Just bought my son a 77 SWB with a 360 auto, carter afb, duel plane 4bbl intake, stock exhaust, stock rear with 2.73 one legger, it is a gas hog (about 10 mpg or less)...considering pulling the 360 and installing a 318. Any suggestions on a gas miserly 318 build? 2bbl/4bbl, cams, induction preference? Or....is there any way to improve the milage of this 360? Thanks

a 318 with a good BBD 2-v,stock 360 4-v cam, stock high stall TC,headers/duels with that 2.76 gear would help it.

I am getting 18+ with a JY-91 #302 headed 318, whiplash roller cam,Holley street dominator intake,6210 Holley spredbore 650cfm,headers/2.5" - 2 chamber muffs/duels out the side, NV4500 5-speed, 8 1/4-3.21 gear turning 235/75/15.

cam sweet spot is 1800 rpm, 55mph is 1500-1600 rpm.

great street/cruzer cam.

try swaping on a set of #302 heads on the 360 to get some torque down low to help the 2.76 gear. add a holley street dominator with a q-jet/spredbore Holley.

not a high reving race engine but does make a nice stump puller in a stockish daily driver work truck.

just bumping the axle to a 3.21 - 3.55 gear is gonna help get it rolling.. IMHO, thats where it is sucking the gas, getting it rolling with a 2.76 needs a heavy throttle.

Ditching the gears would be a big help for an in-town truck. It likely has an 8-1/4" rear. If so, grabbing gears out of a Dakota would likely help.

You can always drop in the steeper gears and a 518 OD to get the cruise RPM down. There's plenty of room under the truck.

What happened to the 360 mileage build thread? It went several pages and the engine had good numbers all the way around.

I would checkout the 360 mileage build and in your current eng I would put a 3 keyway timing set in & adv it 4 deg and dial in the dist subsystems in order: initial/total (initial+slots) at 35 (vac capped) then springs then plug in/adj the can. Not sure if a razor sharp built 318 would be better than a razor sharp built 360 but Scratchn is getting incredibly good mileage numbers with his 318 & he is a truck guy so I would go with his plan. definitely get .035" quench/some mild porting & especially some small tube 1&1/2 or 1&5/8 headers and a free flowing exhaust (mandrel bends/free flowing (somewhat loud) muffs. EDIT the 2.73's and 15" (I'm assuming) tires are hurting you also. As said I would go to a deeper gear

Chances are the truck has been really neglected by the previous owner and it needs a full, proper tune-up.

In a 2wd it should be doing 14 maybe 15mpg without too much trouble.

The biggest weakness I see for lack of fuel mileage is no lock-up converter and lack of dual exhaust. My other guess would be hopefull it has a viscous fan and not a direct-drive.

You may gain little going 318, and if you have the 727 maybe nothing at all. I find that 727 is a power-robbing turd to a 318. Right now I have the a833OD with a 318 and it's night and day difference to every other 318 auto I have/had: With 2.94's, 2bbl, 2wd, and single exhaust it's doing 17 to 20mpg on the highway.

However, if this is all in-town driving you are talking about, then 10mpg is about right.

I'd agree that 10 mpg or less is low for a stock truck, unless that is city mpg, driving in mountains, or driving with a VERY heavy foot. My 360 Ram always got 12 mpg. It had a rather tired 360, 727 and a 3.21 gear. The 12 mpg most likely could have been improved. I never even bothered to tune it up.

The fuel and ignition systems should be examined carefully. I'd guess the fuel / air mixture is overly rich or there is a problem with the timing not advancing. (Make sure both the mechanical and vacuum advance are functioning properly!)

An overdrive transmission is often worth 1-3 mpg on the highway. It would take a while for the fuel savings to pay for the swap, but the overdrive makes highway cruising MUCH more enjoyable! I'd seriously consider making such a swap just for the better highway manners. Any mileage improvements would be icing on the cake.

I'd give the truck a complete going over before considering an engine swap. (Assuming the existing engine is in good shape.) I'm guessing the low mileage can be significantly improved without resorting to major wrenching.

