<VV> engine issue

[kevin nash]

> Message: 3
> Date: Mon, 29 Nov 2010 09:22:27 -0600
> From: "Bill Bicknell" <bicknell at cfanet.com>
> Subject: <VV> Engine issue
> To: <VIRTUALVAIRS at CORVAIR.ORG>
> Message-ID: <001601cb8fd9$3ba2eec0$b2e8cc40$@cfanet.com>
> Content-Type: text/plain; charset="us-ascii"
> 
> I have recently acquired a 1962 Rampside with #2 piston burned from what
> appeared to be detonation. All other pistons/cylinders looked normal.
> After replacing the piston and honing the cylinder to clean up the aluminum
> transfer, the same #2 piston became burned due to detonation. The engine
> would idle fine at 14 degree timing, but with lack of power. At about 18
> degree timing it seemed to run reasonably and with good power, but with
> pinging noticeable when starting from a dead stop. I have replaced the #2
> piston again, this time with a different used cylinder and still notice the
> detonation from start, but haven't driven it much until I can learn more
> about what's going on.
> 
> 
> 
> When I replaced the first piston, I also changed rings and bearings and
> timed the camshaft to the crankshaft as accurately as I could determine.
> This seemed to be a challenge. I used keyway positions checking with
> machine squares. Since such advanced distributor timing is required, I am
> still wondering if this is an issue. What is the best technique for this
> timing operation? But why did the same cylinder position have the problem -
> coincidence?
> 
> 
> 
> I have been rebuilding conventional water-cooled engines for decades, for a
> while professionally, so I know engine basics but something is eluding me
> here. Perhaps something unique to Corvairs. Knowing that
> pre-ignition/detonation can initiate from carbon build up and/or sharp
> edges, I wire brushed all combustion areas, valves, and valve cavities
> clean prior to assembly. All fins were cleaned to avoid hot spots. The
> sheet metal air deflectors are in place. The thermostat properly opens the
> air deflector valve when the engine heats up.
> 
> 
> 
> Can someone help with some suggestions?
> 
> 
> 
> Bill Bicknell
> 
> Home/office:573-364-8586
> 
> Cell phone: 970-218-1352
> 
  Bill- A couple of suggestions that I have would be to check that the compression on #2 is not way different than either #4 or #6. Also, that the
valve lift on both the exhaust and intake on #2 is not way different than #4 or #6. Also, see if both valves start opening at approximately the same
point as #4 and #6. One of those tests is going to tell you why #2 is so much more ping prone than the other cylinders!
 
Kevin Nash, 63 spyder, daily driver