Engine Option I: Type 366 356 The simplest and least expensive path to improving the standard 1,131 cc VW engine was to add carburetion. So the Type 366 engine used Enginology individual left and right intake manifolds with Solex 26 VFI carbs with 22 mm venturi. Compression ratio was increased from 5.8:1 to 7:1 and after these changes the Type 366 engine produced 34 hp @ 3,500 rpm. This 36% horsepower increase over the basic VW engine was achieved without investing in a lot of new hardware or additional labor.

Building The Brand Phil Carney

e are all aware that the engine used in the 356 evolved from the pre-war Volkswagenwerk KdF design. Many Porschep- Whiles speak as if this engine development was a straightfor- Photographs show that after only a few prototypes of Reimspiess’ KdF Emotor ward refinement process but in reality Porsche engineers took several were built (left), an oil radiator was added inside the air duct (right). This cooler false steps. Only scraps of data exist about the earliest 356 engine ex- location was exceptionally effective and was carried over into the engines used periments but I think I have accumulated a pretty accurate history. I do in the 356. Photos courtesy Jens Torner and Porsche archives. not claim my version of events is perfect but I have put several hundred hours into investigating the story behind Porsche’s air-cooled, flat-four Porsche was a bit creative in advertising early 356 engine per- prior to 1954. The story is complicated, however I think it is also pretty formance which has caused some confusion fifty years later. One ver- interesting and I am hoping there are others who might enjoy this his- sion of the rare Porsche “Gmünd” sales brochure lists engine torical Porsche minutia. If you are one of those, put some ice in your fa- displacement at 1,131 cc which equates to the Type 366 engine. Per- vorite single-malt Scotch, flop down in a comfortable chair and start formance of this engine is listed as 40 hp but the explanation for this rat- reading. If this type of trivia does not interest you, consider using this ar- ing is found in the fine print of the 1949 Owner’s Manual. This manual ticle as a sleeping aid. actually shows two horsepower values for the Type 366: “Dauerleistung A Bit of Background 34 PS bei 3500 U/min” and “Höchstleistung 40 PS bei 4000 U/min”. (See Prescott Kelly’s article on page 44.) Dauerleistung implies that the Throughout 1933, 1934 and 1935, engine design for the Type 60 Type 366 could reliably obtain 34 hp @ 3,500 rpm. Höchstleistung VW was problematic. In January 1936 a young Austrian engineer by the means that the Type 366 engine could achieve 40 hp @ 4,000 rpm when name of Franz Xavier Reimspiess produced a table comparing his E- briefly operated above redline. In practical terms I am not sure exactly motor to other VW engine options. He analytically proved the excellence how drivers could benefit from this information since I know of no alu- of his engine design to the Professor and from that point forward, an air- minum 356 being factory equipped with a tachometer. cooled, flat-four was the baseline for the KdF People’s Car. (For addi- tional details see Birth of the Beetle by Chris Barber.) In hindsight, the Engine Option II: Type 367 E-motor proved to be an exceptionally reliable design. The secret was No matter how many were fitted to the original KdF en- that the primary components were much stronger then they needed to be gine, the breathing bottleneck was valve size. One creative solution to this for the power being produced. problem was tried on the Type 367 engine. In this design there was an When VW production restarted after WWII, basic engine displace- individual hemispherical head atop each cylinder. The pushrods re- ment was 1,131 cc based on a bore of 75 mm and a stroke of 64 mm. mained in their original locations but the rocker arms were greatly re- Engine output was 25 hp at 3,000 rpm, which provided the Beetle a top vised to allow the valves to be set at a V angle which in turn allowed for speed of over 100 km/hr along the Autobahn. As most people know, this a larger valve size. was the starting for the 356 engine development program in Gmünd. But For many years it was believed that the heads used on the Type 367 it was only a starting point because the Porsche Sportwagen needed a originated from the Sturmbootmotor, a KdF engine modified for use on performance measure significantly better than a . Ferry a marine landing craft. Perhaps this story originated from a reference in Porsche told a journalist that his engineers knew the KdF (pre-war VW) Excellence Was Expected where Ludvigsen wrote that Sturmboot heads engine was very strong because of wartime experiments such as the Types were considered for the 356. Unfortunately 1943 data sheets for the 115, 170 and 171. During the war a wide variety of engine design alter- Sturmbootmotor do not show individual cylinder heads being used so natives were examined including: larger pistons, larger intake valves, such derivation could not be confirmed. Another possible explanation multiple carburetors, supercharging, overhead cams, hemispherical for the Type 367 cylinder heads came from a retired Volkswagenwerk en- heads and even sleeved valves. Many designs never made it past the gineer who claimed the heads were from an experimental motor used sketch stage but several experimental engines were built and tested. After in the Berlin-Rome Coupe. In his book, Birth of the Beetle, Chris Bar- much consideration, Porsche engineers focused on three alternatives ber describes several engine experiments in connection with the 60K10 for their Sportswagen and they designated them Types 366, 367 and 369. Berlin-Rome Coupe. These included changing compression ratio, single

