Valve guides FH

3

3W Hank

Well-known member
I reseach what valves I will be using in my Merc 41 block.
I guess I go with 5/16” but the new 1 piece guides what size has thoose ?
As I’m a CNC operator I can make them myself in bronze or cast iron.
But a question will I has them press in fit or is the one to bought little loose or press in ?
 
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The commercially available guides can be a bit loose in the bores. Some builders knurl the guides to tighten up the fit. I remember Bored&Stroked did that when he build the 284 with roller cam for his 32 cabriolet. I personally have not done that on any of the engines I helped assemble, and they run smoothly. Many of the engines I helped with have reused guides and valves after close inspection to make sure wear was within limits.
 
Ok that make sense tight them up + 0.0005”, so had B&S that engine build up as a own thread here ?
I asked him on help me with vales but did not hear anything back.
 
You need to be able to move the guides by hand for easy assembly. So a push fit with no wobble would be ideal.
 
I made new guides over 30 years ago. I made mine from mild steel and bored the center to accept after market valve guide bushes. The bushes are made from a aluminum bronze alloy, so I'm not sure how well brass will work.
On the advice of an old man I ran a 5/16" UNC tap through the guides. The tap is a fraction bigger than 5/16" and leaves a light spiral grove in the guides. This will prevent your valves from ever sticking.
I did make the mistake making the groves for the "O" rings on the intake valves the same width as the "O" ring, and I had to widen them. They need plenty of side clearance to allow the rubber to compress when fitting them in the block.
 
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I has not check if I can get in the Isky spring if guides is tight and std lenghts.
One way is make it in steel an drill 0.341” for a K-Line sleeve.
But there is bronze at same material as a K-Line.
 
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