The Ford 427 "side oiler" motor was produced from 1963 through 1967, and was used in a variety of automotive performance and marine applications, most notably in the Ford/Shelby 427 AC Cobra. While the "side oiler" has always enjoyed a cult following among Ford types, interest in this motor is currently at an all-time high, apparently due to a strong tide of Cobra kit car builds. Given this renewed interest, we thought it would be fun to take a close look at this motor from both a restoration standpoint as well as an "upgrade" approach to increase power and drivability for today's performance street scene. The original FE iron motors were not light, weighing in at a hefty 650 lbs. Of course, ours will be considerably lighter, since we're using aluminum heads, intake manifold and water pump. Unlike the 428 engines, the 427 is internally balanced. The 427 FE side oiler also features cross-bolted main caps to provide added rigidity for the main caps, primarily for durability. Screw-in block plugs (instead of interference-fit "freeze" plugs are also used. The "side oiler" FE block is so-named because it features oil feed to the main bearings directly from a large oil gallery that runs along the bottom left side of the block. Oil enters the passage from the oil filter housing near the front of the block. Drilled passages intersect the main gallery to feed oil to the main and cam bearings at each main web (pipe caps are used to cap-off the drillings). An oil pressure relief valve is located inside the rear of the block along the left side. The passage for this valve and for the main gallery is plugged on the block's rear face. Because of manufacturing tolerances in the '60s, the main cap side spacers are individually fitted and labeled. The second main cap's spacers are marked 2L and 2R (indicating right or left side), the third cap's spacers are marked 3L and 3R, etc. Service replacements for these spacers were originally available in thicknesses of 0.3767", 0.3750" and 0.3733" for selective fitting. While it may be necessary to align hone any block during a complete rebuild, if the original spacers have been lost or replaced, it is absolutely mandatory to align the main bores to assure correct centerline. If new spacers are purchased or made, each needs to be labeled for location. It is absolutely critical that all spacers are positioned in the same locations during final assembly as they were located during main bore alignment correction. Don't mix up the spacers! I know that it may sound elementary to mention this, but remember that when the block is upside-down on a stand, and when you're standing at the block rear, the right side will be on your left and the left side will be on your right. Just remember that the "driver" side is the block's left side and the "passenger" side is the block's right side. Mistakes can happen, especially if you're in a rush or distracted. It's best to label (with a marker) the left and right block pan rails to help avoid accidental side-to-side swaps of the main cap spacers.


Whenever you're planning a "427" derivative build, you have two choices concerning the can hunt and find a salvageable OE iron block, or you can ante-up and buy a new iron or aluminum Genesis block. The Genesis blocks are outstanding pieces, and are well worth the approximate $3500 (iron) to $5000 (alloy) asking prices. However, if you get lucky and stumble across an OE block at a good price (and one that hasn't been blown apart in its past life), using the vintage block is certainly viable. We located a 1966 block that showed no signs of having been scattered, so we went with it. However, in my opinion, since good old blocks are becoming increasingly hard to find at under $3000, the best route is to use a new Genesis block. The new block features thicker walls and deck, and allows you to shave the deck to your liking and to finish cylinder and lifter bores to accommodate your choices, rather than being forced to save a 43-year-old casting.

Our old block had once been over-bored +0.030", but we were able to save it by nudging another 0.001", with a finished bore diameter of 4.263". While the stock deck height is supposed to be 10.170", a resurfacing on our aged block resulted in a livable 10.145" deck. In order to achieve zero deck, we turned to Diamond Pistons to make a set of slugs that offer 1.320" compression distance. This new bore and stroke combo provides our build with a hefty 485 CID.

Be sure to closely inspect upper main bearing oil hole alignment to the oil feed holes in the upper saddles. It's common for Ford factory holes to be tad off-center, as you can see here in mains #1, 2 and 4.  

