505-Inch Pump-Gas Cadillac Engine - Full-Frontal Cadillac

When John Walker builds an engine, he builds it in style. Cadillac style. John is one of those rare few who think outside the box and dare to go where few have tread. When asked how he got into the luxobarge powerplants, he chuckled and said it was by accident. Several years ago, he was in the middle of a trade deal and was supposed to get a 454 for his end of the bargain. When it came time to collect, the Chevy engine was a no-show. Instead, he was offered a pair of Cadillac engines. "Of course, I had to pull them," he says.

As he started building more power from the Caddys, he found the aftermarket lacking, so he started making his own parts. This 505ci monster that he built for the 2007 Jegs Engine Masters Challenge is not so much a tribute to GM's highest luxury line as it is a showcase of the parts that John (through his company Torque Inc. and a few other daring companies like MTS) have created for the engine family. Over the last several years, new heads, cams, intakes, rods, and pistons have found their way into the Cadillac engines that Torque offers. This 505 is a good mix of those parts.

When building an engine of this caliber, it takes a good plan to hold up to the abusive torque that the engine makes. The engineers at GM had a few of the bases covered on this point. John used a factory 500-inch block from a generic mid-'70s Caddy. He could have used either the 472 or 500 block built from 1968 to 1976, as they share the same dimensions other than stroke and piston compression height.

There are positives and negatives to the factory block. The small cam tunnel limits the cam dimensions. Choosing a cam with big lift means grinding the base circle smaller, instead of making the lobes bigger. This weakens the cam core, and in a contest where running a factory-style cast-iron core for a flat-tappet cam is mandatory, that can be bad news. On the positive side, John is a big fan of the on-center connecting rods. He explained that almost all V-8 engines use offset rods, meaning the small end of the rod is not directly in line with the big end. The Cadillac, like the newer LSx engines, uses a rod that's directly in line. "We had it right all along," John says, referring to the rod design. His argument was that running an on-center rod will keep the force from the combustion process firmly centered at the base of the rod instead of trying to tip it over and side load it. John often has Scat build several sets of rods at a time, so when it came time to order a set of seven-inchers for the engine, it was no problem for his normal supplier to comply. For many high-horsepower combinations, billet main caps and/or main girdles help keep the caps from walking. In this case, the factory caps-accompanied by a set of ARP main studs-were easily able to handle the forces in play.

Cadillacs, like their Pontiac cousins, have a lifter valley with a massive hole that sits wide open and allows oil to rain down onto the cam and crank. "It's got a great big section in the middle you can stick your hand in." Not bad if you want to make sure oil gets splashed all over creation, but bad news if you are trying to reduce windage. John made a metal block-off plate and welded it into place. After installing that, he installed some plastic plugs in the lifter holes, made some breather stands, and filled the lifter valley with epoxy. He says the red goo was "a high-temperature epoxy coating that they put on the inside of hot water pumps, like in a nuclear plant. Nothing sticks to it." As for prepping, John says after a good washing he "put Sikkens primer on the valley as soon as it dried, so it wouldn't rust up. That stuff is designed to have an epoxy coating put on top of it."

Like the block, the crank was a factory piece. All 472/500 engines used cast-iron cranks, but as usual, there are some good and bad castings. OK, Maybe not bad castings, but not as totally bombproof. The cream of the crop is the 094 nodular-iron crank from the '70-71 cars that weighs a good 9 pounds more than the more common ones. The unit John used here was one of the plain-Jane versions from the mid-'70s that he claims holds up fine. This must be the case, as his huge engine made over 600 hp and 600 lb-ft of torque! He had the specialists at Shaftech give the crank the full tune-up, including cutting down the counterweights and balancing before installation.

Torque Inc. is one of the few suppliers of forged pistons for GM's luxury engines. They keep a good supply on hand and have them made by either Diamond or Probe. In this case, Diamond whipped up a set of forgings with a fairly common .043/.043/3mm ring pack and an uncommon dish design. For lack of a better term, we'll refer to this as the "Altoids box" dish. There have been different schools of thought in piston dishes recently. Some use a traditional inverted dome, some use a spherical dish, and there are some using a "dual quench" design like the Torque Inc. engine. John told PHR: "Since the aluminum head is a little different than the iron head, there's actually quench on both sides of the combustion chamber. I saw what the Sprint Cup guys have been doing, and what some of the piston companies have been doing for pistons with heads similar to the Cadillac, and figured I might as well put all the dish in the middle to even the quench out on both sides. I don't know that it helps, but it certainly lightens that piston a bunch." Any time you can get a big-bore piston down to a measly 579 grams, it takes a tremendous load off the beam of the rod and frees up horsepower in the crank that isn't trying to throw a big weight around.

John had the piston skirts coated with a low-friction, oil-shedding coating, and the tops coated to keep the heat in the chambers. Normally, Cadillacs use a massive 1-inch wrist pin, but in this case, it was knocked down to a lighter big-block Chevy size. The rings were Speed Pro file fits, and as the bore size was fairly common to big-block Chevy numbers, they were easy to get a hold of. John says many of his engines are built this way to keep the cost down. Using a .020-inch oversize piston instead of a .030 oversize really opens up the availability of inexpensive rings.

The Torque Inc. engine used a set of uncoated Clevite main bearings. There is not a tremendous selection of undersize bearings available for the big Caddy, but Clevite has always managed to keep a good variety for rebuilders. In years past, John had become a fan of the legendary Vandevell bearings for connecting rods. Their lead-indium overlay allows them to absorb a good amount of debris and still be very forgiving on the journals. As far as hardness, they lie somewhere between a typical Clevite H-series and their super-malleable M-series microbabbit bearings. Clevite does offer their take on the Vandevell bearings, known as the V-series; however, when the Vandevell company went the way of the Dodo bird, Childs and Albert began to reproduce the bearings to the exact specifications as the originals. John picked up a set of those for use in this buildup, and was quite pleased with the results.

When it came time to work on the oil system, John acquired a Melling pump and immediately tore into it. Using 3M diamond files, he meticulously deburred any sharp edges on the case and gears, as well as sleeving and honing the pressure relief plunger cylinder. His diligent work showed as the oil pressure stayed steady during his dyno pulls, averaging 51-52psi. The only change in pressure was a slight rise and subsequent fall between 2,800-3,800rpm. This range is typically when detonation problems occur, so the extra pressure was not shunned. Whether this was by intelligent design or divine intervention is still unclear. John does feel there is an inherent design flaw in the OEM-style pump. "I think the design of that oil pump has a tendency to turn the oil into foam. The rotor design is identical to a Buick, and they have nothing but oiling problems, especially when you spin them over 4,800 or 5,000. All of a sudden everything just starts going haywire. We've designed a new oil pump; we just need to find a way to make them inexpensive." When asked whether he would prefer a gerotor pump, he expressed his dilemma: "The pump is in the front, and most of the pans are either a mid-rear or rear sump, so you've got that stupid, ungodly-long pick-up that's on a really bad angle. If I went to a gerotor, that's fine, as long as somebody wants to use some sort of a pre-oiler, because the one thing that's bad about a gerotor pump is they don't want to self-prime."