Engine Tips - Biggest Engine-Building Mistakes

Not Port Matching Intake Manifold, Heads, Gaskets

Mark Jeffrey of Trans Am Racing mentioned this one. We don't understand this mistake because it's so obvious. Never assume cylinder-head and intake-manifold ports automatically line up, because they don't-not even when cylinder heads and intake manifolds are from the same manufacturer. Regardless of the performance you are seeking, always port-match cylinder heads and intake manifold. Port-match using gaskets on both manifold and heads. When port-size difference is significant, consider the selection of more compatible heads and manifold. Large manifold ports and small cylinder head ports (and vice versa) don't make sense because it robs power and creates disturbed airflow through the runners.

Getting Head Gaskets Backwards On Small-block Fords

Got an overheating problem you can't figure out? Small-block Ford cylinder-head gaskets can be installed backwards, which is an automatic overheat because head gaskets installed backwards cut off coolant flow to the back of the block and heads. Install one head gasket backwards and you have a hidden overheat issue. Hidden because the engine runs a pinch hotter but doesn't boil over. But because coolant flow isn't reaching the back of the block and head on one side, damage is being done you're unaware of until an exhaust valve fails or pistons crack on that bank.

"FRONT" means FRONT with all cylinder head gaskets, even if it doesn't look right. Position "FRONT" at the front, and make sure coolant passages are at the rear of the block. While you're at it, check for proper steam-hole positioning, too. Sometimes head gaskets come from the factory missing important passages.

JGM Quick Tip:

Pitted block decks and heads are unacceptable. Check cooling passages for corrosion pitting, which can cause coolant leakage. If there's pitting, you need to mill heads and/or decks. If they cannot be milled, replace the casting.

Not Chasing Threads

MCE Engines chases bolt holes and threads on every engine it builds because burred, damaged, and dirty threads yield erroneous torque wrench readings. Clean threads are key to proper torque readings and application. McAfee chases threads on all bolt holes and dresses all bolt threads for smooth installation and accurate torque application. When you don't chase threads, the resistance felt at the torque wrench is actually resistance at the threads, not the assemblies you wish to mate. Chase threads, then lubricate them with molybdenum grease for smooth torque application.

Not Deburring Sharp Edges

Deburring is a crucial step in engine blueprinting. In fact, if you don't deburr, you're not blueprinting. Deburring is the removal of sharp edges (also known as stress risers) that can lead to material failure. High spots and edges create weak points that become cracks. Deburr every part of your engine-block, heads, connecting rods, crank, lifters, camshaft, and a host of other spots.

Not Dynamic Balancing

Most machine shops and engine builders have dynamic balancing as an option. But to Mustang & Fords, dynamic balancing and extreme attention to detail are mandatory steps in an engine build. Dynamic balancing is crucial to engine smoothness and survival because vibration (any vibration, no matter how small) kills. It shakes things to pieces. Not balancing an engine is foolish, courting disaster at worst and shortening engine life at best.

When you dynamic balance an engine, you balance the crankshaft (just as you would tires and wheels) for smooth operation. Then, you balance connecting rods and pistons to match the crankshaft balance. Do this every time you build an engine.

Not Prelubing The Oil System

Although most reputable engine builders know to lubricate moving parts with assembly lube, it is wise never to chance firing an engine without first doing a pre-lube. Pre-lubing is the process of filling the oil pan with SAE 30-weight oil and spinning the oil pump with a pre-oiler to prove out oil pressure and flow. When you don't pre-lube, you risk a dry start-up, which can do permanent engine damage in a matter of seconds.

Not Setting Distributor Shaft EndPlay

MCE Engines stresses always checking distributor-shaft endplay and block clearances. Like crank and cam endplay, distributor-shaft endplay can be a player in engine failure. Too tight or too loose and you can expect cam and distributor drive-gear failure.

Distibutor shaft endplay is commonly overlooked when engine building.

Not Checking Oil Pump To Crank Clearances

Aftermarket oil pumps and stroker kits have created a new challenge for engine builders-oil-pump-to-crankshaft-counterweight clearance problems. This clearance problem nails you whenever you don't make sure there's at least 0.060 inch clearance between the oil pump and counterweight. We stress the 0.060-inch minimum clearance because as engines get hot, parts grow. It may clear by a whisker when cold, and hit when it's hot. Keep at least 0.060 inch between the crank and pump, and stay safe.

