what heads to run on a 273

67 gt said
1wild&crazyguy can i ask you something while we are on this subject and i think you are the person to ask seeing you have played around and dissected these heads, i have a 273 commando 4 v and i wanted to know if it would be any benefit in increasing exhaust valve size from 150-160 as they say it would increase intake flow because of the larger ex valve would this be correct as some say there is some benefits HP gains?Ive read some have to bore them right out as the valves might clip the edge of the cylinders and some say you need to fly cut the edges to provide sufficient clearance.Im undecided as to leave the factory cam or step up to the comp cams 270s which is the largest to go without changing my TQ converter. Cam part number 20-246-4 which is a solid.I have the LD4B manifold and was looking at purchasing a set of flow tech ceramic coated headers, updating the carby to a edelbrock 600 vac sec if i go with the cam or a 500cfm if i leave the factory cam. Should i just leave the heads alone and just go with the cam and carb or go with some slight massaging on the ports as the car will be used as a cruiser but will cope a banging from time to time.Cheers

the valves dont really need to be bigger, when i port them , they go into the 177 cfm range w/1.50 exh valve.
if you mean to say scavenge....i dont think you need anymore...or in theory, u may be pulling raw fuel right out the exh port depending on cam choice.

Honestly....i wish that chrysler would have cast the same exhaust floor shape into the 340/360 heads....for if they did, there would be none left...for everyone would be using them instead of the aftermarket stuff that in reality flows only a hair better than 2.02 stock and needs attention to get any really good numbers. Even the eddelbrock & RHS stuff, it still ootb only go's in the 240's range and needs either port work or new bigger valves and accompanying multi angle valve job to be in what i consider 'good numbers'...number worth the 1400+ plus they go for.

jmo