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Laydown Engine vs Upright Engine - a technical comparison

Posted on January 2, 2010 at 10:01 PM

Laydown Engine vs Upright Engine

Watson/Kurtis vs Sahih/Epperly/Lugie

By 1957, of the ’52 through ‘66 roadster era, the “template” for the Indy roadster had been established.

It included:

• Tubular space frame

• front straight axle

• Offenhauser engine, mounted vertically, approx. 7 inches to the left of center

• driver seat mounted beside the driveshaft, to the right of center

• front and rear cross torsion bar suspension

• 70+ gallon, rear mounted fuel tank

• standard Halibrand steering gear, Model A style transmission, torque tube driveline, Halibrand offset live rear straight axle and Halibrand disc brakes

• Halibrand 18” and 16” mag wheels and spec. Firestone race tires


  For 1957, the top builders were ready to square off with their newest cars, Frank Kurtis with his KK500G chassis and A.J.Watson with his new lightweight Watson chassis.

  But, something, unexpected, happened that threatened to obsolete the top cars.

  A new, Belond sponsored, car, built in a small garage, on a shoestring budget, by George Salih and Quinn Epperly, won the Indy 500, right out from under the big teams.

  This car was a “template“ car, with one exception. Salih rotated the engine, top to the right, on its bellhousing until the engine was just 18 degrees from laying on its side. This lowered the CG significantly and also lowered the nose and hood profile for better aerodynamics.

  This new “set up” was thought to be such a “sure thing” that several of the top builders made plans for their own “laydown” engine cars. Frank Kurtis bailed out on the KK500G, for the “laydown” design and, even, some of the existing 500Gs were converted to “laydowns. Epperly planned his own “improved” version of the Salih car. Even A.J. Watson, who, ultimately, stayed wlth the vertical engine installation, admitted that he had made up drawings for a new “laydown” car.

  Following the ’57 500 win, the Belond/Salih “laydown” disappeared into its garage for the rest of the season.       The next appearance of the “Belond” was in the 1958 Indy 500, where it won again and led three of the new Epperly “laydowns” to 4 of the first 5 finishing positions. Things were looking grim, indeed, for the “upright” engine cars, especially at Indy.

  The “Belond” made one other appearance, during ’58, at the “Monza 500”, where it placed second to the Zink/Leader Card Watson “upright” engine car.

    The continued success of the “Belond” and the new Epperlys encouraged more builders to switch to the “laydown” engine configuration, including “Lugie” Lesovsky and Ed Kuzma. Lugie’s new pink #3 car featured a left side driver seat and the engine mounted on the right side, laid over, top to the left.

      Qualifying for the 1959 Indy 500 saw the new ”Lugie” and the new Kuzma laydowns taking the top two starting spots, with a total of fourteen “laydown” engine cars making the starting lineup.

     With the past performances and the obvious future development potential, this race had all of the possibilities of a “laydown” engine rout, finally putting the vertical engine cars in the museum for good.


  In the race, the “laydown” magic mysteriously disappeared, with the two time Indy winning, Belond Spl. finishing dead last and the “upright” Watson cars taking first and second place. Laydowns finished seven of the top ten spots.

  As suddenly as the “mojo” disappeared at Indy, it reappeared, the following week, at Milwaukee, with the Lugie “laydown” taking the #1 starting spot and leading a “laydown” sweep of the top four finishing positions.

         Following the Indy “blip”, the Milwaukee results refired the “laydown” enthusiasm. More new “laydowns” were built for 1960, including the new Salih/Metal Cal Spl, with the left side driver/right side engine, like the “Lugie” car, two new Trevis/Jim Robbins Spls and a new version of the Epperly, with right side driver/left side engine laid over top to the left, outside the frame, like a supermodified.

     At Indy, the anticipated “comeback” of the “laydowns” never materialized, with upright Watsons taking the pole position and, again, taking the top two finishing spots. The lay downs placed four cars in the top ten finishers.    

       The last three new laydown cars were built for the 1961 Indy 500, including “supermodified” style cars from Epperly and Kuzma and a “Lugie” style car from Herb Porter/Rocky Phillip.

  The 1961 Indy 500 saw the “upright” cars scoring the win for the third year in a row and the top five finishing spots. The “laydowns” had three in the top ten.

  A.J. Watson never fell for the “laydown” fad and “laydown” builders, Kuzma, “Lugie” and Trevis returned to building “upright” cars.

