Poly Stroker,											
	I recently found some new information on the Poly in of all places, the Mopar 
Performance engine book. Because of this I haven’t yet calculated compression ratios. 
But here goes: The A motor is the some as the LA motor with a 0.11..” higher deck. So 
one can use the 9.669” for deck height. The 360 crank will slip in with the only 
modification need being to turn the main journals down 318 standard size. The Poly rods 
are exactly the same as regular 318 rods,720 grams and floating pins. The cylinder head 
volume is 71cc, roughly. With a 3.94” bore, the minimum required deck clearance of 
.040” is 8cc exactly. 3.94 x 3.58 = 349 cubic inches. The cylinder volume is 715.5cc	
	To get 9.5:1 compression you need a combustion chamber volume of 84.2cc, 
meaning the top of the piston should have an additional 5cc dish or else the pistion top 
needs to be an additional 0.025” down. Using a 0.020” steel shim gasket, Math time! 
9.699-6.123-3.58/2-0.045= new piston deck height= 1.745”.				
	The closest piston to that is Silvolite #1266 with deck of 1.741”, meaning 
compression would be just slightly lower. This is just a stock  318 piston! An exhaust 
valve relief may  need to be cut into the piston top with a piston this high.			
	For lower compression use, the Silvolite 318 truck piston, #1278, with a deck 
height of 1.658, gives a compression ratio of 8.10. As the 318 pistons are only about 20 
grams lighter than the 360 pistons, the assembly would balance out very well with the 
360 flywheel/torque converter and harmonic damper. A very small amount of material 
would be removed from the crank.								
	As you can see, the stroker swap is very straightforward and easy, using mainly 
off-the-shelf parts. The use of regular cast pistons saves a whole bunch of money. Speed-
O-Motive would be who I’d contact to put this kit together for me.	If your block sonic-
checks out to have very thick  walls, the Silvolite pistons are available on special order up 
to 0.080” OS which would result in 3.99 x 3.58 = 358 cubic inches!			
	Larger displacements are possible with Mopar Performance stroker cranks and 
custom pistons. This equals dollars. I think 3.79 is tops, although I have seen somebody 
with a 3.88 stroke custom crank. These will run $800 and up. I am working an a stroker 
approach using a 331 Hemi crank with offset-ground rod journals which may be cheaper 
than the MP new cranks, even though would be a whole lot easier!				
					Best Regards,						
					Rich