318 Cylinder Heads

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blackace

blackace

The KING of flats
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I'm planning on rebuilding my 318 and want to change the heads to 302 castings. I have read some where that 92 318 heads used 2.02/1.60 valves? I also read that later years used 1.5 ratio rocker arms? What years can I use up to, 91 correct? Magnum started in 92?
 
92 would be magnums, valves woudl 1.92, 1.65. thats what im about to put on, all 1.6 rockers. if you are really intrested in the 302's i will be sellign mine soon.

I picked up my magnums for $50 at the pick and pull. buy an airgap for the magnum head and your set!

steve
 
Im might be interested in your 302's. I havent decided quite yet on my sons duster. Its a 74 328 with 727 and soon to have an 8 3/4 with 3:91's. this is the car he drives to school so it has to be streetable. I seen the write up on the 318 with 330 hp and figure thats about his speed. I know what my 69 charger was capable of with 450 and he is not quite ready for that yet. Plan on raising the compression a bit, already have an LD340 intake and headers so maybe your heads would work. Let me know if your still interested in selling them.
 
Guitar Jones said:
92 would be magnums, valves woudl 1.92, 1.65. thats what im about to put on, all 1.6 rockers. if you are really intrested in the 302's i will be sellign mine soon.

I picked up my magnums for $50 at the pick and pull. buy an airgap for the magnum head and your set!

steve
Click to expand...

I didn't think you could put magnum heads on 91 and ealier 318's because bolts don't line up? Pardon my stupity but whats an airgap. I'd definitely be interested in the 302 heads.
 
blackace said:
I didn't think you could put magnum heads on 91 and ealier 318's because bolts don't line up? Pardon my stupity but whats an airgap. I'd definitely be interested in the 302 heads.
Click to expand...

Sure can! The heads bolt right onto the block. There are only two lengths of head bolts used on magnums so you need to use magnum specific head bolts. An LA intake will not bolt to the heads unless you redrill the heads or the intake. However, Edlebrock (RPM Air-Gap) has a manifold specific for the magnum head, MP has two and Professional Products has one that is drilled for both style heads.

You need to use AMC style lifters that oil through the push rods and hollow push rods to get oil to the rockers. The only other differnence is the magnum head uses 10 bolts to hold on the valve covers and LA's 5. However, the 5 on the LA line up with 5 of the 10 on the magnums. I am using LA valve covers on my magnum heads and the seal just fine.

The picture blow is of my 360 (78 block) with magnum heads, notice the intake mounting. Also, I am using the Professional Products CrossWind intake which is pretty much a copy of the Edlebrock Air-Gap.

Complete Front.jpg
 
The magnum head is the best flowing small block head that came from the factory. They also have smallish combustion chambers to aid in compression and are a good quench design when used with zero deck pistons.
 
Also, when use on a LA block, you have to stop for a second and do some math. Heres why;
The earlier LA engines use a rocker ratio of 1.5 VS. the Magnums 1.6.
That cam with lets say...480 lift with the 1.5 rockers are now .512 with the Magnums 1.6 rockers.
Do the math like this;
Cam lift divided by rocker ratio X's new rocker ratio, or
.480/ 1.5 = .32 X 1.6 = .512
.500/ 1.5 = .333333X 1.6 = .533333
.525/ 1.5 = .35 X 1.6 = .560

You'll need to make sure the springs work with the new larger lift.
This new rocker ratio also helps intensify the cam. The valves open a little quicker (and higher) for the same duration.
 
So what would be the best cam to get so I can get so I could make a minimum of 400hp?

I am complete novice when it comes to engine rebuilding and this would be my first EVER engine build up.
 
I wonder how drivabilty is with that 750 Demon on top.
 
Any 318 making 400HP without a power adder is not going to be very street friendly!
 
im running a 750 on mine, i don't mind it at all.

i used to have 360 heads, singleplane intake, .508 cam with a a 3800 stall converter with 2.93 gears, and that wasn't bad.

steve
 
I would be careful with any junk yard magnum heads. I work at a machine shp and almost every one, no matter 50k miles or 300k miles, is cracked between the valve seats. We have to send them off to get welded(pricey!) and then do the machine work. Now we started just using new castings because any more they're about the same price as to have them welded and they're alot thicke casting in the places that matter! Just something to be aware of I'd hate to see some one tear their engine apart to swap heads and then have even more problems. I used a set of the 302 casting on my 74 swinger on a mild stroked 318 (325 ci) ported out to 360 valve sizes and they work awesome! I know magazines say you can port them out to 2.02 but I think the valves would be so shrowded in the chamber that it would do more harm than good. I had to un-shrowd the intake alot for just 1.88", and then the porting to get them to flow right would be a nightmare! If any body's interested in the name of the manufacturer of the new mag castings I'll look into it
 
You're right about the magnum heads. I went through 8 to find 2 good ones. Most were cracked. Looking for two more right now but guess I might have to step up to the Magnum R/T heads.

I think a standard magnum head with 1.925 intake and 1.60 exhaust valves are perfect for most 318 builds. No shrouding of the valves and a great combustion chamber. I run a 318 with right at 10:1 compression with these heads on pump gas without cutting the timing back. No detonation.

Building another right now with magnum heads. The quench with flat top pistons and these heads is great. This motor will be running KB167 pistons .010 in the hole with the thin Mopar gasket. Should have .035-.038 piston to head clearance.

Building a 318 like this with a dual plane intake and 600-650cfm carb works great. A Comp Cams XE262H or XE268H camshaft with a decent exhaust and ignition gives you good torque with decent top end power.

I will say that whenever I built a 318 like Dulcich did in Mopar Muscle for 400hp that it was NOT very street friendly with an automatic transmission and 3.55 gears. If I remember correctly, his 400hp 318 went into a standard tranny car with lower gears. The article I read put the 318 at 400hp at 6150 rpm. How often will a street car see 6150 rpm? And it did not show where the horsepower and torque curves were at. I am betting they were pretty high with the cam/intake/carb combo that he used.

I am not trying to put Steve Dulcich down because it was his articles that got me involved with the "lowly" 318. However, they are written to sell magazines.
 
Are the cracks between the valves similar to the ones seen on the 2.2 and the 2.5 cars? These have cracks between the valves almost from the time you start the car new. These cracks are harmless unless they travel to the water jacket which is pretty rare even after regular doses of 18psi boost.
 
The cracks I have seen are between the valve seats and don't appear too deep. I have been told that they normally develop pretty quick but am not sure.

Whenever I buy heads from the salvage I get a guarantee and return them if there is a problem. It is to the point now that they are pretty well exhausted in the Tulsa area salvage yards.
 
for a majority of the ones we've done the crack doesnt' always go to water but the exhaust seats are so hammered that when replacing the seat the crack spreads- I gues its better on the bench than in some ones new engine. I'd say about 50% of them, maybe a litttle less, are cracked into water!
 
The cracking can't be too much of an issue. My son was a tech at a Dodge dealer for a year and for the past year at a Jeep dealer. They never had an issue with cracks in the heads on the magnum engines. The biggy was leaking gaskets on the plate that covers the bottom of the beer barrel intake used on mangum 3.9/5.2/5.9 engines
 
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