360 options for mileage and performance

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71dusterdan

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Hello everybody, just found my way over here from Moparts. I've got a pro touring Duster in the works right now. I want max mileage and respectable power. I keep kicking around injection, like a Magnum motor or even a Hemi. I already have a very low mileage, excellent rv core circa 79. The rearend is a 9inch with 3.50-1 and I have both a straight 4 gear and an overdrive 4 gear. I am not going to really abuse the car, just make a little noise and blast a few on and off ramps, and spank a ricer or two! I really wanna be able to drive this thing every day, and that means I will need to see 20+ mpg. I also need to see 13 second quarters, the lower the better. The hemi we all know is expensive, and will keep the car off the road for some time. Can a Magnum 5.9 turn 20 mpg? On the other hand I have a very well tuned Thermoquad and a performer intake, which could potentially allow me to see the road this upcoming year. Anyone gotten good mileage out of a TQ? The obvious choice is to put together my rv motor with the stuff I have right now, and start driving. Anybody have some experience with similiar combos, and willing to give me some feedback? Thanks in advance,:burnout: Dan
PS....what no wrenchin on our abodies smileys?
 
You won't run 13 flat and still get 20+ mpg without making changes to the gears/convertor 'and then some', unless you have a overdrive, no2 shot, and switch the carburetor out at the track.

Pulling this off will cost you lots of money.

small carb , tiny cam, even skinny tires help milage too, but they won't hook
 
Fergie has a point.

The Magnum FI engine is a good idea. In the Dakotas, there EPA rating was 19mpg's Hwy. There HP rating was I think 260 HP. While that is not setting the world on fire, the OD manual trans is a interesting plus to this idea. The low first gear is great for the smoke show. The final trans ratio is...dang... I forgot. There is another thread, similar, going on here I think.

Well anyways take the trans final gear ratio and multiply it by the ring and pinion ratio for the final gear ratio feel and work it from there. The Dodges have tall tires, something to take into account when sizeing a tire for your car.
 
On a carbed engine, theres a few things you can do, but that ET and mileage combo is something I'm not sure I can do. I haven't tried it myself yet. Best I did a ways back was a 360 in a '79 Magnum that did get 20 mpg's....but.... the internals were stone stock with the only upgrades being a dual exhaust off the manifolds, MSd on a adjustable distributor and a 625 Carter ona OE iron intake.

The car had a 904 and 3.76 gears w/ 236/60/15's. (approx. a 26 inch tire)
The Magnum is approx. a 3700 car.

You could adapt the Performer to a set of Mangum heads forincreased lift which equals HP, select a cam carefuly. Close to a OE 2bbl cam for the 360 or not to far removed will make nice power, but IDK about 300hp. or 13's.

This can be tuff.
 
There ya go, if its impossible today to go 13 flat which is a number cars forty years ago were hitting and getting in the 20's in gas mileage than its the gas that's the culprit. With technology of today we've got 4 and 6 cylinders doing that.
 
???? Please do tell what crs these were!

(Gas does suck....real gas is purple!)
 
ya know mister fish, coming from lawn guyland myself I could remember my new Formula S 65 Barracuda doing 13.2's at Westhampton and getting the in the 20's as I had to get back to the south shore where I lived. Of course my engine in 65 was done by Jack Merkle and .060 over, balanced etc and set up for the limits in a stock class.
 
LOL, if you can show me one stock outta da box from the factory that did this, I'd be happy as hell. And the OE poster...

At the risk of repeat..... what town did ya call home? (BRB, lunch run....)
 
Your quote mister fish of real gas being purple is what puts your car on the street yet not on the road. Not everyone wants just a car for the streets. Real gas had lead in it and all the squawking about government crap I hear here never once mentioned what the past administration done to our gas.

In the 90's When I lived in Haverstraw NY which is in Rockland county I used to drive my Signet to Jersey running a dual quad roller cam 318 and go in to 20's, even the 70 Vega with its 350 did the same and as I learned from my teachers, its all in the heads.

Today, my 1990 truck build with its 350 plus horsepower and six speed has plenty of power and gets appx.18 mpg around town and in the 25 mpg bracket on the road, that's what it was built for in this day and age, and all on regular.

It all depends on what you want in life and what you'll do to get it.

No purest here :)

Oh, I lived in Long Beach and very well known back there even to this day
 
I don't know...

