Poly Lovers, Unite!
Thanks for remembering my post. ALL 318s and 5.2 Mags, as well as all 273s are internally balanced. For sure also ANY 318 or 273 (not sure about 5.2)crank can be swapped into ANY OTHER 273 or 318 without rebalancing. So if the Poly had a crank with the smaller diameter ring for the converter, a later 318 crank can swap right in with no other changes, except the thrust bearing in the new crank's bearing set has to be the older smaller diameter one to fit the block. So the 'bay's $99.95 318 crank and kit may need a different thrust bearing to go into the Poly block.
On to the ports. I believe that if you compare the cross-section of the Poly intake port to the cross-section of the 318 (not 360) intake port you will find that the Poly has more cross-section. I also believe that the Poly head flows quite a bit more than the 135 cfm of the usual 318 port. Old-timers concur that an old 318 is a lot stouter than a new (LA) 318 for pulling a trailer. Old timers like this don't even consider the 5.2 Mag because they haven't owned a vehicle that new. I think an injected 5.2 Mag would be stronger than the Poly pulling a load.
The 4" stroker crank drops right in, rods are the same dimensionally as all LA rods, pistons need to have valve pockets for the intake valve which are different than the Wedge location.
There are two problem areas for the Poly. First is intake selection. Since Holley discontinued the Weiand 7503, there are no new intakes available. The last used Weiand 7503 I tracked on the 'bay sold for $520! There were some 2-4 intakes stock and these are decently priced but try to put carbs on them! The factory 4-barrel manifold from the 1962 is priced at about the 7503 range.
The second problem area is the camshaft selection. Crane and Isky used to make cams but not for a long time now. Chris Neilsen in Utah has a supply of cores and will grind one for you, that's who ground Pavlovich's cam. There is a smaller cam company who advertised new Poly cores about 3 years ago. Figure that the new Poly cam, lifters and pushrods will run you $400 or so. If anyone has better information chime in.
The blocks are pretty stout but Mopar casting quality rules. I would feel safe at 0.060" overbore and I believe Pavlovich's engine ended up with 4.000" pistons. But I'd UT a block before going to 4.000".
The timing set, oil pump and distributor swap from LA motors, not a problem.
Rocker Arm Specialities will rebuild the rockers.
Race Section denizen OU812 claims to have Poly head porting experience.
The Edelbrock P-600 3-2s manifold for Polys has been discontinued for ages. It is cool but uses Stromberg 97 type 3-bolt 2-barrel carbs that either leak or cost an arm and a leg to have work right. There is an aftermarket fuel injection system that looks like a 97 so that may be an option. also the 97 is back in production at cost of ~$400 each.
All for now,
R.