Steel Distributor Gear For Roller Cams

It's a popular misconception that roller cams require a special kind of distributor drive gear, but it's simpler than that. Flat-tappet camshafts are made of iron and call for the use of an iron gear. Roller camshafts are made of steel and call for distributor gears with the same hardness, either steel or bronze. Of the two, steel is preferred over bronze because it lasts longer. Use an iron distributor drive gear with a steel roller camshaft and you can expect failure. The steel shaft will eat an iron gear alive, with iron particles finding their way to your oil pickup.

Overtorquing-Not Torquing Everything

Did you know you should torque every fastener with a torque wrench? Fastener failure is one of the single greatest reasons behind engine failure, caused by improper torquing. From brute main bearing caps to valve-cover bolts, all fasteners should be tightened to recommended torque specifications. Why torque wimpy little valve-cover bolts? To give gaskets proper crush and seal effectiveness, and to prevent bolt breakage. Use a torque wrench on every fastener.

Using Stock Oil-Pump Shaft

Engine builders who can build 600hp small-blocks then insult the message with a spaghetti-thin stock oil-pump shaft stun us. We will say it again-never use a stock oil-pump shaft in your engine build. Opt for an ARP shaft that offers brute strength and added security. Shaft failure equals immediate engine failure.

Not Checking Pushrod Length/Rocker-Arm Geometry

This is an easy mistake to make as enthusiasts tend to install everything right out of the box because it's new. But new doesn't always make it right. Pushrod length and rocker-arm ratio directly affect where rocker-arm tips will sit on the valve stem. You want the rocker tip to sit squarely on the valve stem tip at one-half valve lift to where there is no side load on the stem. Not enough of us get that one right because we don't want to wait for the correct pushrod or rocker arm. Getting this one wrong can lead to valvetrain and engine failure.

ValveSpring Coil-Bind Check

Valvespring coil bind happens when there is more lift than the spring can accommodate. This can (and will) lead to valvetrain component failure-bent pushrods, broken keepers and retainers, and a host of other surprises. If you don't check for valvespring coil bind, you do so at your own peril. The closest the coils can be is 0.060 inch at full valve lift.

Knocking Freeze Plugs Inside Block/Heads

Some mass rebuilders make this mistake because they make money moving at a fast pace. Disassemblers tend to knock freeze plugs inside the block and heads to save time. The problem is, freeze plugs inside water jackets inhibit coolant flow and create hot spots. If you have an overheating problem you cannot solve, check your water jackets for old plugs.

Not Sonic Checking Cylinder-Wall Thickness

It's a good idea to sonic check all engine blocks prior to building. Sonic checking an unknown block clears up any doubt and gives you a good idea of how far you can bore. Sonic checking determines cylinder-wall thickness and integrity. Few things are more discouraging than engine failure because you didn't check.

Not Using High-Temp Sealer On Freeze Plugs

All builders concur: Freeze plugs can pop out when you don't use a high-temp sealant and proper installation technique. A high-temp sealer, coupled with using the right plug and installation technique (getting the plug flush), makes the installation secure. Some builders install screw stops around the plug perimeter if revs-and freeze-plug failure risk-become high.

Using the 2/60 Rule

Marvin McAfee subscribes to the 2/60 rule on every engine build when specifications are not available: minimum 0.002 inch and 0.060 inch clearances. The 0.002-inch rule applies to bearing clearances, lifter bore clearances, run-out, distributor-gear backlash, and more. Clearances like valve to piston, rocker arm to valvespring, oil pump to crank, and the like get the 0.060-inch minimum rule.

28 ounces versus 50 ounces

We've seen this one time and again. Small-block Fords, which are externally balanced, have a given offset balance that mandates a compatible harmonic balancer, crankshaft, and flywheel. Offset balances are 28 and 50 ounces, respectively. Prior to 1982, 302ci engines had a 28-ounce offset balance, which exists outside of any dynamic balancing you may do during an engine build. When reciprocating mass weight increased in 1982 with the 5.0L High Output engines, offset balance increased to 50 ounces.

The mistake comes when you install a 28-ounce balancer or flywheel on a 50-ounce offset balance crankshaft, and vice versa. When you are amassing parts for a small-block Ford, remember the 28/50-ounce difference. It will save you a lot of grief.