What's your tune-up routine? Plus bonus ?s

[jdbubb at verizon.net (Dan Bubb)]

From: "Nate Lowe" <nlowe79@gmail.com>
Sent: Thursday, July 20, 2006 12:46 PM
Subject: Re: What's your tune-up routine? Plus bonus ?s


> Brakes: what size rotors came on the 16vs originally? I've got a swap to the
> 4-wheel discs but there's three rotor sizes listed on Potterman's site: 10.1,
> 9.4, and 8.9. I thought it was 10.1 front and 8.9 rear, maybe the 9.4 is
> from the 8v front? I'll flush the fluid here too if I can find the tools to
> do it.

16V front rotors are vented 10.1" diameter and 20mm/.79" thick.
16V rear rotors are solid, 8.9" diameter and 10mm/.40" thick
Your car probably came with 9.4" diameter solid rotors 12mm/.47" thick but may have been upgraded to the later vented 9.4 which is 20mm thick.

> 
> And since it's comes up so much in the thread, how can you tell if you have a
> solid lifter or hydraulic head and what is the difference?

Easiest way to tell is to remove the cam cover. The solid lifter head has 5 cam bearings. The hydraulic head does not have a bearing between cylinders 3 & 4.
I'm not sure what you're asking about the difference. Performance or the hardware.
As far as performance there are a variety of cams for both heads that progress from stock to race both getting up to 288 degree duration. There is an additional cam for the solid head that has 306 duration. So, basically you can get the same performance from either head until you get to the balls-to-the-wall level. ;^)
Although the two setups visually appear the same the hydraulic head has a hydraulic cylinder, probably no more than 4mm thick, between the cam and the tip of the valve. Oil pressure expands the cylinder to take up the clearance and a check valve prevents the oil from escaping when the cam starts to open the valve. The reason they fail generally is that crap gets in the check valve and keeps it from sealing.
The actual cam profile is different also because the solid lifter cam needs to have a very gradual ramp to take up the clearance so you can't just swap a hydraulic cam into a solid head or vice-versa (not to mention the cam base circle is 1.5" on the solid and 1.34 or something like that on the hydraulic).
TMI I'm sure, but hey, you're a mechanical engineer and if you didn't know, I thought you might like to know.
Dan