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Britbodger's Race Engine #786584 10/08/19 5:44 pm
Joined: Aug 2011
Posts: 106
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Brid Caveney Offline OP
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We recently took in a partly built 1976 T140 engine, which was to have been the late Malcolm Dixon's (RIP) race engine. Bottom end was built, with nicely polished con rods, and Johnson J 380 cams. No cam card - nor cam info -- and as Johnson Cams are no longer in business due to Keith Johnson's passing (RIP) we are looking for last bit of info on the cams. According to Malcolm's notes, he degreed the cams -- but, the crank has been 'shaved' slightly, with a pocket for cam lobe clearance cut into the O/D of the bob weights. Seems any info we have found on cams requiring the cranks machining, also need the tappet blocks machining for clearance -- but no figures saying how much? NO info found on the J 380 units - at all.
Other questions are - do the tappets need further radiusing? Lastly - what rocker clearances do the cams need?
The head we are using was ported by the late Dwain Williams (RIP) - before his untimely demise in 07, and has as big an inlet valve as will fit in the combustion chamber. Lot's of sad RIP's in the post - but we're happy to be finishing a job which would have been very dear to Malcolm's heart. I helped him get through his Ahrma race school, and his first ever couple of races.
Any cam help very gratefully appreciated.
Brid.

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Re: Britbodger's Race Engine [Re: Brid Caveney] #786629 10/09/19 10:20 am
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Mike Baker Offline
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Will we see that motor on a track at some point?

Re: Britbodger's Race Engine [Re: Brid Caveney] #786712 10/10/19 3:40 pm
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shel Offline
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I really enjoyed reading the Bodgers posts


When given the choice between two evils I picked the one I haven't tried before
Re: Britbodger's Race Engine [Re: Brid Caveney] #786716 10/10/19 4:30 pm
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Hillbilly bike Offline
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I am not an expert but did build several Triumph race engines, they ran at the front of the pack and didn't blow up, yet....My advice is to set up the cams on 105 degree lobe centers, intake and exhaust, a common set up for many Triumph performance cams.Cam timing for a race engine is a variable figured out by testing on the track or dyno.....Do a mock up with the cams in the right side case ony, bolt on cylinder and cycle the cams to check tappet to block clearance.Kevin Roberts has posted photos in the Performance forum on this procedure...Then install the crank and left side case and check cam lobe to flywheel clearance...About .050 is usually recomended...There's opinions on larger intake valves ,not all of them favor the largest valve that will fit, far more important is the port shape..But generally more than .1.660 might find the valve seat running off the insert and into the aluminum...Every single component must get indivdual attention and check for fit before assembly.


79 T140D, 96 900M Ducati ....On a bike you can out run the demons..
Re: Britbodger's Race Engine [Re: Brid Caveney] #788138 10/25/19 4:01 pm
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MarksterTT Offline
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Sorry to hear about Keith Johnson's passing...following info is from his website I copied a couple years ago:

J380/262 cam for the Triumph 750 short rod engine, works well for dirt track and is used in Johnson's flattracker.

In. cam lift .375" - LCA 102* - Lash .008" - Tappet 'S' - Duration 300* - Open 49* Close 71* @ .020" or Duration 276* - Open 36* close 60* @ .040"

Ex. cam lift .375"- LCA 110* - Lash .008" - Tappet 'S' - Duration 300* - Open 80* Close 39* @ .020" or Duration 276* - Open 68* close 27* @ .040"

Hope this is what you needed...Mark


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