13-05-2025, 05:34 PM
Not going very well and my hopes of an cheap and easy fix didn't come to anything.
As suggested I put some soapy water around each of the spark plugs and there was some degree of leakage from all of them.
The new seals from Green Spark Plugs arrived and I tried both types. The budget ones, which are a "U Section" ring didn't help at all but the copper ring types did reduce the leakage and Cylinder 1 and Cylinder 4 now seem OK although to achieve this I did have to tighten them more than the suggested finger tight plus 1/4 turn. Cylinders 2 & 3 however still leak slightly.
I did wonder if the pocket in which the spark plug sits is really too small in diameter causing the outside diameter of the plug to rub against it and push the plug sideways. The HC Head which has been drilled and tapped for 18mm plugs has a pocket diameter of 25.11mm whereas the original low compression head which was on the engine when I got it has packets which are 27.94mm. The 18mm plugs have a body diameter of 22mm so I would have thought 25.11 would be fine but I can't see anything else. The sealing face in the head was spot-faced when the head was originally modified for 18mm plugs but I guess this could be out of square with the thread.
Unless there's no alternative I'm reluctant to get them machined as it always cost more than I expect and takes longer meaning more time without being able to use the car. (But see below).
However, I have now found that the hissing sound seems to actually coming from the carburetor inlet and occurs when Cylinder 1 is on it's compression stroke so I'm guessing this is probably a leaking inlet valve. I've tried to check the tappet clearance but, working on my own, it's almost impossible to do with the engine in place. I did however manage to get hold of the tappet screw and with No 1 at TDC there is apparent movement up and down so frustratingly it's not just a sticky valve.
I suppose the only way forward is to take the engine out and the head off so I can investigate it properly but it's getting increasingly difficult to justify continuously spending money on a car I hardy ever get to drive.
John.
As suggested I put some soapy water around each of the spark plugs and there was some degree of leakage from all of them.
The new seals from Green Spark Plugs arrived and I tried both types. The budget ones, which are a "U Section" ring didn't help at all but the copper ring types did reduce the leakage and Cylinder 1 and Cylinder 4 now seem OK although to achieve this I did have to tighten them more than the suggested finger tight plus 1/4 turn. Cylinders 2 & 3 however still leak slightly.
I did wonder if the pocket in which the spark plug sits is really too small in diameter causing the outside diameter of the plug to rub against it and push the plug sideways. The HC Head which has been drilled and tapped for 18mm plugs has a pocket diameter of 25.11mm whereas the original low compression head which was on the engine when I got it has packets which are 27.94mm. The 18mm plugs have a body diameter of 22mm so I would have thought 25.11 would be fine but I can't see anything else. The sealing face in the head was spot-faced when the head was originally modified for 18mm plugs but I guess this could be out of square with the thread.
Unless there's no alternative I'm reluctant to get them machined as it always cost more than I expect and takes longer meaning more time without being able to use the car. (But see below).
However, I have now found that the hissing sound seems to actually coming from the carburetor inlet and occurs when Cylinder 1 is on it's compression stroke so I'm guessing this is probably a leaking inlet valve. I've tried to check the tappet clearance but, working on my own, it's almost impossible to do with the engine in place. I did however manage to get hold of the tappet screw and with No 1 at TDC there is apparent movement up and down so frustratingly it's not just a sticky valve.
I suppose the only way forward is to take the engine out and the head off so I can investigate it properly but it's getting increasingly difficult to justify continuously spending money on a car I hardy ever get to drive.
John.