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Join Date: Jul 2002
Location: Canberra Australia
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Gunter,

The heads were sent without valve springs. I have new EBS springs and will build the heads myself. The valves are new I would have expected them to be shipped back with the valves in the port that they were lapped into.

I do not know if the heads are the same height now as I mentioned I have not had time to look at anything else but the chamber diameter. I will measure he head height on the weekend.

I am still looking for information regarding the chamber diameter.........anyone out there with a head that they can measure?


Cheers

Mark...............
Old 11-28-2005, 02:20 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #41 (permalink)
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Help guys..........I need to know the diameter of the chamber on a 78 3.0 SC. Without this it is hard to know what to do with the rebuild

Cheers

Mark......
Old 11-29-2005, 05:54 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #42 (permalink)
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you are probably going to have to as Henry S. as that's not a reg problem around here???
Old 11-29-2005, 06:04 PM
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Ok.....I will email him directly.

Thanks......
Old 11-29-2005, 06:10 PM
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Quote:
Originally posted by Mark McClure
Help guys..........I need to know the diameter of the chamber on a 78 3.0 SC. Without this it is hard to know what to do with the rebuild

Cheers

Mark......
By chamber, do you mean the area where the heads meet the cylinders? There is a crush-seal there. Is that it?

The measurement should be the same for all SC-3.0 liter.
I just had the heads done from an '82.
Tell me exactly what you need.
__________________
1980 Carrerarized SC with SS 3.2, LSD & Extras. SOLD!
1995 seafoam-green 993 C2, LSD, Sport seats.
Abstract Darwin Ipso Facto: "Life is evolutionary random and has no meaning as evidenced by 7 Billion paranoid talking monkeys with super-inflated egos and matching vanity worshipping illusionary Gods and Saviors ".
Old 11-30-2005, 06:19 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #45 (permalink)
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Gunter,

I am trying to establish if I have an issue with the heads. My understanding is that the head, where it mates to the cylinder should have exactly the same diameter across the chamber as the cylinder.

The heads that I have have been reworked and are between 96 and 97 mm in diameter. This means that the chamber overlaps the cylinder possibly causing detonation issues and the potential to compromise the ce ring by the additional pressure placed in this area.

I would like so understand the issue so that it can be addressed before I finalise the rebulid. An example of chamber diameter will help and input for an Porsche rebuilder would be fantastic.

Thanks

Mark.......
Old 11-30-2005, 02:30 PM
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If they are '78 SC-heads, they have a groove machined into the top of the cylinder to receive the Alu crush seal. Do you have the grooves? Have these heads been machined in the spigot where they mate with the cylinders?
(3.2 Carrera engines don't have these grooves)
As I see it, the diameter is not so important.
What is important is the equal height of the cylinders, and the equal height of the heads so that when you mate the cam tower to the heads, no height difference in the cylinders/heads results in leaks.
Are your cylinders of the same tolerance group?
Have the heads been machined to the same, equal height?
The cylinders, and heads, from one bank (1,2,3 or 4,5,6) have to have the same height.
A competent machine shop will know these issues and can check the measurements for equal height.
When heads get a valve job, this spigot where the cylinders mate with the heads, get a slight, equal shave, just a few thou unless there is damage there and more has to be taken off (Equally on all 3 of one bank)
It sounds to me that you need a competent shop to check these issues.
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1980 Carrerarized SC with SS 3.2, LSD & Extras. SOLD!
1995 seafoam-green 993 C2, LSD, Sport seats.
Abstract Darwin Ipso Facto: "Life is evolutionary random and has no meaning as evidenced by 7 Billion paranoid talking monkeys with super-inflated egos and matching vanity worshipping illusionary Gods and Saviors ".
Old 11-30-2005, 03:38 PM
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Latest update........

Firstly Bob Whyms called to see how things are going. I have to point out that although an initial mistake was made, it happens to all of us, he did all he could to fix it and in a very timely fashion. Just following up is a rare occurance and shows good customer service. As far as dealing with machine shops and repairers Bob's attitude stands out above the rest in that he does not have the "it will be right mate" approach that we experience so often in Australia, of other shops. He also understand, as many other shops do not, that reviewing work is not "wingeing" but a matter of a customer getting the job they requested.

As for the heads ( not Bob's work )........a master Porsche mechanic reviewed them and recommended against using them. A second head specialist also reviewed them and said that any further attempt to fix up the work done would further damage the integrity of the head.

So since all the work has been a waste of money I will source replacement heads when the budget allows.

Cheers

Mark.......
Old 11-30-2005, 07:26 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #48 (permalink)
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