Expert: ryan mahaffey - 4/15/2003

Question
I just bought a 74 duster w/318 2v 904 auto.How do I tell what rear end it has and the ratio.Also how do I tell if it one of those poly tech engines,and if it is .What does that mean?
Could I put 340 or 360 heads on it,what would be
better?
Thanks for any info.

Answer
thanks for your question mike. your 318 is not a poly, unless someone has swapped it, which would be, well, just a bad idea. nothing to be gained, except weight. for the rear, look up mopar rear end identification, as pictures are worth a 1000 words. ill tell you, you probably have a
7 1/4 rear, probably open as well. i skipped part of your question. the poly engines referred to poly spherical combustion chambers. they have wide heads, and a y shaped block. for their day, they were quite advanced, but the la series engine, which includes 68 up 318's were far superior, due to weight savings and other small changes. you can put 340/60 heads on it, but if daily driving is your goal, youd be better off with late 318 "302" castings. worth noting, the e48 police interceptor 318 was a 318 set up with 360 hp heads, via little red express. the 302 castings are good, but benefit from larger 1.88" valves (standard 360 valves). stainless valves are an asset, as they fight seat recession. ive heard 2.02's will fit, but they may be overkill below 5000 rpm. a must have cam....go with the comp cams xtreme energy high lift, maybe 270 grind. with a #302 head(port matched to a good aftermarket 360 intake and larger valves installed), 9.5 compression, xtreme energy high lift cam(thats the series mind you), and a good set of headers, plus a good 650-750 carb (i prefer demon series) you should have a stout combo. however you may grenade the 904-look into an a833 conversion or a 727, however a 727 is heavier, less efficient, and longer than your 904. i hope i have awnsered your question, and feel free to ask more. i do ask that you rate my response on the site. thank you. happy moparing!