LA 360 or 5.2 magnum

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H20loo

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I have a 69 Dart(motorless 318 car) coming and I have a good '71 360 motor and a 91 Dodge pickup with a nice running 5.2 magnum.
I would use a 904 and 3.55 diff.
I'm just curious if there would be any performance difference as they are? would the 5.2 magnum flex plate clear the 904? I think the 5.2 is internally balanced but I don't know for sure.
I have to check the truck to see if it has an A518. maybe the 518 with 4.11 gears would provide more performance but still be a cruiser
This is to be sold to my son but since he buys without exchanging money- I don't want use what I don't have.
Any thoughts??
 
Your '91 5.2 is not a magnum. The 1st year for the magnum was '92. So, your looking at a LA 360 vs a 318 with roller cam and 302 heads. All 318's are internally balanced. Both engines would serve well, depends on the use of the car. The roller cam 318 would work well with todays oils, and it already has heads for todays gasoline. The 360 offers more cubes, torque, and in the end more power. If you use the 360, you would need a balanced flex plate from B&M or have the 318 flex plate balanced and use that with the 360. Truck motors need a car oil pan and oil pickup tube to work in a car. 360's and 318 take different oil pans.
 
Strength wise, that 360 will mop up the road with the 318. The 71 360 was a one year only engine that used pistons with a longer compression distance that got compression in the 9:1 range. No other 360 was like that........except the Magnums which have a shorter deck height to achieve the same basic thing. So IF the 360 is really a 71 and IF it has the factory pistons and they and the bores are good shape, use it. Since the 71 was a one year only engine, the industry uses the 72 and forward pistons as the replacement, so the 71 pistons are not available.
 
10-4 and thanks for the info. I didn't know that about the '71. The 360 was out of a 71 Monaco. Although a 2bl it was very quick for a big car and ran very well.
The 91 truck is afarmers down the road and I was sure they had started the Magnums that year. Thats to bad because its a 40,000 mile truck and I would have used motor and tranny in the Dart.
So its going to be a 360/904/ 8 3/4 car

"the 71 360 was a one year only engine that used pistons with a longer compression distance that got compression in the 9:1 range"
So Rusty- does this mean they had a lower wrist pin or how was this accomplished?
 
I'm pretty sure '91 is still LA territory...I don't think the 5.2 Magnums debuted until '93 with the new body style.
 
H20loo said:
"the 71 360 was a one year only engine that used pistons with a longer compression distance that got compression in the 9:1 range"
So Rusty- does this mean they had a lower wrist pin or how was this accomplished?
Click to expand...


Taller compression height on the pistons. the distance from the center of the wrist pin to the top of the piston is where the increased compression comes from.

The early 360's also had thicker cylinder walls. :cheers:
 
txstang84 said:
I'm pretty sure '91 is still LA territory...I don't think the 5.2 Magnums debuted until '93 with the new body style.
Click to expand...


91 is the last year before they went "magnum". It has roller lifters and you can bolt up the LA intakes and exhaust to it.

We just finished building a 91 360 for my oldest son's 71 Valiant 4 door. :D
 
THe 91.........Easy to tell......count the valve cover bolts and look at the intake bolts. Do the intake bolts go "straight down" plumb like a flagpole, or are they "canted" with the head angle?

Should be an LA "roller block" IE roller cam

Even as old as a 91 is, it could have a different engine in, by now!!!
 
Yup- I ran down this morning and had a look. It's a original to the truckLA 318. Still a one owner sweety for its age but wish it were a 360. I may not ever use it but it will be too good to throw out and I will be storing it for nothing. It looks like an 8 1/4 rear end in the truck. I thought it would have had a heavier diff than that
Thanks for all the replies
Doug
 
krazykuda said:
Taller compression height on the pistons. the distance from the center of the wrist pin to the top of the piston is where the increased compression comes from.

The early 360's also had thicker cylinder walls. :cheers:
Click to expand...

Do you know what years. Would a 360 out of a 72 cuda have any more value than a later 360. Not money wise but just build quality value.
 
H20loo said:
Yup- I ran down this morning and had a look. It's a original to the truckLA 318. Still a one owner sweety for its age but wish it were a 360. I may not ever use it but it will be too good to throw out and I will be storing it for nothing. It looks like an 8 1/4 rear end in the truck. I thought it would have had a heavier diff than that
Thanks for all the replies
Doug
Click to expand...
That 91 318 is a good one. Already set up as a roller cam motor and having 302 heads, this is a very appealing start for any light
A-body street car. Remember, the throttle bodies on those 318's were much, much smaller than the '91 360's, which had a 670 cfm throttle body. Giving a 600 cfm 4bbl carb and intake, that 318 is responsive.
 
H20loo said:
Do you know what years. Would a 360 out of a 72 cuda have any more value than a later 360. Not money wise but just build quality value.
Click to expand...


I'm not sure how long that the 360's used the 340 cylinder cores for the thicker walls. 71 for sure, I'm not sure if it went till 72 or 74 or more... :banghead:
 
H20loo said:
10-4 and thanks for the info. I didn't know that about the '71. The 360 was out of a 71 Monaco. Although a 2bl it was very quick for a big car and ran very well.
The 91 truck is afarmers down the road and I was sure they had started the Magnums that year. Thats to bad because its a 40,000 mile truck and I would have used motor and tranny in the Dart.
So its going to be a 360/904/ 8 3/4 car

"the 71 360 was a one year only engine that used pistons with a longer compression distance that got compression in the 9:1 range"
So Rusty- does this mean they had a lower wrist pin or how was this accomplished?
Click to expand...

Yes. The wrist pin was placed a little lower in the piston to raise the piston in the bore for more compression.

I guess the correct way to say it would be that the 72 forward had the pin location raised for less compression.
 
I'm going the '71 360 2bl route with the 904 and 3.55s.

I am curious though which would perform(1/4 mile) best- the 360 with a 70 340 intake and carb(because I have it) running through the 904 and 3.55
or
the '91 318 with the same 340 intake, 500 trans and 4.11 gears

Same 69 dart(was a 318 ), one has more cubes and compression, the other has more gears and shorter rear end.
 
Not sure that your 360 has more compression than the 318. The 318 has 302 heads which are closed chamber heads. Anyways, the A518 is a heavier tranny than the 904 and if the A518 has the stock converter, it would be a little tighter stall than the 904. But back to your question, this particular 318 vs the 71 360, it might be closer than what one would think. The roller cam and swirl port closed chamber heads really adds low end torque, which in stock form is probably the biggest advantage the 360 has on the 318. We know there is more potential in the bigger motor, but in this situation "as they sit", it would be closer than most would want to admit. But IF the 360 has excellent compression (those valves would tend to leak if too much unleaded fuel had been run through them), and is up to snuff, I say the 360 pulls this one out. But one thing not right on the 360, that 318 "up to snuff" might pull out the win, and I'm talking same tranny's and gears (904 and 3.55's)
 
Pistons for higher compression are cheaper for the 360 .u will also get more advise from other members on a 360 build.if I had both I vote 360.
 
I went with the 360. We bought it new and It was a 70,000mile motor and was pulled in 76 and stored in our warehouse. It will have the 904 and my kid can update both as he has time.
I will watch for another a body to put the 318 and automatic4 spd in.
 
A good choice,of the two. You know the history, & it's a low mileage unit.
 
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