Our Hemi engine building challenge is in full swing, with the invited builders in the thick of assembling their combinations for the shoot-out to come. Chrysler's Hemi is more popular than ever, as the legendary status of these powerplants just continues to grow. What's the key to the Hemi's magic? It's not the crankshaft, pal-it's all in the heads. Though Hemi-configuration cylinder heads had been toyed with by various manufactures since the early days of the automobile, it was Chrysler that embraced the design and put them out in the kinds of numbers that got people's attention. The early Hemi of 1951-1958 set the precedent, but it was Chrysler's limited-production iron elephant-the 426 Hemi-that solidified the legend. Whether the venue was the street, or virtually any form of sanctioned racing in which it competed, the Hemi was supreme in its domination.
Chrysler had enjoyed great success with the early Hemi, however, production costs and complexity as the primary corporate V-8 powerplant saw it give way to the more modern big-block wedge. The wedge offered a very practical balance of output and manufacturing efficiencies, however, when it was time to step the power up beyond what was practical with the wedge at the time, Chrysler once again turned to the Hemi. The edict came straight from the top, with Chrysler's chief executive officer at the time, Lynne Townsend, leaning on engineering to come up with an engine package that could shatter the competition from other manufactures. Chrysler's engineering team looked at the track record of the early Hemi, and the power that combination was capable of, and set out on a course of adapting Hemi heads on a slightly revised wedge block. The eventual outcome of this effort was the famed 426 Hemi.
The 426 was closely related to the wedge big-blocks that preceded it, retaining much of the wedge motor's architecture in the bottom end. The differences were aimed at increased strength and reliability, as well as revisions necessary to accommodate Hemi cylinder heads that defined the new powerplant. The Hemi heads featured domed combustion chambers with the intake and exhaust valves set in an opposed orientation across the cylinder bore. The deep dome allowed for large valves set at an angle of 58 degrees, and a centrally positioned spark plug. With the intake and exhaust valves set at opposite extremes of the cylinder head bank, each row of valves was operated by an individual rocker shaft. This arrangement resulted in a wide cylinder head and the wide Hemi valve covers, pierced with a provision to route an ignition secondary lead to the spark plug buried within. The characteristic look defines the Hemi.
Contemporary standard wedge heads were capable of intake port flow of 200-215 cfm, and the big-port race Max Wedge heads, which immediately preceded the Hemi, delivered in the 230-240-cfm range. In contrast, the Hemi intake ports, breathing through large 2.25-inch valves, supported a massive 300 cfm of flow volume, and, with modifications, could be urged to the 400-cfm mark. Contributing to the Hemi's flow, the head design offered a much improved approach angle from the port into the cylinder, and, as is inherent in the design, the valves move away from the cylinder wall as they open, minimizing the flow-restricting effect of bore shrouding. Hemi heads are born to flow.
Over the original production life of the 426 Hemis from 1964-1971, Chrysler produced around 11,000 Hemi-equipped cars. While that number was low, it was enough, and the legacy of Hemi power never faded away. Today, Mopar is casting blocks, heads, and can provide everything required to build one of these legendary powerplants brand-new. In fact, with the aftermarket offerings in the realm of Hemi components, the range of options in just how a Hemi can be built has never been broader. While the builders in our Hemi Challenge have all earned a name for their expertise with the Hemi engine, the engine's exclusive status means that not many of us typical Mopar guys have had the honor of wrenching on one. So we'll take a detailed look at the top-end components that make a Hemi a Hemi, and let the builders in the Hemi challenge tell us what they like.
With the Royal Purple/Mopar Muscle Hemi Challenge just on the horizon, we were curious about what these Hemi engine builders had going for their top-end combinations. We know cylinder heads will be a major factor in the power production of the various engines, and we're sure the competitors thought long and hard about the direction they would take in building their Hemi competitors. we found the builders seemed to each have their own approach and philosophy about how to get the most out of their engines, and we were pleased to see quite a variety in hardware. Without a doubt, there is more than one way to make power, and we thought we'd share some of the ideas of our feature builders. The variety of ideas makes us sure the final competition will be a real eye opener.
