Jim Smart
June 13, 2014

The true origins of Ford’s oddball 351 Cleveland 335-series engine family may never be completely known. Suffice it to say this was an engine born for racing that never realized its true potential as a factory high-performance engine. What makes the 351C an oddball is how out of synch it is with the rest of the vintage Ford V-8 engine bloodline. It was produced for just four years in the United States though there were the tall-deck 400 and de-stroked 351M through 1982. Ford Australia never lost its love of the 351C where production continued down there well into the 1980s before the Aussies concluded the 351C was too much of a good thing.

JGM Performance Engineering tipped us off about a 351C it was building in the suburban Los Angeles community of Valencia in conjunction with a CarTech Books project with author George Reid. Their Cleveland was going to make unheard power thanks to an Eagle stroker kit that would bring displacement to 408 ci and the all-new Trick Flow Specialties CNC225 cylinder heads and single-plane induction topped by Holley. Jim Grubbs and Jeff Latimer of JGM were confident this engine would make at least 650 horsepower. They never expected it to make more than 700. What’s more, they’re planning a return trip to the JGM dyno for a shot at 800 horsepower with a few in-house improvements Jim has up his sleeve.

JGM Performance Engineering didn’t make this much power with an aftermarket block or custom made speed parts. It did it with off-the-shelf parts from Summit Racing Equipment, Eagle Specialty Products, Trick Flow Specialties, Jesel, Holley, and Comp Cams. This is a four-bolt main 351C D2AE-CA block Jim had put away for safe keeping years back. He hauled it out for book author George Reid and suggested they build a monster Cleveland. You get real horsepower and torque from displacement and stroke. You also get it from compression and good cylinder head flow. This is where Trick Flow’s expertise shines handing us the unexpected horsepower bonus.


The Valvetrain

Because we are aiming for 7,500 rpm, everything inside must be ready to march with lockstep precision when the heat gets hot. We want valves slapping their seats in just the right synch with piston timing events, which means we need to fill the cylinder bores with the densest charge possible before ignition takes place and consumes the mix. This is why JGM went to Comp Cams for its PN 32-000-9 custom grind mechanical roller camshaft, thick-wall one-piece Comp pushrods, and Jesel Pro Series shaft-mounted precision 1.650 rocker arms. Jim Grubbs did a lot of computer time coming up with the Comp custom grind, which is available to anyone who wants aggressive 351C performance.

Cam Specs
Manufacturer Comp Cams
Custom Grind FC 3207 /1660 SR108.0
Lobe Separation 108 Degrees
Lobe Lift 0.441/0.420-inch Intake/Exhaust
Duration at 0.050-inch 260/275 Degrees Intake/Exhaust
Gross Valve Lift 0.762/0.726-inch Intake/Exhaust
Duration at 0.020-inch 296/307 Degrees Intake/Exhaust
Valve Timing at 0.050-inch
Intake Open 22 BTDC
Intake Close 58 ABDC
Exhaust Open 65 BBDC
Exhaust Close 29 ATDC
Valve Adjustment
Intake 0.020-inch
Exhaust 0.026-inch

Rocker Arms

JGM wasn’t about to leave anything to chance in the Cleveland’s valvetrain system, which is why it went with race-ready Jesel shaft-mounted Pro Series rocker arms for spot on valvetrain stability. Jesel achieves this kind of excellence with its own 7000 Series aluminum alloy, which yields a super lightweight rocker with unprecedented strength. Our Jesel rocker arm assemblies aren’t just off the shelf, but ordered and manufactured to JGM’s specifications on Trick Flow heads. Surfaces are shotpeened for strength, which also relieves stresses at the same time. Our Jesels are also needle bearing supported for friction reduction and stability. ARP shaft bolts are engineered for spring pressures exceeding 800 pounds.

Seal It Right

Although a lot of us struggle with oil leaks in fresh engines, it never has to be this way if you properly prepare all contact surfaces going in. Engines leak oil and coolant when we fail to prep. With all sealing surfaces, you must perfect the surface. All contact surfaces must be hospital clean, flat as the American prairie, and free from scoring.

One mistake we see is a lot of excessive use of gasket sealer. Remember, gaskets are there to seal all by themselves. The only reason you should ever use sealer is for gasket security and small imperfections. That means you need only the gasket and, at the most, a very thin layer of Permatex’s The Right Stuff available from Summit Racing Equipment.

