Author Topic: 318 vs 360 for towing  (Read 3821 times)

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Offline JohnB

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318 vs 360 for towing
« on: September 14, 2007, 07:57:09 PM »
I have a pretty much stock 318 1990 ramcharger, with alot of miles on it.  It runs good, but has somewhat low oil pressure and bad valve guides.  Pukes alot of oil smoke out the tail pipe after sitting at idle.  It actually only uses about a quart every 1000 miles.  At some point in the future I am either going to rebuild this one, or put a 360 in.

This vehicle is used to tow a 23' boat that weighs about 4500 pounds.  I am in Florida, so there are no hills to speak of, just the ramp pulling the boat out.  My question is, if I "refreshed" this 318 motor with some minor cam/perf tweaks, what would I gain or lose vs putting in a 360.  If memory serves, the 318 has an internal balanced, steel crank, and the 360 is external and cast, which makes me lean toward the 318.  I have a lot of experience building/tuning the big blocks, but I am not up to speed on the the little guys.  Is there much difference, especially in the low end rpm and torque area between the 360 and the 318? 

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Re: 318 vs 360 for towing
« Reply #1 on: September 14, 2007, 08:11:45 PM »
with a MAG motor a CAM would cost you over $400 bucks with lifters / that and the MAG motors do not like cam changes / well the fuel injection does not respond well to changes / do a VALVE job and timing chain and gears and run the bitch
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gen1dak

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Re: 318 vs 360 for towing
« Reply #2 on: September 14, 2007, 10:49:52 PM »
And now for an answer about the 1990 318, not the "MAG" motor. CompCams offers a bolt-in replacement roller cam that has .450" lift, but is a stock-replacement, meaning, and I asked them, it's a bolt-in as far as the electronics are concerned -under $300. You will need to replace the valvesprings because of the very nice increase in lift. The stock 318 cam is a joke (.385"/.400" intake/exhaust). The stock valvetrain is easily able to handle these upgrades. By all means, do it. If you're using the TBI, open up the exhaust with a good cat-back system. If you wanna go carb, that's another matter....more options. A fresh 318 will respond very well to just a cam change, easily more than a stock '90 360. Naturally, an equally modded 360 will always be more since, especially where torque is concerned, it is swinging 42 more cubes. Your other memories about the two engines are correct. The pre-Magnum 318's have smaller ports which are great for maintaining high flow velocities which really fills the cylinders. The stock '90 318 has a torque peak at something like 2,000 rpm, so you can imagine just how even a modest cam will help.

Offline JohnB

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Re: 318 vs 360 for towing
« Reply #3 on: September 15, 2007, 05:55:01 AM »
At this point, I am inclined to go with the 318, just easier, and less headaches with the TBI, computer, etc....
I will probably stay with the TBI.  As for the 318 heads, when I pull them to have the guides redone, is there anything else I can do to them to make them run better?
As for the cam, until I do the total rebuild, I will leave the stock one in there, and just put a new timing chain on, and move the advance up 8 degrees.  If I get around to changing the cam, I may look at Edlebrock, I have had great success with their stuff on the big block performer series mods. 

Offline Major Ramifications

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Re: 318 vs 360 for towing
« Reply #4 on: September 15, 2007, 09:54:20 AM »
Have you tried changing the valve stem seals? Cheap and relatively easy to do. You just have to remove the valve covers. If you are getting that much oil into the chambers, then the seals aren't doing their job.
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Offline ToxicDoc

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Re: 318 vs 360 for towing
« Reply #5 on: September 15, 2007, 10:05:57 AM »
  As for the 318 heads, when I pull them to have the guides redone, is there anything else I can do to them to make them run better?
 

Yes, but it will cost money.  A regular head (a pair) rebuild will run about $350-400. 

To get more performance, you can shave them down .010" for a boost in compression.  That will be the best bang for the buck. 

For more money, you can have them gasket match the exhaust and port-match the intake.  The bowls can be cleaned up and blended gently.  You can also add a mutli-angle valve job and larger valves.  Alll that would cost $$$. 

