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  #1  
Old 06-30-2003, 01:57 AM
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Question 318 Fuel Mileage ?

I just am about to road trip out to the west coast to pick up my next beauty (Unless you talk to my wife who just rolls her eyes at me). It is a stock 72' 318 no frills 2 door Satellite. I plan on making this car into a daily commuter. Now my commute is pretty expansive. About 55miles one way but nearly 90% or that is freeway with flowing traffic. From the sounds of it despite the 105,000 + miles on the car, the 318 runs like a champ. However, since I need this to be dependable transportation for next year I am contemplating rebuilding the motor this winter.

Any ideas or thoughts on reliable reasonably priced buildups that would achieve good dependability and economy?

Currently i am thinking about a near stock rebuild with a Perfromer intake and a re worked TQ for the top, but i am looking for cam, head, and piston recomendations.

Is it worth it to get the '302 heads?

Should i stick with the stock manifolds? The car already has 2 1/4 inch dual exhaust.

What compression is needed to run 87 octane?
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  #2  
Old 06-30-2003, 07:19 AM
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I would go with the stock rebuild.... maybe add a slightly hotter cam such as the type for RV just to help torque..don't forget to add a good high volume oil pump...

But since you are rebuilding anyways... why not build a 360...more free torque and looks the same....

I would suggest the 308 casting truck head but a lot of guys here will say the 302 is the one because of the smaller chamber...Either one would be good and perform better than the stock heads..

The thermoquad sounds like a good choice...before shelling out for a new intake... start doing the swap meet or e-bay thing.. should be alot cheaper..add a 1 inch hole hole spacer under the carb just to help it at the bottom end...and to help with heat..

If it is for reliability.. I would stay with the manifolds just 'cause they are less likely to leak... but a set of 1 5/8 headers and 2 1/4 exhaust would help it breath a little better.. a set of flowmasters would be my choice of muffler...

I set of 3.23 gears with a sure-grip would round out a great package..
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  #3  
Old 06-30-2003, 09:00 AM
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Use euther of the later heads suggested already. They will help compression and have a more efficient combustion chamber.
I have used the cheap summit rv cam with good luck in a 318.
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Old 06-30-2003, 01:17 PM
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I'll stick with the 318 because I will already have it and it is the original motor for the car. I will do this in the winter when I won't need to drive it anyways. Besides I am after fuel mileage and dependability, not overall power. That is what the Super Bee is for!

Sounds like a set of 302 heads is what I need.

Does anyone know what Compression ratio is needed to run 87 octane?

Are stock replacement pistons okay or should I go for KB Hyperutectics?

I think I will try either a hughes or maybe a Racer brown cam. i suppose i should give them a call.

The rear end will come out later, but for now I will stick with those 2.76's and 8 1/4 housing for freeway ease and optimum fuel economy.
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Old 07-01-2003, 12:07 AM
Billydelrio Billydelrio is offline
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If the 318 is only 105,000 miles old and still doing fine, I would not make the engine the main priority. For dependability purposes, I would look at the cooling, electrical, suspension, and the brakes first. Just an idea.

I agree with keeping a near stock 318 over the 360 for the 100+ miles of daily driving.

Billy
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Old 07-01-2003, 01:33 PM
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bump....

any other opinions? Engine builders? Cam guru's?

I know it technically is not a performance topic, but since allot of readers have experience building motors i thought that this would be the best place to ask. Besides a 4bbl and better cam is going to wake this little 318 up quite a bit so it is sort of perfromance rated. i am just hoping for 18+ MPG.
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Old 07-01-2003, 02:17 PM
GaryS GaryS is offline
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I'm currently rebuilding a 318 for my '73 truck and it will have a Performer Plus cam to enhance the existing Performer intake and carb. Other than that, it's basically stock with all the emissions junk removed. I'll let you know what happens to mileage.