Swapping from a 360 to a 318 should improve the fuel mileage. If you have to buy the 318. Rebuild the new engine, and swap it into the truck, I'm guessing the truck would have to be driven for many, many miles before any savings would be realized.

find a 318 magnum donor computer and all and install.more power better milaege

Thanks for all the replies and tips...I'm going to start with the basics this weekend and see what it looks like from a tune up perspective before I do something nuts like swapping engines...it was early this morning when I posted and I have a 318 sitting on the stand that needs freshened so I kinda went into f-it mode and jumped straight to engine swap...

If you want good mug use a Magnum engine

Your son's gas mileage problem might be driver related. If it is, adding performance parts will probably not improve mileage at all, and may make it worse. Gene

Is the 10mpg city , highway or a mixture? 10mpg in town for that truck while being driven by a kid is quite normal.

Yes it is quite possible that the mpg is driver related...but he has driven my 74 318 2bbl auto truck quite a bit and it never used this much gas so I'm kinda leaning toward tune up on this 77...we shall see once I get some time this week to wrench on it...

Al of the 360s I've owned would get about 2mpg less that a 318 version of the same thing. 77 was about the worse case for trucks concerning fuel mileage, it was a time when the car companies were prolonging adding the converters, so the motors were choked with hang on emissions stuff. Gene

The 4x4s use a lot more fuel than the 2wds do too...

Get a roller cam 318 from a Fifth Avenue, '85 or '86 up through '89. Have someone do a good valve job and assemble it with the Mr. Gasket thin head gaskets. Use the rest of what is on your current engine. You should pick up a few mpg, that engine in my '64Dog D100 gets 20mpg at 70 on the highway.

R.

any of the 85-91 318 2-v carb or tbi roller cam engine is a good starting point.

the 2-v carb or tbi roller cams respond well to a small 4-v carb/headers.

the whiplash roller is a very street friendly cam with a nice chop at idle.

I like the Fifth Avenues for a lot of reasons, most have to do with the car itself:
1. 2-barrel carb is small, engine never developed a lot of cylinder pressure so rings, bores, etc. are not worn out.
2. The cars came with 2.24 rear ends, meaning the engine didn't see much high rpm use.
3. They were "grandma" cars, meaning they were driven easy.
4. Many of the "grandma" cars I have encountered were very well maintained. Grandma knew she couldn't afford a new car so she took it to the garage every 3000 miles.


Other things:
The cast iron used in these engines is pretty hard.
The hydraulic roller cam stuff is already there.
You can have the stock cam (it's a single pattern cam with 110LSA) reground by Bullet for something like $120. The largest lobe that will fit is the 209 degree@ 50, 0.316 lobe lift. That's from Patrick, who is the patron saint of this engine. A note about going to a higher lift: Retainer-to-guide clearance will probably have to be opened up, the tool costs less than $50 and I did all mine in around 15 minutes. Also, valvesprings become an issue because of the short installed height of the stock setup. Patrick used Hughes 1110 springs, IIRC. On my engine I used Crane 833 springs, and actual valve lift will have to stay under 0.474". There's also the old favorite Comp 901s, and those too have a maximum lift of less than 1/2 inch. The stock retainers worked just fine on my Crane 833s and will work on the 901s I have on the shelf.

Another note: The 318 roller cam valvesprings are stouter than stock 318 flat tappet springs and would be a cheap upgrade for a mild cam in a flat tappet 318 or 360.

About the 302 heads: They have a lousy stock valvejob. They are quite easy to open up to the 360 gasket size, at least on the outside side of the runner curves, where much of the flow is. There is quite a lot of material clogging the topside of the port around the valve guide. The air holes into the exhaust port can be plugged with 1/4" setscrews or bolts. Run the correct size drill through the hole before tapping and be careful tapping. I broke a tap off and had to use some goop to plug the hole. The AIR holes in the exhaust manifolds are not connected to the exhaust after you plug the holes in the heads.

The 5-blade fan clutch assembly on the Fifth Ave is the same as the MP low drag fan.

R.

Now that's a lot of info

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