1970 318 Cylinder Heads

[DY31970]

Hi, I have a 1970 Challenger with the 318 engine, all original. Does the engine have the small port cylinder heads, with the port diameter of 1.09w X 1.55h?

 

[Beekeeper]

It should have smaller intake runner ports but I’m not sure on exhaust ports.

 

[moparleo]

It sounds like you may be considering manifold swapping. The can of worms starts to grow...

 

[DY31970]

Thanks Beekeeper.

 

[DY31970]

moparleo, I want replace the old headers with new TTI headers. If the engine has small port heads, then for the headers to seal properly, additional material will be added to the ports for headers to seal properly. I have to let TTI know ahead of time.

 

[340challconvert]

Edelbrock once made an intake manifold specific for use on the 318, the LD4B that was made for the ports on that engine. That manifold or it's equivalent would really perk up your 318. Combined with headers; it will enhance the performance. Not sure how the newer Edelbrock Performer 318/360 intake matches up. I hear good things about the Air Gap rpm manifold with a 318. Port matchups make a big difference in how an engine responds to the modifications. (But in opening up the proverbial "can of worms" with this topic, changes like this require other mods such as cams and exhaust upgrades to get any benefit) What are you looking to achieve?

 

[340challconvert]

Port size comparisons for reference

1968-1974 273-318 casting 2843675
Intake Gasket Size....................1.05" x 2.07"
Exhaust Gasket Size..................1.14" x 1.59"

vs.
1970 {340 T/A} Casting #3418915 'J-Head'
Intake Gasket Size.......................1.16" x 2.27"
Exhaust Gasket Size.....................1.25" x 1.75"

Thanks to 69 Cuda 440 for the info!

 

[DY31970]

Thanks for the information 340challconvert. I'll check out the LD4B and Air Gap rpm manifolds. My engine is all original but for the headers which were added along the way. At least one of the headers has a hole in it by where the collectors meet. So I'm trying to decide if I'd get the TTI headers and their dual exhaust system or get a pair of original 340 exhaust manifolds and match them up with a factory dual exhaust system from Accurate Exhaust. There is a guy selling a set of the 340 exhaust manifolds for $1099 and just before sent an email accepting offers. What is a fair price for the 340 exhaust manifolds? I have been thinking about adding an Edelbrock intake and a 4 barrel carb. On Edelbrock's website they recommend one of their cams to compliment the intake and carb. Can a new cam be added to a good running 318 with 95,000 original miles?

 

[moparleo]

Here is my recommendation for what it is worth. The 1970 heads do not have hardened valve seats which were mandatory after the elimination of leaded fuel which softened the pounding of the exhaust valves on the vale seats.
So your heads should either be rebuilt with new guides, exhaust valve seats and oil seals OR better yet is to get later set of 318/360 heads that already have the unleaded modifications and also have better ports. And they will be cheaper than rebuilding the old heads.
That way you don't need special intake manifolds or worry about exhaust ports size. Win, Win.

Or pull the 318, put it aside and get a later 318/360 engine. They are still very reasonable and you get a new start with an automatic Horsepower boost.

 

[DY31970]

moparleo, Thanks for the recommendation. I didn't think about having to rebuild the original heads. I've read about using 360 heads, I have to look more into that.
On Youtube there is a good channel, Uncle Tony's Garage and he specializes in Mopar info. He has a video, the 318 the most under rated mopar V8. He talks about the 1967-1969 318 as having a forged steel crank, with closed chamber heads which give a compression ratio of about 9.2 to 1. In 1970 chrysler went to a cast crank and open chamber heads which lowered the compression ratio to about 8.75 to 1. I've thought about getting a 67-69 318 and rebuilding the 318 using the cars original block, and using the forged crank and the heads (rebuilt) from the 67-69 318.

Another option is getting aluminum heads from Edelbrock. I've also considered getting an original forged steel crank 440, big block 727 trans and install an 8 3/4 rear end. I was planning to install an 8 3/4 rear end any way. These options are more involved. I'll see what I find out in further research and go from there.