If I had to do it, I would shave the head and do the multi-angle valve seat cutting. (they used to call them 3 angle, then they went to 4 angles, now it's just "multi-angle" - who knows how many they are doing now)
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Offline Tman

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Re: 318 vs 360 for towing
« Reply #6 on: September 15, 2007, 11:28:44 AM »
I'd do the valve seals before pulling the heads.  They may be bad from old age.  The valve guides may be fine.

Rather than adding power in the engine, the other option is to run lower gears.  This is especially important when running larger than stock tires.  If you have the overdrive transmission, it will offset some of the gear reduction on the highway.  Example:  4.10 rear axle with .69 overdrive = 2.82:1 in overdrive.  A 3.21 rear axle with .69 overdrive = 2.21 in overdrive.  The change from a 3.21 to a 4.10 is .89   The change from 2.82 to 2.21 is .61

Lastly, your 318 is a cast crank.  (the early 318s had forged cranks)  It's a fine crankshaft.  Don't worry about it!
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gen1dak

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Re: 318 vs 360 for towing
« Reply #7 on: September 15, 2007, 02:38:17 PM »
A bump in compression will yield little power, but will increase your octane requirements. Not worth it on that setup. The heads could stand to be cleaned up a little. Even if you just take a grinder and remove some metal flash, it will improve flow. Every little bit helps.
« Last Edit: September 15, 2007, 02:51:11 PM by gen1dak »

Offline warlock4x4

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Re: 318 vs 360 for towing
« Reply #8 on: September 15, 2007, 06:02:46 PM »
I would dump the 318 for a 360 in a minute.  ofcoarse it would depend on money but before I would dump a bunch of money into a small small block why not do it to a large small block and get the biggest bang for the buck.
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Offline JohnB

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Re: 318 vs 360 for towing
« Reply #9 on: September 15, 2007, 09:14:02 PM »
Thanks for the input.
The valve guides were changed a while ago, and it is still sucking oil when idling.  I have a great machine shop that is used to tweaking heads.  They do my big blocks, and I have been very happy with the results.  As for the 318 vs 360, if I have enough power with the 318 to tow, that is all I care about.  As best I can tell, advancing the cam will probably be the only thing I change.  It has stock 4:11 gears, and stock size tires.  I NEVER use oversize tires on a tow vehicle.

Offline chrysler300le

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Re: 318 vs 360 for towing
« Reply #10 on: September 16, 2007, 02:48:48 AM »
To use a 360 in place of your 318 TBI you will need to either go carb or get a 360 computer and TBI unit.  They have to be used as a pair or it won't run at all or run right.  I've seen a 360 put in place of a 318 TBI running the 318 stuff and it ran crappy and back fired when taking off (too lean for the 360).

Mods you can do for the 318 are mill the heads(may require higher octane), put 360 size valves in the 302 heads. Use a comp cam designed for the TBI engines.  Edelbrock does not make anything for the TBI's and really they don't make good cam grinds for Mopars anyway.  Open up the exhaust.  Doing these mods could lean the 318 out similar to using 318 fuel injection on a 360.
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Offline JohnB

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Re: 318 vs 360 for towing
« Reply #11 on: September 16, 2007, 07:09:17 PM »
If I find a 1990 360 with the TBI and the computer, is that all I would need to swap it in?

Offline chrysler300le

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Re: 318 vs 360 for towing
« Reply #12 on: September 16, 2007, 07:38:27 PM »
If I find a 1990 360 with the TBI and the computer, is that all I would need to swap it in?

yes but good luck
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Re: 318 vs 360 for towing
« Reply #13 on: September 16, 2007, 07:38:53 PM »
I would dump the 318 for a 360 in a minute.

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Re: 318 vs 360 for towing
« Reply #14 on: September 16, 2007, 09:27:10 PM »
yes but good luck
Well, that and you'd need to open the 318's intake a smidge. Use the 360 TBI base gasket as a template, then take a grinder to it. Otherwise, the larger 360 TBI throttle blades will not open fully. Mopar sold this as a 318 hop-up back in the day.

