Thanks for this great video, especially the uncut cylinder head heights. These dimensions seem difficult to find in the Porsche literature. The 87.1 mm dimension from the boss surface to the cam housing surface appears in the original 65-71 factory shop manual, p. E 78, and in the spec booklets, e.g. p. 53 in the 84-87 Carrera spec book. But for the newer heads, the distance from the cylinder mating surface to the cam housing surface is hard to find. The 964 factory shop manual from 1992 gives this as 84.48 mm on p. 15-10e (Refacing the cylinder head), but here it is shown in the diagram with the label "New dimension". Can we be sure that the 84.48 mm dimension also applies to the pre-964 heads, that is up through the 1989 Carrera? Does this value appear somewhere in the earlier (pre-964) shop manuals? Thanks again for providing these important details.
Mark, So yes I agree finding the cylinder head thickness information from porsche is tough and we have to make some assumptions based on the information available. What I have found is the cylinder head thickness from the 911SC models on start out life at 84.5 mm (nominal), and I will base my cuts based on the deepest damage. For shim pack thickness I will look at a case thickness, chamber volume, and desired compression ratio. I think when the information is limited use your best judgement. Measure what you have first before cutting. If a number does seem right stop and work out the issue first before machining any material off. Kurt
Another really informative video. I'm no expert in turning, but how do you make sure your cam box mating surface is square in the plane of rotation? Does this need to be measured on the back plate and adjusted in the chuck before you tighten the jaws, or do you insert shims between the surface and your jig, or do you just trust in everything sitting square in your chuck?
I never trust anything to be square and true unless I have verified this to be true. We do not show set up in our videos but it is a normal part of any machine operation. The mounting plate is mounted using a 4-jaw chuck that allows me to adjust for concentricity to the cylinder head gasket area. Then I use a dial gauge to check and adjust runout on the face of the jig to be 0.01mm or less. This ensures that the cambox sealing surface and the head gasket surfaces are parallel to each other. Kurt
@@klassikats cool thanks, so to confirm it's measure with the dial gauge then adjust runout by tapping it in the chuck and tighten the chuck once runout is acceptable.
When measuring the later cylinder head, why not make a ring that will stand he cylinder up off the surface plate? If you do that, you would just 0 the height gauge on the top of the ring and measure in exactly the same way you did the early heads.
Another great video in the series. Keep up the good work.
Thanks, will do!
Kurt
Thanks for this great video, especially the uncut cylinder head heights. These dimensions seem difficult to find in the Porsche literature. The 87.1 mm dimension from the boss surface to the cam housing surface appears in the original 65-71 factory shop manual, p. E 78, and in the spec booklets, e.g. p. 53 in the 84-87 Carrera spec book. But for the newer heads, the distance from the cylinder mating surface to the cam housing surface is hard to find. The 964 factory shop manual from 1992 gives this as 84.48 mm on p. 15-10e (Refacing the cylinder head), but here it is shown in the diagram with the label "New dimension". Can we be sure that the 84.48 mm dimension also applies to the pre-964 heads, that is up through the 1989 Carrera? Does this value appear somewhere in the earlier (pre-964) shop manuals? Thanks again for providing these important details.
Mark,
So yes I agree finding the cylinder head thickness information from porsche is tough and we have to make some assumptions based on the information available. What I have found is the cylinder head thickness from the 911SC models on start out life at 84.5 mm (nominal), and I will base my cuts based on the deepest damage. For shim pack thickness I will look at a case thickness, chamber volume, and desired compression ratio. I think when the information is limited use your best judgement. Measure what you have first before cutting. If a number does seem right stop and work out the issue first before machining any material off.
Kurt
Another really informative video. I'm no expert in turning, but how do you make sure your cam box mating surface is square in the plane of rotation? Does this need to be measured on the back plate and adjusted in the chuck before you tighten the jaws, or do you insert shims between the surface and your jig, or do you just trust in everything sitting square in your chuck?
I never trust anything to be square and true unless I have verified this to be true. We do not show set up in our videos but it is a normal part of any machine operation. The mounting plate is mounted using a 4-jaw chuck that allows me to adjust for concentricity to the cylinder head gasket area. Then I use a dial gauge to check and adjust runout on the face of the jig to be 0.01mm or less. This ensures that the cambox sealing surface and the head gasket surfaces are parallel to each other.
Kurt
@@klassikats cool thanks, so to confirm it's measure with the dial gauge then adjust runout by tapping it in the chuck and tighten the chuck once runout is acceptable.
Yes
Kurt
A lot of machining on these engines, I can see why they are so expensive to overhaul.
Yes, there can be a lot of machine work. It just depends on how many miles the engine has seen.
Kurt
When measuring the later cylinder head, why not make a ring that will stand he cylinder up off the surface plate? If you do that, you would just 0 the height gauge on the top of the ring and measure in exactly the same way you did the early heads.
Jason, sure that would also work. Thanks for the comment and thanks for watching.
Kurt