Nailhed 400 : Valves clearance in guides

B

bertrandboss

Member
Hi, I need explanations about the information given in the chassis shop manual about the valve clearance in guides : two types of measurement are indicated "top" and "bottom", what do these terms mean about the valve clearance ?
So, how do i measure valves clearance in guides ?
If I change the valve guides, do the guides install directly in place of the ancients or do i have to perform a machining job at the location of the guides, in other words do the aftermarket guides are at original dimensions? Thank you .
 
You don't mention what year you are referring to.

Top and Bottom will refer to the opening at the top (spring end) or the bottom )valve end). Valve guides generally wear in an "hour glass" shape. The rule of thumb is intake clearance is .001" - .003" clearance, and exhaust is .002" - .004".

You probably don't have the tooling necessary to accurately measure the clearances, so they really don't matter too much. Most experienced builders simply give them a "wiggle" and make a judgement call.

The odds are, if you are reconditioning an old motor, you need to replace the guides and valves to end up with a nice tight motor. Some may not agree with this, but it is a matter of what you want when you are finished and your experience. The Nailhead uses replaceable guides, so, yes, you do drive out the old and drive in the new. A little warming and cooling can make the job go better. After you have installed the new ones, you do need to check them. You may have crushed some interferance in the driven end and they would at least need a reamer passed through them to clean them up. A better quality install will include honing (not nessecary except when trying to achieve tighter tolerances).
 
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