Date: Mon, 24 Jul 2000 10:20:13 -0700
Reply-To: Daniel Schmitz <djs@gene.com>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Daniel Schmitz <djs@gene.com>
Organization: Genentech, Inc.
Subject: Re: The writings of Gene Berg and ETC.
Content-Type: text/plain; charset=us-ascii
Just one correction...
Mark Stephens High Performance has recently gone out of business. I found this out from the Porsche listserve to which I subscribe, where aircooled engine mods like Robert describes are very popular.
Dan
Robert Lilley wrote:
> Mark
> <<The obvious ones are the balanced crank and ratio
> rockers, but what else?
>
> I would also add counterweights to your crank. should cost @$150, in addition to having ALL the rotating parts balanced as a UNIT not seperatly.
> Have the rods lightened and balanced
> Lighten the flywheel about @two lbs on the outside edge.
>
> (Think two lbs spinning 4000 rpms x length of drive x math formula for the weight difference from the center line of the crank= the amount of weight the engine has to move= more power, acceleration and gas mileage.
>
> The ratio rockers for the T4 engine are expensive unlike the T1 style because they are different styles.
>
> I would add the 96mm pistons and cylinders JUST KEEP the compression ratio to 7:1 to 7.2:1 any higher, you can make more power but the engine life is cut short.
>
> If you keep the stock FI setup, increase the cam just a little, one small step up, agin too much and the FI does not work correctly with the total reduced vacuum larger valve overlap creates. The low end power is also gone.
>
> If you are going to swap FI systems with aftermarket, then you can go with a bigger increase.
>
> CB Performance sells a torque special cam for the T4 engine. Increases power and better low end responce.
>
> The later T4 engine rocker arms use a 10 mm adjusting screw. Find a set of rockers from a 1.7 or 1.8 Bus or Porsche T4 engines with the 8 mm screw and tap them to the 9 mm fine pitch thread to use the 911 style swivel head adjusting screws. They reduce side loading of the valves to increase guide life.
>
> I would have Mark Stephens rebuild you a set of heads. Install the largest stock valve during the reuild: 41 intake 33 exhaust. The square port heads have smaller valves. With the larger cam it will provide a small power boost.
>
> **Also IF you go to the larger pistons, the valve increase will keep the engine balanced. Bigger pistons will need more air volume to run efficently. Bigger pistons with smaller valves will not fill the cylinder, produce less power and might cause mileage to decrease.
>
> ** If you increase valves but not cam or pistons again the engine does not make the power it could because it is not balanced.
>
> I would also have the heads Zero decked and the valves unshrouded. This move more of the combustion heat to the piston side and out of the head. Therefore the heads run cooler, mine are around 225 winter and 250 to 275 summer.
>
> I would clean up the ports to remove casting mismatches only. Do not polish and the rough surfaces are needed for low end turbulance to keep more of the fuel/air mixed as it flows into the head. Less gas will fall out and be wasted. Polish them and low end can suffer along with increased emmissions, bad for smog tests.
>
> I would make sure the air runners match the intake ports. They could be slightly off-set causing a disturbance in the flow, mild effect on the low end but bigger as the airflow speed increases.
>
> Do the same for the entire exhaust system match the ports.
>
> Use the Bosch quad tip plug. The main benifit for the T4 engine is in that flame kernal is changed from going sideways toward the top of the piston to downward toward the bottom of the piston. More of the volume of fuel in the chamber is burned, the piston has the force of the explosion spread out over more evenly over the face of the piston, rather than the the top and spreading to the bottom. Pistons can last longer.
> The plug also has four grounding points as opposed to one or three. For my engine another benifit is that it runs cooler than the tri-electrode plug that I tried(my head temps went to over 400 with the tri).
>
> Convert to electronic ignition, if not already.
> There are drop in points converters.
> I would perfer the computer controlled distributerless system. It eliminates any spark waste by eliminating the cap and rotor and is direct fire.
> You could use it with your stock distributer(the system actually sits in the top of the distributer to replace the points and uses the rotating shaft as the trigger).
>
> I would use a free'er flowing muffler.
>
> I would use a K&N Drop in filter for the stock air box.
>
> The oil pump is one of the best pump made not much to do here but match the inlet and out let to the case. Generally the oil pump holes are smaller than the case and can be matched ported. The oil volume is increased, pressure is still controlled by the relief spring.
> I would not get a the cast iron Melling oil pump because it will leak at the inlet/outlet when it gets hot. The aluminum pump matches the heat growth.
>
> What I propose is a lot of small improvments over one or two major changes, that way the engine runs balanced.
>
> ***When changing parts THINK balance, balance, balance, a change one area usually means a change some where else so the engine makes the most power and is most efficient.
>
> Building the engine to last will take some money, but for me, I would rather spend the money to build an NEW*
> engine that can turn 5000 rpms all day long, then to put in a used engine and hope that it lasts.
>
> CLEAN CLEAN CLEAN ALL parts used in rebuild.
>
> A book "How to Rebuild your VW engine" by Tom Fisher is very helpful in along with Bently.
>
> Robert
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