The Ford Barn

3W Hank · 09-18-2025, 05:30 PM

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 ?

38 coupe · 09-19-2025, 05:27 AM

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.

3W Hank · 09-20-2025, 11:11 PM

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.

69a · 09-21-2025, 01:33 AM

You need to be able to move the guides by hand for easy assembly. So a push fit with no wobble would be ideal.

69a · 09-21-2025, 07:13 AM

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.

38 coupe · 09-21-2025, 10:09 AM

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Quote:

Originally Posted by 3W Hank

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.

The build thread is on the HAMB, the forum that until recently was where the serious hot rodding for flatheads was widely discussed. Thread here: https://www.jalopyjournal.com/forum/...-build.862832/

3W Hank · 09-21-2025, 02:56 PM

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.

09-18-2025, 05:30 PM	#1
3W Hank Senior Member Join Date: Feb 2022 Posts: 577	Valve guides FH 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 ? Last edited by 3W Hank; 09-19-2025 at 05:23 AM. Reason: Wrong title

09-19-2025, 05:27 AM	#2
38 coupe Senior Member Join Date: May 2010 Location: South Texas Posts: 2,135	Re: Valve guides FH 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.

09-20-2025, 11:11 PM	#3
3W Hank Senior Member Join Date: Feb 2022 Posts: 577	Re: Valve guides FH 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.

09-21-2025, 01:33 AM	#4
69a Senior Member Join Date: Aug 2020 Posts: 321	Re: Valve guides FH You need to be able to move the guides by hand for easy assembly. So a push fit with no wobble would be ideal.

09-21-2025, 07:13 AM	#5
69a Senior Member Join Date: Aug 2020 Posts: 321	Re: Valve guides FH 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. Last edited by 69a; 09-21-2025 at 07:20 AM.

09-21-2025, 02:56 PM	#7
3W Hank Senior Member Join Date: Feb 2022 Posts: 577	Re: Valve guides FH 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.