Mike Ware, Muscle Motors
"One of the things we looked to balance in this competition is real world cost versus all-out glory. In a competition like this, there is really no end to how far you can go with exotic one-off modifications and edgy dyno-bomb combinations. We built our reputation on practicality versus cost, and giving the customer real sensible value for his performance dollar. I know the cost of the engine is going to be tallied in the results and scoring, but there will always be a level of unaccountable custom work to optimize a combination like this. I really want to put together a Hemi engine that will be legit as far as what a customer enlisting our services can expect for real-world output. Given the constraints of the rules, I feel this competition is targeted towards the hot-street guy, and, for most of them, bang for the buck and, ultimately, reliability over the long haul is what matters.
"For cylinder heads, I've decided to go with the Mopar Performance aluminum heads. From a cost-to-performance standpoint, this head is the way to go. The exhaust port is in the stock location, which saves untold headaches to the final user because, ultimately, engines are built for cars, not dynos. We are going to have the heads fully CNC ported because it is exactly the same port configuration we can give to the customer on a cost-effective basis. I can spend 80-plus hours hand-rubbing the castings just for the contest, but at shop labor rates, you do the math. The bottom line is keeping it real, and, in real terms, what we'll show is what the customer can expect. Airflow is power, so our CNC heads will be more than up to the job, but the whole combination will play to make our number."
August Cederstrand, Speed-O-Motive
"I figured most guys will be using either the Indy heads or modified Mopar Performance heads, either the iron or aluminum heads. We wanted to take a different approach and decided upon the Stage V street replacement heads. This was kind of interesting to us, since they are a local west coast manufacturer, and we like the angle of this unique product. We are taking a set of these heads for hand porting and polishing here in-house rather than just using the standard off-the-shelf CNC ported heads, though there is nothing wrong with that. We have the expertise to do the ports our way, and I think it will be an advantage. We are going to go with Comp's beehive springs to reduce the weight and internal harmonics of the valvetrain in the rpm range of the competition from 3,000-7,000 rpm.
"I'm going to use 2.250-inch valves on the intake and 1.900-inch valves on the exhaust. That's smaller on the exhaust than the stock Hemi, but we're doing something a little different here, and, in fact, I think this valve size will work better in the overall combination. This isn't a particularly big head, but is sized right for this contest, and, of course, I'm using the Stage V rockers. in terms of flow numbers, once we have them ported, we're looking to see numbers in the range of what can be seen with the Indy 426-1 heads. We're also going to go with a full-coating package (thermal barrier), including the chambers, valves, and so on, to keep the heat transfer and detonation in check, and we do all that in-house. This should be a combination that will deliver a strong showing."
Ken Lazzeri, Indy Cylinder Heads
"For an engine of the specs required under the rules of the Hemi Challenge, we need to go with the smallest units we have: the Indy 426-1 CNC 285. These heads have a 285cc intake runner, 123cc exhaust runners, 166cc chamber, and 2.25/1.94-inch valves. We're going to fit them with Comp's 928 springs, and Comp's 10-degree locks and titanium retainers. Even with our smaller heads, we have way more capacity than what the rpm range of the competition dictates, and anything bigger will be way out of its range. These heads can take you all the way to 8,200 rpm, but even at the rpm range we're limited to, it will make all kinds of power.
"One of the keys with the Hemi is valvetrain control, especially with the flat tappet. You need the spring load to make the rpm, and we would normally use a roller with the Hemi. We're going to use our full valvetrain. We're going to build this with exactly the parts we sell, though we've never sold one with a solid cam instead of a roller in eleven years. It's just not a real sensible combo with the solid flat tappet when looking for reliable power, but we have to build it by the rules. It's not exactly the combination I would recommend to the customer, just because of the built-in compromises, but it will be a very strong running Hemi, I'll see to that."