Offline JohnB

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Re: 318 vs 360 for towing
« Reply #15 on: September 17, 2007, 07:44:19 AM »
yes but good luck

I was thinking of finding a complete motor, pan to aircleaner, rebuilding it, and putting it in.  The only other change I would need would be the computer, correct?

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Re: 318 vs 360 for towing
« Reply #16 on: September 17, 2007, 02:31:55 PM »
I was thinking of finding a complete motor, pan to aircleaner, rebuilding it, and putting it in.  The only other change I would need would be the computer, correct?

Computer, injectors or whole throttle body, balancer and flywheel/torque convertor if it doesn't come with it, and driver's side engine mount.  otherwise it's all the same.
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Offline Thelek

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Re: 318 vs 360 for towing
« Reply #17 on: September 17, 2007, 04:53:09 PM »
To put my $.02 in here. You already have the 318, and have already put some money into rebuilding it. Stock 318 is rated for towing 5,500 lbs, and stock 360 is rated for towing 6,500 lbs. This is straight from my owners manual. Since you already have so much invested into your 318, just finish it up. It isn't worth the extra trouble just for an extra 1,000 lbs. and you could probably get that extra 1,000 pounds by a small stroke and bore which it sounds like you will be doing anyway. You do know a 318 can be stroke and bored to 390, right? I am not saying doing anything that drastic, but a little would help you. In the end the final decision is yours. I am just saying don't throw away the money you have already invested in the old 318. You have done the heads, might as well at least replace the piston rings, hone the cylinders and maybe install a performance crank to go with the cam you installed.
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Offline EY8s

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Re: 318 vs 360 for towing
« Reply #18 on: September 18, 2007, 07:17:10 PM »
If I find a 1990 360 with the TBI and the computer, is that all I would need to swap it in?
I have a '91 TBI 360 (roller cam LA) with 114K miles on it that came out of a 1 ton truck that I purchased for the D60's/NP205/and A518.  Let me know if you're interested.  I don't have the ECU.

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Offline JohnB

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Re: 318 vs 360 for towing
« Reply #19 on: September 18, 2007, 08:28:08 PM »
I have a '91 TBI 360 (roller cam LA) with 114K miles on it that came out of a 1 ton truck that I purchased for the D60's/NP205/and A518.  Let me know if you're interested.  I don't have the ECU.

How much difference is there between the 91 and 90?
Is it complete from the oil pan to the TBI? how much?

Offline JohnB

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Re: 318 vs 360 for towing
« Reply #20 on: September 19, 2007, 08:28:40 PM »
Well, basically it comes down to if the 318 with minor tweaking gets the job down, that would be the least hassle.
If I can find a complete 360 that runs good, at a good price, and could swap over easily, I might go that way.
How much difference is there in the 1990/91/92 engines/etc.
If I find a complete TBI to pan, and grab the computer, do the harnesses/etc all hook up?

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Re: 318 vs 360 for towing
« Reply #21 on: September 20, 2007, 07:40:57 AM »
Here's some pictures of the 360.  When I picked it up, it was sitting in the bed of the truck which was off the body.  It has 114k miles on it and was running when the truck was totalled (pass side door hit).   I bought the whole drivetrain and will use everything but the engine (I have a 360mag crate engine) so the tranny doesn't come with it.  Some of the accessories are bent (from him loading it into the bed) and the oil pan has some dings that could be hammered out, this would require removal of the pan.  Anyway, if your interested, $200 and I could meet you in Savannah, GA with it in the back of my P/U.

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Offline JohnB

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Re: 318 vs 360 for towing
« Reply #22 on: September 20, 2007, 07:41:11 PM »
Here's some pictures of the 360. 

Catfishn,
That might have some possibilities, let me check around for the computer?
« Last Edit: September 20, 2007, 07:42:46 PM by JohnB »