My engine ate up the bearings in less than 4000 Miles, the crank being the culprite. Im getting it shaved (machined) .010 / .010 is being removed. Im bolting a 144 Roots Blower, and would like a LONG bearing life. Dont forget the 75 Shot of NOS beneath the blower. yes the rods / crank / pistons are forged. but the crank is the only old thing, being .010 thinner. What are the best things i could do with this engine to make sure the bearing live a happy life
I.E. My timing advance, Air/Fuel Ratio, Balance issues etc...
I dont want to reubild this engine every 5 runs. Its also a decent street car, so its gota last. no i wont be spraying on the street unless it looks like im losing

 

one of the dangers, in any blown application is side loading of the front main bearing from the belt tension from the flex of the snout. if you have a steel crank then dont worry about the .010-.010 undercut part. not only is that not deep enough to get through the surface hardness treatment but when you consider that guys that run non forged crank (stock cast 400) 396/415 small blocks are using a crank that has been severly offset ground at the rod journal to make a small journal rod fit on it and create the extra stroke, and these are commonly used in IMCA MOD circle track cars at high RPM.

 

What do you suggest, use only enough belt tension to keep it from slipping? if it matters, im using a very good fluidamper to keep the vibration down to a minimum.

 

except when using a cog belt it seems you can never have them tight enough.

 

hmmm so slippage may become a problem eh? well hmm...

 

Never had a problem with the little 6-rib belted Weiand 142 (almost identical to your Holley 144) regarding bearings. The "pull" is straight down so very little side loading happens, unlike a typical centrifugal setup with the unit off to the side.

Judging by the boost curve I doubt you will get any appreciable belt slippage at moderate boost (6 PSI). I never have that I'm aware of. I figure the boost would fall off on the top end if it was slipping and that hasn't happened to me.

 

Curious, how was the crank the culprit in bearing failure??

 

weel the crank sits on bearing right? the crank is supposed to turn round and round... 360* over and over...
Not supposed to wobble up and down...
since the crank is connected the the flywheel in back, and harmonic balancer + pullys in front, any UNBALANCE in front OR back and cause Wobble at high RPMS which = Bearing FAILURE. and quick too... only took 3K Miles to spin a bearing the last time around.
<b>Kingtal0n: My engine ate up the bearings in less than 4000 Miles, the crank being the culprite. </b>
THAT was because the crank was re-used and NOT RESURFACED, it had gouges in it when it was re-assembled (I DIDNT DO IT!) and it ate the bearings up quick with that crappy balancer + UNbalaced rotating assy.

 

I think everyone on this board knows how a crankshaft works, no need to get cynical.

I was just curious what the mechanical was for failure. And you eventually got to a rough surface on the crank and an imbalance with the rotating assembly.

 

the side loading and failure I spoke of was in reference to the crank and crank bearings, and side loading doesnt necessarily have to be from the "side". we shred the hell out of those 6 rib belts on the centrifugal blowers (they have a lower inertia, lower rotating mass, and have less resistance than even baby roots blowers.

 

Im not getting cynical sorry if it sounds that way. you guys are correct. im just looking for a way to keep the "side loads" to a minimum...

 

thats cool I just see alot of blown cars with shot front bearings and even broken crank snouts on cast and cast steel (newer style aftermarket, not like like your stock steel) cranks. alot of blown cars run no balancer at all because the belt absorbs alot of harmonics for you, but thats not what I'm talking about, but it seems to work OK to my surprise (I wont do it)