Ken Hensley, Hensley Performance"We're in a real tizzy right now just looking to make the competition, since we are unexpectedly short-handed. We have major work with our race customers, and we are just jammed up something fierce with keeping our racers running. We are going to go with the Indy heads, since I know they make power. We were going to go with whatever we could under the rules to prep them for the competition, and we have the expertise to do full race porting. It is just a very time-consuming process. For this type of motor, we are not going to go crazy with port size, because if you do, its going to have to have some really high-rpm to pull that power out of there. Our plan was not to get the ports to where you can stick your leg in them."
Chuck Lofgren, Lofgren Auto Specialties
"We're going to go with the Mopar cast-iron original cylinder heads. They are very good heads. We just find we are getting much better low-lift flow out of them than the aluminum heads. The question is on the intake valves. We are looking at how nail-head-style valves react with the ports. They look good at the 3-4-.500-inch lift numbers, but we need to look at the blow-through situation with that angle of valve, and we've got to get it on the dyno. The problem is, we got our block so late that we are limited in time to test valves. In the past, it's just like any other engine, the more intake flow you seem to throw at it, the better. You have to be careful on the exhaust side with the blow-through at low-lift flow.
"Since cost is a factor, we are going to go with the stock rockers, and I am trying to keep the cost down. One thing with the valvetrain I ran into is, the lifter bores of the block needed correction, and this adds to the cost. With the iron head, I think it may be an eye opener for some of the guys in this challenge. With porting and the right combination, it will be a strong engine."
David Burns, Mid America Racing Engines
"We're looking at the Indy cylinder head, going with the CNC ported heads as delivered by Indy. The port layout of the Indy heads are a distinct advantage. We are also going to use Indy components for the valvetrain, as well as their valve sizes. I think these heads with their ports are the best choice."
Larry Shepard, Hemi's Only
"I'm going to use the Mopar Performance iron head. I had a friend in that business port and polish them; his name is Mark Lepole, and he is excellent at that. Basically, we just kissed the surface about .010 inch and did a normal valve job. I'm going to use the Landy rockers; there is nothing special there, just normal shaft pedestals and normal shafts.
"I went with the iron heads because of the 93 octane; I wanted the thermal efficiency. Since we can't put 12:1 compression in it because we are not running race gas, I wanted the thermal efficiency that iron gives; aluminum steals a lot of temperature out of the chambers. Those are my thoughts, maybe I'll be wrong, or maybe I'll have more horsepower than anyone else, but that's what I'm thinking. Everyone has their own views on making torque and horsepower, but with the fuel they give us, and, naturally, the compression levels we're stuck with because of that fuel, this is my choice. Basically it's a stock iron head with the modifications I've talked about."
Jeff Dickey, J.D. Engine and Machine"I'm going to use the Stage V heads. I had Total Flow go through them for me, and the main thing we focused on was port velocity. The idea was not to let the port volume get out of hand, but building a lot of velocity and a lot of swirl. That in turn could make all of this work. I'm not going crazy with compression ratio. I'm building this thing at 11:1, I could have gone 12:1, but I'm building it at 11:1 because it is more streetable in the post-dyno testing. The Stage V heads were used because the normal guy will grab the Indy head and build the cookie-cutter 500-inch Hemi. I'm a little more unorthodox and cutting edge on this deal. The high-velocity cylinder head will work. The valve sizes will be the normal 2.25/1.94 inch, since I don't feel there is a whole lot in valve sizes with such a small bore ... I don't think there is anything there. I'm using Indy rockers and the rocker stands from Mancini."
2005 Royal Purple Engine Challenge Participants
J.D. Engine and Machine
900 Spencer Ave.
Columbia, MO 65203
4131 South Main St.
Akron, OH 44319
6928 Clinton Hwy.
Knoxville, TN 37921
Indy Cylinder Head
8621 Southeastern Ave.
Indianapolis, IN 46239
Lofgren Auto Specialties
18130 Dahlia St. NW
Cedar, MN 55011
Mid America Racing Engines
1945 West 18th St.
Washington, IA 52353
2085 Glenn St.
Lansing, MI 48906
131 West Lang Ave.
West Covina, CA 91790