<VV> '63 Turbo crank journal clearances
Frank DuVal
corvairduval at cox.net
Fri May 30 23:32:02 EDT 2014
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.
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