Hemi Help

Rod and main bearings are...        read full caption Rod and main bearings are crucial wear items in any engine, so the fact that early Hemi bearings are scarce and expensive is a deterrent to those considering one of these engines for rod projects. Howard has found alternatives for both the rods and mains. The main journals of a stock 331 and most 354s measure the same as those of a Chrysler 318 small-block (2.50 inches). However, the main saddles of the small Hemis measure 2.6570 inches, while the 318’s saddles are 2.6930 inches. With a simple align-boring procedure, Howard enlarges the Hemi saddles to accept the thicker 318 bearings.

There is a minor conflict...        read full caption There is a minor conflict with the 318 thrust bearing, as its thrust surfaces are also thicker than that of the Hemi. To correct this, the sides of that main cap are machined, as is the thrust-saddle area in the block, to provide the extra clearance. All main-bearing saddles and caps require new notches for the 318 bearing lock tangs, as they are in a different location than those of the Hemi (arrow), but this is simple procedure.

The stock main-journal diameter...        read full caption The stock main-journal diameter on a 392 is 2.6880 inches; a Chrysler 440 main journal measures 2.7505 inches. Howard welds the stock main journals on the 392 crank to build them up, and then machines them to the 440 dimension. The 440 main bearings also require new lock-tang notches, but otherwise, they drop right in.

The rod journals of the 331/354...        read full caption The rod journals of the 331/354 measure 2.250 inches, which happens to be extremely close to the Pontiac 389’s 2.2497 rod journal. The rod saddles of the 331/354 measure 2.3755 inches while the 389’s are 2.3750 inches. With a minor resizing of the Hemi rods and the addition of new lock-tang notches, the 389 bearings fit perfectly in the small Hemi rods. The difference in crank-journal diameter is easily corrected by polishing the journals down to the proper spec. The rods of the 392 accept 440 rod bearings with only the addition of new lock-tang notches.

For rod bolts, Howard uses...        read full caption For rod bolts, Howard uses 440 pieces, which fit right into the early Hemi rods, requiring only a minor trim to shorten the length slightly.

This shot illustrates the...        read full caption This shot illustrates the differences between early Hemi oil pumps. In the foreground is an N.O.S. 392 pump; a used 331/354 pump is behind it. The general dimensions of the two are quite different, and the 331/354 uses a pinned pickup while the 392’s threads in. Despite the differences, Howard is able to modify the pump from a Chrysler 360 to fit both applications.

In the foreground is the 360...        read full caption In the foreground is the 360 pump, which shares fairly similar dimensions with the 392 pump behind it. To use the 360 pump with the early Hemi, Howard fabricates a steel plate, seen here at the mounting face of the 360 pump. This particular pump is modified to fit a 392. The plate relocates the outlet of the pump, aligning it with that of the Hemi. The bolts seen here on either side of the outlet in the 360 pump are temporarily fastening the plate; longer through-bolts will mount it to the 392.

This view of the 360 pump’s...        read full caption This view of the 360 pump’s underside shows the additional alterations for the 392 application. Howard has silver-soldered a modified valve guide to the pump housing to provide a mounting lug for the 392 (A). He prefers the low-heat silver-solder method because the heat generated during welding can affect the housing dimensions. One of the stock 360 mounting holes is not used (B) while the other (C) is used to fasten one end of the adapter plate. A fourth hole is made for mounting by machining and drilling the housing (D).

This is another modified 360...        read full caption This is another modified 360 oil pump mounted to a 331. It’s actually simpler to adapt the 360 pump to the 331/354 as no additional holes need to made in the pump. One of the stock 360 mounting holes is used to bolt the pump in place (A) while the other is used to fasten the adapter plate (B). A modified 360 Dodge pickup truck oil pickup is used for both Hemi applications.

An additional benefit of using...        read full caption An additional benefit of using the 360 oil pump is that it uses a hex shaft rather than the slotted drive of the early Hemi. Howard says the slotted arrangement was prone to failure in high-performance applications, but the hex shaft is fairly bulletproof. The best part is that the 360 pump driveshaft drops right in without modifications.

The camshaft with the threaded...        read full caption The camshaft with the threaded snout (bottom) is from a 331/354, while the other is from a 392. The smaller Hemis used an elaborate timing-set/fuel-pump drive, which is pretty much unavailable today and not a great design anyway. Fortunately, the 440 timing set is very similar to the 392, and can be adapted to the 331/354.

The 440 timing set can then...        read full caption The 440 timing set can then be installed using a 392 fuel-pump drive.

Since a 392 cam cannot be...        read full caption Since a 392 cam cannot be used in a 331/354 due to the different placement of half of the lifters in the smaller engines, the 331/354 cam must be modified. First, the threaded snout is cut off, and then a sleeve Howard makes from stainless tubing is pressed on the remaining snout to enlarge its diameter to that of the 440 camshaft. The keyway is cut into the sleeve and the end of the cam is drilled and tapped.

Valve lifters are yet another...        read full caption Valve lifters are yet another item that can be difficult and expensive to obtain for the early Hemi. Howard uses mildly modified later-model Chrysler V-8 lifters instead. Shown from bottom to top are a stock early Hemi lifter, a stock late Chrysler lifter, and a modified late Chrysler lifter. The only major difference between the early and later lifters is the height of the oil groove. Howard simply machines the groove of the later lifter to match that of the earlier design. The scribed marking in the machinist’s dye on the stock late lifter illustrates where the machining will be.

Chrysler’s first hemispherical-headed V-8 engines seemed light-years ahead of the competition when introduced for the ’51 models, and stayed on the leading edge of performance into the ’60s. But by the mid-’60s, the new 426 Hemi made the early models obsolete; even Brand X big-blocks became a more favorable choice for many racers. Though the die-hards kept their 354s and 392s running, parts dried up over the years, and today, building an early Hemi can be a difficult and pricey venture.

Some of those hard-core Hemi racers resisted parting with their early iron and refused to shell out exorbitant sums for ancient replacement pieces. One such motorhead is Howard Allen of JMS Racing Engines in Monrovia, California. Howard is a seasoned machinist, but also a veteran of Southern California’s dry lakes and dragstrips. He’s even held a record or two at Bonneville over the years.

These days, most of his working hours are spent as the crankshaft specialist for JMS, but one of his passions is updating and improving vintage engines for performance and reliability. We happened upon a 331ci Chrysler in the process of being refurbished at JMS and had Howard walk us through the updates he’s devised for these engines, including tips for 354s and 392s. Most of these changes provide a means for Hemi-builders to create a fully operational engine without relying on expensive replacement parts that may no longer be produced. The accompanying photo captions outline the various tricks Howard and JMS have come up with.