Two-piece rear main seals need a thin film of The Right Stuff around the perimeter, then, seat the seal with the lip pointed toward the crankshaft. Apply a modest amount of The Right Stuff to the seal tips and stagger the gaps away from main cap parting lines for best results. Use The Right Stuff at gasket ends only where pan gaskets meet end gaskets. JGM is using a deep-sump Canton race pan from Mustangs Plus.


1. JGM Performance Engineering is using a stock standard bore D2AE-CA four-bolt main Cleveland block for this exercise massaging it in every way possible to ensure success. To keep the bottom end from peppering the concrete floor of a dyno cell, JGM gave the block a good line honing and installed ARP studs.

2. Block has been prepped and fitted with ARP studs and Speed Pro tri-metal H-series bearings that live happily with a steel crank and a whole lot of stroke. Cam bearings have been pressed in place and we’re ready for methodical assembly.

3. Eagle Specialty Products has provided JGM with a complete 408ci stroker kit including an ESP treated 4340 steel 4.000-inch stroke crank, 6.000-inch H-beam rods, and Mahle positive dish forged and coated pistons sized to achieve 13.0:1 compression. Our Eagle steel crank has been ESP Armor treated for extraordinary strength. ESP isn’t a coating, but instead a treatment that hardens and protects the surface. It also perfects the surface with a mirror surface designed to minimize any risk of scoring.

4. Eagle’s 4340 steel crank is checked for endplay before main caps are installed and torqued. Endplay for an engine like this needs to smack in the middle of 0.004- and 0.010-inch. As main caps are installed, endplay needs to be checked again.

5. ARP studs have been threaded deep, but not seated. You do not want to seat them, but instead get them within 1⁄8- to ¼-inch of the bottom of the hole. With caps properly seated and alignment, ARP locknuts are torqued in one-third values from the center outward, then, torqued again and marked as torqued with a felt tip.

6. During mock-up phase, JGM found the pistons needed to be fly cut to clear the CNC 225’s larger than anticipated 2.08-inch intake valves.

7. Though a lot of builders like to roll compression rings on, Jim Grubbs prefers to use a ring expander and strongly suggests its use to prevent ring distortion. Did you know only the top ring is considered a compression ring? The second ring is an oil ring. Bottom rings are considered oil wiper rings that thrust oil back into the crankcase.

8. With the short-block assembled, piston deck height is checked. These Mahle forged and thermal coated units are a pinch out of the hole at 0.002-inch on average. The Cometic MLS (multilayer steel) head gaskets will provide necessary clearance.

9. Because JGM is running 13.0:1 compression, it has been decided to stud the block with ARP fasteners for added security. Never bottom the studs out. Leave about 1⁄8- to ¼-inch of space beneath the stud.

10. An adjustable timing gear allows you to custom tune valve timing based on what you want from the engine. Advance valve timing and you gain low-end torque. Retard valve timing and you gain high-end horsepower. JGM decided to keep this cam straight up at zero.

11. Cometic multilayer steel (MLS) head gaskets are JGM’s choice from Summit Racing Equipment. These gaskets offer extraordinary sealing capability.


Sweat The Details

If you’re really on top of your engine building game plan, your blueprint will include chasing and repairing bole holes and threads. To achieve accurate torque readings when you are tightening fasteners, threads must be clean to where a bolt can glide through smoothly and don’t forget lubricant on bolt threads. Never torque fasteners dry.

JGM Performance Engineering didn’t make this much power with an aftermarket block or custom made speed parts. It did it with off-the-shelf parts from Summit Racing Equipment, Eagle Specialty Products, Trick Flow Specialties, Jesel, Holley, and Comp Cams.

Developing A Great Cylinder Head

Trick Flow has never been known for a lame cylinder head. The CNC225 head took months to develop and with a tremendous amount of flow bench and dyno time. JGM knew this head was being developed and could not wait to try it out. Trick Flow built its own 383ci Cleveland stroker for cylinder head development and wound up with 524 hp at 6,000 rpm and 480 lb-ft of torque at 4,500 rpm. The results have been remarkable considering Trick Flow never had to push its Cleveland test mule very hard.

Look at these flow numbers.

JGM Flow Bench Trick Flow Flow Bench
Valve Lift Exhaust/cfm Intake/cfm Exhaust/cfm
0.100-inch 84.2 55.4 68 55
0.200-inch 134.7 106.2 146 115
0.300-inch 201.6 151.8 223 162
0.400-inch 255.6 180.9 282 204
0.500-inch 289.4 200.5 313 231
0.600-inch 309.6 211.1 336 240
0.700-inch 317.2 216.8 339 244
0.800-inch 327.1 218.8

Note: JGM Performance Engineering used clay as an entry, short exhaust tube. Data courtesy How To Build Max Performance FORD 351 Cleveland Engines by George Reid, CarTech Books, #SA252.


