Better fuel economy from Goodwrench 350

[Fairlane514]

I have an 84 C10 short bed 2wd, with a Goodwrench 350, 700R4, shorty headers, 2 1/2 duals and no smog equipment. I changed out the ESC HEI to a regular HEI. Rebuilt the original quadrajet recently. Engine runs fine, so no complaints there.

Motor is bone stock as far as the Goodwrench stuff, but only gets around 8-9 mpg in the city. Pretty sure it has 3.08 rear end gears, it had a 305 originally. I have 255/60/15 on corvette rallies all the way around. My initial timing is 12 degrees and the motor does not complain.

Thoughts are to jet the carb down a little, maybe ad 3.42 gears (easier to get moving). Smaller carb, although the quadrajet has tiny primaries and should be good for mileage.

[79gmc15]

Keep the qjet, it's ideal for economy, 3:73 is ideal. Maybe put a rpm intake.

[gildardo01]

ive heard of people that put an adapter plate on the intake to remove the 4bbl carb and install a ford type 2bbl carb... they do it to improve mpg... dont know by how much the improvement is though...

[Smarttravis1511]

I had almost same set up, besides having long tubes and a pro comp intake with 272 gears and a 480 lift cam and was gettin 12 13 on hiway, swapped to 373 gears and got around 16 16.5. I believe a lower gear is needed with an over drive because it lugs the motor to much with that tall of gear

[Stewart G Griffin]

Where and how are you going to use the truck will be a key factor in how much you can improve mpg.

[werewolfx13]

8-9 mpg in the city isn't awful IMO. I see 6-9 mpg city/13 highway @55 mph in my '83 c10 w/ a th350 and 3.42 gears.

[Fairlane514]

I guess I was expecting 13-14 mpg around town, I really don't see why this isn't possible.  Honestly why not closer to 16-17?  I have been reading a lot of articles and forums, but that leads to frustration and LOTS of different opinions. 

I am considering vortec heads, either original GM or the Summit brand ready to go for about 620.00.  I would also consider a small torque cam and better intake and keep the quadrajet. Rear end gearing may help too, it does have the 2.79 and shifts into OD at 43-45 mph. It seems the engine lugs at that rpm where maybe it has to work harder.......if I had more torque at that OD rpm, it may make the engine more efficient.

I could also keep the transmission in Drive (around town) instead of OD and see what that does.

One thing I did do is put a locking gas cap on it, just in case some Ahole is stealing gas!  : )

[werewolfx13]

1. Aerodynamics. You're driving a brick.
2. Weight. You're driving a brick, its heavy!
3. Technology. Its a carbed 350, its not going to be stellar.

New trucks ARE heavier than our squares, but they're also a LOT more aerodynamic. With the same engine, you can squeak a LITTLE better in-town mpg out of one of our squares compared to a very late model truck, but above 60 mph, the new trucks do better.

[muddnutz]

My 86 has a4" lift sitting on 35's edelbrock intake and carb on a good wrench 350 (carbsux)   I'm getting 10 in the city.   

[Fairlane514]

I am considering going to a Vortec motor, I found one for 350.00 (1996). Advantages: better heads, roller cam,better bottom end, should be an easy install.

I will go with a carburetor(qjet), looking at cams (possible LT4 production).  My goal is MPG and low end torque, not concerned with peak hp.

[454Man]

I am considering going to a Vortec motor, I found one for 350.00 (1996). Advantages: better heads, roller cam,better bottom end, should be an easy install.

I will go with a carburetor(qjet), looking at cams (possible LT4 production).  My goal is MPG and low end torque, not concerned with peak hp.

what will you to for a fuel pump?

[Fairlane514]

Electric.   Some say the provision is on some of the blocks but not drilled for the rod.

[DanInMichigan]

I have a carbed LT1 and you may not get great mileage with a carbed vortec when the weather is cool.  You don't have exhaust crossovers in the intake with that head.

I would not do another LT1 in Michigan unless it was a summer only vehicle.  Its really noticeable when it's cool/cold.  With a quadrajet I had a lean stumble when revving in neutral if that tells you anything.

The LT4 cam probably isn't as good for a truck that needs good mileage.   I have the b-body LT1 cam and it comes on around 1800 rpm and builds hard to 3500-4000 rpm.  If I was racing I'd shift around 5000 rpm.  I think an LT4 cam rpm range is a bit higher with a loss if low rpm torque.

If you really want mileage you would be better off with port fuel injection.  Its more complicated but its easier to tune in the long run.

Dan

[Fairlane514]

I live in Houston, so its warm here most of the time.

The LT4 production cam has specs of 203/210, 476/480 on a 115 with 1.6 rockers.......with 1.5 its more like .450 on lift. The LT4 Hot Cam is higher in the power band and I agree not great for a truck.  The 115 lobe separation also seems more suited for fuel injection vs. carburetor. Comp cams has a cam with similar specs on a 110, but that is a little too tight, I was hoping to find on a 112LS and Crane makes one, but it is over 400.00.

This link shows the specs for the LT4 production and the LT4 Hot cam

http://www.gmpartsdirect.com/performance_parts/store/catalog/Category.jhtmlCATID=826.html

The 1995-1997 LT1 cam has some nice numbers.......201/208  447/459 on a 112

[DanInMichigan]

My b-body cam is pretty decent for a truck.

It specs at:

191/196 @ .050
.418/.430
111 lobe sep