Spitfire mk4 1300 starting issues (in Herald)

[jiggawhat2k]

Gave the choke linkage a clean up today, they seem less sticky. 

While doing it, I noticed that I had the trumpets on what I think is upside down, covering the 2 holes at the face of the carb. 

Probably a very noob question, but what are these holes? Would it alter carb performance? Pic of what I mean below:

I took it for a longer drive yesterday, drive there was OK once warmed up, drive back it wasn't happy at all and seemed to not be firing on 4 cylinders, or intermittently. 

Thanks all! 

[KevinR]

Those holes must NOT be blocked !

[jiggawhat2k]

7 minutes ago, KevinR said:

Those holes must NOT be blocked !

Thanks Kevin. Glad I checked! What are those holes? Some sort of breather? 

[KevinR]

Not exactly sure, but a friend who shall remain anonymous, drove up from London to the Duxford Triumph show in his MKIII Spitfire - and when he came to drive home the car was suddenly running like an absolute pig.  So bad in fact that he abandoned the car in my garage and borrowed my turd brown Acclaim to get home (the shame of it !).

A couple of days later I started looking at the engine to try and find the problem and found that the bolt on one of the pancake filters had come out and the filter rotated to block the hole.  I rotated the filter, refitted the bolt and the car ran perfectly again. 

[jiggawhat2k]

1 hour ago, KevinR said:

Not exactly sure, but a friend who shall remain anonymous, drove up from London to the Duxford Triumph show in his MKIII Spitfire - and when he came to drive home the car was suddenly running like an absolute pig.  So bad in fact that he abandoned the car in my garage and borrowed my turd brown Acclaim to get home (the shame of it !).

A couple of days later I started looking at the engine to try and find the problem and found that the bolt on one of the pancake filters had come out and the filter rotated to block the hole.  I rotated the filter, refitted the bolt and the car ran perfectly again. 

OK sounds similar to what happened to me. Have swapped over and will try again, cheers!! 

[NonMember]

The holes provide air to the underside of the piston that regulates the fuel. If blocked, the piston won't lift properly and your fuelling will be miles out.

[jiggawhat2k]

1 hour ago, NonMember said:

The holes provide air to the underside of the piston that regulates the fuel. If blocked, the piston won't lift properly and your fuelling will be miles out.

Thanks makes sense, in that case it's no wonder it wasn't happy yesterday... Cheers! 

[yorkshire_spam]

Pictures! Have a look at this: https://sucarb.co.uk/technical-carburetters-introduction

The holes effectively serve the purpose in the simple diagram at the top of #5, on the 3rd (bottom) diagram they are item 19.

Cheers, Sam

[jiggawhat2k]

21 hours ago, yorkshire_spam said:

Pictures! Have a look at this: https://sucarb.co.uk/technical-carburetters-introduction

The holes effectively serve the purpose in the simple diagram at the top of #5, on the 3rd (bottom) diagram they are item 19.

Cheers, Sam

Cheers Sam great link, have now read. 

Swapped the trumpets over and it fired up beautifully. I'm a plonker... 

[Badwolf]

In my case the bent linkage was putting a sideways force on the jet which meant that it could not simply pop back out, due to the friction involved. Only a little, but enough to hold it in. I think that it was Pete that gave me the idea. Must check the postings in my restoration thread.

[jiggawhat2k]

1 minute ago, Badwolf said:

In my case the bent linkage was putting a sideways force on the jet which meant that it could not simply pop back out, due to the friction involved. Only a little, but enough to hold it in. I think that it was Pete that gave me the idea. Must check the postings in my restoration thread.

Interesting, the tolerances for the whole linkage seem pretty tight, not something I'm used to. Just a bit of old grime had stopped one of my jets popping out. Lots of wd40 and a clean and it's right as rain. 

[yorkshire_spam]

I have a can of PTFE and silicone grease, I can't remember where it came from. I tend to give parts like the jet a blast with it before assembly. Dunno how long it lasts, but it seems to work so far.