Technical crack between valve seats on 650 head

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Technical crack between valve seats on 650 head

mhatzis

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So I was exited to start rebuilding one of the engines until I found a crack between the valve seats on one of the cylinders. does anyone know if this can be fixed considering its aluminium or is it throw away?


Second question.. I just took the filter out and who ever had the car before had the filter turned around so the intake pipe to the carb was blocked by the rubber on the filter... and idea why this is done... is it some Italian tuning trick......:bang:
 

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First of all, the humerous answer---how the heck does blocking OFF a fuel feed make an engine go faster? I think that the answer to that question is that some muppet has put in the wrong way round!
Now the serious answer---cracking between the valve seats on the 126 heads is quite common. When I was building up a ported head for my 652cc engine, I was having slightly larger inlet valves fitted, so had the head repaired at the same time. One school of thought is"don't worry about slight cracking---it doesn't get any worse". The head is definately NOT a "throw-away"---if you ARE fitting larger inlet valves (you only need to go up 2mm on a 'road-use only' engine, then I would get the engineers to repair the cracks at the same time. If the cracks ARE only slight, I wouldn't worry too much about them.
 
So I was exited to start rebuilding one of the engines until I found a crack between the valve seats on one of the cylinders. does anyone know if this can be fixed considering its aluminium or is it throw away?


Second question.. I just took the filter out and who ever had the car before had the filter turned around so the intake pipe to the carb was blocked by the rubber on the filter... and idea why this is done... is it some Italian tuning trick......:bang:

Hi Mike, Re your crack(s) Having had to make the same repair on both of my heads, and having discussed the process with my engine man it is recommended that with an alloy headed air cooled engine you should repair Both valve pockets as this will add strength to the area. I will add that Tom (@the hobbler) is correct in saying you do not have to repair a small crack, but it is future proofing your engine.
Ian.
 
Don't freak out just yet - they may not be cracks. On top of what the hobbler said, these heads seem to have a casting mark in that location. When I tore mine down for rebuild, I was worried too. When the machinist cleaned up the head and took the valves out, there was zero cracking - it was a casting line and no damage into the seat area.

You'll know for sure when you take the valves out and see if there's damage into the seat area.

After & before pics of my head attached.

Edit - I see those are cracks, but fear not, pull the valves to see how deep they are and go from there. Not a difficult repair for a machinist.
 

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Don't freak out just yet - they may not be cracks. On top of what the hobbler said, these heads seem to have a casting mark in that location. When I tore mine down for rebuild, I was worried too. When the machinist cleaned up the head and took the valves out, there was zero cracking - it was a casting line and no damage into the seat area.

You'll know for sure when you take the valves out and see if there's damage into the seat area.

After & before pics of my head attached.

Edit - I see those are cracks, but fear not, pull the valves to see how deep they are and go from there. Not a difficult repair for a machinist.

I took the valves out and and it would seem to be only a surface crack as stated. the valve seats are in good condition. I do have another question... do these normally have dual valve springs? as I have a feeling this may have already been worked on before.
 
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