Tuning a DD 383 for optimum mileage / 1/4 mile performance

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GRANCUDA

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Starting to do the tuning on my 67 Barracuda 383 to get optimum mileage. I use the car as a daily driver for 78 mile round trip & ocassional track use. I am going to get the best mileage out of this car as I can but I am not going to hurt its strip performance, trying to improve it as well.

Right now the car runs 12.88 @ 107.9 1/4 mi & gets an average of 11.8 mpg. I am shooting for 11.9 1/4 mi & 14 mpg.

The car is currently equipped with a 383, 75cc Edelbrock heads, XE274 Comp cam, Mallory Dual Point, Edelbrock RPM intake, Holley 850 DP, 1.875 Hooker fenderwell headers, mechanical fan, 727 w/stock style converter, 4.10 SG 8 3/4" & 28" tires.

I am about to pull the dual point, non-vacuum advance & replace it with a Uni-lite w/vacuum advance. That should help get the timing up on the highway & help with mileage.

Found an interesting thing after taking it to the track, I had bolted up a 850 DP in place of my 670 VS & I really liked the throttle response on the way home. I decide to try it for a few days to see how much it killed my mileage but it actually got around 1.5 mpg better.

Right now I've got the timing set @:
17* @ 750 rpm
39* @ 3000 rpm

I'm planning on dropping in the vacuum advance distributor & setting it @:
15* @ 750 rpm
35* @ 2800 rpm
50* @ cruise w/vacuum adv. added

Not sure but that's just where I'm starting & I will play with the springs & adjustments & drive for a week & readjust.

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GRANCUDA said:
Starting to do the tuning on my 67 Barracuda 383 to get optimum mileage. I use the car as a daily driver for 78 mile round trip & ocassional track use. I am going to get the best mileage out of this car as I can but I am not going to hurt its strip performance, trying to improve it as well.

Right now the car runs 12.88 @ 107.9 1/4 mi & gets an average of 11.8 mpg. I am shooting for 11.9 1/4 mi & 14 mpg.

The car is currently equipped with a 383, 75cc Edelbrock heads, XE274 Comp cam, Mallory Dual Point, Edelbrock RPM intake, Holley 850 DP, 1.875 Hooker fenderwell headers, mechanical fan, 727 w/stock style converter, 4.10 SG 8 3/4" & 28" tires.

I am about to pull the dual point, non-vacuum advance & replace it with a Uni-lite w/vacuum advance. That should help get the timing up on the highway & help with mileage.

Found an interesting thing after taking it to the track, I had bolted up a 850 DP in place of my 670 VS & I really liked the throttle response on the way home. I decide to try it for a few days to see how much it killed my mileage but it actually got around 1.5 mpg better.

Right now I've got the timing set @:
17* @ 750 rpm
39* @ 3000 rpm

I'm planning on dropping in the vacuum advance distributor & setting it @:
15* @ 750 rpm
35* @ 2800 rpm
50* @ cruise w/vacuum adv. added
Click to expand...
That all looks good, on the right track and within a degree or two of what I think you'll find as best. Good luck with the tuning and mileage finding. It takes a bunch of playing around but it will be worth it in the end. You are going to find mileage with the vacuum advance distributor.

(To bad there isn't a drop in MoPar OD trans for you.I wonder, can it be done? Take the 518 rear OD section on to a big block 727? Just thinking out loud......)

What is the cruise RPM?
Have you thought about Rhodes lifters?
Rhodes says there lifters start pumping up around (IIRC) 3,000 RPM to restore full lift & duration. Possible benefit?
 
JW transmissions in florida has the adaptor to the 518 to BBM. after that you need a lighted rocker switch up were you can see to put in OD. oh, mileage and performance is an oxymoron.
 
JW Transmissions? Do you know the price tag on it off hand? Perhaps?
 
My advice, get a spreadbore design carb, QJ, or TQ, or even a Holley spreadbore.

What do you have for gearing? That is probably a large factor for your mileage and of course will "adversely" affect strip times, as you are likely running low

I realize "different era" here are two examples

Before my old 440-6 RR scattered all over I-5 up near Stockton LOL with a stock cam it would get 13.8 mpg, 3.54, 4 speed, headers. This was with an 800 Holley

Later on I swapped a bone stock low miles 340 into the car. With headers and "some sort" of spreadbore, it would get over 17 mpg at 70 mph. Same 3.54 gear, it ran right at 3K RPM at 70

I was an am "not" a careful driver

Also I don't know your budget constraints CONSIDER EFI. Even TBI (Holley or FItech) can be calibrated better than carb.

GET A WIDEBAND O2 if you don't have
 
rumblefish360 said:
What is the cruise RPM?
Have you thought about Rhodes lifters?
Rhodes says there lifters start pumping up around (IIRC) 3,000 RPM to restore full lift & duration. Possible benefit?
Click to expand...

My cruise RPM is 3,200 @ 60 mph. I have never heard of the Rhodes Lifters.

bOb shingler said:
JW transmissions in florida has the adaptor to the 518 to BBM. after that you need a lighted rocker switch up were you can see to put in OD. oh, mileage and performance is an oxymoron.
Click to expand...

