spacers between intake manifolds and carbs

[Scutty]

I'm reassembling my 68 912 after an engine rebuild. I just discovered the 1/4" thick spacers between the intake manifolds and the original solex carbs are different materials. 2 are made from a bakalite-like dark orange lightweight insulating material, and 2 are made of stamped steel. Neither appear to be home-made so I am assuming both were factory made for something.
What is a 68 912 suposed to have? Wouldn't aluminum spacers be better due to a better heat transfer to the carbs? Don't I want to keep my carbs warm for good fuel atomization?

[craign]

Scutty,

My 69 has aluminum spacers with my webers, I would think aluminum or steel would be prefered. Wouldn't bake-light stuff tend to absorb oils and fluids over time?

Craig
www.bay912.org

[WFBowen]

Scutty: It's been my experience that the blocks are there to isolate the heat from the carbs. Most of the older Detroit iron have the bakelite blocks under the carbs. Here's an example (I definitely learned the hard way.) In the mid 70's I bought a 330 GT 2+2 Ferrari from England - RHD, rusty, real POS, but dirt cheap. I shoved a 340 hp 327 in it and had major fuel boiling problems. There wasn't much room between the hood & air cleaner, so a friend suggested adding the thin (1/8") fiber insulator gaskets under the carb until the problem went away. One gasket did nothing, two - nothing, but three & the problem went away forever! I think the carbs get warm enough from ambient engine compartment air, but then I don't live in PA in the winter!
Bill

[Scutty]

The bakelite spacers appear to be in like-new condition, still hard and dry.
I believe weber conversions come with aluminum adapters, can anyone tell me if this is true? I wonder what spacers your 69 had when it had solexes.
Those of you with solexes, or webers I guess, what spacers do you have, has anyone changed spacers?
I don't drive the porsche in the northern pa winter, but there are some october mornings where its 35deg on the way to work and 75 on the way home.
Any differences between the front engine/water cooled, and our rear engine/air cooled that would make us want a different spacer?

[ron69912t]

Scutty:
My 69 had Solex carbs and aluminum spacers. When I switched to Webers I used the recommended (by the Maestro) aluminum adaptor plates on top of the Solex intake manifolds. There were only thin gaskets used on both sides of the aluminum adapters. The adaplerts are needed due to the different bolt hole pattern on the Webers.

In either case I have never had a carb over-heat problem.

Good luck,
Ron D

[Jones Low]

Hi Scutty,

My 69 with Solexes came with the metal block spaces. They are quite heavy if they are aluminum. The two left and right spacers closest to the rear of the car had vacuum fittings. These were connected by rubber vaccum hoses to a t-fitting and a single rubber vaccum hose from the t-fitting went to the vacuum advanced unit on the distributor (type 061 ??). There were also vacuum fitting coming out of the base of the carbs that also had were connected by rubber vacuum hoses that led to a t-fitting and from the t-fitting a single vacuum hose to the idle compensator that sat on top of the fan housing just to the left of the oil filter canister. I believe most of this plumbing was needed for smog emission control. I believe you will find that pre 68 cars and 356s used the spacers without vacuum fitting.

Currently I am running a 050 distributor and in the process of switching to it, I replaced the metal spacers with the bakalite ones since I no longer needed the vacuum lines for the distributor. I tend to think the bakalite versions would help keep the carbs insulated from the heat of the manifolds. The vacuum fittings on the carbs have rubber caps on them now. The engine seems to be very happy with this setup.

Jones Low
69-912
00-Box

[Green 912]

Use the insulating spacers if you can. You can also get real nice 1/8 inch thick gaskets from PMO for the adaptor plates. Good practice to insulate the carbs from the head heat. 912s have short intakes compared to most cars and get from plenty to too much heat to the carbs. When you install the adaptors and or gaskets fit them first before you bolt things together. I have found many times the gaskets protrude into the intake airflow right where it will do the most harm to laminar flow.

[Jones Low]

Green is right about the 2 gaskets that sandwiches the block spacers. I've found some that when you install on the manifold riser the intake was partially blocked by the gasket. The gasket set was not die cut correctly and could have caused me problems that I would have noticed once the carb was bolted back on.

Jones Low
69-912
00-Box

[Jones Low]

I need to correct some mis-information. The set of vacuum lines coming from the carb base goes to the vacuum unit on the distributor. The vacuum lines from the riser plates goes to the idle compensator unit (sits on the top of the fan housing). Last time I mixed them up the engine running very poorly.

One of the reasons to switch to an 050. no vacuum hoses to mess with.

Jones Low
69-912
00-Box