The main bores were about 0.0015" askew, so we had the mains align honed for correction. Luckily, there's enough wiggle room at the main cap side bolt areas for cap cutting and alignment honing. The original blocks featured individual side-bolt spacers, which are location-etched for right/left and cap number. Even though these spacers are marked for location, it's still necessary to fully install the caps, spacers and bolts (to full torque value) before checking main bore diameter, out-of-round and bore alignment. If deviations are found in alignment, it may be necessary to custom-cut one or more spacers in order to optimize the alignment issue. With spacer locations optimized, you minimize the amount of material removal during align honing. Once our bores and decks were corrected, we checked the fit of our upper main bearings. On the old FE blocks, it is very common to find that the oil holes in the number 1, 2 and 4 mains don't line-up very well. Yes, holes do intersect, but in order to improve oil flow to these main bearings, you'll need to slightly chamfer-blend the main saddle holes to more efficiently align with the oil holes in the bearings. I first installed the upper main bearings and marked the exposed portions of the saddles with a market pen. With the bearings removed, I then used a ¼" die grinder to carefully blend/extend the saddle oil passages. After a careful wash, scrub and rise with hot soapy water and a compressed air blow-dry, I installed the upper main bearings in the block and the lower main bearings in the caps and fully tightened all main cap bolts using ARP's main cap bolt kit. The ½" primary (vertical) bolts were torqued to a final value of 95 ft-lbs (in 3 increments) with ARP moly applied to the threads and underside of the bolt heads. Once the ½" cap bolts were fully tightened, the No. 2, 3 and 4 cap 3/8" side bolts were snugged to 40 ft-lbs (with moly), in two steps (25 ft-lbs, followed by 40 ft-lbs). With caps torqued in place, our main bearing bores measured 2.7505".  Our crank main journals measured a consistent 2.7490", providing a bearing clearance of 0.0015".

Our stroker crank is a cast unit from Scat, featuring a 4.250" stroke and smaller (bigblock Chevy) 2.200" rod journals. The smaller rod pins allow for better rod clearance at the block.

Scat, as always, did a magnificent job of finishing the crank. Each oil hole was neatly chamfered, with no need for additional massaging.

Generous fillet radius on all journals provide extra insurance against stress failure, and provide excellent rod big end clearance.

Next, I removed all main caps and lightly lubed the bearing faces with Royal Purple Max Tuff assembly lube, and installed our Scat crankshaft. With caps re-torqued, the crank hand-rotated effortlessly (using a beam type torque wrench on the crank snout bolt, the torque wrench beam wouldn't move at all). Crankshaft endplay measured a mere 0.010" - 0.011". Next, all connecting rods were assembled to pistons. The Diamond full-float pins were lightly lubed with Royal Purple Max Tuff assembly lube, as were the upper and lower Clevite rod bearings. With rods and pistons installed (no rings), and the moly-coated 7/16" x 1.400" ARP 8740 rod bolts temporarily tightened to 40 ft-lbs (I'll perform final-assembly tightening according to the rod bolt stretch method, stretching each bolt by 0.0046"), the crank was rotated to check for block clearance (naturally a critical check when building an engine with increased stroke length).

Our rods are Scat's I-beam forged steel units, with bigblock Chevy size big ends (for ur 2.200" rod pins). Center to center length is 6.700".

Rod caps feature a strengthening rib. Scat designed the big ends with minimal meat to reduce weight and aid clearance.

Both rod and cap are mared on adjacent mating locations. While you always want to place the chamfered edge of the big end facing journal fillets, this provides an easy visual reference for orientation.

At above-left is a Scat rod (with big end sized for a 2.200" journal). At right is a Ford OE Lemans rod. Clearly, the Scat rod big end provides reduced mass for improved block clearance.

Our Scat rod ends are bronze bushed and finished to an I.D. of 0.9905".

The forging mark on the Scat rod I-beams clearly indicate rod center-to-center length for easy reference.

Our main bearings are Clevite MS-863P (standard FE size). These are designed for our 2.749" diameter main journals, providing an oil clearance of 0.0025" (as measured).

