318 unleaded heads

[Timmayy]

After 20 years the 318 in my 69 Sport Satellite finally gave up. It was a good run. I've pulled the motor and ready to go to my buddies shop. I have a set of truck heads from the mid 80s. Looking for the unleaded heads to run the crappy gas in todays world. The heads have these little holes under the exhaust ports. What are they for? Am I better off sending out an older set of heads and just having hardened valve seats installed?

 

[Cop car wagon]

The advantage to running air port heads is, if you want to run headers, they will actually seal.
The air port head has enough material around the port for the 340 sized headers. Early 318 do not, and would leak.

 

[Timmayy]

The advantage to running air port heads is, if you want to run headers, they will actually seal.
The air port head has enough material around the port for the 340 sized headers. Early 318 do not, and would leak.

I am using the stock manifolds off my 69 318. Will they seal?

 

[Dodge33]

They are emission ports. I have never done it before, but you can drill them out some to an SAE thread, and then use counter sunk ........
Help me out guys....... I'm having a brain lapse!

 

[Vaanth]

After 20 years the 318 in my 69 Sport Satellite finally gave up. It was a good run. I've pulled the motor and ready to go to my buddies shop. I have a set of truck heads from the mid 80s. Looking for the unleaded heads to run the crappy gas in todays world. The heads have these little holes under the exhaust ports. What are they for? Am I better off sending out an older set of heads and just having hardened valve seats installed?

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The small holes below the exhaust ports on the pictured heads are the air injection ports. The additional boss material and holes first appeared in 1975 and continued in later years. The matching exhaust manifolds had additional boss material cast into the manifold to either use the ports with an air pump injection system, or additional boss material to cover the ports if air injection was not used, as shown in the following images:

To use the heads with exhaust manifolds or headers that might not cover the holes, resulting in exhaust leaks, drill and tap the holes to 1/4"-20 and install set screws with locking sealant to seal them. Ensure the head of the screw is below the exhaust port machined surface. With the air injection port blocked in this manner, the stock 1969 exhaust manifolds will work without any possible exhaust leaks in this area.

Example of drilled and tapped hole with a set screw:

 

[Cop car wagon]

I am using the stock manifolds off my 69 318. Will they seal?

Yes they will seal. Best seal is no gasket.
Plugging the air port is a given. I have tapped and put a 1/4-20 set screw, but lately I just clesn with a drill, pound a 1/4" dowel in, cut off and on to the next one.
Those heads will allow you to upgrade to 71 360 manifolds, which look the same, but bigger.
Bigger exhaust will add power or mileage, if you don't care about more power.

 

[Timmayy]

Ok, I never realized this. I may just have the machine shop put in hardened valve seats in the older heads.

 

[guy gadbois]

I would agree with using the earlier heads; put in hardened seats, bronze guides and posi lock seals. do a little gasket matching and smoothing with you big dremel and Bobs yer uncle...imnsho and no expert on LA heads opinion.

 

[PRHeads]

My preference would be be to recon the 1969 heads and install hardened ex seats.

If you decide to use the 80’s heads be sure to have them magnafluxed.
Cast iron heads with induction hardened seats tend to be crack prone.