What Is This Part Of The Engine Called?

[Justin]

What is the part of the engine called Im pointing to in the picture below, Is it the pre-heating block? The carburretor is sat just above it.


It's here that my car is leaking petrol as you can clearly see in the picture, i have a replacement insulator block for the one below the black pipe but have been told I will also need another one to replace the one above the black pipe which is slightly thinner?

j

[mac]

Hi Justin,

It's called either an "insulating flange" or an "insulating gasket" and the alloy pre-heat flange has one on either side of it (they are as you say different).
Originally each of these flanges (a plastic spacer) had separate gaskets but by the end of 300 production the flanges were supplied with pre-fitted gaskets.
You will be very lucky if Volvo still supply any of them but I include the part numbers case you want to try.

Upper insulating flange (between the carb and the pre-heat block) is 3287828 (with fitted gaskets).
The pre-heat flange is 3267705.
The lower insulating flange (between the pre-heat block and the manifold) is 3267284 (with fitted gaskets)
The "lower" gaskets when available were 3267284.

The reason for leakage in the position you show is often caused by distortion of the base flange of the carb, and this should be checked for - and if found reduced as far a possible by careful attention to the base.

Below you will see the pre-heat flange with its upper insulating gasket (note the plastic peg which positions it on the carb base).



This picture shows early and late lower insulating flanges (with and without separate gaskets).



There is nothing to stop you reverting to the earlier top insulating gasket by removing the "old "fitted" gaskets and making new ones (use 0.4mm material).



Voila - a "new" upper insulating flange!



Hope the above helps,
Mac.

[Justin]

Thanks, am I correct in thinking there are in fact then three insulating flanges on the carburettor, two obviously on the alloy pre-heat flange but where does the third live?

Also you mentioned the reason for leakage in the position Im pointing to is often caused by distortion of the base flange of the carb, and that this should be checked for - and if found reduced as far a possible by careful attention to the base, how would I go about doing this?

I have managed to find a supplier online called Gower & Lee who have sent me the bottom insulating flange but it doesnt have two circles like the one you've pictured, this one is completely oval in the centre, I think it's about 5mm thick and it has the gaskets already fitted. My car is a Volvo 340DL-1988-1.4

J

[mac]

Hi again,

No there are only two, one above and one below the alloy pre-heat block. Each of these two will consist of a plastic spacer which will either have sealing gaskets stuck to it , or have separate gaskets (either side of it).

As for the base of the carb - it should be perfectly flat where it fits to the upper insulating flange but age and often overtightening of the securing nuts can distort the base causing it to "bow" causing poor sealing. You can check for distortion using a straight edge (a steel ruler is fine). If the bow is less than, say, 1.0mm - 1.5mm you can carefully "sand" down the base using "wet n' dry" on a flat surface. (something like 320 grit should be about right).

If the carb is badly distorted - look for another carb!

Mac.

[Justin]

Thanks Mac, regarding the thicker, bottom insulating flange that I already have, should it have two holes as the one I have is oval and doesn't have the plastic mounting peg either?!

If I had to get another carb this wouldn't necessarily help if the bow was on the top of the manifold?

[mac]

Hi again,
The lower insulating spacer and its gaskets have ONE "oval" hole (not two round ones). It does NOT have the locating pegs.

It is very rare for the manifold flange to distort - in almost every case it is the carb that suffers. If the manifold has a bow it should be possible to re-surface it flat, but the carb mounting studs would have to be removed first. Plainly a replacement carb would have no effect on the manifold.

Mac.

[Justin]

Great so it seems my leak is either because the current insulator flange is cracked or the carb is slightly bowed.

Im assuming the insulator flange in your picture with the two rings and plastic peg is the next one up which is slightly thinner?

J

[mac]

Yep, it's the upper one, between the pre-heat flange and the carb.

Mac.