New question of the day, You could be the winner

[tomgt6]

I have a 1300cc spitfire engine that I am tuning.

I put new needles in the car last night. I had needles in the SU carbs for a 1147 and wanted to change them to the right needles.

After changing the needles I was getting no power out of the back carb and the power was down on the front carb.

So I know I have to redial in the jets.

I played around with them and tried to do it by sound and feel and got close but the back carb still just seemed weak. So I reset the carbs to 12 flats from stop and started the lift the piston trick. Here is what I found

The front carb would die if I started to lift the piston. So that means it is to lean (I think) and I need to go anti clockwise (this I remember for sure) with the nut.

I turned that carb anticlockwise about 15 flats I bet or more and I am sure I was at the end of the nut and still it wanted to die when I lifted the piston.

So the question is what is causing this? The carb has a new rebuild on it with about 300 miles.

The next question is why does the back carb not seem to sound the same. I put the air meter on both carbs and got them air flowing at the same rate.

I can't seem to get this carb to lean out. It just seems like it is always dogging when I rev it.

I do plan on taking the colortune out tonight and working with the carbs again but hope you guys have some good suggestions as to what may be going on.

 

[tdskip]

Sure there are no vacuum leaks?

 

[tomgt6]

There is no vacuum line on the front SU. Now I will retest the carb to the manifold and make sure there isn't another vacuum leak anywhere else. Where else would you look?

 

[JodyFKerr]

Tom,

My mum's spitfire did the same thing. It was a fuel delivery problem. Are you sure it's getting enough?

Jody

 

[tomgt6]

I will make sure the hose is clear to the back carb. Good point.

 

[tomgt6]

OK, did some work on the carbs and I keep forgetting what car I am working on. I forgot the front carb has the vacuum advance port on this car.

Here is what I found. The back carb had a issue with the hose to the jet. It would get kinked. So I cut it down a bit and things started to work better for that carb. The front carb I just kept playing with it until I was able to get it to stop dieing every time I lifted the piston. I did have on the colortune at one point then ran into issues so I took it off.

I will tomorrow put the color tune back on and see how I did by ear and feel. Thanks all for the help.

So who was right. All of you. I still have some sorting to do but it runs better and will idle smoothly. So something got done. I guess I will have to come up with a new question for all tomorrow.

 

[tdskip]

Hey - progress then. Good to see.

Let us know she comes along.