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Old 27-08-23, 06:14 PM
Roger Morrall Roger Morrall is offline
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Stefano.

Andrews comment in the previous post puts me in mind of another potential cause of your under bonnet temperature problems.

He mentions a phenolic block. This is often recommended with a view to isolating the carburettor from the inlet manifold - which raises another question. Why should the inlet manifold get particularly hot in the first place?

Sure, it’s in the centre of the block, but the block itself will not exceed about 105 Celsius which is not particularly hot at all. So why should the Chrysler original equipment manifold get any hotter than that? The answer lies, perhaps, in the exhaust transfer ports that Chryslers introduced with a view to attaining a rapid warmup, and alleviating the Los Angeles smogs. These transfer ports run across inside the inlet manifold between the left-hand and the right-hand exhaust ports with a view to warming the manifold on a cold start. They were originally brought into play by a rather crude flap in the left hand exhaust manifold driven by a bimetallic coil. This closed when “cold" and opened when "hot"

It seems rather unlikely that this bimetallic coil and the flap has survived on your car to cause the inlet manifold to be over heated, but I have heard that some have survived. If it hasn’t the transfer ports will still remain if your car retains its original inlet manifold and gaskets and will continue to heat the manifold to some degree. The heating will be exacerbated eg by an imbalance in silencer back pressure or, indeed, some blasted bambino inserting a potato up one of the exhausts, emulating said flap, whilst idling in Italian traffic

It might be worth checking on the surface temperature of the inlet manifold in various circumstances - these simple stick on temperature recording strips might prove invaluable. https://temperature-indicators.co.uk...vel-indicators. (I’m sure there will be an Italian equivalent)

Should you perceive that the inlet manifold is getting unduly hot (and that the original equipment flap and bimetallic arrangement is not to blame) I understand modified inlet manifold gaskets may be available that simply omit the holes for the transfer ports and thereby block them off, if not I’m sure this would not be beyond the scope of an Italian engineer.

Worth thinking about perhaps and certainly a lot cheaper than SLJs magnificent tubular manifolds?
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