340X heads vs late model LA heads vs Magnum.

340dartley said

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.

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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.