Part Two in a Two-Part Series
Last month, MCE Engines invited us into their shop to share in the rebuild of Craig Moore's '72 vintage 351 Cleveland four-barrel engine. Expecting the worst, MCE's Marvin McAfee was fortunate to end up with a salvageable block that could get by with a 4.030-inch bore cleanup. Marvin really didn't want to take it to 4.040 inches, which would have disturbed the calculated compression ratio and made the block a loss the next time around. This month, we're going to get into how Marvin built this 351C into a terrific street engine that combines performance and durability.
There are a couple of directions you can head with a 351C, or even the 351M and larger 400M, which were never available in a Mustang but can be installed in one. The tall-deck M-series Clevelands were conceived to replace FE big-blocks in full-sized Fords, Mercurys, and F-Series trucks. The 400M first appeared in 1972 to replace the 390 in big Fords and Mercurys. In 1975, Ford axed the 351C for cost reasons and destroked the 400M to 351 ci to create the 351M. The M-series engines have a 429/460 big-block bellhousing bolt pattern along with a taller deck block, which doesn't make them a very good substitute for the 351C in a Mustang.
When Craig's 351C arrived at MCE Engines, we were stunned to find Boss 302 heads on the Cleveland four-bolt-main block. They work on a 351C with proper water passage modifications, but they were a waste of early (C9ZE, December '68) Boss 302 castings (many '69 Boss 302 owners would love to have them!) when 351C-4V heads or even Australian Cleveland heads would have been a better choice without modifications.
When we suggested Marvin find a set of 351C-4V heads or the desirable Aussie heads with 4V chambers and 2V ports, he looked over his glasses at us and went back to work. There was no time for such a search. He was on a tight timeline to get this engine finished and back to the customer. The Boss 302 heads have all the same attributes as a Boss 351C head, and that's how Marvin saw it.
MCE Gotcha Chair Dyno Estimate
MCE Engines has a formula here for success on the street and racetrack. Torque begins to come on strong at 2,500 rpm and pulls like stink through 4,000 when it passes the torch to horsepower at 4,500 rpm. At wide-open throttle, horsepower runs with this street engine, maintaining the Cleveland's reputation for power. This isn't a 500-horse monster mash, but instead a reliable street engine with a lot of grunt, which will allow Craig Moore to smoke his skins aggressively on Main Street, yet be able to make the morning commute.
Marvin checks ring end gaps...
Marvin checks ring end gaps on every bore, even with pre-gapped rings. He prefers a ring end gap of .018-.019-inch top and .020-.022-inch for secondary. Proper ring end gap is crucial to good cylinder sealing and internal friction. Ring tension is a huge factor here.
Dynamic balancing is important...
Dynamic balancing is important to durability and smoothness. Marvin has a unique relationship with Revco Automotive Balancing. He models his balancing program off the lightest piston and Revco takes it from there. Marvin likes to get it within one-tenth of a gram, which is hard to achieve, but Marvin is coyote stubborn. He wants pinpoint accuracy and gets it because he understands how destructive vibration can be.
When assembling a short-block,...
When assembling a short-block, be it mock-up or final assembly, always install the camshaft first because it's easier to carefully guide the cam in place without the crankshaft in your way. Marvin looked to his Comp Cams catalog and picked out #SK32-431-8, a roller camshaft kit with matched components designed to work well together.
Before Marvin sets the crank,...
Before Marvin sets the crank, he gives the rear main seal grooves a dressing of Permatex's The Right Stuff to ensure a good seal between the block/cap. Marvin will tell you the whole point of a gasket is to seal, adding that many builders overdo the sealer. Just a thin film of The Right Stuff is necessary. Don't forget to remove the original rear main rope seal pin if it's still there. Otherwise, it distorts the rubber seal and you will have leaks.
At 76, Marvin can still haul...
At 76, Marvin can still haul a heavy crank off the floor. Here, he sets the crank after the bearings get a dressing of Marvin's own special-mix engine assembly lube. This MCE assembly lube has tremendous staying power.
Marvin carefully sets each...
Marvin carefully sets each four-bolt main bearing cap, then torques to specifications in third values.
Marvin prides himself on methodical...
Marvin prides himself on methodical technique. Each main cap gets torqued in third values for smooth seating and clamp. With each torquing, Marvin checks crankshaft freedom of movement in order to isolate any trouble spots. You should be able to turn the crank at the snout without a tool if clearances and torque are correct.
Crankshaft endplay is checked...
Crankshaft endplay is checked next; it should be .004- to .006-inch. Marvin also checks camshaft endplay, which should be .005- to .0055-inch. When a dual roller timing set is employed, don't use the crankshaft sprocket oil slinger to ensure proper timing cover and chain clearances.
Piston ring installation takes...
Piston ring installation takes patience and the right tools. Many builders roll the top two rings on, which is not the way to do it, according to Marvin. When you roll the top two rings on, you distort them, causing poor ring seating. Use a ring expander instead, staggering ring end gaps 180 degrees opposite each other.
Oil rings must be rolled on,...
Oil rings must be rolled on, which won't harm them. The expander ring goes on first, with ends butted, not overlapped. Ring end gaps should be 180 degrees opposite, but not aligned with compression and oil ring gaps.
Connecting rod side clearances-.010-...
Connecting rod side clearances-.010- to .020-inch-must be checked. Maximum allowable clearance is .023-inch. Proper clearances support good oil flow and alignment.
This is where the truth comes...
This is where the truth comes home on everything. Here, Marvin degrees the camshaft and checks true top-dead-center. Manufacturing tolerances can vary in crankshafts, connecting rods, pistons, bearings, and camshafts. This is why, at the least, Marvin degrees the cam to check out true timing events. He also checks the #1 piston for true top-dead-center. And if you're really on the ball, you check all eight cylinders.