340X heads vs late model LA heads vs Magnum.

[2 Darts]

I am not sure but I thought late model 318 heads used the same port size as 360/340. I know the valve sizes are smaller but that could be changed.

The only 318 to use the larger port heads, as far as I know, was the E48 cop car engine of the mid-80s. The valves were 1.88/1.60 IIRC.

 

[Infecteddog]

How much is gained from switching from ported x heads to 1991 318 heads or 1992 and newer Magnum heads. I am basically looking at gaining some quench with a closed chamber head. I am on a budget so that eliminates aftermarket heads. I own a 1991 318 so I have those heads. I can pick up Magnum heads easily as I work at a Chrysler dealer. I am aware of the changes I will need to make to run the Magnum heads on the LA block.

Well the heads flow about as good, but you'll gain compression. The "stock replacements" flow better.

Do you have the low-comp pistons or the high-comp? With the high-comp the Magnums'll land somewhere in the 11s but shouldn't be much worse trying to pump gas than what you've got now. I guess if those are unknowns- does it have a big cam in it or pretty tame, does it run on pump gas or are you using something with higher octane, and what year's the block?

'92-'02 318 heads are the same as '93-'03 360 heads. 318 heads prior except for the 4bbls with 360 heads were inferior in airflow by large margins.