My friends Demon at Vegas, ran 14.2's at 103 mph (2.20 60's, babied out of the hole because of the 7.25 rear)) with 2.76 gears and a 2500 hughes converter. If the car could have 60'd,it would have easily run in the 13's. The 360 made 347hp and 400 tq on Brian's dyno at IMM. It also got 20 mph running 60-65 mph going to Spring Fling with an OOTB Holley 750DP.

Can you get a car an old car to run 13's and still get 20 mpg, yep if you do it right.
 
I like dcg333's recipe.

(Clipped from another thread)

When I built my 360 I wanted a strong street motor, I resisted the temptation to use a big cam, big carb and very high compression. I had read about the benifits of a quench combustion chamber and wanted to take advantage of it.

It's much harder with open chamber heads (you need to make custom pistons to follow the chamber profile) so I chose closed chamber magnum heads (they are stock). The quest for a proper quention combustion chamber is the reason vertually all modern engine designs have a closed chamber design.

I hemmed and hawed about whether to use a flat to piston or a step dish piston, either would allow a good quench, the step dish would keep the compression below 10:1. Since I had the idea that I would like a set of alumnium heads sometime I went for the flat tops and had my fingers crossed that the mid 10's compression ratio would run on pump gas.

I built the short block with KB107 pistons. I had to machine about 0.020" off the deck to get the surface square with the crank. This put the piston at zero deck and I used a common 0.040" thick head gasket.

What I wound up with was a 10.6:1 360 with a Comp XE268H Cam (224/230 @ .050" and .509/.512 lift), themagnum heads use 1.6 ratio rockers which accounts for the addtional lift over the advertised numbers. The cranking pressure measures between 185 and 195 psi which is close to the limit for pump gas but in actuallity the quench and high swirl design of the magnum heads allows me to run 89 octane and in a pinch I have used 87.

I have had carbs between 600 and 750 cfm on the engine and finally settled on a Holley Street Avenger 670. This carb produces all the power (by the butt dyno) of the 750 and still has the throttle response and low rpm driveability of the 600. Plus the car gets 5 mpg more with the 670 over the 750.

My Barracuda has an A833OD tranny with 3.55 gears and a 27" tall tire. The only 1/4 mile times I have were with a 25" tall tire and the 600 cfm carb. It ran a best of 13.7 @ 102 mph with a very traction limited 2.2 sec. 60' time. If I get the traction issues straightened out it shoudl be a low 13 maybe a high 12 sec car. Both Engine dyno and the 102 mph trap speed support that this engine is making approx. 370 HP.

The car will idle in traffic in high 90 temps all day, will accelerate from 1000 rpm in 4th gear and pulls hard from 1500 rpm to 6000+ rpm. It gets between 16.5 and 18 mpg around town and 21-22 mpg on the hiway.

I couldn't be happier with the preformance of this engine and I have been putting approximately 7500-8000 miles a year on it since 05 when I installed it.
Click to expand...
 
When the convertor locks at 2500, I think you're cruise ends up 2600+ unless you like the slipping and loss of milage, but then again a $900 convertor can help that.

It's not impossible, but 4 bangers are not the correct example in comparing mpg, thats 4 less cylinders to feed, let alone the ones doing it are fi/OD and usually turbo.

I've run into 13's w/ a stick car and sbm, same 60's as the friend you mentioned, and with all dialed in timing wise, w/o vac advance 15-16 mpg was the best, and that was on a 300 mile trip to REALLY figure it out in a REAL driving situation, NOT ideal driving situations like most people do 10-20miles at a time.-not assuming thats what the friend did, just saying.

If you simply were to build a stock 340 but limit the comp to crummy pump gas capability, then use 3.55-3.73 gears and high end convertor for about the same 2500-2600 stall and 25'' tires, you'd still be looking at a cruise of around 3000 rpm to get 70 mph.
I don't know anyone who drives below 70mph on the freeway that is not a trailer or geriatric.

If you can drive around in the full advance and advertised/installed rpm range at 60 mph, I'm sure you can accomplish the goal, but it may take you forever to get anywhere.

Add the OD and it changes, then you can realistically keep up with the flow of traffic and get the goal.
 
HotLines said:
Your quote mister fish of real gas being purple is what puts your car on the street yet not on the road. Not everyone wants just a car for the streets. Real gas had lead in it and all the squawking about government crap I hear here never once mentioned what the past administration done to our gas.
Click to expand...