     The “laydowns” continued to run well and score good finishes in “62 and into ’63, but they never fulfilled their destiny, of the late 50s, to obsolete all of the upright engine roadsters.  The last “laydown”, to race at Indy, finished midpack in 1964.

   The “upright” cars, particularly the Watsons, survived the “laydown” threat of the late 50s and raced on through the mid 60s until the last roadster ran at Indy in 1966.

    During the years of the “laydown” challenge. ‘57 through ’64, the Watson chassis won 6 of the 8 Indy races.


After writing the “Laydown Engine Roadster” blog, I decided to do a closer comparison of the upright engine roadsters vs the laydown engine roadsters, using four basic physics principals that most effect vehicle dynamics. I compared various aspects of the five main “players”, the Salih/Belond laydown, the Epperly laydown, the “Lugie” laydown, the Kurtis 500G upright and the Watson upright, by the “numbers”, by staring at design drawings and by learned opinion.

For our purposes, we will use the following definitions:

Frontal Area - The area, in square feet, of the vehicle's maximum cross section, as viewed directly from the front. The square feet of surface that directly faces the oncoming airflow. The size of the hole required for this car to pass through the oncoming air.

Coefficient of Drag (CD) - The ratio of the drag on a vehicle moving through air to the combination of the velocity and the frontal area of the vehicle. The efficiency with which the “leading edge” of the vehicle splits the oncoming airflow and rejoins the airflow at the “trailing edge”.

Center of Gravity (CG) - An intangible point representing the weight center of a vehicle. The point about which the vehicle balances in all axis. On racing cars, CG usually refers to the location of vertical weight mass of the car.

Weight Distribution(bias) - The longitudinal and/or lateral dimensional location of the Center of Gravity. On racing cars, usually referred in percentage of front/rear and RS/LS weight or pounds of RF/LF/RR/LR corner weight distribution. The amount of weight supported by each of the four tires.


   Frontal Area – The frontal area of these cars include the maximum cross section of the chassis/body, any part of the cowling/windscreen that protrudes beyond the maximum chassis/body cross section and the forward facing cross section of the tires

  The maximum cross section of the chassis/body of these cars, both laydown and upright, is the plane located at the front edge of the tail, directly behind the driver’s seat. The maximum chassis/body cross section of both the “laydown” and the “upright” are almost identical at 5.6 sq ft. for the upright Watson roadster and 5.3 sq.ft. for the “laydown”.

They all use the same tires, whose cross section is 2 sq ft.  

The windscreens are variable shapes according to the driver preference, but I doubt that there is much variation in actual frontal area. Actually, the cowl and windscreen are a little bigger for the laydown cars.

  Bottom line is that there is no significant advantage in frontal area for the laydown engine configuration…… certainly not as much as most people would think.


   Coefficient of Drag (CD) – This is the most difficult comparison to make because to get an accurate analysis requires having access to a Watson roadster, the Salih/Belond laydown and a wind tunnel. Lacking those three ingredients, I will have to make a few comments from experience and logic. Certainly, any of you, with more knowledge and better articulation of this subject than I, are welcome to add comments and corrections.

        Drag is the result of turbulence, which develops in low pressure areas on the “backside” of any part of the car that faces the oncoming air stream.

   On the Indy roadster, the greatest generator of “drag” is the open wheels & tires. The fact that they are spinning, greatly increases the amount of turbulence. Since all of the roadsters used the same wheels & tires, this is not a factor in comparison.

  The next high drag area would be the cowl/windscreen area with the large driver cockpit opening on the backside. While there is some variation in windscreen size and shape, usually depending on driver preference, I doubt that there is much difference between upright and laydown cars.

  Other somewhat less significant “high drag” bits and pieces, that add up, include the front and rear axles, shocks, suspension linkage, steering linkage, roll bar, bumpers etc. Collectively, they account for a fair amount of the total drag of the vehicle. Again, these are all common components to both the “upright” and the “laydown”, so there is no comparison.

   Viewing the side profiles of both the Salih/Belond and the Watson would lead one to believe that the lower nose & hood of the laydown would be more efficient at splitting the oncoming air ……. On the other hand, the Watson nose & hood, even though higher profile, has good streamlining……… There is probably not as big an difference in CD, as it would appears.

