General Hemi Info Part 1

**Mike P** · 05-16-2005 08:04 PM

I started to write a short post with some general HEMI information and ended up getting very carried away. Hopefully at least a couple of you will find it of interest/use.

It seems like were starting to get a few HEMI owners on the site, so I figured I’d throw out a few thoughts. Let me start by saying that I do not consider myself an "EXPERT" on Chrysler's HEMI. I've worked on a few starting in the late 60s (some of the early HEMIs and the 426s) and currently have 2 early HEMI projects in the works; A 57 Plymouth 354/4 speed project and a 37 Dodge Pickup 331/727 project.

Believe it or not there are a LOT of people out there who have never actually seen a real HEMI (and couldn't identify one if they did), of course that doesn't stop them from wanting one to put in their project.

Chrysler started offering the HEMI in their production cars in 1951. Even in stock form the engine quickly gained a reputation as a high HP engine (in it’s day) which over time eventually led to the legendary status it enjoys today. The head design was/is possibly the ultimate for producing horsepower and torque (after over 50 years variations of the HEMI head are still what are found on the quickest cars in the world, the top fuel dragsters).

In addition to actually making very good HP/Torque numbers in relation to their displacement, no one can deny the visual impact these massive engines have sitting in any engine compartment. Generally just the bragging rights of owning one is worth the price of admission.

That being said, it raises the question of why do you see so few of them on the street or at car shows? I personally believe it can be boiled down to simple availability and cost. The early HEMI was pretty much limited to Chrysler, Dodge and Desoto's top of the line cars and in many cases it was an extra cost option (no early Hemi was available from the factory in a Plymouth), and the 426 was in it’s time a very expensive performance option. Relatively speaking not a lot of people stepped up to the plate to buy the HEMI in relation to those who opted for the less expensive poly/wedge motors. With the interest/demand for the HEMI always being high in relation to the numbers produced they always demanded a premium price when one comes up for sale.

Besides a relatively high initial investment for the engine, parts for rebuilding them and performance parts are also expensive and in some cases very difficult to find. Then there’s the problem associated with actually putting one of these engines in vehicle. HEMIs are wide and heavy (the average iron head HEMI is well into the big block weight area and sometimes up in the 700+ pound area), in a lot of cases real ingenuity is required to make them fit along with front suspension and brake upgrades.

**Mike P** · 05-16-2005 08:07 PM

Chrysler Corporation made a LOT of different HEMIs. They are generally broken down into three major categories:

Early HEMI: These engines were introduced starting in 1951 and this style continued through 1958. They can further be broken down into 3 major sub-categories by division; Chrysler, Dodge, and Desoto. Despite what many people believe Chrysler did not offer a HEMI in the Plymouth line until 1964 when the 426 was released. Displacement ranged from 241 cubic inches to 392 CI. All together there were a total of 14 different engines offered over these years.

Chrysler: 301, 331, 354, 392(RB)
Desoto: 276, 291, 330(RB), 341(RB), 345(RB)
Dodge: 241, 260, 270, 315(RB), 325(RB)

These were production engines, designed to move the heavy top of the line road cars of the day. Many of these engines were also fitted with cheaper, lighter Polysphere (Poly) heads and used in the cheaper lines/models. While there is a fair amount of parts interchangeability within each division’s engines (i.e. some parts will interchange between the 301,331,354 and 392 Chrysler engines) virtually nothing interchanges between divisions (Chrysler Hemi parts will not fit Dodge or Desoto HEMIs, nor will Dodge and Desoto interchange). To further confuse the issue within each engine family there were standard and tall deck (or Raised Block (RB)) versions, different crank journal sizes and different valve sizes. In general terms the Early HEMI was the start of a long evolution that ended at the SB Chrysler "LA" engine. This is very helpful as it results in SOME interchangeability for what would be hard to find parts (i.e. the SB Chrysler timing chain set can be used on the Chrysler Hemi's, and the bellhousing bolt patterns are very close).

426 HEMI: While the Early HEMI could be considered the start of an engine evolution, the 426 HEMI might be seen as the end result of another. Chrysler introduced the big block wedge in 1958 as the top of the line engine for all Divisions except Chrysler (1958 was the last year for the early HEMI and it was only available in the Chrysler line). During the factory Horse Power wars in the early 60's Chrysler went back to its proven HP maker, the HEMI. In 1964 Chrysler brought back the HEMI heads, but this time they were fitted to a block that was based on the RB (Raised Block) Wedge block design. While there are a lot of similarities between the block on the RB wedge engines (413/426/440) and the 426 HEMI, they are not directly interchangeable (in large part because of an extra set of head bolt bosses located in the lifter valley of the HEMI block). While the Early HEMI started out as a good motor for a heavy car and was jumped on by the hotrodder and eventually the factory, and turned into a performance engine, the 426 HEMI was DESIGNED to be a race motor and was the ultimate engine based on Chrysler’s big block. These RB based HEMIs were ONLY offered in one displacement 426!!!!! There was no factory 383, 440 or 413 HEMIs

Chryslers "NEW" HEMI: Chrysler has decided to cash in on the HEMIs proven reputation once again. Frankly I have yet to even drive anything with one of these new engines in it, let alone play with one. Only time will tell where it will fit in the long history of the HEMI. I've seen some pictures of New HEMI powered projects under construction and frankly the future should prove interesting (although I prefer my engines and cars on the older side).