Holy Syst, WHOA WHOA WHOA Wait a minute here HOtlines. What gives. I feel like this 2nd use of "Mr. Fish and the following post is like an isluting crack at me not to mention the tone of this is feeling ill.

WTF did I do to start getting this kind of reply?

Lets go over this a bit. First up!

When I was a kid pumping gas, I remember it being purploe and when it was no longer colored, the guys would ***** and run that line of "Real gas is purple"

Your remark of current fuel not being up to task may be correct, but this I do not know. Perhaps your making mention to the fuel the OE poster has purchased/is purchasing? To that end, i agree it could be the cause of poor mileage.

The OE poster is looking for something. I think I joined this discussion and added 2 cents (Worthy or not) in trying to help and figure something out with examples of what I did. The mention of my '79 Magnum inculded the words, stone stock except..... As a '79 engine, it runs on 87 octane. I made no mention to the OE poster about fuel or anything about fuel at all. But yet I feel jumped on with YOUR CAR, words. 3 out of 4 rides at my house use 87. My Cuda, which is a total horse of a different color use's 93.

So your shoving of that statment is off baseless and rude. Not to mention missleeding to others that might have missed what Isaid, or forgot when they come back to this post. Your remark makes it look like I have not read the OE posters post and went on some tanget on the use of purple fuel. WTF is that all about?

And then you go off on some Gov. statement? Ploitcal forums ? Scrool down1 I'm not interested in a political discussion or otherwise on what or what not the gov. did to our fuel. Theres no place for it in this thread.


In the 90's When I lived in Haverstraw NY which is in Rockland county I used to drive my Signet to Jersey running a dual quad roller cam 318 and go in to 20's, even the 70 Vega with its 350 did the same and as I learned from my teachers, its all in the heads.
Click to expand...

I'd love to know the whole combo... if ya can remember it.

Today, my 1990 truck build with its 350 plus horsepower and six speed has plenty of power and gets appx.18 mpg around town and in the 25 mpg bracket on the road, that's what it was built for in this day and age, and all on regular.
Click to expand...

Excellent! Now, how do we get this to the OE posters car? With the use of parts he has/selects?



Oh, I lived in Long Beach and very well known back there even to this day
Click to expand...

In bold, what do you mean? I do not understand. Your well known there?
Click to expand...
 
DionR said:
I like dcg333's recipe.

(Clipped from another thread)
Click to expand...

I like it as well. This being the best part of the read;

My Barracuda has an A833OD tranny with 3.55 gears and a 27" tall tire. The only 1/4 mile times I have were with a 25" tall tire and the 600 cfm carb. It ran a best of 13.7 @ 102 mph with a very traction limited 2.2 sec. 60' time. If I get the traction issues straightened out it shoudl be a low 13 maybe a high 12 sec car. Both Engine dyno and the 102 mph trap speed support that this engine is making approx. 370 HP.
Click to expand...

The issue so far with this all is the OE low compression 360. While I guess you could raise up the ratio some by way of head milling, the east may have to come by ethier a piston change and/or deck milling. DGC's high quench area makes a low octane fuel possible.

All in all, I'm not sure if a total rebuild is within the OE posters plans or pocket. I'm just going with the parts he posted and a additinal idea of a Magnum head swap for a more intense, higher lifting cam.
 
And when you dial in the vac advance...
This is how they really work inside, just a screw that limits the total travel of diaphram or arm movement, controlling the amount of timing added at cruise, many thought it was simply delaying the adv by winding up the spring which would neccesitate more higher vac, nope.
 

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Ahh, thank you man.

OK, to carry on with the math then..... 3.50 X .73 = 2.55!
 
BallzDeep said:
And when you dial in the vac advance...
This is how they really work inside, just a screw that limits the total travel of diaphram or arm movement, controlling the amount of timing added at cruise, many thought it was simply delaying the adv by winding up the spring which would neccesitate more higher vac, nope.
Click to expand...

Ballz, Pretty sure you're incorrect there. If you look at the arm that the diaphram pushes on you'll find it's a step on the arm that contacts the cannister side that limits the degrees of advance. The spring is the preload, and the plate with the screw changes the preload on that diaphram. You cannot alter the advance amount with that screw. You can only raise (or lower) the vacuum level requried to move it.

To the OP - I think the OD trans is the way to go, and I dont see a problem with being able to get hig teens maybe low 20s witha carbureted 360 but injection would be a btter wat to go. Some of the simpler TBI systems would be perfect. The idea is not to get too greedy trying to go quicker, and be smart about parts choice. A cam in the 112° range, heads that flow decently but are not too large... You'll be revving fairly low so you need to build with torque and a flat torque curve in mind.
 
rumblefish360 said:
When I was a kid pumping gas, I remember it being purploe
Click to expand...