      One of the things, that I see as a, possibly, more significant aero advantage for the “laydown”, is the hood & nose have a relatively flat top surface that angles downward from the cowl to the nose. This is a high pressure surface that puts more downforce on the front tires for better “turn in” to the corners. I have been told, by a couple of drivers, that the Watson steering got very light by the end of the straight away, from air pushing up under the nose, requiring a tap of the brakes to settle the front tires back down to the track, before turning into the corners.

    The tails of, both, the “upright” and the “laydown” are of similar size and shape. They, probably, both do a good and equal job of rejoining the trailing airflow without contributing much to the overall drag.

     As I said, to do this comparison accurately would require a wind tunnel and I doubt that will ever happen. I will try to talk to some smarter guys than me, for their opinions.

    The bottom line is that I might give the “laydown” a slight edge in airflow but not nearly as much as many people think.


Center of Gravity (CG) & Weight Distribution(bias) -- Now, back to something that is a little easier to evaluate.        There is one absolute advantage that the “laydowns” have over the “uprights”. Laying the engine over on its side, significantly, lowers the vertical Center of Gravity……….but there is another factor to consider. By distributing the weight of the engine across the entire width of the chassis, the car loses a significant percentage of its left side weight bias, thus, reducing some of its CG advantage.

   Weight distribution comparison of the Watson “upright” roadster and the Belond/Epperly style “laydown”(RS driver, LS engine, laid over top to the right) is as follows:

The standard Watson roadster (with driver, 5 gal. fuel) has the following weight bias:

Front-43% Rear-57%      LS-56% RS-44% 

The Belond/Epperly style “laydown”(with driver, 5 gal. fuel) has the following weight bias:

Front-46% Rear-54%      LS-50% RS-50

 Difference in “front to rear” weight bias is due to the laydown engine being located approx 6” further forward in the chassis than the upright engine

Difference in the LS/RS weight bias is, of course, due to the weight of the laydown engine being distributed across the entire width of the chassis.

The “Lugie” style “laydown” uses the LS driver, RS engine, laid over “top to the left”. but the mass of the engine is still distributed over the entire width of the chassis. The “swapping sides” of the driver and the driveline would not be a significant change of weight distribution.


The cars that should have had it all, were the final two “laydowns”, built by Epperly for 1961. He used the same layout as his earlier cars, with the RS driver/LS engine, but, on these two cars, instead of laying the engine “top to the right”, he laid the engine over “top to the left”, with the cylinder block(& head) sticking outside the left frame, like a supermodified. He, also, moved the engine approx. 6” further back in the chassis. similar to the upright Watson.

  This car had the lowest possible CG, the maximum left side weight bias and equal engine setback to the Watson. On paper, these cars were the final and ultimate development of the “laydown” design. While they were very competitive and scored several top 5 finishes, they never were able to fulfill the expectations of winning.


Other Factors!

  At first look, it would appear that the low profile aero of the nose and hood were what the “laydown” cars were all about, but the real “game” was CG and weight bias. Some of these weight bias factors are adjustable and can be manipulated through corner weight jacking, spring rates, etc. but some weight masses “are what they are”.

  Certainly, the greatest weight bias, effecting roadster handling was the weight mass of the full fuel load. This weight mass was cantilevered behind the rear axle, which added to its effect and was constantly changing from approx. 450lbs.(full) to approx 30lbs between pit stops…. Wow! What a setup problem. This was the greatest flaw of the roadster design.

  Both the “upright” and the “laydown” had the cantilevered, rear mounted fuel tank so, for our comparison, there was no advantage for either setup.

Another developement by A.J. Watson in the early 60s was “chassis offset”. With some basic suspension linkage modifications. A.J. was able to offset the entire chassis(including the fuel load and engine weight) approx 1.5 inches to the left of the wheel track centerline. This resulted in a very useful addition to left side bias percentage.

  "Other Factors" must also include differences in suspension geometry. While all of the roadsters, "laydown" or "upright". had, basically, the same type of suspension, small differences in "track bar" and "radius rod" lengths, angles and mounting points can cause big differences in handling characteristics.

    Such dynamic characteristics as rear roll steer and front castor change can be minimized with proper suspension linkage design.

     I do not have accurate drawings and dimensions for the various cars, so I am unable to do a proper analysis of their relative suspension geometry.

      It would be very interesting and informative to put these cars on one of the current "seven post" chassis test rigs to compare dynamic suspension characteristics.

  Suspension geometry can mean the difference between a car that is predictable and easy to drive and one that is a "handful" and tiring to the driver.




In Conclusion

The laydown roadsters may have been the greatest enigma in Indy history, always creating more questions than answers.

