Posted by MoparNorm on Wednesday, September 01, 2004 at 1:50PM :
In Reply to: Is one better than the other? posted by Fred on Whidbey on Wednesday, September 01, 2004 at 12:16PM :
....that you have missed my plethora of posts about the superior features of the 318 Poly.
For starters, the term 'Wide Block' is a misnomer, the Poly block is not wider than the later wedge block, it is the same external casting, it is the HEADS that are wider, because the Poly is the direct decendant of the Hemi. Chrysler was trying to save cost over the expensive (for it's time) Hemi production costs. The Hemi was Chrysler's first mass production V-8, but the perfect combustion chamber layout required two rows of rockers to fit the spark plug into the center of the 'Dome'. The Poly retained the 'Dome', but the spark plug was moved to the side to allow one row of rockers, this resulted in the 'canted' valve effect in a Hemi chamber, a design, by-the-way, that Dodge still uses in the new 'Hemi' (actually a Poly) and Nascar race motor.
A stock 1960 318 Dart motor would indeed be a Poly. If some misguided soul replaced it with a 318LA 'wedge' then that is too bad as Poly parts are available if you know where to look. If his motor has small straight valve covers it is a wedge and parts are everywhere for those. In fact, with enough money, a wedge LA (which is a very good motor) can be made to run almost as good as a 318 Poly. = )
As for the differences, a Poly has better breathing, both intake and exhaust because of the semi-Hemi design. It has a forged crank, solid lifters, and superior oiling. The down side is that the heads and block weight 80 lbs more than the Wedge as the heads are huge and changing casting techniques for the Wedge considerably lightened the Wedge block. The Poly will put out 202 HP stock with a 2bbl carb, 260 HP stock with a 4 bbl carb and 330+ HP with a RV cam, headers intake and Mopar Performance Electronic ignition. It is a torque monster for a small block.
MN
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