18 Volume 32, Number 6 • 356 Registry The left sketch is from a 1949 Porsche owner’s manual. It shows the stock cylinder heads Volkswagenwerk was using on the post-war Beetle were also being used on the Type 366 engine. The drawing on the right shows the heads used on the Type 369 engine It is quite possible that Type 369 cylinder heads, like the Type 367 heads, were initially designed during the war and that there was some units left in Porsche’s Gmünd inventory after the war. The Type 367 cylinder head design almost certainly traces back to wartime experi- YYYYYY digits were the serial number and it is easy to see where it changed ments but it is difficult to pinpoint exactly which project they were used on. At least from a Volkswagenwerk assigned number to a Porsche assigned number. eight of these heads remained in Porsche’s Austrian inventory after the war. One After this change took place only 356-1 and 356-2 engines were installed set was sold to Petermax Müller for use in a race car engine. Another set was used in cars but the limited examples still existing do not support the idea that to build one prototype Type 367 engine and it was later sold to another racer, Otto engine serial number relates to engine type. Another interesting observa- Mathé. Both of these engines still exist. Photo courtesy Franz Rathkolb. tion is that Porsche initially used aluminum cases and later switched to using magnesium cases. This switch occurred sometime after Porsche re- and double inlet manifolds, single or twin carburetors, and larger valves. turned to Germany but the exact timing and rationale is not known. He finishes by stating, “There were reports of the (Berlin-Rome Coupe) engine giving up to 40 hp but the entire mechanical variations attempted The Path to 1,500 cc on these three cars were poorly documented, as they ran under the ‘Ver- Ever since Porsche went into the commercial business, the suchsabteilung’ (experimental department), which meant that they were company has had a fetish for squeezing more and more performance into used in one-off trials with virtually no paperwork.” its rear-engine sports cars. So in 1950 Porsche targeted two new displace- After the war several of the Type 367 heads remained in Porsche’s ment sizes, 1,300 cc and 1,500 cc. Although there was a 1.3 race class in Austrian parts inventory and some of these were sold to German racer Pe- Europe, the primary rationale for selecting 1.3 liters was likely to increase termax Müller. Müller employed the services of Volkswagenwerk engineer sales potential. The Type 506 engine became available in 1951. Its 1,286 Gustav Vogelsang to build a special race engine for the 1.1 liter class. It used cc displacement was achieved by increasing the bore to 80 mm. But the four individual cylinder heads just like the Type 367 engine. This Vogel- compression ratio was decreased to 6.5:1 so that the engine was more tol- sang engine has been restored and resides in the Petermax Müller race erant of the lower octane fuels commonly available. Nevertheless, the 1.3 car displayed in the Protoyp Museum in Hamburg (see page 19). As for the liter Type 506 engine had a 10% horsepower increase over the previous 1.1 Porsche Type 367 engine design, one example was built. After evaluation liter Type 369 engine. it was sold by Porsche to Otto Mathé presumably for use in his racing en- The 1.5 liter displacement size equated to Europe’s favorite racing deavors. It is not known how successful the engine might have been in engine classification since the 1920s. This displacement was also a com- races but it still exists in Austria today. Apparently cost was a significant mon engine size for high quality European motor cars of the time. Short of factor in the Type 367 engine not being used in commercial 356s. designing a completely new engine, Porsche had two possible routes to 1,500 cc: continue to increase bore or increase stroke. Both of these routes Engine Option III: Type 369 were very problematic. Documentation shows that Porsche built an exper- The third option considered for the Porsche sports car was a realis- imental engine numbered 356-V-000003 that displaced 1,485 cc via a bore tic compromise between the performance-limited Type 366 and the com- increase to 85 mm. It is easy to appreciate why such a solution would have plex Type 367. The Type 369 used a dual cylinder head like the KdF cylinder had serious manufacturing issues. The stock two-piece, Volkswagen en- head but like the Type 367, the rocker arms were redesigned to allow larger gine case allowed 86 mm for the cylinder sleeve to fit in the case. If the pis- valves to operate in a V angle. This new engine design also used domed ton bore is 85 mm and a doable cylinder wall thickness is ~2 mm then the pistons with a 73.5 mm bore and the compression ratio was set at 7:1. All altered case opening would have to be around 89 mm. At this size there is of these changes resulted in a higher redline 1,086 cc engine that com- little meat left around the cylinder head bolts. Especially considering met- fortably produced 40 hp @ 4,000 rpm and allowed the 356 to be raced in allurgy and machining tolerances in the early 1950s, an 85 mm piston bore the 1.1 liter class. was not a realistic option. In fact stated that the upper bore The Type 369 engine became Porsche’s first standard engine after limit for the VW case was considered to be 80 mm. their return to Germany but it is not clear how many were installed in alu- So if an 80 mm bore was the upper limit, it would take a stroke of 74 minum 356 cars. Engine numbers on the Austrian cars are in the form mm to come close to 1,500 cc. Unfortunately the crank and cam in the two 356-X-YYYYYY. The X values were 1, 2, 6 or 7 and in all likelihood this ini- piece VW case are so close together that the stock VW piston rod cap hits tially equated to the Volkswagenwerk engine type: 1 = Beetle engine, 2 = the cam lobe at this greater stroke length. An expensive solution was found Kübelwagen engine, 6 = Industrial Motor and 7 = Schwimmwagen. The however, when Porsche decided to use a thirteen-piece, roller bearing

