john.r.davies Posted May 21, 2021 Report Share Posted May 21, 2021 REcently I found a six cylinder Triumph engine, with a cross drilled crank. It was loosely attached to a block with a number starting "MG", which is a 2.5L saloon, but obviously it may not have started life there. Does anyone know if the factory issued six-pot engines with cross drilled cranks? Or was this modifed later? And, if the first, how 'important' is this relic? Sad to say, it has had a hard life, and is badly worn about the thrust washer area, but that could be repaired if worthwhile. Some pics below. The plug in the web blocks off the chamber that links the diagonal drilling from the main bearing and the cross drilling. The original opeing of the drilling from the main is partly blocked by an orifice, that is about a quarter the original size. John Quote Link to post Share on other sites
RogerH Posted May 21, 2021 Report Share Posted May 21, 2021 Hi John, the 4 pot crank received cross drilling shortly after TS2 was born. Rumour has it that is was to stop centrifugal forces throwing the oil out too readily. I suspect the oil pump of the day simply couldn't keep up as the 6 pot cranks were all TDC drilled. The original TDC oil hole in the crank was retained but reduced in size to something like 5/64". I suspect the original drilling machinery was retained and the hole was simply plugged. The 5/16UNF grub screw plugs the hole to link the original oil gallery with the cross drilling. You'll be pleased to know that Fergie TE20 does not have the cross drilling. Roger Quote Link to post Share on other sites
ntc Posted May 21, 2021 Report Share Posted May 21, 2021 Early TR5. Quote Link to post Share on other sites
BlueTR3A-5EKT Posted May 21, 2021 Report Share Posted May 21, 2021 1 hour ago, john.r.davies said: REcently I found a six cylinder Triumph engine, with a cross drilled crank. It was loosely attached to a block with a number starting "MG", which is a 2.5L saloon, but obviously it may not have started life there. Does anyone know if the factory issued six-pot engines with cross drilled cranks? Or was this modifed later? And, if the first, how 'important' is this relic? Sad to say, it has had a hard life, and is badly worn about the thrust washer area, but that could be repaired if worthwhile. Some pics below. The plug in the web blocks off the chamber that links the diagonal drilling from the main bearing and the cross drilling. The original opeing of the drilling from the main is partly blocked by an orifice, that is about a quarter the original size. John 149748 is the part number of the drilled brass plug for the journal. The original parts books suggest they were always fitted. It is in the catalogue and I remember selling them to the racing engine builders. Have you read this about cross drilling of cranks? http://www.strokerkits.com/crankshaft-tech-say-no-to-cross-drilling/ Peter W Quote Link to post Share on other sites
john.r.davies Posted May 21, 2021 Author Report Share Posted May 21, 2021 (edited) Thank you, all! So this was a carry-over in design practice from the TR4 to the TR5? (No doubt, this is a six-cylinder crank!) Did it stop with the TR6? If so then with less than 3000 ever made, more half of which were LHD and bound for export, and about 500 left in the country, this has to be a rare find? This block is numbered MG7845HE, which makes it a 2500 saloon engine, which were in production before the TR5, and three times as many were made. Engine numbers went up as far as 85579. Could this be an early version with a crossdrilled crank? The plug/orifices are brass, which makes it more likely to be original? John Edited May 21, 2021 by john.r.davies Quote Link to post Share on other sites
Richard71 Posted May 21, 2021 Report Share Posted May 21, 2021 I have two of those crankshafts currently gathering dust in a machine shop (I must call them). One came from a TR5 and the other a Saloon, so I'm not so sure they're a rarity John. Richard. Quote Link to post Share on other sites
john.r.davies Posted May 21, 2021 Author Report Share Posted May 21, 2021 Ah! So at least one other from a saloon, and that must have been the practice in the 60s! Do you know the block number, Richard? I've asked the 2500 Register if they know about cross drilled cranks. I'll pass on anythinmg they can tell. Quote Link to post Share on other sites
ntc Posted May 21, 2021 Report Share Posted May 21, 2021 You will also find it will be a long back and they are now hard to find if serviceable Quote Link to post Share on other sites
saffrontr Posted May 21, 2021 Report Share Posted May 21, 2021 Cross drilled cranks were used up to engine number CP52320HE for the TR6 and to MG10324 for the 2.5PI hence used on both long and short back cranks. The deletion is detailed in Triumph Newsletter 255 dated 27th November 1970. For you doubters out there a copy is attached. Derek Quote Link to post Share on other sites
Richard71 Posted May 21, 2021 Report Share Posted May 21, 2021 1 hour ago, john.r.davies said: Ah! So at least one other from a saloon, and that must have been the practice in the 60s! Do you know the block number, Richard? I've asked the 2500 Register if they know about cross drilled cranks. I'll pass on anythinmg they can tell. It was definitely prefixed MG with BW suffix suggesting it was originally married to a Berg Warner auto gearbox, I don't know the full engine number, I scrapped the block, it was too far gone to be salvageable for me, it must have worn through the thrust washers and #2 main bearing cap was too loose a fit. Richard. Quote Link to post Share on other sites
Waldi Posted May 21, 2021 Report Share Posted May 21, 2021 The post from Derek clarifies it all. John, My 1970 CP-TR6, with an earlier CP block has the same drillings. Off course one cannot tell if the crank shaft and block are “matching numbers”, and I couldn’t care less:) Cheers, Waldi Quote Link to post Share on other sites
PodOne Posted May 21, 2021 Report Share Posted May 21, 2021 My April 1969 CP TR6 with matching numbers had a crossed drilled long back crank which was fortunately in good nick. The machine shop said at the time they had not seen it in a TR6 and it was unusual and usually seen in race engines of the era. Andy Quote Link to post Share on other sites
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.