I am not that worried about mileage, just want to tune to the max this set-up is possible of.

If I were to put an OD I would get a Tremec 5 speed or a Gear Vendors. I was going to do that several times but I just can't justify dropping $3-4K on an overdrive. Every time I get that money saved up I just can't do it & end up getting a motorcycle or old fun 70's truck.

67Dart273 said:
What do you have for gearing? That is probably a large factor for your mileage and of course will "adversely" affect strip times.....

Also I don't know your budget constraints CONSIDER EFI. Even TBI (Holley or FItech) can be calibrated better than carb.

GET A WIDEBAND O2 if you don't have
Click to expand...

I'm running 4.10 gears & 28" tires. RPM's are somewhat high on the highway.

I'm not interested in fuel injection. I would rather tinker on a carburetor than have to worry about messing with sensors, plumbing in high pressure fuel pump, figuring out trouble codes & high idle speeds.

Whatever MPG this set-up gets after I've tuned it is good enough.
 
How about a pair of 30" rear tires to make your final drive ratio higher without changing gearsets, then it's just a tire swap on track night.
 
...and that opens the door for drag radials etc.
 
Performance and gas mileage do not go together in the same sentence. Secondly your going to need 475-500HP to dip into the 11's
 
Anything you can do to increase efficiency will help both.
 
I have a 81 Club cab dually with a 400 big block and automatic transmission getting 10 miles to the gallon. I added a 6AL and picked up two miles to the gallon. It has a stock 76, 400 with headers and a 1406 carb. It eats malibu chettys for some reason from a standing start or on the top end.
 
YY1 said:
Anything you can do to increase efficiency will help both.
Click to expand...
Thumbs up!
Fisher said:
Performance and gas mileage do not go together in the same sentence. Secondly your going to need 475-500HP to dip into the 11's
Click to expand...

Agreed but....

He isn’t looking for 30mpg’s and run low 11’s. What he is looking for is max efficiency with what he has and any tricks that gain mileage. Which IMO means low rpm torque, low fuel consumption at cruise rpm and that would also include efficient ignition for complete mixture burn.

Concentration on these aspects will or should provide best fuel economy for what he has. Granted! Your not going to get 20mpg’s with the equipment needed for 11’s on a N/A engine but wasting the fuel is just simply that.

If your street strip mill runs 11’s, great! Now when you cruise around town, would you rather get 5 mpg’s or 11? This is his hunt. Maximize what he has in mileage and E.T. I enjoy doing just this. And I do realize it is what it is and it will be what it will be. And so does the thread starter.
 
It's gonna take a cam in the 240- 250 range @.050 to get into the 11's.
 
Those who bluntly say Performance and Mileage don't go together are fairly short sighted, as they are exactly the same thing!
The goal in both cases is to make the engine run more efficient in the rpm-range of choice.

First step I would make is to go digital with the timing advance curves.
You can only do so much with springs and weight in a mechanical distributor. With a digital ignition you can tailor every rpm-range and every vacuum-range (work-level) of the engine.

Focus on getting an engine to run more efficient in all rpm-ranges and you'll get rewarded by better mileage and performance.
 
BigBlockMopar said:
Those who bluntly say Performance and Mileage don't go together are fairly short sighted, as they are exactly the same thing!
The goal in both cases is to make the engine run more efficient in the rpm-range of choice.

First step I would make is to go digital with the timing advance curves.
You can only do so much with springs and weight in a mechanical distributor. With a digital ignition you can tailor every rpm-range and every vacuum-range (work-level) of the engine.

Focus on getting an engine to run more efficient in all rpm-ranges and you'll get rewarded by better mileage and performance.
Click to expand...


Yes and No

Yes if you can increase the efficiency of your engine you can increase mileage and power.

But really that only can take you so far. Most things you do to gain performance especially on an already built engine is gonna be by adding more fuel and air (less mileage) or by increasing mileage at the expense of performance (less fuel and air).

But yes I agree you should dail in your combo to get the best of both best as you can.
 
Take fuel away from the primary jet till it surges at cruise, then go up 1 or 2 jet sizes for optimum cruise. Add fuel to the PVCR for WOT max MPH. I have found around .003 increase in PVCR is close to 1 primary jet size.
 
mderoy340 said:
Take fuel away from the primary jet till it surges at cruise, then go up 1 or 2 jet sizes for optimum cruise. Add fuel to the PVCR for WOT max MPH. I have found around .003 increase in PVCR is close to 1 primary jet size.
Click to expand...

What is PVCR?
Power Valve? I have it sized by 1/2 of my idle vacuum.
 
Power Valve Channel Restrictor
The 2 holes for fuel added by the power valve circuit.
Here's a link to dialing in a holley based carb. If you follow this method you will end up with an optimum tune.
Carb Tunning
 
GRANCUDA said:
What is PVCR?
Power Valve? I have it sized by 1/2 of my idle vacuum.
Click to expand...
That is calibrating the timing of the enrichment, not sizing, the number of the valve has -0- to do with the amount of enrichment.
What temp thermostat are You running?
 
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