Part Numbers printed in the rocker side of the heads.sraey8 wrote:what do i look for in a head to distinguish the difference between 1.7, 1.8, and 2.0? How do i look at a head and know what it came off of when the seller doesn't know?
WANTED: 412 2 LITER PORSCHE HEADS
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tuna
- Posts: 2531
- Joined: Fri Apr 14, 2000 12:01 am
Check out this web page in identifying the different cylinder heads. You can also use this other web page to find out the part numbers, valve sizes, etc.
Tuna
Tuna
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I was searching for it when you posted it, THANKS TUNA!-
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raygreenwood
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- Joined: Wed Jan 22, 2003 12:01 am
Don't mess with the intake port openings. Just polish them and match port them to the FI runners (if you are using the FI). If you go up to a 1.8...then try to get a hold of some of the larger 3 bolt pattern 2.0 914 FI runners and use them with the 1.7/1.8 plenum...and a 2.0 TB from a bus. Drill the extra two holes in the flanges to use the 2.0 runners wit the 1.7/1.8 intake olt pattern. The 2.0 runners are slightly larger in diameter. The 2.0 bus TB is the same size as the 914 2.0....but is configured properly to fit on the 1.7/1.8 plenum. Buy a tail-pipe expander for about $20 and carefully expand the TB opening in the sheet metal 1.7 plenum.
Port the exhaust side of the head only....and only on the outer radius...and slightly from side to side. Have new seats put in. Use 42 x36 or 44 x 36 valves. Carfully look at the 1.7 combustion chamber. See those flat ledges? DO NOT REmove them. See that dimple on the large flat edge...keep that if possible. But...since you are flycutting these heads...and the ledges will now expand outward farther, have the head guy.....cut the ledges outward...while keeping the exact original shape, and have them unshroud the valves. Why keep the dimple? Well...first, calculate what combustion chamber volume you will need to get the compression you want. During these plans.....think about having whatever pistons you want...either trimmed in a lathe around the edges of the piston (if possible on your pistons)...to create a dome of about .079" high...to match up with that dimple. This in keeping with a deck of no greater than .045 and no less than .035. Then, remove metal while unshrouding and re-shaping...to get the combustion chamber size you need to get your compression.
I would suggest calculating all of this first, mapping it out...then have some Kieth black pistons made...with the domes on them, to give you the deck height and pin height you need, with maybe only a single barrel shim needed to correct with. Use o head gasket. I would suggest a compression ratio of about 8.5:1 with this deck height and using domed pistons. The shape of the chamber on the 1.7 heads was directly made to run high compression and work with the domed piston. It ran very well.
Ray
Port the exhaust side of the head only....and only on the outer radius...and slightly from side to side. Have new seats put in. Use 42 x36 or 44 x 36 valves. Carfully look at the 1.7 combustion chamber. See those flat ledges? DO NOT REmove them. See that dimple on the large flat edge...keep that if possible. But...since you are flycutting these heads...and the ledges will now expand outward farther, have the head guy.....cut the ledges outward...while keeping the exact original shape, and have them unshroud the valves. Why keep the dimple? Well...first, calculate what combustion chamber volume you will need to get the compression you want. During these plans.....think about having whatever pistons you want...either trimmed in a lathe around the edges of the piston (if possible on your pistons)...to create a dome of about .079" high...to match up with that dimple. This in keeping with a deck of no greater than .045 and no less than .035. Then, remove metal while unshrouding and re-shaping...to get the combustion chamber size you need to get your compression.
I would suggest calculating all of this first, mapping it out...then have some Kieth black pistons made...with the domes on them, to give you the deck height and pin height you need, with maybe only a single barrel shim needed to correct with. Use o head gasket. I would suggest a compression ratio of about 8.5:1 with this deck height and using domed pistons. The shape of the chamber on the 1.7 heads was directly made to run high compression and work with the domed piston. It ran very well.
Ray