Getting a 2.0 8v, Tuning help please!!

[maardak at yahoo.ca (Mark)]

 --- Adam J Garside <adam.garside@uk.ibm.com> wrote: > Hi Everyone,
> 
> I have now secured a 2.0 8v (from an Audi) to go into my Rocco.
> I'm planning on stripping it down on the bench then rebuilding it, anyone
> got any recomendations of tuning to be done during the rebuild?
> So far I have plans to send the head off to be polished and flowed (any
> tips for this?) I'm also going to get a new Cam and fit an Audi Throttle
> body to a modded inlet manifold. I was also thinking of sending the
> flywheel off to be lightened
> 
> What are my other options to squeeze more power from it? What are my
> options for the bottom end? lightening and balenceing?

Well the old adage "Speed costs money, how fast do you want to go" is definately true...

For the head, make sure you send it to someone who knows how to get power out of a VW
head...  Anyone can hog out a head and call it polished.  Have the shop flow bench the
head and give you a printout to make sure they did a good job of balancing the flow (you
don't want a cylinder running lean because it flows more than the next one)...

The trick here is not so much removing alot of material, but to smooth the passages. 
Send them your intake manifold so they can properly match the ports.  The exhaust ports
should be left alone (other than being smoothed and crossbuffed).  You want the exhaust
port on the head to be a bit smaller than the port in the manifold to create a "reversion
dam", so don't get them hogged out...

Get a multi-angle valve job, and get them to open up the throats with a 90 deg cutter. 
The throat should no bigger than 90% of the diameter of the valve for a proper venturi
effect - another area where simply hogging it out as big as possible will hurt torque... 
Make sure the shop has a modern seat cutting machine, so each throat can be machined
EXACTLY the same as the others, both in width and height.

If you're looking for maximum flow, have the seats made .040" instead of the usual .060".
 You'll sacrifice a bit of longevity for performance here though...

After the seats are done, and the valves butt/chamfered/polished/ground, use a very fine
lapping compound and lap each valve in.  When you use a very fine compound it leaves a
very accurate "mark" where the valves contact the seat.  Backcut the valves within a c*nt
hair of this "mark".  Depending on the valves you use, backcut them on as many angles as
necessary to make a smooth profile.  Also polish the backside of the valves (especially
the intake) to make it smooth.

If you want to raise the compression, get them to shave about .040" off of the head. 
That'll raise the compression of a 10:1 engine to somewhere around 10.5 - 10.75:1. 
You'll have to run premium fuel, and at the very least graft in a knock sensor ignition. 
Also, this combo will now be an interference engine...

As for the bottom end, if funds permit, get the crank knife-edged.  This both lightens
the crank and allows it to spin through the oil with less parasitic drag.  Use good
quality bearings, and get everything balanced.  If you're assembling the engine yourself
after getting machine work done, don't assume everything is fine.  Plasti-gauge the
bearings to see if the tolerances are correct.  Make sure all the oil passages are clear.
 There's alot of shitty shops out there - a bit of time checking things out at this stage
will save alot of headaches later...

I highly recommend a lightened flywheel - just send out your pressure plate with it to
get balanced.  I just had mine done, and it was WAY out after lightening...  

I'm sure I'm leaving some stuff out, but this is what's coming off the top of my head...

HTH,

Mark.
80 S
81 S






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