VW - PERFORMANCE #3/5 ===================== Author: Robert Collins Some editing: Jan Vandenbrande =============================================================================== Disclaimer by the editor (& presumably the author): These articles should be regarded as opinions and not fact. If any product's name or company is mentioned, no connotation should be taken for its actual quality, value or use. There is NO guarantee any of this information is correct. Neither the authors, editors, or those who maintain these archives take any responsibility for the consequences that may result from applying any of the ideas presented within these articles. Severe damage, injury or loss of life may result from applying the ideas presented. Furthermore, before implementing any of the ideas, check whether such modifications are allowed in your state, province or country. All articles may be distributed freely and copied (unless otherwise stated) as long as the original authors or origine are identified if available. =============================================================================== PART - 3 - >From: rob@conexch.UUCP (Robert Collins) Subject: GTI High Performance (Microview Part 3) Keywords: horsepower Date: 20 Apr 88 07:19:23 GMT Organization: The Consultants' Exchange, Orange County, CA. (714) 842-6348 This is the third installment in VW High Performance (Microview). You didn't miss part 2, I haven't posted it yet. I'm still waiting for some specs to come in before I post it. This issue deals with cylinder head basics, both eight and sixteen valve versions. It's no secret that VW has manufactured both 8 and 16 valve cylinder heads for the VW motor. But, how many of you know about the European 8v head (or what distinguishes it from the American head), the carbureted 1.6 and 1.8 heads? Yes, VW makes a carbureted 1.8 head down in Mexico. (Believe me, it was quite a surprise to see one come in Drake for the racing treatment.) In this article, I will give an overview of all the heads VW has made, and all the aftermarket heads I know of. In the next issue, I will give a microview of the various cylinder head components, and what parts work well for a high performance head, and a list of parts to stay away from. I will also point out why there is a drastic difference in high performance (big valve) head prices and let you decide what to buy. 1.6L head: >From 1974 - 1976 VW used a carbureted head. This head featured 36mm intake and 32mm exhaust valves. The head had a combustion chamber built into the head and was the precedent for all subsequent head designs. Specifically, the camshaft pushed directly onto a cam follower, which sat on top of the valve tip. Thus the camshaft pushes the valve directly, without rocker arms. The camshaft was supported by five journals, each without a traditional bearing. The aluminum in the cam journals was the bearing, and received its oiling via a pressurized oil galleys in the head. (In the next issue I will cover how this bearing surface is repaired should it become damaged.) Flow was in a U configuration, as the intake and exhaust ports are located on the same side of the head. In 1977 VW introduced the fuel injected head (f/i). It afforded the same basic design as the carbureted head, except the extra ports for the fuel injectors. Valve size was the same at 36/32mm. Also about this time, though I don't know what year, VW introduced its first high performance motor based on the 1.6 block - the (European) GTI. The GTI featured 10.0:1 compression, and 40mm intake, 33mm exhaust valves. The head, though the same basic design, was actually quite different. There was no combustion chamber - as the bottom of the head was perfectly flat. The combustion chamber was built into the pistons. The valves were much longer than the American heads. Longer, because of the lack of combustion chamber; hence, to keep the same valve train geometry and spring tensions, the valve stem had to be about 10mm longer. The motor's output was rated at 110hp DIN. 1.8L head. In 1983 VW introduced the 1.8L motor to America. With the new motor came a new cylinder head. The head was still the same basic design, but had been refined to fix some oiling problems in the 1.6 head. The head was most noticeably different by examining the oil return galley's. The main galley was much larger, and there was a new second galley the 1.6L head didn't have. The head had a combustion chamber built into it like its predecessors. And as I found out a year after its introduction, it was manufactured in Mexico in a carbureted version. Design flaws (relative to high performance): >From a performance point of view, the 1.6 & 1.8 heads leave much to be desired. They have a U shaped flow configuration, as opposed to a cross flow configuration. The intake and exhaust ports are perpendicular to the combustion chamber, and flow is inhibited by the sharp corners in the aluminum casting. The valve guide boss is a further flow inhibiter. The boss measures approximately 12mm long by 15mm diameter. VW 16v head: The VW 16v head is a performance nightmare. I think VW introduced the head merely to say they had one, as they obviously didn't care about performance when they designed it. VW began design of the 16v head about 1980. It went through various metamorphasizing phases before it was released. On one version, the exhaust cam was gear driven, but VW ultimately chose chain drive because it was the quietest way to drive the exhaust cam. (The quietest way they would consider; they obviously chose not to allow the exhaust cam to be belt driven with