History of the ported VW head? Styles that have come and went....
Bryan67:
Years ago I bought a $100 set of IDA`s at work too. But my boss got pissed and made me sell them to him. Only because I was on his time. He never used them. After looking at the old show pictures I can see that I need to get mine out. I was at the same shows.
Fiatdude:
On my car right now -- -- a glutton for punishment
Bruce:
Quote from: Rome on October 22, 2016, 18:39:07 pm
The heads were flycut 1mm (0.040") and reshaped into a semi-hemi combustion chamber which provided 9:1 compression ratio.
Something doesn't add up here.
If you take a stock DP head for a 1600cc engine at 7.5:1 CR and ruin it with a hemi cut, you'll be down around 6:1 CR (or lower). A 1mm flycut isn't going to get you up to 9:1.
I wonder what they really did?
modnrod:
Quote from: Bruce on October 23, 2016, 20:35:12 pm
Quote from: Rome on October 22, 2016, 18:39:07 pm
The heads were flycut 1mm (0.040") and reshaped into a semi-hemi combustion chamber which provided 9:1 compression ratio.
Something doesn't add up here..........
Stock chamber 43cc, +9cc for the head step, +9cc for the piston height = 7.5:1 comp.
Stock chamber, flycut away the step and a further .040" = 36cc, add 8cc or so for a shallow hemi-cut as the pics seem to show then new chamber = 44cc.
Piston deck height at .040" gives 6cc, so new comp is now set at around 9:1.
I've just gone through all the figures on my 1584 I'm putting together, so it's still fresh in my mind.
andrewlandon67:
Man this is a good thread... definitely makes me feel spoiled for choice with any variation of CNC wedgeports available for pretty much whatever you've got to spend. Currently running a set of the EMPI GTV-2 Stage 1 Wedgeports (40x35.5, 170 CFM) with some light polishing in the ports, 44 HPMXs, 8.75:1 plus an FK-8 on a 1914. Hasn't been down the track since tuning, but we're hoping for 14s at 6000 feet. I'm having a hard time imagining the time and effort the old guys really put into their heads, back before computerized CNC mills and flow benches, but it really gives one an appreciation for their efforts.
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