changing the electric switch. I will set the engine running temps to 190-210.

Conclusions: ram air systems works, higher temps are preferred by the ZZ4 aluminum heads, bed cover makes a difference.