318 to 360

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ColeTrickle74

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After taking the car down the track a few times, I've decided against building up the 318. My car is a 74 Dodge Dart S.E with a 318 and 727 t.f trans. The 318 ran high 16's this weekend, but I was mostly in the 17's. What am I looking at here exactly? Can I use the 360 heads? Can I keep my trans and drive shaft? What about torque converter and engine mounts? I have a 600 or 650 cfm carb. Just looking for somewhat of a parts list or any recommendations. I'd like to hit 13's and still be street friendly.
 
If you swap to a 360, you'll need to swap to a different driver's side motor mount bracket (available at most parts stores) and either get a new torque converter (recommended), or rebalance the one you have. Other than that, most things should match up.

Of course, you might want to go to 360 manifolds and headers, and other such things to take advantage of the larger engine.
 
So just one mount I would need? I planned on using everything I could off the 360. I think its just the motor, so I'll need headers. What pistons would you recommend? Could/should I use the 360's rods and crank?
 
I would use KB107s in it. They are a flat top and can be set at zero deck.
 
I ran a 14.57 at 96.55mph in my 71 Duster with a 360/727 w stock converter/3.23 gear. It was a mid 80s 360 from a van. It got a cheapo ball hone/rering job and fresh bearings.
I got my mount from Schumachers, but I've also cut and welded a 318 one to work too.
All I added was an alum intake with 650 carb, a MP cam that is only a little bigger than the stock 340. I used 340 exh manifolds and a full 2.5"exhaust.
I used a B & M balanced flex plate from Summit so I didn't have to swap out converters, but for only a little more you could get a converter with a better stall.
Don't use the cam unless you get fresh lifters and do the cam breakin procedure again.
If the exhaust ports have the Emissions passages just run a tap in there and plug them with some hardware store allen screws. I also did a halfass gasket match to open up the exh ports a little.
 
P.S. It still had the low compression and ran on 87 gas.
Mine had the flat motor mts, if you have the spool then TOO Cool Toms right. its a parts store
 
Doing the same thing except the 360 is out of a 75 duster and using the 8.25 out of the the Duster with 3:55s and sure grip and the 904 and b and m flex plate.
 
I think the pistons I was looking at should give me around 10:1 compression? Are the stock 360 rods good up to about 400-450 horse? What rear ends would you recommend as well. I was thinking 8 1/4 and 3.73's
 
stock rods with new bolts will be fine. The 8-1/4 will live all right on the street and 373s are a great street gear.
 
Any recommendation as far as who to buy from for the rear end?
Also, I was reading about just using some 360 magnum heads, anyone have experience with these?
 
For the 360 engine balance get a flexplate that is weighted for the 360. B&M and a few other vendors have them. About $50-80 This way you can use your current torque convertor.

Drivers side motor mount is different. I've heard you can get them at a local parts house for spool mount set ups. Might check it out.

Most everything else will bolt up. The exhaust really needs some detail as the 318 ports on your exhaust manifold might be a bit smaller than the 360 heads.
 
I think its a good intake, but won't work with the magnum heads. Magnum heads oil thru hollow pushrods. Early ones oil thru a passage in the heads to the rockershaft.
 
Go to the thread by AdamR - 340 manifolds and Magnum heads- alot of info there.
If you can find some 88-92 360 heads, casting# ends in 308, those are the best pre magnum production heads.
The 308s and Magnum heads can crack in the gap between the intake and the exhaust so look close before you buy.
 
Cole, do you have the 360 now?

The KB107 pistons are good to use. They will give you a 9.8-1 ratio with a .039 thick gasket and normal 360 heads which are open chambered.

The Edelbrock intake is a gem.

Exhaust manifolds or headers?

A Mangum head swap requires the hollow pushrods and you will have to recalculate the cams lift due to the 1.6 ratio like this;

Cam lift / rocker ratio X new rocker ratio = new lift

>500 / 1.5 X 1.6 = new lift at valve. Math looks like;

.500/1.5 = .33333333333333

.333 x 1.6 = .533

Your spring selection for the Magnum head should handle .533 lift.

Schmaucker creative services have the motor mounts you'll need and there a bit expensive. But wort it on the older sandwhich types since there blow proof/interlocking.
 
I don't HAVE have it now, a family member has one lying around. I'll know for sure tomorrow if I'll have it. All those numbers....kinda got me a little scared. Can you explain a little bit?
 
I thought I did well, rats!!!

OK, the standard head has a rocker ratio of 1.5. It magnifies the actual cam lift from off the lobe. When you change to a Magnum head, there rocker ratio is 1.6. This means the lift at the valve will be greater due to the rocker ams great ratio.

What your doing to find out what the new actual valve lift is, simple math.

The current lift is, for say, .500 with the standard rocker arm. Divide the rocker arms ratio into the cam lift. That is 1.5 into .500 which equals endless amount of 3's. (.333333333333333333333)

We'll just use .333 which is the actual cam lobe lift and multiply it by the new rocker ratio from the Magnum head which is 1.6.

1.6 X's .333 = .533

The change to the Magnums rocker arm
 
Ah, you did a good job of explaining, but I'm lost. I don't know too much about any of that just yet. I'll just have to figure it out as I go along I guess, Sorry :cheers: Thanks a lot for trying to explain
 
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The magnum head has 1.6 rockers which will lift the valve up higher than the standard heads that all have a 1.5 rocker ratio.

You'll simply needs springs to handle the new lift. When you order up your cam, tell them you have an older 360 and you did a Magnum head swap with a 1.6 ratio rather than the standard 1.5 ratio and you need a spring to cover the new lift. They'll hook you up.
 
Ah! Okay, I must be dumb or didn't read or something. Thanks 8)
What cam and springs would you recommend?
 
I wouldn't at the moment. I do not have any books on hand to look at. Just let the cam manufacturer know that you swapped on Magnum heads onto a older 360 and you need springs to match the new lift.
 
ColeTrickle74 said:
So I should try to find a set of magnum heads or pre-magnum 308s?
Click to expand...


Any used head you get will need to be rebuilt.

You can get new magnum heads from EQ. They outflow the originals and are thicker in the area's prone to cracking. Check out ebay for them.

Magnums offer more potential and tolerance for shitty gas than the la head.

But it's more money as you either need a magnum intake/valve train or drill the heads for la intake pattern.

You need more than just pushrods to put on a magnum head. Magnums use a specific head bolt also. La valve covers will work but the magnum ones are less likely to leak.

Lots of good info here.

http://www.moparts.org/Tech/Archive/smallblock/7.html
 
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