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Author Topic: 318, 340, or 360?  (Read 17211 times)

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270SE

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Re: 318, 340, or 360?
« Reply #30 on: September 23, 2010, 14:45:45 »

My main goal, is at least 300hp, and still keeping the fuel mileage above 12mpg, since it will be my daily driver. I really don't want to get into cam work, boring it out,  and all that mess, but if it needs to be done to reach my criteria, then it needs to be done. I want the motor to have the power, but not be junk in the ohio winters. Also, to switch a magnum engine over to the carb setup, is it just simply getting the proper intake and carb on there or is it more of a hassle. And once I get everything swapped, I don't plan on modding it unless it needs fixing.  At least until I have another vehicle and a nice chunk of change.
Thanks
If it's flat tappet, a cam swap is probably a good idea. If it's a roller it may not be necessary.

12mpg should be readily attainable from any of these motors easily in town and on the highway with 3.23 or numerically lower gears.

For the carb swap you have to get an intake/carb that will work with the heads one way or another. (either get the head's bolt pattern in the intake or the intake's bolt pattern in the heads)
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brotherGood

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Re: 318, 340, or 360?
« Reply #31 on: September 23, 2010, 17:59:08 »

how will i know if its a flat or roller cam? or does it just depend on if i get the magnum motor or not? and for the intake/carb..just find one that will line up to a magnum motor if thats what i get, or just get a 360 intake/carb, and drill holes?
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'86 Dodge Diplomat AHB. Rebuilt 318 LA/Magnum, cop 904, 8.25 rear

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joeblo

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Re: 318, 340, or 360?
« Reply #32 on: September 23, 2010, 18:13:06 »

I'm still voting for the Hemi!!!
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Re: 318, 340, or 360?
« Reply #33 on: September 23, 2010, 18:17:29 »

thats for the "when i have another car and a nice chunk of change".. ha.
only by that time, i'll be like 40, and the 6.4 will be as abundant as the 360 is now.
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patrickgrossman

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Re: 318, 340, or 360?
« Reply #34 on: September 23, 2010, 19:45:18 »

fwiw, my old combo was 3.55's, an A500, and a 360 that was a reringed shortblock with home ported 360 heads, XE262 comp, RPM air gap, headers, eddie 600.  combo would keep up with a stock 5.7 LX car, and I averaged 15mpg in mixed driving (19mpg best on an all highway run) on 87 swill (8:1 compression)....

I sold that motor, took my stock '86 short block, reringed it, had some junkyard mag heads redone with the suggested springs/retatainers, home ported them,  had bullet regrind the cam with their HR259/316 lobes.  used the same intake, carb, and headers. (9:1 calculated compression, runs fine on87 swill still)

power is pretty much the same as the 360, and I'm averaging 17.5 mpg in mixed driving, best tank was 19, have yet to do an all-highway run.

btw, a 273's bore is 3.625"....a magnum head's valves are 1.92/1.625"....that adds up to .080" under the 273's bore...plus add in the space between the valve faces...not enough room on a 273's bore....
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270SE

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Re: 318, 340, or 360?
« Reply #35 on: September 23, 2010, 20:18:50 »

TBI is roller cam. I don't think 360s were roller before that. 318s after '85 were all roller blocks even if they have flat tappet cams. The TBI 360s have awesome heads, they were made from 1989 to 1992. They are open chamber like all the others but with swirl ports.

The A500s and 3.55s is a difficult comparison but I think that sounds like it should be right for a 3.23 gear 360 tuned well though. I'm bottom 13 (very, very slow traffic), top 23, average around 19. My 360 gets about 2 less than the 318 did. Don't know compression, only run 93. It's above 8.5. It has flat-tops and very lightly worked Magnum heads. (the nice part about early 360s)

You can get an intake actually for a Magnum motor or just redrill the heads for the 318/340/360 bolt pattern. This probably is best done by a machine shop. The pattern isn't easy to drill because of the angle the heads have to be in. Crack checking is important on Magnums too. That's why the aftermarket heads with core heads to donate the rest aren't a bad idea.

