Every so often they get a customer at the Trans Am Racing engine shop who thinks a large displacement Windsor stroker just isn't big enough. For those folks, a 427 is at the bottom of the displacement range, not the top. These are the people who order a 385 series big-block engine for their project. The original 429s are getting fewer and farther between, and, for this crowd, the displacement baseline is 460 ci. The cubes just go up from there. For applications where over 500 hp is desired, a big displacement delivers the goods and eliminates the peaky characteristics of an engine that has to wind to the stars to make big power.
The 385 series engine we have planned at Trans Am Racing is going to be sized at 545 ci. With this much displacement, stratospheric rpm levels won't be necessary to deliver the horsepower and torque numbers we're after.
With a power level target of 600 horses, we're still going to need over 1-hp-per-cubic-inch. this is our goal, while simultaneously keeping the engine tractable enough to have acceptable street manners because the street is where this engine will be doing business. Home will be beneath the hood of a '69 Mustang Mach 1. The car has had the shock towers shaved to allow installation, and custom-made headers will also be required. We're going to start with a '74 Ford 460 block that has been cleaned up and bored 0.030-inch oversize. The relatively small overbore means that almost all of the extra displacement in our 545 is coming from a big stroke increase. The stroke length on the original 429 was 3.59 inches, while a 460 has a 3.85-inch stroke. The stroke length on our 545 is 4.50 inches. That's an increase of .65 inch, or almost two-thirds of an inch over the 460 and almost a whole inch longer than a 429.
Let's see what parts TA Racing has selected for this build, and then we'll look in on the construction of the short-block. Next month we're going to top the engine off with the rest of our induction, including some customized Edelbrock cylinder heads. Then we'll take a trip to the dyno shop and see what the engine dyno tells us.
Rings And Wrist Pins
Larger displacement strokers often use a special piston with the wrist pin location raised to accommodate a longer connecting rod. Sometimes, as in the case with our combination, the wrist pin will be moved up until it intrudes upon the oil ring lands.
In a racing engine where the running time is limited, this situation isn't a problem. For a street engine, however, this is an undesirable condition. The opening underneath the oil ring can cause excessive oil consumption and fouled spark plugs. However, this condition can be controlled using gapless piston rings in conjunction with a lower support ring.
The reciprocating assembly...
The reciprocating assembly for this engine is available at Trans Am Racing (1531S-460, $1,850). this cast-steel crankshaft is manufactured by Scat and has a long 4.50-inch stroke. The cast-steel construction is a big step up from a gray-iron casting and is also less expensive than a forged-steel piece. Balancing the whole setup will run you $155 and is good insurance.
For piston rings, Total Seal...
For piston rings, Total Seal gapless rings (RM269035, $175) were selected. Although more expensive than conventional piston rings, they have a super-low 111/42-percent leak down. For an engine equipped with regular rings, expect a leak-down figure in the area of 8 percent. Every little bit helps, and any compression that stays above the rings means horsepower; any that leak down end up in the crankcase. This photo shows the rings required for one piston.