Performance Modifications for Bugs
For generations, the VW Beetle has been celebrated as a simple and reliable means of transportation for people all over the planet. While the Beetle’s engine displacement steadily grew from 1100cc to nearly 1600cc (and, in turn its power output doubled during the car’s life), the car was never thought of as a “performance car,” at least as it came direct from the factory. Despite its lightweight, the Beetle was always characterized as a “slow” performer. With less than 60 SAE horsepower, its lack of performance is not surprising.
In the 1960’s, however, a few individuals looked beyond the Bug’s meager performance. Individuals such as Dean Lowry, Darrel Vittone and Gene Berg found that the VW’s flat four was extremely accepting of performance modifications. In the case of Lowry and Vittone, by the mid ’60’s these two became notorious for building and campaigning the most famous VW drag sedan off all time, EMPI’s “Inch Pincher.” Though it vaguely resembled the same Beetle that was available at the local VW dealer, eventually the “Inch Pincher” was making FOUR times the stock Beetle’s horsepower, topping 200hp. This was enough to push the car to a quarter mile e/t of less than twelve seconds. The VW had become a serious contender!
The successes of these early drag race VW pioneers led to a cult following of VW fans that were bored with the stock pace of their VW’s. By the 1970’s a huge wave of post-college-age individuals found they could mimic much of what was going on at the drags with their own street cars (especially in Southern California, where the hot rod VW was born). Soon it was common to know someone that knew someone that was driving a very quick VW. Clubs, focusing on such hot-rodded VW’s, sprung up all over So California… each club doing their best to “outgun” the others, with what else? Horsepower. Most serious clubs had a few front running street cars that were running the quarter mile in 13 seconds or less, much to the dismay of those that felt they needed a V8 to go fast. This popularity of speed-tuning the VW, underdog that it was, led to an industry that grew to legendary status.
Still today, over 40 years after those first VW drag sedans made their mark on the history of hot-rodding, people are still on the quest for more “go” from their Bugs. While it is entirely possible (and easier than ever) to build a full-on, screaming 2000cc+, 12 second Bug, most people are after a bit less of an extreme. Even the stock 1600 dual port is a good candidate for performance tuning. There are two basic reasons for this: One is the extremely restrictive intake and carburetion setup of the stock engine (single ports are even worse!) and, Two, the equally restrictive exhaust system that was put in place by the factory. You might ask, “If the carb, intake, and exhaust were SO bad, then why did VW equip the car as such?” The answer is VW was known for building simple and reliable cars, not performance cars. The restrictive manner of these parts was “engineered in” in an effort to keep the power output at a reliable level that would not risk damage to the car. For fuel economy, ease of maintenance, and long life the stock set up was hard to beat.
The very nature of these restrictive systems makes the stock VW so easy to tune for power (that and the somewhat exotic design of the flat four itself and the materials it was built of). Take a stock 1600cc that is in healthy running condition; add dual carburetors, an extractor exhaust and a centrifugal-advance ignition, and your stock 1600cc will be transformed. By doing away with the single and diminutive carburetor (and its strangling, stock intake manifold) and replacing it with (at the very least), two-single-barrel, small carburetors (one for each bank) you can (with tuning) realize a 12-15% increase in horsepower. More importantly, the very character of the engine will blossom. What was a lethargic, unwilling, and asthmatic motor now becomes a sharp, hard-edged, and very enthusiastic power plant. The car becomes much more fun to drive. Add a good tuned extractor exhaust and free flow muffler and the power grows. Both the carburetors and the exhaust are relatively simple “bolt on” modifications that can usually be attacked and successfully installed by anyone with some patience and a good set of metric tools. Tuning the dual carburetors can be a tricky undertaking for the novice, but certainly not impossible. Again, it takes patience, and paying attention to details. Modifications to the camshaft and larger, “ported” cylinder heads would be the next logical steps in the sequence of hot-rodding the stock 1600, and are really, beyond the scope of this short article. Instead, here are some specific suggestions for simple “bolt on” mods….
Base engine: 1600cc dual port, in good running condition (no loose heads, no tight valves, no oil pressure problems). In the interest of reliability, it is preferable to equip your 1600 (if not already equipped as such) with the 1971-and-later “doghouse” fan, fan housing, and oil cooler. These cooling parts were designed by the factory to supply more cooling air to the engine, and keep the oil temperature down.
Suggested Carburetion: Dual 40mm Solex-Kadron carburetors on cast aluminum manifolds (try 55 or 60 idle jet and 135 main jet); dual Dellorto 36mm DRLA (2bbl each carburetor) on cast aluminum manifolds, w/ 30mm venturis (try 50 idle jet and 120 main jet); dual Weber 40IDF (2bbl each carburetor) on cast aluminum manifolds, with 28mm venturis (try 50 idle jet and 120 main jet). Do not go larger than 40mm dual Webers on the stock 1600 or you will lose low and mid range engine response.
Suggested Ignition: Bosch centrifugal advance distributor (if available), model #’s “010,” “019” or “009.” (all three are out of production, and are getting hard to come by, if you can find a good “010”, it is generally referred to as THE BEST). Use a stock Bosch blue coil, stock plug wires and maybe step down a heat range in spark plugs (stock is Bosch W8AC, colder would be W7AC). Gap plugs at .028″
Suggested Exhaust: For best horsepower and fuel mileage, a 4-into-1 “header” cannot be beat. Look for one that will connect to stock heat exchangers and, if running dual carbs, has provisions to “block off” the heat-riser ports at cylinders 2 and 4. Mufflers are really up to your taste. “Quiet Pack” mufflers have long been a favorite and have a great deep tone. “Glasspacks” can be (annoyingly) loud, and despite their “fast” sound, rarely make any more power than the “Quiet Pack.” To preserve your header, it’s best to strip all shipping paint off and give it a good few coats of high temperature “exhaust ” paint or for the ultimate finish and longevity, have it ceramic coated.
And remember, after bolting on your “mods,” it’s now even more important to keep your motor regularly tuned and maintained. By letting services slip… you will be sacrificing the performance you paid for (new parts) and the reliability you should enjoy.
More than anything… HAVE FUN.