And on the 273 it's very similar to the 2.02/1.60s on the 318s. (more space between valves on the open chamber heads I think) I've wondered if the thicker gaskets now available make a difference. I haven't tried it myself yet.
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S-type

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Re: 318, 340, or 360?
« Reply #36 on: September 23, 2010, 20:22:04 »

Big block.
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Re: 318, 340, or 360?
« Reply #37 on: September 23, 2010, 20:25:00 »

yeah, i just dont know anyone around here with a machine shop to do the porting and whatnot, and i dont want to get into messing with the gearing unless its absolutely neccesary.  

kinda what im wondering, is if i can switch a magnum 360 to run a 4bbl, and put better exhaust manifolds on it, i know i'll probably have to do more, but where will that get me with my goals?
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'86 Dodge Diplomat AHB. Rebuilt 318 LA/Magnum, cop 904, 8.25 rear

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270SE

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Re: 318, 340, or 360?
« Reply #38 on: September 23, 2010, 20:29:23 »

yeah, i just dont know anyone around here with a machine shop to do the porting and whatnot, and i dont want to get into messing with the gearing unless its absolutely neccesary.  

kinda what im wondering, is if i can switch a magnum 360 to run a 4bbl, and put better exhaust manifolds on it, i know i'll probably have to do more, but where will that get me with my goals?
The porting was nothing fancy at all and unnecessary. Done in the back of the shop. Any machine shop should be able to do the rest.

Headers or exhaust manifolds both would work fine

You don't have to mess with the gearing, it's not necessary.

A Magnum 360 w/4bbl should meet that fine.
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Re: 318, 340, or 360?
« Reply #39 on: September 23, 2010, 20:39:07 »

will i need to swap out the lean burn system because im swapping out the motor?. so, after the 360 magnum w/4bbl and added aftermarket exhaust manifiolds, i'll at least have around 300hp, and at least 12mpg? and the only mods i'll have to do it just to balance the motor externally and put spacers in the motor mounts?
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Re: 318, 340, or 360?
« Reply #40 on: September 23, 2010, 22:08:08 »

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Re: 318, 340, or 360?
« Reply #41 on: September 24, 2010, 07:38:15 »

Big block.

Problem solved!

408 X block making at least 496 hp is a lot easier than a BB and you get more HP :whist:
Dang...Herb really sold me :whist: :w00t: Gonna look for a block today in a pile of motors.
I have his recipe :evil:
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Re: 318, 340, or 360?
« Reply #42 on: September 24, 2010, 09:21:15 »

Big block.

Problem solved!

408 X block making at least 496 hp is a lot easier than a BB and you get more HP :whist:
Dang...Herb really sold me :whist: :w00t: Gonna look for a block today in a pile of motors.
I have his recipe :evil:

You could make any block 408 make less than 496hp, but that is probably where you'll get with good heads and compression with a nice cam/intake.

A stroker would be a great way to go up to that kind of power and speed. But for 300hp it's not necessary.
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brotherGood

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Re: 318, 340, or 360?
« Reply #43 on: September 24, 2010, 11:36:37 »

Well, I'm just not sure that I would want to go big block in this car...I'm not sure why, but my gut (and wallet) are saying no.
Also, I may have a spare magnum 318 that I know needs a couple things done it, but if I put a set of 360 heads, aftermarket exhaust manifolds, and convert it to a 4bbl carb setup, where will that get me with that motor rather than going out and buying a 360 and building up?
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'86 Dodge Diplomat AHB. Rebuilt 318 LA/Magnum, cop 904, 8.25 rear

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DobaMark

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Re: 318, 340, or 360?
« Reply #44 on: September 24, 2010, 11:42:15 »

Magnum 318 and 360 heads are the same, no need to swap.
The LA engines used different heads 318 or 360 (or 318 cop).
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