540” to 572” Big H.P. Mopar
This month I will go over the foundation of what I use to do battle with the Bowtie-powered racers in bracket racing, Super Comp and Top Dragster.
This engine started out as a 540” Indy Cylinder Head built complete engine. The basics are as follows: 4.5” stroke Callies crankshaft, Eagle steel rods (Mopar length and rod journal size), Indy ported 440-1 heads, Comp Cams roller, Indy single line oil system all based on a 4.380” bore Indy Cylinder Head-prepped Mopar Mega-block. In today’s bracket world it was a pretty basic and solid performer from the minute we removed it from the Indy Cylinder Head dyno. As a matter of fact, it won the first 8.90 race it was entered in only a
After the third season we decided that we wanted to enter some Quick 16 races and race IHRA Top Dragster more often. The cylinder walls were a little worn after three seasons, and the pistons and pins were a bit heavier than we wanted to make the most horsepower, so we decided to rethink our plans a little bit. Rather than just freshen the engine with a hone and a new set of pistons, pins, bearings and rings, we decided to go ahead and bore it out from 4.380” to 4.500” and make it 572 c.i. with the current 4.500” stroke crank in the 540 combination. What the heck, I had to buy pistons and rings anyway, right? They say you can’t go wrong with more cubic inches, right? WOW, they are right! Bigger was better, read on and you will see what I mean.
The first order of business was to get a set of pistons made and get the ring package sorted out. We called CP Pistons where Ric was a great help in getting us the best combination for power and durability. The piston and pin came back weighing in at only 598 grams (that saved us over 60 grams per piston!) and that was with a larger bore. We went with a .043 top and second ring and a 3mm oil ring.
The guys at CP also suggested their lateral gas ports, which allow compression to get behind the top ring and push it out against the cylinder wall. This is a very low-tension ring package and requires a vacuum pump to work at maximum efficiency. We already had the 4-vane Moroso vacuum pump so that was not a problem.
The cylinder walls were honed with a torque-plate in place and finished with a 400-grit stone. The key to the honing operation is accuracy. If the cylinders are “truly round” and the rings get the best possible seal you will see more power and more consistency. Find a shop that has the best equipment and a reputation for attention to detail when it comes to the cylinder block work. The dividends will be less problems further down the road.