www.356Registry.com • March / April 2009 19 Porsche Engine Development Using Two Piece Volkswagen Case Porsche Engine Development Using Two-Piece Volkswagen Case Engine Stroke x Displace- Compressio Carburetors Crank / Performanc Years Type Bore (mm) ment (cc) n Ratio 1 Bearings e hp @ rpm

VW 64 x 75 1,131 5.8:1 Solex 26 VW 25 @ 3,300 Post WWII E Motor VFI2 Plain Bearing

ÜM38/4X3 64 x 73.5 1,085 - - - - VW 32 @ 4,000 1939 - 1943 Plain Bearing

4 The lower rod in this photo was inherited from the 366 64 x 75 1,131 7:1 Solex 26 VW 34 @ 3,500 1948 1949 VFI2 Solex Plain original Volkswagen design. The connecting bolt re- 26 VFJ Bearing quired a beefy boss (arrow) on the cap for drilling and tapping. This area caused interference with the 367 64 x 75 1,131 Solex 26 VW 1948 VFJ Plain cam if the crank stroke was increased to 74 mm. The Bearing problem was inexpensively solved with the Type 546 engine rod (assigned part no 502.03.105) where the 369 64 x 73.5 1,086 7:1 Solex 26 VW 40 @ 4,000 1948-1954 VFI2 Plain connecting bolt was forged with the rod cap. Solex 32 Bearing PBI5 crank built by Albert Hirth AG. (Porsche used Solex 32 6 Hirth in this same role for the Auto Union racers PBJ back in 1935.) The Hirth design eliminated rod V-000003 64 x 85 1,453 - - Solex 26 VW 60 @ 5,200 Circa caps allowing a 10 mm greater stroke and total VFI2 Plain 1949-1951 displacement of 1,488 cc. Porsche’s new 1.5 Bearing liter engine was designated Type 502 and it pro- 502 74 x 80 1,488 7:1 Solex 32 PBI Hirth 55 @ 5,500 1951 duced 55 hp at 5,500 rpm. Only some sixty Type Roller 502 engines were built before it was succeeded Bearing by the Type 527 which produced 60 hp @ 5,000 506 64 x 80 1,286 6.5:1 Solex 32 PBI Alfin 44 @ 4,200 1951-1954 rpm. Solex 32 Plain The Hirth crank was far from an ideal so- PBJ Bearing lution. Not only was it expensive to build, it 506/1 74 x 74.5 1,290 6.5:1 Solex 32 PBI Alfin 44 @ 4,200 1954 gained a poor reputation for its short life span. Solex 32 Plain Karl Rabe is credited with coming up with a new, PBJ Bearing simpler and cheaper solution in 1954. The orig- 509 - - 1.3 liter 6.5:1 Single side VW - - 1950 inal VW rod used a separate bolt to connect the prototype draft Plain top half of the rod with the cap. Such a design Bearing requires a beefy portion of material on the cap 527 74 x 80 1,488 7:1 Solex 40 Hirth 60 @ 5,000 1951-1952 (arrow) that could be drilled and tapped for the PBIC Roller connecting bolt. Rabe’s idea was to forge the Solex 40 Bearing connecting bolt with the cap thus eliminating the PBJC large boss section. The idea was first tried out on 528 74 x 80 1,488 8.2:1 Solex 40 Hirth 70 @ 5,000 1951-1954 engine Type 546 which was plain bearing ver- PBIC Roller Solex 40 Bearing sion of the Type 527. The design was successful PBJC and the new rod became the standard from that point forward. 546 74 x 80 1,488 7:1 Solex 32 PBI Alfin 55 @ 4,400 1952 - 1954 Solex 32 Plain Two Piece Epilog PBJ Bearing In 1954 Porsche took the dramatic step of designing a completely new case for their boxer engine. The old Volkswagen case just had too Chart Notes: many limitations if Porsche was to continuously 1. All Porsche engines were equipped with dual carbs except for testing done with the Type 509 prototype. meet its desire for steadily increasing engine 2. The pre-war Kdf Beetle was fitted with a single Solex 26 VFI carb. Immediately after the war, carbure- tors were not available from Solex. To address this issue, Major Hirsch, the British officer who was helping to performance. The new case was made from return the Volkswagenwerk to production, reverse-engineered the Solex 26 . The Beetles produced three pieces of cast aluminum and the easily immediately after the war were equipped with this carburetor which had no model number scribed on it. identifiable external features included a remov- 3. Multiple engine configurations were used in the three Berlin cars. Displacements ranged from 985 to 1,131 cc and outputs of up to 44 hp were reported. Specifications in this table relate to engine Ü38/43 in the able case face and a significantly larger oil Type 60K10 car sold to Otto Mathé July 1949. “pan”. These changes and many more less visi- 4. According to 1949 Ownerʼs Manual, 40 hp @ 4,000 rpm could be achieved for brief periods of time if re- ble refinements would eventually allow Franz liability was sacrificed. Xaver Reimspiess’ 1936 flat-four design to pro- 5. Austrian cars equipped with VW version of Solex 26 VFI, German cars equipped with Solex 32 PBI. 6. Original Porsche documentation indicates Solex carburetor designation changed from “PBI” to “PBJ” duce 95 hp by the time Porsche 356 production and “PBIC” to “PBJC” sometime during 1952. Verbal history indicates this was done to avoid the letter I being ended in 1965. mixed up with the number 1.

