Wildguzzi.com
General Category => General Discussion => Topic started by: shiskowd on September 10, 2019, 10:28:49 PM
-
I've seen a few posts were there's a reference to a Guzziology suggestion to chamfer oil holes on the crank. I have two editions of Guzziology (1st and last) and for the life of me cannot find that anywhere. Can someone point me in the right direction??
-
If you want to have the drilling's champhered take the crank to your local engine shop, speak to the crank man about what you want, have him measure the journals to be sure it is in spec. champher the drilling's and have the crank polished after the procedure. Easy and affordable. You are likely thinking about the radius at the ends of the crank pin, nothing to worry about on an 850T, unless a crank grind is under taken. DonG
-
Thanks Don - I have a crank guy lined up who has experience with the older Guzzi big twins. I believe my crank is OK, just want to check against the bearings and polish up.
-
I don't know about any reference to this in Guzziology but chamfering the oil holes on the crank was a trick used by one Charlie Rice who had a Guzzi tuning shop called Rennsport located in Ojai CA around the late 1980s.
It is, I believe, an old Nascar modification. It has been mentioned on a Guzzi forum before (not sure which one) and I recall that there were significant differences of opinion as to its value!
Tony
-
It's been done on hot rod engines for millennia. You are just getting rid of the sharp edge, which is a stress riser.
-
After a dive into the archives I found the magazine (Motorcyclist August 1988)!
Summarising, the modification (in response to a tendency for oil cavitation) was to port the oilways in the block and crankshaft and fishtail the oil pickup holes in the crank itself. The modified holes then scoop up more oil than normal improving the oil flow to the big ends. Necessary no doubt for the 9,500 rpm red line.
If anyone is interested in a bit of history I can scan the article.
Tony
-
I served an Automotive Machining apprenticeship in the late 60s to early 70s.
Hamilton New Zealand.
It was standard practice in our workshop to chamfer the oil holes before polishing any crank journal that was reground.
Just a quick touch with a drill bit in an air drill.
Brrrt, brrrrt, brrrt, I still remember the noise.
Cheers Voncrump.
-
It just seems to make sense, a square edge would act like a scraper, I remember the huge bearings on grinding mills had a taper to encourage the oil into the bearings.