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Reaming bronze guides


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Hi! I’m about to fit a set of bronze guides but I can’t find a supplier to sell me a reamer. Also, I’m not sure what size? My engine is a 73 CF, according to the brown book and my vernier the stems are both 7.87- 7.88 mm, does this equate to an imperial fraction? Any help would be appreciated. Regards Alan.

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hi Alan

 the imperial conversion is 0.3098 - 0.3102

You can get an expanding reamer from       https://www.tracytools.com/

The reamer needs to be held precisely square to the  head.  Use plenty of cutting fluid.

It may be best to get a workshop to carry this out.  

Bronze guides need different clearances than the standard steel guides

 

Roger

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1 hour ago, Coops said:

Hi! I’m about to fit a set of bronze guides but I can’t find a supplier to sell me a reamer. Also, I’m not sure what size? My engine is a 73 CF, according to the brown book and my vernier the stems are both 7.87- 7.88 mm, does this equate to an imperial fraction? Any help would be appreciated. Regards Alan.

You will need stainless valves and inlet seals

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2 hours ago, Coops said:

Hi! I’m about to fit a set of bronze guides but I can’t find a supplier to sell me a reamer. Also, I’m not sure what size? My engine is a 73 CF, according to the brown book and my vernier the stems are both 7.87- 7.88 mm, does this equate to an imperial fraction? Any help would be appreciated. Regards Alan.

In my view this not a do it your self job and you would have to have access to engineering work shop facilities and know what the running clearances s/b. I suspect that this can only be done with a purpose made reamer that has got a special set taper machined on it with the correct o/d further up the flutes using a pillar drill with the head fully clamped.

Bruce. ( who served a toolmaker's apprenticeship )

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My bronze guides fit perfectly on the valve stems before they were installed.  After installing the guides, the stems were pretty tight.  A 0.3125" chucking reamer made them just right.  So little material was removed that I could easily do it by hand.  In fact, I could never even see any swarf..

Ed

DSC08791a.JPG

Edited by ed_h
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Andreas (Triumph V8 on here) told me that on bronze guides (esp. on the outlet valves) should not be reamed too tight. Andreas helped me cutting the valve seats once the guides were ok.

My bronze guides came from Goodparts with the seal cups.

Waldi

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FWIW, I’ve used those expanding reamers Roger linked to and for pretty much the same reason you mentioned. I put new gudgeon pin bushings in a Landcruiser i overhauled the engine in, they were a nice fit until I pressed in the bushings then the pins were just tight. I used the reamer by hand and it took absolutely nothing to just make for a nice snug fit. The beauty with those adjustable reamers is they lend themselves well to getting them square, started with them adjusted slack and in very small bites adjusted them up until they take a tiny bite. They’re tapered so it’s not hard to do that. I took a view that if you go slowly you’re unlikely to do harm and will get everything square. Engines still running 30k later so some indication it is possible at home. Best of luck with it.

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