underhead question
05-23-2006, 08:13 AM
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underhead question
OK, here's the deal. I posted about a week ago about stripping out what I thought was the glow plug threads in the head, when in fact it was the threads in the underhead. The part number for the s-25 underhead is 1444. That is for a 4.0, or .25 engine. Now, I have the underhead for a Nitrostar F4.1 enigne (part number 1448) That is for a .25, or 4.1 engine. Will the underhead I have for the F4.1 engine work for my s-25 engine. I would say yes, but I wanted to be sure.
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05-23-2006, 08:35 AM
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RE: underhead question
What you are calling the under head is really called the head button. The .25 and the 4.1 are in fact the same engine design (.25 refers to the c.i.d. and 4.1 is the CC displacement) and the head button from the .25 should work. I believe the difference has to do with the clearance in the combustion chamber. From what I see it looks like the 4.1 has a tighter squish area and more compression. If this is the case then you might see a small power loss by using the .25 button head but it won't hurt anything.
