CDH polygon head

Spare_Parts

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The head came in and it's pretty nice. It is a true performance head and not just to add cooling. Chamber is about 47.2mm wide and the squish brand is 8.4mm. Haven't checked the chamber but it is advertised as 5.5cc. The machine work is about equal to CR Machine withr the chamber and bottom being excellent and the cooling fins are not great.

Use NGK BxS. Fill in the x with 5,6 or7. This head takes a 3/8 reach plug.




 
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Spare_Parts

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Just checked the measurements with the calipers and came up with 47.2mm chamber and 8.4mm squish. First post updated.
 

gary55

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Just checked the measurements with the calipers and came up with 47.2mm chamber and 8.4mm squish. First post updated.
How wide did you go on the exhaust port of the engine that lost the ring? Was it on the G5 jug?
 

Spare_Parts

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How wide did you go on the exhaust port of the engine that lost the ring? Was it on the G5 jug?
Yes, a g5. It's 31 and safe is 32.9mm. The cylinder is fine actually. The ring broke right at the pin. Nothing to hang up on there. Think it was just a bad ring this time. It was the bottom ring anyway lol. Back together and running about the same but went to a 0.8mmhead gasket and the 6cc head. Ordering some wider wrist pin bearings and putting this head on when they come in.
 

gary55

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Yes, a g5. It's 31 and safe is 32.9mm. The cylinder is fine actually. The ring broke right at the pin. Nothing to hang up on there. Think it was just a bad ring this time. It was the bottom ring anyway lol. Back together and running about the same but went to a 0.8mmhead gasket and the 6cc head. Ordering some wider wrist pin bearings and putting this head on when they come in.
I thought I remembered you going quite large with it, but after taking forever to find on page 111 32.9mm is dead on the money for a max size elliptical exhaust port. Did you stretch it out to look like a football? Not being a wise guy, just don't want to see any dents in the chamber of that new head.:)
 
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