Rebuilding An Early Hemi

Part II

Once the block has been properly prepared its time for assembly. There are a couple things you need to know that are particular to early hemis and they will be covered below. Surfice to say that generally speaking assembly is pretty much the same as any other V8 including checking main bearing clearances, crankshaft end play, and rod bearing clearances so these techniques will not be covered in this demonstration.


One item often found missing on early hemis is the rear main cap locating dowel. Its a hollow dowel that fits into the block (orange arrow) and positivly locates the oil pump drive shaft so it is in alignment with the intermediate shaft. Failure to install this item may significantly shorten the life of your motor. As you can see from the photograph mine was missing. Replacements are available from HotHeads for about $10.

Here you see the dowel properly installed.

Also make sure the oil bypass plug seats flush with the block (arrow). When installing this item make sure the slots are aligned with the oil output hole (lower hole on the side of the block). The oil traveles from the pump into the bypass plug and out to the filter. The slots need to be aligned to allow the oil to flow freely. Failure to align these slots may lower the volume of oil the pump can supply to the engine.

The crank is installed and the block is now ready for the pistons and rods.

Here you see the complete set of pistons, rods and pins ready to install. The pistons are very early J&E (stock compression ratio) cast aluminum units which accept stock rings. These pistons are full skirted and have no taper which was common for performance pistions way back when. Because they are full skirted and will expand more than modern pistons, cylinder wall clearances were enlarged slightly (to .005) to ensure there will be enough room for expansion. Normally the clearance would be about .002. This extra clearance may result in a little noiser engine when cold but as far as I'm concerned thats not a problem. The rods were resized and rebushed by the local machine shop.

*** Technique ***

When installing the pins make sure the snap ring gap is located facing the top or bottom of the piston not the side. If it faces the side it could come out under load with predictable results.

Early hemi rods have what is known as a "spit" hole (arrow) on one side of the rod cap. This allows oil to pass through to lubricate the cam and thrust side of the cylinder wall.

The arrow shows the little notch in the bearing that lets the oil through to the spit hole.

When the rod is properly assembled and installed the spit hole will face down or towards the camshaft (assuming the engine is upside down on an engine stand). Most times (but not all) the spit hole is on the opposite side from where the number is stamped (arrows). I had one rod that was stamped on the same side as the spit hole so always check to make sure you're installing the rods correctly. This is an old rod from a freshly disassembled engine and its a very good example of what happens to bearings when they aren't lubricated properly.

When the rod is assembled correctly the locating tabs for both halves of the bearing will be on the same side. They are usually located on the side that is stamped with the rod's number. You can see the spit hole (orange arrow) on the side that is not stamped in this photo. The bearing tabs (green arrow) are on the other side.

Installing a camshaft is a delicate procedure because the last thing you want to do is nick a bearing. If you don't happen to have a cam installation tool a long bolt of the proper size will accomplish the same task. This is a '56 or later cam. Hemi cams cam in three basic varieties. The pre-'56 long snout version, the 56 and later version which had a short snout as seen above, and the 392 short snout version. Don't try to use a 392 cam in a 331-354 block. It will fit but the lifter bores are at different angles in the 392 which will result in improper valve timing. Because the availability of the earlier long snout cam is limited most people opt for the later short snout version as I have done here.

Before installing the retaining plate and cam key there is a small chamfered washer that must be installed. The chamfer goes against the cam away from the timing chain gear. Don't forget to install this washer. Failure to do so will mean instant valve train distruction upon start up.

This cam retaining plate was purchased from HotHeads but if you have one from a '56 or later block you can use that one. You can see the key on the right side of the cam snout. The chamfered washer sits just behind it. Remember the washer goes flat side out, chamfer in towards the cam.

This shot shows the timing chain and gears installed. The chain is an OEM replacement 340 Mopar unit available from HotHeads. Just like on a small block Chevy the gears both have a mark for proper alignment. The orange arrow shows the oil slinger which must be modified if you're using one of HotHeads aluminum front covers. Yes the cam was degreed in.

The outside edge of the oil slinger must be flattened so it won't rub on the inside surface of HotHead's front cover. You can easily do this with a hammer or a vice.

This is the HotHeads front cover installed. It comes in either polished or cast finish and allows pre-'55 hemi blocks to use a small block Chevy water pump which is available at just about any auto parts store. If you have ever tried to locate a rebuilt early hemi water pump you'll understand why this is one of the best mods you can do to an early hemi. Especially if you are going to drive it farther from home than you are willing to walk.

The fluid damper is a modified 340 Mopar unit. These are available from HotHeads and are worth every penny. Remember, do NOT install this thing with a hammer. Always use the proper installation tool. You can damage bearings and heaven knows what else otherwise.

Now is the time to install the intermediate shaft. Early hemis use a geared shaft driven off the cam to operate the oil pump. This can be a bit difficult to get into place but not if you do it the way I do.

*** Technique: ***

When installing the camshaft also install the intermediate shaft. It will mesh with the cam gears and slide into place easily. Once it's in use a large screwdriver to turn it slightly to make sure its fully seated against the bushing. Just be careful not to pop the cam out in the process. It works best if you just hold the front of the cam in so it won't slide out while you turn the intermediate shaft (which will turn the cam) with the screw driver. Once its in and seated just remember not to turn the engine upside down on the engine stand. If you do it could fall back out.

Now is the time to install the oil pump. Turn the block 90 degrees (on its side) and look to see how the intermediate shaft key is oriented. Adjust the oil pump shaft to match and it should slip right in. Make sure you hold the intermediate shaft in place while you do this. Now you can tighten the oil pump bolts to 35 ft. lbs. and you're done.

When you install the oil pan and gasket simply put a rag on top of the intermediate shaft and wedge a screw driver against the rag and the top of the block to make sure the shaft stays in position while the block is upside down.

This oil pump is a modified high performance 360 Mopar unit available from HotHeads. It installs using a small billet adaptor (arrow) supplied with the pump.

Make sure the pickup clears the bottom of the oil pan by at least a quarter of an inch. Also use locktite during assembly. You don't want the vibratiion of the engine to cause the pickup to come loose.

Well here you have the completed short block assembly. Note the remote oil filter adaptor (arrow). This will allow me to mount the oil filter on the lower section of the firewall where it can easily be reached.


Remember, several steps in the assembly process have been left out of this demonstration because they are the same as any other engine assembly. To help the novice hemi builder, I've tried to point out some of the more unique procedures and techniques that are peculiar to this engine. Also please keep in mind that my techniques are by no means the only way to do things, just the way that works best for me.

One final word on balancing. The rotating assembly should be balanced every time any components other than rings and bearings are changed. A couple grams out of balance translates to several pounds of force every revolution of the crankshaft. This will rob your engine of power and longevity. It's the best couple hundred bucks you'll ever spend.

Part III