'69 manifold gasket query ?

[Pettycoatloose]

Removed the webbers to rebuild and there was just one standard manifold gasket for each cylinder. Pet shows 3 gaskets for each cyl, one of which is an insulator which is quite thick. Problem is with the 3 in place as showing in PET there is not enough thread left for the nut. Maybe one or two turns. All the studs look original and are all the same size. Question is is the insulator gasket really necessary ?
Thanks for any suggestions

[haasad]

Its better to have one. Its intended to stop heat transfer to the carb from the head and reduce associated fue and fuelling issues. Usually the inlet studs are easy enough to remove. I would change the studs for longer new ones which are cheap as chips from beale supplies .

[mycar]

Whilst you're in there you might as well but you may find the phenolic spacers are only available from the States.

viewtopic.php?f=2&t=49311&p=416725&

[fetuhoe]

I have been wondering it is better to insulate the carburettor from the manifold or the manifold from the head?

The Delta T at the carb to manifold flange may be lower so it may be an easier job.

It also means that one spacer will cover all Weber and Zenith Carbs as they all have a nominal 40mm bore. Cylinder heads all have several different port sizes so it means several different spacers are needed.

[mycar]

Often, in a situations like this, the answer comes from asking the question 'How did Porsche do it ?'

How did Porsche do it ?

[fetuhoe]

Porsche clearly isolated the manifold but they also fitted a fuel reservoir into the Solex manifold and sat it directly onto the heads of a '65 car which wasn't their greatest move.

The majority of carbs that are insulated have spacers fitted between manifolds and carbs and not between heads and manifolds. Lots of Webers on Fords insulate the carb, lots of Holleys insulate the carb - the list is fairly long.

Manifolds are often water heated so it would seem warm manifolds aren't an issue.

If the only issue is percolation then isolating the carbs alone is probably the best place.

I would modify the question and say 'why did Porsche insulate the manifold and not the carb?'

The standard insulator with Part Number 901.108.131.00 is available though at about £3.50

[Pettycoatloose]

A lot of good points.When i dismantled the carbs for a service there was only 1 standard gasket between the head and manifold. Maybe the phenolic will fit between the carb and the manifold and the other 2 between the manifold and head. Will have to have a look in the morning and see if its possible.

[haasad]

Heineken ...Smeineken...head to manifold or manifold to carb either solution will work; either way you probably need longer studs.

[Lightweight_911]

I've always fitted the phenolic insulating spacers between the heads & the manifolds - you can buy a kit from Larry Turner at youroil.net which includes everything you need:

- 6 spacers (of the correct size for your intake ports)
- gaskets (12) to fit either sides of the spacers
- set (12) longer studs
- gaskets (6) to fit between the manifolds & carbs

[Pettycoatloose]

The question in the back of my mind now is " why " are all the studs too short if Mr Porsche had the correct setup day 1.Its highly unlikely that someone changed out all the studs for shorter ones. With the Phenolic and the other ones on each side there is barely one thread visible. Engine is correct 2 ltr ' 69 . Bit Bizarre.

[Lightweight_911]

What is the engine number ?

[Pettycoatloose]

Engine No is 6195798

[fetuhoe]

The 1969 engines were fitted with 2 different length studs on the intakes - 22mm for the S and E engines and 25mm for the T engine.

I would have thought that the extra stud length was to deal with the spacer, which was around 2mm thick, and the extra gasket.

[Pettycoatloose]

Very interesting and raises another question . I was told by the second owner that the engine had been rebuilt in the US and fitted with S cams etc. I have no proof of this without opening up the case but is saying that this 2 ltr T always felt quicker than it should have. That might account for the short studs and a single gasket.