As mentioned earlier, a common glitch with Ford FE blocks is seen here. The main oil feed holes do not perfectly align with the bearing oil hols (in our particular block) at saddle locations 1, 2 and 4. While oil delivery is likely adequate, oil feed can be improved by slightly chamfering the saddle hole to better align with the bearing hole. A slight ramp-chamfer is all that's needed.

The original "vintage" 427 FE side oiler block features additional main cap side bolts at cap locations 2, 3 and 4. Each side bolt location requires a steel spacer placed between the cap and block as seen here. The clamping load factor of these side bolts dramatically affects main bore alignment, so never assume that the spacers that came with your old block are correct in terms of length. The original spacers were etched with location marks. If your spacers are marked in this manner, keep them in the original locations. If one or more spacers are not marked, this indicates that they have been replaced at some pointEven if the spacers are marked, there is no guarantee that they were originally fitted to that particular block (maybe the originals were lost and someone replaced them with spacers from another block). In any case, always install and fully torque all main caps (with spacers in place), and check for main bore alignment and bore concentricity. Once the main bores have been align-honed, be sure to mark each spacer for locations (2R, 2L, 3R, 3L, 4R, 4L) and keep them organized.

The main cap numbers 2, 3 and 4 side bolts feature a thick washer that nestles into a relief in theblock. The side bolts should be tightened to a final value of 40-42 ft-lbs. Reminder: always keep your main cap tightening and lubrication (at threads and bolt underheads) consistent. Use the same torque values and the same lubricant whenever installing the main caps for measuring, align honing and for final assembly. This is important to avoid possible changes in main bore concentricity.

During crankshaft test fitting, once the main caps have been fully tightened to value, check crankshaft thrust (fore/aft movement). Using a magnetic-base dial indicator, place about 0.050" preload on the dial indicator and then zero the gauge. The indicator probe should be parallel to the main bore (avoid mounting at an angle). Using a clean flat-blade screwdriver as a lever, carefully force the crankshaft fully rearward (place the screwdriver between a main cap and a counterweight). Then force the crankshaft forward, monioring the gauge for the amount of movement. In our case, our Scat crank provided 0.010-0.011" of thrust movement. Als while the cranksaft is installed (with lubed main bearings!), check crank rotation. Minimal effort should be required to rotate the crank (it should roll like butter). If not, re-check bearing oil clearance and main bore alignment and concentricity.

Using an in-lb torque micrometer type torque wrench, the crank (with rods and pistons) rotated at an observed 32 in-lbs (2.6 ft-lb). In other words, it rolled like butter. Happily, the rod big ends cleared the block bore bottoms by a mile (about 3/16" to ¼"). Use of the 2.2" rod pins and smaller-overall Chevy rod big ends contributed to the no-glitch clearance. FYI: The Ford OE rod big ends measure 4.070" wide at the big end widest point, and 3.893" from outside bolt washer to outside bolt washer edges. By contrast, the Scat BBC rod big ends measure 3.763" at the widest point (parting line area) and 3.553" from bolt washer outer edges. So, at the bolt head washer areas (the usual clearance problem areas), the Scat BBC rods are 0.307" narrower at the parting line areas and 0.340" narrower at the bolt washer areas, saving 0.170" at each bolt side as compared to the OE rods.

The pistons for this build are custom-made forged billet slugs from the pros at Diamond. Our piston set included pistons, pins, rings and pin locks.

Our custom Diamond pistons feature 5.8cc total pocket volume.

Diamond features a handy access pocket for installing/removing the pin locks.

For reduced mass, the pistons feature sidecut reliefs adjacent to the pin bores.

The CNC machining of the Diamond pistons is extensive. excess weight has been precision-carved under the dome in order to provide light weight while maintaining strength.

Clevite rod bearings were sized for bigblock Chevy, to accommodate our Scat rods and our 2.200" crank pins.

Rod sideplay was measured at 0.024" at each rod pin location. Note: generally speaking, sideplay is acceptable anywhere from 0.015" to 0.025". Pistons were checked at TDC for deck clearance. Our "zero" deck spec actually measured just a tad under zero, at about 0.0002" below block deck.

