I've been getting the itch to build a VW engine again and I've been doing some math. I've always loved it when someone has been negative and told me I can't do something and I expect to hear the same thing from someone somewhere. LOL! Like the time someone told me that you can't mount a bus transmission in a bug with the rubber mounts. I did after flipping the mounts around and some other horsing around.
Anyway, I found a video online where a guy was able to pull out the venturi from a 34-pict-3 carburetor. This surprised me because I didn't know you could do that. You have to disassemble the throttle butterfly to get it out but it does come out and opens the carburetor venturi up to 34mm. He is running it on a 1.9L bug engine and although it is turbo'd, he did rejet it and says guys are floored when they find out he was running a single barrel solex and beat them! I've always liked the simplicity of a single barrel carburetor. Although it doesn't give you the best mileage, it is simple and it does work. The original VW engineers knew what kind of power they needed to make and they had a certain space to fill in the cars and so they made the requirements they needed without much flare. A stock 1600dp is a 60 hp engine. If you put on dual carbs, k&n filter, SVDA or some other dizzy, couterbalanced crank and balance and blueprint the engine, you end up with something that really can put out some serious horsepower. You can even turbo it or put a supercharger on it and get more. But is it that practical? Are you going to be able to drive it without fiddling with it all the time? Point being, if you want power, what's it worth to you? I hate the fact that dual carbs don't have chokes and the single barrel duals with chokes don't idle correctly. As soon as you deviate from the original package, then troubles start. I propose to duplicate the stock form factor by scaling everything up to match. I think it might work. LOL! I just can't seem to be happy with just a stock engine. I like to see if I can do something to up the power. I don't need a screamer engine and I certainly don't need a 45 degree climb into infinity on the power curve chart. So let's look at some numbers: A stock 1600cc engine in a type 1 is 60hp on a good day (actually it's a true 1584cc engine which comes from an 85.5m piston and a 69mm stroke.) The carburetor on a 34-pict-3 has a 28mm venturi. It's a nice little torquey package and it does what it does well and with long life. There is always some element of detuning of an engine which helps longevity. The extremely example on the opposite end of the spectrum is top fuel drag racers who basically rebuild and inspect after every race. We don't need that much power and that much hassle here. Now a nice engine size I've always likes and was one of the biggest sizes you could build on Gene Berg principles was a 2180cc engine (true size 2180.4cc.) That is using thickwall 92mm P/C with an 82mm stroke. By scaling up the measurements, you should be able to make 81.75 horsepower from this engine and have a nice torque increase as well. Sure could slap dual carbs on get over 120hp and make it scream, but we want longevity and simple tunability. This would be using a single barrel 34-pict-3 with the venturi pulled out and rejetted. Also, it would require scaling up the intake manifold appropriately as well as fitting on a set of heads with larger valves and end castings to make sure you are scaling up everything in proportion. I don't know what the torque increase would be, but it would be more, modest, and long-lasting. The only problem with the 2180cc engine, is that you need about a 38mm venturi in order to feed it in proportion so the original engine form factor. So with the largest size being achieved with the 34-pict-3 being 34mm, we gotta find out what the largest size we can achieve is. That leads us to the the closest engine size that matches 1942.8cc Using a displacement chart, the closest match would be a 1950cc engine which is using 87mm P/C with a 82mm crankshaft. The problem now is that the "B" series P/C don't exist in 87mm due to how thin the tops and bottoms of the cylinders are. So the next closest size that isn't oversize is 1904cc which would be using the 90.5 P/C in the "B" series and a 74mm stroker crankshaft. I figure I can do the math on the jetting with ratios and find the closest match that would work. The math shows that you should get 72.85 horsepower by adhering to the stock form factor ratio where 1584cc = 60hp. This is interesting because the stock 2L Type 4 engine was rated at 70hp so that means the 1600cc Type 1 engine has a slightly larger displacement to horsepower ratio than the T4 engine although the difference is so close that it's neglible. The entire idea is to copy what old US engineers accomplished in the past. They took an inline 6 cylinder engine, threw a single barrel carburetor on it and a head with small valves. The port velocities made the engine a torque-monger stump puller to get up to speed. Once you achieved your speed, the port velocities were maxed out, and the power tapered off pretty quick but it would maintain the designed top speed, with load, all day long. That's *exactly* what a person needs to accomplish when moving a VW bus down the road. Now in creating a larger intake with built-in heat riser, you would soon find your clearance between the alternator stand and fan shroud would be causing an issue. The answer is the Mexican style alternator stand. It's superior in many ways and only costs about $35 from CB Performance. It's deeply clearanced on the back side to clear the fuel injection intake runners, has a built-in oil baffle so you don't have to use the metal one that comes in the gasket rebuild kits, and an o-ring milled in the base so as soon as you tighten it down, it seals itself with no gasket and no sealant required. The only thing left to compute would be how to enlarge the dual port manifolds and to find a set of heads that have been opened up proportinately in the intakes and valve sizes. That could very well prove to be the undoing of a project like this because the dual port end castings are a work of art. And if you can't get them larger, you introduced a restriction that pretty much negates everything else you've done. In my case, the idea is simply to build an engine that produces the torque needed to get a splitty bus up to speed in a real simple package. Yes, I might not be making 120hp but the original engineers had to set limits and compromise on what kind of power they could make and have their engines last a long time. If you built a stroker and only asked it produce 12 more horsepower and a little bit more torque, you might even have to question if it's worth it in the first place for such a modest gain and worse fuel economy? That's up the individual to decide. After doing this math, you start to see how even a stock engine is very modest in it's horsepower production as compared to what other people are getting out of their engines. In the end, I'm somewhat forced to admit that the best bang for the buck, is a finely tuned, balanced and blue-printed, stock engine for use in a split-window bus. You get decent fuel economy, the gearing matches the engine, the engine cools well, and you have decent torque from the gearing to get you around. Best of all, you just have a lot of fun driving it around and going places. NQ _______________________________________________ vintagvw site list [email protected] http://lists.sjsu.edu/mailman/listinfo/vintagvw
