BMC 1.5 Injector 'Top Hat' heat shields

Guy J

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Heat shields

On removing my injectors I discovered cylinder 1 injector was without a ‘top hat’ heat shield, just the lip in the hole and nothing beneath, neither was there a heat shield stuck on the top of the injector, as in photo 1.

Cylinders 2, 3 and 4 have the lip and then a washer, seated in the hole, as seen in photo 2. This is definitely a washer as we rotated one by 90 degrees. Cylinder 1 piston head had significant scoring, which could have been caused by the washer disintegrating and falling into the combustion chamber.

I bought one heat shield to try in cylinder 1, with all correct washers in place and the ‘top hat’ shield is too big to go down beneath the lip, so the injector is not inserted far enough, as shown in photo 3

The outer diameter of the ‘top hat’ heat shield is 17.4mm, and the diameter of the hole bored beneath the lip is 14.5, therefore there is no way the shield will fit in the hole. The diameter of the injector nozzle is 13.8mm. When the top hat shield is fitted over the injector nozzle, there is about 1.5 mm of play. The new injectors are exactly the same dimensions as the old ones, the engine is standard, as far as I’m aware, probably 1980s, and was running, seemingly very well, without heat shields but with these washers balanced in place for quite a few years.

What should I do?

Guy
 

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  • injector inserted with heat shield sm low.jpg
    injector inserted with heat shield sm low.jpg
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Rappey

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Mine is a pre 1965 model and has not got any of those heat shields you mention. Cant see how they would shield anything from heat ?
The injector seals with a crush washer at the bottom of the injector hole so it would not be possible for anything to get in the cylinder ?
I would suggest talking with calcutt boats as they are bmc specialists. They may be able to shed some light on your situation

Looking at the date i would assume youve solved it by now
 

Guy J

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Thanks for the message. I found that the heat shields were stuck in the injector holes, one without its bottom and the others firmly wedged in place. All BMC engines appear to have them - they resemble top hats and fit over the injector, and it seems clear how they shield the injectors from the heat. I wonder if yours are wedged in the holes. Calcutt sells them, as far as I am aware, for all BMC diesels.
 
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