**Mike P** · 05-16-2005 08:10 PM

The new HEMIs are starting to show up but I suspect that the price will be a major deterrent to all but the very high buck hot-rodder for a while. Additionally, you will also either have to live with computer controlled fuel management and ignition systems or find a work-around.

The 426 HEMIs are also pretty much in the high buck hotrodder area. They are out there, both original versions and the newer crate motors and they DO demand a premium price. Your chances of walking into a wrecking yard and finding one in a wrecked Charger or Road Runner are going to be about non-existent. Go ahead and ask, you never know, if nothing else the yard owner could probably use a good laugh

For us poor boys, that pretty much leaves the early style HEMI. This is not a necessarily a cheap proposition either (when compared to other more modern and readily available engines). Even if you find and buy an affordable, complete and somewhat running example of an early HEMI, chances are it will need to be rebuilt. The machine work it will require shouldn’t cost any more than doing any other V8, however the cost of parts can hurt. You are looking at over $200 for rod and main bearings, $200-250 for cam and lifters, $125+ for a gasket set and on and on (these prices are based on the more popular 331/354/392 engines, parts for the Desoto and Dodge versions can be considerably harder to find and more expensive).

Mechanically, all the early HEMIs were good engines. They were made of quality materials and for a mass produced passenger car engine made in the 50's the tolerances were held pretty close. In spite what many believe there is nothing magic about a HEMI. The head design allows
the POTENTIAL for the most HP per CI of any design, but in stock form many of the early HEMIs were small displacement and low compression and as already mentioned there is a pretty hefty weight penalty associated with running one. The key to really keep in mind is that no matter how efficient an engine of 350 cubic inch is it’s still a 350 cubic inch engine (or 241 or 392 or what ever). When trying to make HP the old rule that bigger is better still applies.

Doing a 1954 and up non-extended bellhousing Chrysler 331/354/392 engine is a pretty straight forward proposition at this point. Parts to rebuild them and both new and used speed parts are readily available. The extended bellhousing version of the 331 or the Desoto and Dodge HEMIs can be done but do have a couple of drawbacks in my opinion.

1. Compared to the latter (54-56) non-extended bellhousing 331/354s they have smaller ports and valves, and the water crossover was in the intake manifold rather than at the front of the heads. This limits the choice of intake manifolds to a large extent. This in and of itself is not a show stopper a simple head swap can cure this and there were a bunch of latter 331/354 heads out there. (Avoid the 57/58 392 tall deck heads for the 331/354 low deck engines. They physically fit, but are wider and unless you are planning on running a 2 piece log manifold your not going to find an intake that will work.

I recently came across a bit more info on the 331 heads.
I should expand this a little bit as it's not quite correct or complete. In 1954 Chrysler increased the valve size on the 331s (the water still exited through the intake). In 55 the cooling system was redesigned and the 55 331 requires a special 1 year only head gasket. The bigger valve 54 heads would be a direct bolt on, but I'm not sure about the latter 55 up heads.

2. There is a VERY limited availability of transmission adaptors to allow the use of a more modern tranny on the extended bellhousing 331 HEMIs. If you do get one of these engines and plan on running either a stock transmission or are planning on using an adaptor that bolts to the existing bellhousing be sure you also the lower half of the bellhousing as the transmission also bolts to this and it is where the starter mounts. The adaptors for most latter automatics require cutting off of the tranny bellhousing, and the stick setups I've seen are limited to Ford top loaders. This to me is the main reason for the average hotrodder to avoid them. The trimming of the bellhousing (either on the block or the tranny if the automatic adaptor is to be used) is NOT for the faint of heart or mediocre machine shop. With access to a good machinist it is doable and the parts to convert to a short bellhousing and stick are not really all that expensive but IT"S GOING TO BE LABOR INTENSIVE!!!!! ($$$). I discuss cutting the bellhousing for a 4 speed in this post.

http://www.clubhotrod.com/forums/sho...threadid=14794

3. The Desoto and Dodge HEMIs are sometimes referred to as the “baby HEMIs” both due to their displacements and their physical size. The Desoto is slightly shorter and narrower than the Chrysler HEMIs and the Dodge (Red Ram) HEMIs are smaller still. The difference is not a lot, but they might be just the ticket for a really tight engine compartment. These versions also generally seem to command a little less money than the 354/392 HEMIs. The real down side is that there is generally a lot less information available, the parts to rebuild them can be very difficult to find and very expensive when you do. Additionally new aftermarket speed parts are virtually non-existent and not much used speed equipment shows up either.

**Mike P** · 05-16-2005 08:13 PM

**gary_ls** · 06-27-2005 06:33 PM

Mike, nice run down on the early Hemi info. Let me add my 2 cents. Trans adapters for all (except c51-c52-c53) are readily available for the torqueflite and a-833 4-spd. There are several sources including myself. Sorry, no web site (yet), but info is free if you want to call and shoot the breeze... Like most of my parts, I am still somewhat stuck in the '50's so e-mail is about as tech savvy as I get.
541.390.8085

**Les Lebsock** · 07-17-2005 10:45 AM

what is needed to put a 241 in a 45 dodge pickup

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