* Why was the very first “laydown” engine car, the most successful one??

* Why wasn’t there ever a consensus among the builders as to the definitive layout of driver, engine, layover direction??

* Why didn’t the ultimate Epperly “laydown” version, with maximum left side weight bias, lowest possible CG and lowest possible hood & nose profile, perform any better than any of the earlier “laydown” versions??? Could this layout have ultimately succeeded if the rear engine cars hadn’t appeared when they did???

Bottom Line

* The perceived aero advantage of the low hood and nose was vastly overrated, because the actual frontal area was very similar for both “upright” and “laydown” engine cars.

* The real lower CG advantage of the “laydowns” was neutralized by spreading the engine weight across the entire width of the car. This eliminated much of their left side weight bias, which was, at least, as important as the lower CG.

* While all of the “laydown” builders were scrambling and searching for the ultimate layout, A.J.Watson remained focused and developed his original ’56 design. A.J. understood his car and how it worked. He was always able to come up with a new “tweak” or idea to stay one step ahead of the competition.

At the end of the day, as good as they looked on paper, the “laydowns” were, technically and practically,  just not that much better than the “uprights”.

mac miller in INDY

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9:45 PM on January 3, 2010 
Mac... Great blog...
Very well researched and thought out sumary.

I do think the reason that the laydowns never won again after "57, '58 was the final ride of Big Tony.
Tony B in 1961 had finally found the ride he was searching for. The car that could, and in my opinion, would have, taken him to victory: The Epperly laydown, the Autolite..
He tested the Autolite early on and begged his owner to buy the car for him to run at Indy.
Tony had, by then, more miles at Indy than anybody else running and finally figured how to get around the big oval. He was the odds on favorite for the pole and was SERIOUSLY flirting with the magic 150 MPH lap. He had continually turned laps above 149 all practise. He had the car, the talent, the expertise and the finnese. The pole and the 150 MPH lap would have been his...
Then he took a favor ride for old Chicago gang member Paul Russo.
When Tony died in testing, I think the era of the laydown died with him...
Reply ★ Owner
7:10 AM on January 5, 2010 
This car was actually at the Indianapolis Speedway in May of 1960, as the Braund Plywood Spl, but never attempted to qualify.
Following Indy, the car was tested by Tony Bettenhausen and, also, Parnelli Jones.
Both drivers wanted the car but Tony had first "dibs" on it, so Lindsey Hopkins bought it and it became the Autolite Spl.
Tony said he could run 150 in the car, but never got the chance to prove it.
Between 1961 and 1964, the car never turned a 150MPH lap with Ruby, Branson and Marshman driving.
Ironically, It was Parnelli, in 1962, driving a Watson, that did the first 150.
I don't recall Parnelli ever driving a "laydown" car in a race.

mac miller in INDY
Reply ★ Owner
3:53 PM on January 8, 2010 
While checking some records, I find that Parnelli drove an Epperly laydown in the August race at Miwaukee in 1960.
mac miller in INDY
Reply Roy
2:21 AM on March 6, 2011 
VERY interesting blog Tom!
Reply Jim Young
3:30 PM on May 25, 2018 
Other factors? Perhaps heat affecting the driver's performance.

Earlier races in the 50s seemed to have many drivers unable to take the heat for the entire race, letting relief drivers take over, and even reentering as a relief driver in a different car once they recovered enough. I noticed what seemed to be earlier cars that had various sized plexiglas deflectors (like little windshields), at the right front portion of the hood openings, too. I can imagine a few reasons why, but would like better info from someone with far better experience or knowledge of why they were used (at least in the 50s). Could it be that there was enough reduction in driver "heat" to give them and advantage for a year or two, at least?

The photo of George Salih and a laydown car found on the Whittier Museum site (seems to have been mirrored by an upside down negative) shows the exhaust exiting from the left side (upper side) of the engine, though all other photos I found show the intake on the left for that type of laydown car. I hadn't considered how the switched between left and right intake versions but it sure looks like the basic integral cylinder and head "block" could be installed in either direction, with the cam drive separate and cams able to swap sides.

P.S. One of our Air Frame and Powerplant (A&P Tech) students, worked at Peterson Aircraft restorers, on Carroll Shelby's Howard DGA, which I found out, Shelby had
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Reply Walter Bell
10:33 AM on October 29, 2020 
great site. I will be building an 1/8 scale model of the Epperly laydown car soon and appreciate your facts you have posted.
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