Yesterday after I returned the borrowed laptop I came home and bolted a clean but otherwise untouched AAH head to a clean but otherwise untouched intake manifold. I installed an AAH cam in the stock head/IM combination and rotated it to max lift on the intake valve using a urethane rod ground to size instead of a lifter as I wouldn't have oil pressure to pump the lifter up.

I then bolted a stock throttle body clamped to WOT on the stock IM with a stock plenum, accordian hose and MAF housing.

Then I built an identical assembly with the ported/polished head, the remaining AAH cam, another urethane rod, ported/polished IM, RSXTB throttle body, S3 hose kit/recovery sleeve and S3 MAF.

Valves were set at 10mm lift in both heads. And it's important to note that both valves were stock 8mm stem diameter. In other words I can reasonably expect an under-cut valve to flow a minimum of 12-15% better. All testing was done on intake runner #1 as this is too time consuming to set-up/repeat for all 6 cylinders and cylinder #1 "should" be the furthest cylinder from the MAF inlet and the one with the most indirect airflow path (most extreme turns to get to). Since heads are identical it's easy to do this with both cylinder heads #1 by rotating one head 180 degrees to the way its mounted on the engine, thereby creating two separate but identical cylinder #1 assembley configurations.

Flow rates at 48" H2O were as follows:

Stock assembly: 52SCFM
Ported polished assembly: 96.4SCFM
Projected flow with modified valves: 108SCFM

With our engines you can "guesstimate" that we can produce 1HP per 1.8SCFM of air or 28.8HP per cylinder multiplied by 6= 173.3HP. Very close to published numbers for our car.

Using the same formula with the ported/polished/S3 setup we get a potential of closer to 53.75HP per cylinder 322.5HP. And closer to 360HP with under-cut valves.

It's important to consider none of this takes into account the exhaust side of things which I'll go back and flow today/tonight for comparison. I anticipate that will remove or diminish some of the above potentials as the exhaust simply cannot compete with the intake side of things as it relates to flow. And of course all of the above interpolations are done using stock valve head diameters. I would expect even more gains from larger valves. But nothing has swayed me from my intent of going with 1mm larger intake AND exhaust valves rather than the way TDL approached it with just a 2mm larger intake valve. I'm also a little suspect of the larger intake valve in that it looks like the stock seat could support a 2mm larger valve. But it wouldn't realize as much potential benefit as is possible with a larger valve seat. While the valve seat will definately accept & seal a 2mm larger valve the seat I.D. would remain the same size.

Stock valves on these cars are 40mm/33mm for intake/exhaust. But the valve seat I.D.'s are only 34.5mm/29mm intake/exhaust. So while there would be some gain associated with larger valves on stock seats those gains would be significantly less than larger valves on larger seats.

Does anyone remember or know the price TDL was getting for their big valve heads or just their ported/polished heads with stock valves? That would go a long way towards knowing if the intake valve seat size was increased when the larger valves were installed. Would also shed some light on if new guides were installed at the same.