View Single Post
boosted79 boosted79 is offline
Registered User
Join Date: Jan 2015
Posts: 1,336
Mains clearances

I checked these both ways, using a mic and bore gauge and plastigauge. I used a Mitutoyo 104-137 calibrated to the 2" standard to mic the journals then I zeroed the Fowler bore gauge to the journal diameter so I could read the clearance directly off the bore gauge with no subtraction. The red PG was placed on top of the journals.
These are thousandths of an inch.
main mic plastigauge
#1 3.2 3.0
#2 3.0 3.0
#3 3.4 3.0
#4 3.6 3.4
#6 3.3 3.2
#7 3.5 3.1

Pretty good correlation between the mic method and the pg method with the exception of #3 and #7. Having to interpolate between 3 and 4 thou on that pg scale is not very precise. Since all of my journals are right about at low std. I think I'll try to get some Motorsports GT3 "blue" shells which are half a thou tighter than the std. street GT3s. Wayne's book says a clearance range of .010 to .072 mm or .0004 to .0028 in.? Four tenths of a thou. seems awful damn tight compared to the traditional rule of thumb of one thou. per inch of journal diameter. That would say about 2.3-2.4 thou would be good? Maybe that doesn't apply to these engines ?
Old 02-15-2016, 07:23 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #31 (permalink)