<VV> '63 Turbo crank journal clearances

[Frank DuVal]

I also say do not use cast iron for turbo use.

I have used cast iron for simple re-ringing of worn Corvair engines back 
in the day, and might do it again on 145 cu in (those pistons do not 
grenade like used 164 cu in do). But turbo engines need to hold in a lot 
of compression/combustion gases. Much higher combustion temperatures.

As long as you are in there, put in new bearings. Unless you are 1. not 
going to drive the car hard 2. not put over 10k miles on it. Again, like 
cast iron rings, you could get away without replacing these in a low HP 
engine, but not for long term use. I did a lot of this "get by" work to 
keep used Corvairs on the road 30 years ago.

Frank DuVal


On 5/30/2014 9:31 PM, BobHelt--- via VirtualVairs wrote:
> Do what you think best, but my Shop Manual says that 3 thou is  max SERVICE
> clearance. I'd suggest that you replace those main bearings.  Running with
> your clearances will lower the oil pressure at idle and likely  illuminate
> the dash light when the oil is hot.
> Also, why do you think 5 of 6 rings were cracked? DO NOT use  cast Iron
> rings for your rebuild. Go Moly and the best you can  find.
> Just my opinions.
> Regards,
> Bob Helt
>   
>   
> In a message dated 5/30/2014 5:27:08 P.M. US Mountain Standard Time,
> virtualvairs at corvair.org writes:
>
> Hi
>
> I'm rebuilding my '63 Turbo motor. This is my first  Corvair engine rebuild.
> Today we plastigaged  the main bearings for  clearances. We did it by the GM
> Service Manual.
>
> Clearances were like  this.
>
> Main Journal #1= .003 (has the different style bearing with  thrust
> surfaces)
> #2= .003
> #3= .003
> #4=  .002
> We are thinking that these numbers are within tolerances and I will  not
> benefit from replacing these main  bearings with brand new main  bearings. I
> would be interested in hearing from more experienced Corvair  engine
> rebuilders out there so that I might draw valuable input from  more
> experienced Corvair mechanics.
>
> I will not be torture testing  this motor, exceeding red line.
> (Intentionally that is!) I do not want to  reassemble it with bearings that
> will cause my motor to grenade when I  spool the turbo a bit now and then to
> keep the turbo limber. I understand  that missing a gear can undo all of my
> hard work by causing an over rev. No  racing.
>
> The problems I found when we opened the engine up were as  follows.
>
> 5 of 6 top compression rings were cracked.
>
> #1 piston  skirt was cracked across the skirt but intact.
>
> All 6 skirt clearances  were about .005
>
> I've sent the heads out for rebuild by an experienced  Corvair technician.
>
> I plan on buying new rebored cylinders pistons  & cast iron rings .020 over
>
> The camshaft measured out with very  little wear. I plan on reusing it with
> new lifters.