Coops Posted May 4, 2022 Report Share Posted May 4, 2022 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. Quote Link to post Share on other sites
RogerH Posted May 4, 2022 Report Share Posted May 4, 2022 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 Quote Link to post Share on other sites
Coops Posted May 4, 2022 Author Report Share Posted May 4, 2022 Thanks roger! Quote Link to post Share on other sites
ntc Posted May 4, 2022 Report Share Posted May 4, 2022 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 Quote Link to post Share on other sites
astontr6 Posted May 4, 2022 Report Share Posted May 4, 2022 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 ) Quote Link to post Share on other sites
ed_h Posted May 4, 2022 Report Share Posted May 4, 2022 (edited) 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 Edited May 4, 2022 by ed_h Quote Link to post Share on other sites
Coops Posted May 5, 2022 Author Report Share Posted May 5, 2022 Thanks guys, all useful info! Quote Link to post Share on other sites
BlueTR3A-5EKT Posted May 5, 2022 Report Share Posted May 5, 2022 Off topic slightly. Here are the real world dimensions for 4 cyl TR sb guides. Which half of are also TR6 anyway. http://www.tonydrews.com/uncle_jacks_engine_building_tips.htm Quote Link to post Share on other sites
Waldi Posted May 5, 2022 Report Share Posted May 5, 2022 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 Quote Link to post Share on other sites
Coops Posted May 5, 2022 Author Report Share Posted May 5, 2022 Thanks guys! Quote Link to post Share on other sites
TRier Posted May 6, 2022 Report Share Posted May 6, 2022 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. Quote Link to post Share on other sites
Coops Posted May 7, 2022 Author Report Share Posted May 7, 2022 Cheers! Quote Link to post Share on other sites
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