12. Trick Flow’s new CNC225 alloy cylinder head sports right-sized, drive-through 225cc intake ports that offer a nice balance of volume and velocity with 2.08/1.60-inch intake/exhaust valves in high-swirl 60- to 62cc chambers yielding minimal valve shrouding and extraordinary flow at 0.800-inch valve lift. Trick Flow has positioned the 14mm deep-reach spark plug in the middle of the action. Excellent quench minimizes the risk of detonation.

13. JGM considers itself fortunate to have a shot at CNC225 head castings from Trick Flow. There are certainly several options out there for Cleveland engines. The Trick Flows were the most logical choice for this engine and objectives. According to George Reid, who has authored an excellent 351 Cleveland book from CarTech Books, the CNC225 will bolt onto the 289/302/351W engines. The challenge here is finding an induction system that will mate to the CNC225 heads on a Windsor block.

14. This is Trick Flow’s TFS-5160111-C single-plane intake manifold, which has been engineered specifically for the CNC225 head. When you stroke the Cleveland to 408ci, this manifold is right at home in terms of high-end horsepower because these generous and well thought out intake ports deliver real velocity at high rpm and a lot of displacement. Remember, when you stroke a Cleveland to 4 inches and 408 ci, you no longer have a small-block. You have a big-block. You get horsepower and you also get generous amounts of torque.

15. Holley’s 950-cfm HP carburetor is exactly what JGM wanted for the 408C project because it delivers a sweet combination of horsepower and torque. JGM was anticipating 600-650 horsepower, and that’s what it produced before Reid’s Cleveland book went to press. By the time JGM was finished performance tuning this 408C; it achieved 704 and torque on the order of 600-plus lb/ft with the first and only pull. It will go back to the dyno shortly and we will report the results.

16. Jesel Pro-Series slotted 1.650 shaft-mounted rocker arms offer incredible stability. These guys don’t come cheap, however, they are comforting when you start courting 8,000 rpm.

17. Initially, JGM went with a stock harmonic dampener, but wound up with a certain amount of vibration at high rpm. This is when they opted for the ATI Super Damper, which is also properly marked for the 351C.

18. Absolutely never remove this coolant flow restrictor from a Cleveland block. It controls coolant flow at the thermostat.

19. JGM has opted for an Edelbrock high-flow aluminum water pump for more aggressive coolant flow because they’re going to need it.

20. Comp Cams offers a new line of break-in oil for fresh engines that has the ZDDP zinc additive engineered to ensure proper break-in especially with flat-tappet cams. The ZDDP shoulders the wear that happens in new engines. Jeff Latimer has filled the sump with Comp Cams Break-In 10W30 oil and is priming the oiling system to get everything nice and wet inside for a safe start-up.

21. At press time, no one manufactures a long-tube header designed specifically for the Trick Flow CNC225 cylinder head, which is bound to arrive in time as these heads become more plentiful. Ford Powertrain Applications (FPA) manufactures an excellent line of perfect fit long-tube headers for the Ford 351C; however, they weren’t available to us at the time. These are 2-inch primary long-tube headers, which actually caused us a certainly amount of restriction. And to think JGM made 704 horsepower with these dyno room off the shelf headers.

22. This is the MSD Pro Billet (PN 8577) distributor. Nice thing about the Pro Billet is size—5⁄8-inch smaller than the factory Autolite/Motorcraft distributor. Mechanical advance is easy to tune and curve. The magnetic pick-up is virtually maintenance free. The 8577 arrives with an iron gear designed for flat-tappet cams. JGM is installing a steel gear for use with the mechanical roller cam. This is something you must do when you opt for a roller tappet cam.

23. JGM’s dyno session with the 408C consisted of two pulls due to time constraints. This engine is going back to the dyno for additional development. We will keep you posted.


Cleveland Book

Author and Technical Writer George Reid has written the latest in a long line of good technical books on Fords from CarTech Books. How To Build Max Performance Ford 351 Cleveland Engines, #SA252, is loaded with plenty of 351C, 351M, and 400 information and builds performed by some of the best engine builders in the industry. The short-lived 351C is long on great potential and this book shows you how to make the most of your Cleveland project. For more information contact CarTech Books, (800) 551-4754, (651) 277-1200, www.cartechbooks.com.