Stock '72's did not get great mileage, since that was the first year of serious emissions controls. When I bought my truck new, it averaged around 10mpg, but over the years I got it up to 14. I'm hoping this rebuild and new cam will bring it up to 17. If not, it will get a Gear Vendors overdrive to offset the 3.55 gears.
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Old 07-01-2003, 04:13 PM
Dr. Righteous Dr. Righteous is offline
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Biggrin Keep an eye on your CR

Hey, a swap to 302 is a great move but keep in mind that these are closed chamber heads and they will increase your compression ratio. If you run flat top KBs you will probably have over 10:1!! Sweet, but you would have to run 93 octane and that is outside your performance goal. I believe KB has a line of dish "magnum" pistons to match the newer closed chamber heads. Check their website out.

www.kb-silvolite.com


NOTE:

I checked and they don't list one for a 318, but for the 360 ythey do.
Maybe their website isn't up to date. You might want to call them.
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Old 07-01-2003, 06:04 PM
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Billy,

I too am in the don't fix it if it ain't broke camp. This weekend is the ultimate test because i have to drive it from Seattle to milwaukee in 3 days! That is about 30+ hours of driving at 2700+ miles! So i will definately find out the condition of everything this weekend.

The wires, carb, and radiator were supposedly changed recently. From the pictures this thing looks unmolested and it really does sound like it is a straight car.

The brakes are non power assist discs.

Any thoughts on running 87 with this thing? Is 8.2:1 ideal for 87 octane?
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Old 07-01-2003, 07:16 PM
Bigfoot Bigfoot is offline
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I have a 85 Diplomat with the 302 heads, I converted to 4 barrel and removed the lean burn stuff and added electronic ignition with a vacuum advance distributor and 2 1/4 duals no cats. According to Dodge it is supposed to have 9 to1 compression from the factory. I have the crappy 7 1/4 2.2 rearend and with 87 octane I can get 17 in the city. I don't know what cam or pistons you are running but they have to be better than what my smogged out 85 would be. I have 350,000 on my engine with only 100-115 compression and the rings are blowing blue and needs to be rebuilt. I don't think it would be out of the realm to get at least 17 on the highway with your setup then.
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Old 07-02-2003, 08:51 AM
Dr. Righteous Dr. Righteous is offline
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Thumbs up Yeah, can't loose......

If the engine is unmolested and well maintained there isn't a reason you can make a road trip.
I would put a timing light on it and make sure that timing mark stays dead on. If it is jumping around a bit your chain is probably worn out. That is usually the first thing to get weak on a high milage engine.
Also check the operation of the choke, heat riser ect. Those are likely to fail just from being old. Most likely the vehicle lived in a garage and didn't see much daylight.
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  #12  
Old 07-02-2003, 11:08 AM
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I had a Dodge Magnum awhile ago. It came with a 360, 2bbl. The mileage was 10 on the hwy. (This wil not do!)
A conversion to the cast iron 4bbl, 625 cfm Carter, 2 1/4 duals w/ 'h' pipe and turbo mufflers, trashed the lean burn for an MSD and vaccum advance distrib.
The tranny was a 904 and the rear was a 8 1/4 w/2.76 gears. Tires were 235/60/15's on all 4 corners.
Careful atten. to what your doin and you'll get a good reward.
Mine was 20 MPG's on the hwy.
I was doing a simalar comute years ago. All hwy for near an hour.
I never changed the cam or used headers. Shame, I could have gotten more mileage if I did.
For your 318, a 360 cam would also be good. 252/.410
A taller tire would help the hwy. mpg search.
Other things like an open air element, a viscous fan or electric fan and synthetoc oil through out.
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  #13  
Old 07-02-2003, 11:39 AM
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An SP2P intake and a tweaked TQ - for sure.
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  #14  
Old 07-02-2003, 01:38 PM
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Great that is good to hear. My girlfriend who is making the trip with me is a little nervous about the ride back, but I know these 318's are strong engines.

I think that as long as i am swaping the intake in the winter it might be worth it to just yank the motor and give it a once over. When i get it home i will do a compression test and that should determine what i need. maybe just a timing chain change and an intake swap is all it needs.

The guy i am buying it from says that he uses 92 octane and lead additive. The additive i can see, but i thought these 72 318's were lower compression and could handle regular gasoline?
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  #15  
Old 07-02-2003, 02:24 PM
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A timing chain and gears is the ticket tooooo BUT if you have a good running engine that does not burn or dirty the oil too quickly - spend the money on something else....IMO.
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