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t-head · 06-05-2010, 11:38 AM

PART 1 Machining your own Valve guides.

Zach (SUHRsc) Posted a question on a different thread in the new Ford Barn T section but it may help some of you here with overheads. The valve guides for his BBR Rajo Head are missing and he needs to know what to do for new valve guides.

I decided to post it here on the racing thread as it will be easier to find later and really only applies to overheads as a stock T the guides are part of the block.

I would use cast iron, I machine my own if I cannot find something to adapt that will fit. Then get your valve stems hard chromed because if the stems are stainless you may have gauling and sticking. Send them to http://www.calvalves.com/ they will do a good job or have a local plating shop do them for you. You only need .0005 - 1/2 of a thousandth of chrome. The second photo shows a valve that a local plating shop masked the head of of and plated for me. The rough spot at the end of the plating needs to be smoothed off before using it, photo 2.

Ream the guides for .003"- .004" exhausts and .002" for the intakes. If you have a good machine shop near by you can get a better and smoother surface by having the id if the guide honed out the last .002 or so. Set up this way they will work very well with little to no oil. The graphite in the cast iron will help along with whatever oil you can put on them.

I generaly finish off the OD of the guide where it sits in the head 1/2 thousandth- .0005 bigger than the bore in the head for a good tight fit which will also transfer the heat better.

I have used this on a lot of T-Head and L-Heads (like an early T with exposed valves) with exposed valves which get no oil and it will work beautifully. The photo shows a new guide machined here on the lathe along with an original one. A piece of cast iron bar and a reamer.

This is what is being done in modern cars and trucks as the modern valve guide seals keep almost all of the oil out for emissions purposes. This is the only way that really holds up well unless a seal that meters just the right amount of oil is used, then bronze might work.

Zach you can get cast iron from Mc Master-Carr. They have everything under the sun and more. They also have a great website.... here is a link for the cast Iron...... http://www.mcmaster.com/#iron-rods/=7csahk

06-05-2010, 11:38 AM	#23
t-head Senior Member Join Date: Jun 2010 Location: In my machine shop. Posts: 1,047	Re: Model T Racing Thread PART 1 Machining your own Valve guides. Zach (SUHRsc) Posted a question on a different thread in the new Ford Barn T section but it may help some of you here with overheads. The valve guides for his BBR Rajo Head are missing and he needs to know what to do for new valve guides. I decided to post it here on the racing thread as it will be easier to find later and really only applies to overheads as a stock T the guides are part of the block. I would use cast iron, I machine my own if I cannot find something to adapt that will fit. Then get your valve stems hard chromed because if the stems are stainless you may have gauling and sticking. Send them to http://www.calvalves.com/ they will do a good job or have a local plating shop do them for you. You only need .0005 - 1/2 of a thousandth of chrome. The second photo shows a valve that a local plating shop masked the head of of and plated for me. The rough spot at the end of the plating needs to be smoothed off before using it, photo 2. Ream the guides for .003"- .004" exhausts and .002" for the intakes. If you have a good machine shop near by you can get a better and smoother surface by having the id if the guide honed out the last .002 or so. Set up this way they will work very well with little to no oil. The graphite in the cast iron will help along with whatever oil you can put on them. I generaly finish off the OD of the guide where it sits in the head 1/2 thousandth- .0005 bigger than the bore in the head for a good tight fit which will also transfer the heat better. I have used this on a lot of T-Head and L-Heads (like an early T with exposed valves) with exposed valves which get no oil and it will work beautifully. The photo shows a new guide machined here on the lathe along with an original one. A piece of cast iron bar and a reamer. This is what is being done in modern cars and trucks as the modern valve guide seals keep almost all of the oil out for emissions purposes. This is the only way that really holds up well unless a seal that meters just the right amount of oil is used, then bronze might work. Zach you can get cast iron from Mc Master-Carr. They have everything under the sun and more. They also have a great website.... here is a link for the cast Iron...... http://www.mcmaster.com/#iron-rods/=7csahk Last edited by t-head; 06-12-2011 at 11:04 AM.