the same timing belt as the intake cam...which would have been the quietest by far.) According to my sources, VW was planning to introduce the head as early as 1984-85, and some 80000 units were produced. Then it was discovered that some engineer forgot to design water in the casting around a pair of exhaust valves. Overheat = cracked head ==> junk 80000 castings <==> put the program back a couple of years. Before the head came out, rumors were circulating as to its design characteristics. All of us in the high performance business cringed at what we heard. We heard that VW had designed the head with the exhaust valves top dead center over the combustion chamber; the intake valves cocked over about 20 degrees. We said if that was true, the head was junk. We couldn't believe VW (read that ANYBODY) would introduce a high performance head with such awful flow characteristics. When I saw my first 16v head (off the motor), all my nightmares turned into reality. Actually, it was worse than I thought. The exhaust valves were top dead center, but the exhaust ports exceeded a 90 degree bend to allow the gas to exit. This head was obviously not designed for performance. The valves spacing is too close together, thus putting in bigger valves would be near impossible. The only possibility of obtaining higher performance was porting and polishing. ----------------------------------------------------------------------- Aftermarket 16v heads: There are three aftermarket heads that I know of. Of which, only two can I review - as the third I don't even know the manufacturers name. Oettinger: Oettinger has long been considered the venerable 16v head manufacturer for water cooled VW motors. They have been making the head about 8 years. For the most part, it is a good design. But like the VW head, it wasn't designed for racing, just a little high performance. The head is a two piece head, with the cam housing as one piece, and the combustion chamber/valve housing as another piece. The intake and exhaust valves meet the combustion chamber at approximately 30 degrees. The ports for the valves meet approximately 75 degrees with the combustion chamber. This isn't so good for racing, but is adequate for street use, and immeasurably better than VW's own head. The exhaust cam is driven via gear from the intake cam, and it is a cross flow head. Oettinger went through some pain and expense to make the head California street legal. The kit they offered was based on a 1588cc motor. It had 10:1 compression ratio, and all the parts necessary to put the motor together. It cost $5500.00 and developed 136hp. (Remember $5500 is NOT a complete motor, just the cost of the kit.) Drake: It isn't well known that Drake Engineering also makes a 16v head for the VW. Drake never marketed the head for street use, and instead chose to develop it for racing only. Since Drake is a racing company with a long history of development, they weren't afraid to engineer a head that had no performance compromises. The head is also a two piece head. But unlike the Oettinger, the Drake head afforded all the creature comforts that make working on a motor real nice. For example, head bolts: The openings in the cam housing were designed to be big enough for the head bolt tool (10mm 12point socket) to fit in, but smaller than the heads of the head bolts. What this means is that (picture the head attached to the block) when the head bolts are loosened, the head lifts itself away from the block. No prying or hitting with a rubber mallet. Another byproduct, is that the head bolts made a convenient stand for the head; thus the valves could NEVER get bent by setting the head down. Intake and exhaust valve ports are 21 degrees with respect to the combustion chamber, and the valves themselves are approximately half that. This is the ultimate performance design for ports. Practically a straight shot into the combustion chamber. Because of the port design, the head is slightly wider than Oettinger or VW, but is thin enough to work on a street motor. Austrian 16v: There is a company in Austria that makes a VW 16v head also...but I know nothing about it. 16v performance review: The VW head is junk for racing or high performance. I have little regard for this head at all. For 8v owners, you are best to build the motor you have now, as you can get MORE performance out of it, than VW's 16v. For comparison, I will give specs for both 8 and 16v performance heads: Motor Cam HP Induction 8v 1781cc .426 130 @ 6500 Fuel injection 8v 1805cc .496 178 @ 8000 1 Weber 45 DCOE 8v 1977cc .475 185 @ 7500 2 Mikuni 44pph 8v 1588cc .500 210 @ 9000 Hilborne F/i (supervee motor) 8v 1588cc .410 145 @ ? 8# boost Callaway turbo 8v 1588cc .410 165 @ ? 11# boost Callaway turbo 8v 1781cc .423 175 @ ? 11# boost Callaway turbo 16v 1588cc ? 136 @ 6500 2 Mikuni 44pph (Oettinger 16v) 16v 1588cc ? 178 @ 7000 2 Mikuni 44pph (Drake 16v) 16v 1781cc ? 123 @ ? KE Jetronic (VW 16v stock) 16v 1781cc ? 140 @ ? KE Jetronic (High performance version) Racing 16v's: 2021cc 210 DIN VW 16v 2021cc 225 DIN Oettinger 16v 1935cc 295 SAE Drake 16v Who's head performs best? The results are obvious. I will admit that my specs for racing 16v's for Oettinger and VW were taken from printed literature. That's not to say that more power isn't possible (but I doubt it!). Until next time. -- "Worship the Lord your God, and serve him only." Mat. 4:10 Robert Collins of Sykes Systems, Inc. (714) 995-7344 (home) Specializing in APL. (714) 229-0284 (work) (818) 704-9894 ----------------------------------------------------------------------------