20 Volume 32, Number 6 • 356 Registry It took the efforts of several people to compile and check the data in this article and their valuable assistance deserves to be recognized: Ken Daugherty, Thomas König, Jacques Mertens, Franz Rathkolb and Vic Skir- mants. If you have any additional information about early Porsche engi- nology, I would appreciate you sharing your data with me.

From the early A shop manual, a 1600 Super engine showing the roller crank’s rod orbit in the crankcase (red circle).

The Müller/Vogelsang Engine The Volkswagen based engine shown at left uses quad carburetors and the same cylinder heads as the Type 367. The heads were in Porsche’s post war inventory and sold to Peter- max Müller, a Volkswagen dealer and racer. Müller employed the services of Volkswagen- werk engineer Gustav Vogelsang to use these heads to build a special race engine for use in the 1.1 liter class. The engine was installed in a custom, single-, streamliner built on a VW chassis (above). In 1949, Müller and his racer The T-97 Engine dominated that class in Germany and set eight In 1937 Tatra of Czechoslovakia unveiled national and twenty two international records. their proposed version of the people’s car, the This engine and Petermax Müller’s stream- model T-97. It bore numerous similarities with liner and are on display at the Prototyp Museum the KdF car from the Volkswagenwerk. Ferdi- in Hamburg, Germany along with many other in- nand Porsche and Tatra’s designer Hans Led- teresting cars and pieces of automobilia. winka were well acquainted and frequently www.prototyp-hamburg.de. Photos and infor- shared information about what they were work- mation courtesy of Thomas König. ing on. So it would not be surprising if Porsche did use some of Ledwinka’s ideas. Stories relate that when Tatra expressed patent infringement The CFM engine. claims prior to WWII, Porsche suggested to This engine is a four-cam, flat-four de- Hitler that Germany pay Tatra for use of their signed and built in 1949. It displays the three concepts. Hitler dismissed the idea knowing that initials, CFM, which stand for the Italian com- Czechoslovakia would soon be under German pany of Luigi Chinellato and Carlino control. After the war Tatra sued Volkswagen Francescon located near Venice. The basis for and they eventually reached an out of court set- the engine was a Kübelwagen flat-four whose tlement. displacement had been reduced to 750 cc. The Ledwinka idea that had a major impact The unique cylinder heads were designed by on Volkswagen design was use of a fan that Chinellato and Francescon and fabricated in a drove air into metal ducts that directed cooling foundry near their company. The overhead where it was most needed. Prior to this inven- camshafts were driven by bevel gears, a mag- tion, temperature control in air-cooled engines neto provided the spark and two Weber car- motor. It is not known exactly what influence the had always been problematic. Ledwinka applied buretors supplied the air/fuel mixture. With meeting may have made on the creation of the his ducted-air idea to a variety of engines but its an 11.5:1 compression ratio, 84 hp was gen- Porsche Type 547 but the Italians stopped de- application to the four-cylinder boxer engine on erated at 6,500 rpm when burning an alcohol- velopment of the engine shortly after Porsche re- the Tatra T-97 most closely parallels the design based mix. Just prior to the 1949 Mille Miglia, turned to Germany. Photo and information also used on the Volkswagen. traveled to Italy to see this courtesy of Thomas König.

www.356Registry.com • March / April 2009 21