<VV> Question on Hot Knocking - Update

[Todd Miller]

Frank.  I will check the compression, but I am thinking that shouldn't be the issue as the engine was completely rebuilt after a piston ring break less than 2000 miles ago.  It is a 110 hp, desmogged, with a Pertronix ignition.
 Todd 
In a message dated 10/26/2023 11:40:42 AM Central Daylight Time, virtualvairs at corvair.org writes: 
Sounds like you have high compression. Higher than GM made it. The 
compression can be high from carbon build up.

Do a compression test and see what numbers you get.

The old decarbonizing trick is to fill a "pop" bottle with water. Warm 
engine up. Take off air cleaner assembly. With engine running, dribble 
water into a carburetor (Corvair), increasing speed as engine slows 
down. Do NOT pour enough water in to stall the engine, as it can 
HYDROLOCK and that is very hard on connecting rods. Use a bottle (or 
whatever you can dribble from about 12 to 16 ounces) in each carburetor 
(assuming  two cab Corvair, no need to do secondaries on a 140, and 
turbos are too hard to do this trick 😉).

I've had to do this an several cars back in the day, inlne 6s and V8s.

GM makes a top engine cleaner if you want to use a more expensive 
product. That is a solvent, so it will cut more carbon/dirt along the 
intake path that water does not do. Water just steam cleans the piston 
tops and combustion chamber. I also do this before taking an engine 
apart, as it is nicer to work on cleaner parts!

Frank DuVal

On 10/26/2023 10:57 AM, Todd Miller via VirtualVairs wrote:
> I thought I would provide an update on the Hot Knocking (or pre-ignition) in my 69 Monza Convertible, 110 hp, 4-speed.
>   I bought some Boostane Professional Octane Booster from Amazon and added enough to bring the 93 octane fuel up to 98.  They have an app that tells you how much to add to whatever octane you put it in to bring it up to your preferred octane.  I drove the car 65 miles yesterday to deliver it to my son's for the wedding and it ran really well.  When hot, I might have heard some very brief, much quieter pinging/pre-ignition one time while taking off from a stop sign.  I might be sensitive to the sound, but it is SO MUCH BETTER!  I didn't want to retard the timing because the car runs so well.  I only need 4.5 ounces of the stuff to bring a tank of 93 octane to 98.  Adding a little more would raise the octane to 101 or more.  So, for the price of one gallon of Premium per tank, I am able to raise the octane up and have the performance I expect as well as severely reducing or completely eliminating the pre-ignition when hot.  I will play with the amount as I go on but I am guessing that the more I run it the better it will get.
>   Thanks for all the responses.  Great people and a great forum! Todd in Texas69 Monza Convertible 110/4spd65 Corsa Convertible 180/4spd
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