I am thinking of changing the heads on my bracket racer 1969 Dodge Dart. It has a set of ported X heads. The car runs mid to low 12 seconds at 108. I just purchased the car but I have been familiar with it for more than 20 years.
I ran a best time in the car of 12.00 back in 1994 or 95. I dont remember my mph.
What I know about the motor is it is a 340. Cast iron stock intake. Holly 750 dp. Ported x heads. Locked weights in the distributor. Electronic ignition. Msd 7AL. Unknown cam. Unknown compression ratio. Headers but not sure of diameter.
With my mile per hour at 108 I am making around 300 horse power.
Was thinking of going through the engine just to update it. Maybe some late model heads and either a Victor 340 or performer Rpm air gap manifold. I think mid 11s are possible.
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.