Yeah and when the lead started gettin gone, the best kinda gas there was was the Ammoco "white" gas, remember? The way I remember it, the red (some call it purple) gas was the 99 or 101 depending on where you were, and the bluish/green was the 110. The good stuff. We gotta BP station like 5 miles down the road that sells Cam2 114 leaded right outta the pump. ....course it ain't cheap.
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moper said:
Ballz, Pretty sure you're incorrect there. If you look at the arm that the diaphram pushes on you'll find it's a step on the arm that contacts the cannister side that limits the degrees of advance. The spring is the preload, and the plate with the screw changes the preload on that diaphram. You cannot alter the advance amount with that screw. You can only raise (or lower) the vacuum level requried to move it.
Click to expand...

Actually you are still not correct.

See the screw winds the spring and does require more vac to move the arm, but the engine can only make so much vacuum, therefore the screw limits the amount of diaphram/arm travel, be it by spring or not.
This tab you mention actually has to do with the rating or amount of timing the canister is rated to give, no matter how much you adjust the screw it will only add as much as it is rated to give by the stamp located on the arm.
If you were cut the tabs off or relocate them, you would either lower or raise the rating/amount of timing added.

My name is not ballz, mope'r
 
moper, I now see where you can be confused by my statement.
I should have said that people thought the spring would just RAISE the rpm/take a higher vac to initiate where the vac adv would come in, in that you would always have the the rated amount come into play.

The point was you won't... cause the there is only so much vacuum against the spring.
 
Considering the nature of the car, why not look at a turbo?

You could use the mild build direction of the 360, but add the turbo that gives the additional HP with a tip of the throttle. When not in boost it is a minimal restriction, and the heat that does come with boost tends to help fuel atomization. You could flip a set of Ram / Dakota / Durango headers with minimal cost and a little tweaking.

With the use of the turbo, you could use what would likely be the most mild combination you have listed (to work towards MPG goal), and the turbo would make the HP number you want with ease.
 
Nitrous, TQ carb, overdrive 4-speed, light cam and reasonably high compression.....then maybe, just maybe you'll achieve 20 MPG and 13's.
 
Me personally I think todays cars get good mileage from a combo of things;
A) ligghtweight building materials
B) tecnology like direct injection,fuel inj,multispark ign,modern combustion chambers etc etc
C) Multiple gear tranmissions like 5,6 and 7 speed transmisions are a huge advantage
D)Aerodynamics.Flush mount glass,door handles and slippery shapes really help mpg. I think this is where many restomods fail to take advantage. Not many guys mod the body for better air flow! Heck even a simple splitter on front and diffuser out back will help.
But for our cars and tec its a different story. Much tougher to get 13's and 20 mpg with a low comp cast iron 60's tecnology engine. I think myself that the easest route is a modern plug and play drivetrain,plus lightening your ride up.
 
For sure run the OD. I have run them in a mild 318 volare road runner. With 3,91s. Nothing like being locked solid with a clutch in your OD gear (4th). Easy on the mileage and transfers torque to the ground efficiently during cruising down the freeway. I would not use the regular 4 speed for your application based on the need for reasonable cruising rpm and gas mileage. The motor, it appears the post by DionR shows a nicely sorted 360 build. On top of that motor I would run a nicely tuned Thermoquad until you can get a fuel injection setup sorted out. I agree with trying to lighten the vehicle where possible.

Rolling resistance is a factor. Fat soft wide tires will suck some mpg. Modern low profile tires that are not too wide, and a good street suspension all tuned for the highway, will reduce slop and rolling resistance improving efficiency.

I see you have a 360 rv motor with non quench heads, I would set it up with a mild synergistic well tuned arrangement of quality basic ignition (I am doing the HEI recommended by SlantSixDan) or MSD / cam / intake / heads / and exhaust system with the TQ and the OD. You will probably get pretty good mileage in an a-body. The great thing about the OD is the low first gear and the OD gear. If you were at the track, disconnected the front sway bar, swapped in some drag shocks on the front and ran slicks in the rear, that 11-1 gear ratio will probably launch you quite well. There is a little bog when you go first to second since you drop to 1.67 in second. Thats really the only birch of the chrysler OD, the gear spread.
 
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