...can you explain...the difference between the 445 and the 780?
...As a side motive, i am thinking about going with less cam...
To pickup where Byron left off, and just for the record, so it's available to everyone who may ever want to see any of it...
The following notes are the result of my chat with Barry at Shadbolt Cams, August 20, 1998
With regard to the L-series Datsun...
Streetable Regrind : $120
Track Regrind : $160
Extreme Regrind : $200
The price reflects the amount of material to be removed from the base circle. i.e. even just the 445 profile requires 0.060” to be taken out of the base circle on the backside.
445 Profile:
Duration: 280 degrees (30-70-70-30)
Overlap: 60 degrees
Lift: 0.507” at the valve
"Good for about 7200 rpm max"
449 Profile:
Duration: 256 degrees
Overlap: xx degrees
Lift: 0.492” at the valve
"...?..."
651 Profile:
Duration: 296 degrees (38-78-78-38)
Overlap: 76 degrees
Lift: 0.487” at the valve
“...this never worked as well as it should have worked; Andy said if you already have a 445, don’t waste the time of putting one of these into your head; it isn’t worth much more” - Barry referring to Andy from Specialty Engineering
NOTE - From a conversation years later (late 2003) with Geoff Bardal from Colt Cams said, "I never liked the 651, because it's numerically almost identical to a worn out 445 with it's lobe tip worn off, so pick either a 445 or a 780 instead"
780 Profile: The Datsun Radial Challenge Cam (DRC)
Duration: 304 degrees (44-80-80-44)
Overlap: 88 degrees
Lift: 0.522” at the valve
"Should be good for more than 8000 rpm easily"
The mild TURBO Profile: 445 Intake, 449 Exhaust
Intake = 280 degrees @ .507 lift
Exhaust = 256 degrees @ .492 lift
Total Overlap : 48 degrees (VERY low overlap)
Lash: 0.008” Intake, 0.012” Exhaust
"...has very low overlap, early exhaust opening and intake closing..." - Barry
"...there is not much growth in those motors (L-series), maybe 0.001”...Give it 0.009” & 0.013” respective & then check it when it has warmed up..." - Barry
Also, for those of you who don't know the Colt Cams story, after well over a decade (maybe even two decades, but I don't remember what number he said it was) of service at Shadblot, Geoff Bardal broke out on his own to start Colt Cams in Langley BC (
http://www.coltcams.com) and is the guy who ground most of the Datsun L-series cams while Shadbolts were cranking them out in the Datsun's heyday because after all, Geoff used to run a L-series himself.
Barry’s (from Shadbolt) version of cam theory with respect to turbocharging...
"...you don’t want too much overlap because the cool intake charge will blow right through the motor and cool off the turbo..."
Later note - Sean Kearny had a “721” grind (45-81-81-45) which he says is 0.582” lift with 306 degrees duration which is purported to be a copy of the Racer-Brown model 391-R from page 54 of the later Steve Smith book.