Phenolic spacers still necessary

[Harpo]

Good afternoon everyone,

We have always used phenolic spacers under our carbs to prevent heat soak. To the best of my knowledge they are not used in the factory EFI. Assuming that is true do I need to use them under my ITB's?

Thanks

David

[Harpo]

If I don't need the phenolic spacers I can use the existing studs.

[winders]

My At Power ITBs on my 3.6L come with thermal insulation gaskets.

The EFI that came on my 3.6 from the Porsche Factory used plastic adapters bolted to the heads.

I would think that you would want to use some kind of thermal insulation gaskets.

[Steam Driver]

I think the purpose of the phenolic spacers used with carbs was to prevent heat from the heads heating the fuel in the float bowls causing it to percolate and upset the mixture. This was primarily an idle thing and why carbed cars would run weird after a hot engine was restarted after a pause. I suppose it could also happen sitting in traffic.

Since injected engines don’t have float bowls and there is essentially a constant flow of fuel through them I don’t see a reason for using the insulating spacers myself. I’m sure other opinions may vary.

I remember adding these to my 914-6 when they became recommended. What I don’t remember is that they made a whole lot of difference!

[winders]

Fuel rails can get hot too......cool fuel is better than hot fuel.

[trond]

should not be required with EFI. Fuel rails are far away and fuel is circulated. Injectors themselves don't require the thermal spacers. Thermal spacers are required with carburettors. Also not easy at all to get thermal spacers I have noticed when I tried to find for my ITBs. Could not find anyone to sell them to me because of the CIS injector notch in the inlet...

[Henry Schmidt]

Phenolic spacers may be as much about vibration reduction as heat transfer.

[Mark Henry]

Originally Posted by trond

should not be required with EFI. Fuel rails are far away and fuel is circulated. Injectors themselves don't require the thermal spacers. Thermal spacers are required with carburettors. Also not easy at all to get thermal spacers I have noticed when I tried to find for my ITBs. Could not find anyone to sell them to me because of the CIS injector notch in the inlet...

Only PMO manifolds will except the phenolic spacer because they have extra meat at the CIS notch area.
In the below pic was my solution, I used a spacer made of 3/16" aluminum plate to back up the notch.
Note that the two spacers are the wrong way around in the pic.



This is why you have to do this with stock carb manifolds. Without backing the CIS notch up the phenlic spacer will deform and cause a leak in this area.

[r lane]

3.2 cars have the plastic spacers. If not to reduce heat transfer, what is their purpose? Bob

[Mark Henry]

A bunch of later P-cars had part or all plastic intakes.

[otto_kretschmer]

Both my BMW motorcycles have a nylon or phenolic sleeve between the heads and the carbs. Their purpose it to keep the gas in the float bowls from boiling. Some of these bikes can get toasty down there. A R100RT running two up at 80 mph may need both petcocks open and that waste heat has to go somewhere.

I would use the insulators.

[otto_kretschmer]

I had a 914 with the 1.7l D-jetronic and it would vapor lock in the summer. I fixed it by moving the fuel pump into the trunk.

If you have EFI you probably don't need the spacers but it can't hurt.

[Speedy Squirrel]

They are to reduce fuel injector temps, which are highest after an engine shutdown. The objective is to reduce injector deposits.