Once you're happy with crank fit at the main bearings, test-install all connecting rods and pistons (make sure the bores are well lubed with 30W oil) and lube the rod bearings with oil or Royal Purple Max Tuff assembly lube. Install rods in pairs on common journals before tightening the rod bolts. As each pair of rods are installed on the same journal, lightly rotate the crank to verify smoothness of rotation. In our test assembly, the crank, fitte with all eight rods, required a mere 32 in-lbs for rotation. While the crank and rods are in place, slowly rotate the crank while observing clearances between rod big ends and the block. This is cricial, especially when dealing with a longer-than-stock stroke. If rod big ends (or rod bolt heads) contact the block, or provide less than abot 0.080" clearance, mark those spots on the block for grinding/relieving. In our case, even with our 4.250" stroke, we had plenty of clearance (we had close to 5/16" clearance, so no block grinding was needed). In other words, we were lucky.

Next, check each pair of rod big ends for sideplay. Spread the big ends apart (on each shared journal) with your fingrs and insert a feeler gauge. Keep moving up in gauge thickness until the gauge fits sugly between the rods. We measured 0.024" sideplay in our test assembly. Generally, you should have at least 0.015" to 0.025" sideplay. If too tight, the big end faces may need to be lightly refaced to provide adeauate clearance. Perform this check before the balancing phase. It's also a good idea (especially when building a stroker) to test fit the camshaft (place the cam in time with the crank and rotate slowly, checking for rod big end to cam lobe clearance to verify that the rods won't hit the cam).

Here we check piston deck clearance using a dial indicator and depth gauge. We measured zero deck, which was our objective in this build.

Now it;s time to disassemble back to a bare block. Any clearance issuescan now be addressed, followed by a thorough washing of the bock.  

At this point, I disassembled the short block. Always remember that it is absolutely critical to keep the No. 2, 3 and 4 main cap side-bolt spacers in order (each spacer should be location etched).          


427 (7.0L) BORE (STD)...........................4.230" (+.020"  4.250")

STROKE................................3.780" (428 crank optional for 3.980" stroke)

RODS CTC............................ 6.488 (6.497" rods for 428 crank)

RODS BIG ID..........................2.59"

RODS PIN..............................0.9751" (FLOAT)

ROD JOURNAL.......................2.4380"

MAIN JOURNAL.....................2.7484"

DECK HEIGHT.......................10.170"

ROCKER ARM RATIO.............. 1.76:1 (SHAFT MOUNTED)


BORE SIZE...........................  4.263"

COMPRESSION HEIGHT......... 1.320"

EFFECTIVE VOLUME............  -5.9cc

VALVE DEPTH...................... INTAKE 0.250" ;  

EXHAUST 0.197" TOP RING........ 1/16"

2ND RING......... 1/16"

OIL RING......... 3/16"

LOCK RING....... ROUND WIRE (one per side of pin bore)

LOCK RING PART # 01-5112


WRIST PIN LENGTH....... 2.930"

PISTON WEIGHT........... 505 GRAMS

NOTE: These pistons are designed for 0.0065" wall clearance, measured 90-degrees to the pin hole @ 0.850" below the oil land.


Block deck height..............................10.150"

Bore..................................................  4.232"

Rod length........................................  6.490"

Stroke................................................ 3.780"

FOR OUR STROKER (w/zero deck)

Block deck height..............................10.145"

Cyl bore diameter.............................  4.263"

Conn. rod length.............................  6.700"

Stroke.............................................  4.250"

Piston compression distance...........  1.320"

Main bearing clearance..................  0.0025"

Rod bearing clearance......................0.002"

Crankshaft endplay..........................  0.010"

Rod sideplay....................................  0.024"


4.250" stroke divided by 2 + 6.700" rod + 1.320" CD = 10.145" deck


With 4.250" stroke and 4.263" bore ..... 485.289 CID

Bore x bore x stroke x 0.7854 x number of cylinders   4.263 x 4.263 x 4.250 x 0.7854 x 8 = 485.289 CID


(We'll discuss balancing, piston to rod assembly and more)