Looking for knowledge. I installed a cgr-30 on my O-360 and one of the cht probes is bottoming out. Has anyone heard of this before? EI mentioned drilling it a little deeper but didnt really tell me to do it. Superior wont return my calls. Lawson that overhauled it said he wouldnt do it. Lycon hasnt got back to me. I only need about 1/8". They are millennium cylinders about 4 years old. Thoughts?

I spoke with my two colleagues in sales/support and neither of us could recall suggesting to drill and tap the cylinder wells deeper. That's getting into an area of liability that we certainly would not be comfortable suggesting and recommend consulting with a certified mechanic before proceeding. Maybe there was a misunderstanding, but I wanted to clear up our position.

Have you tried to install a different probe in the suspect cylinder in an attempt to isolate the issue to a single cylinder, or possibly a manufacturing defect on a single probe?

I totally understand your position. All the probes are identical. I only posted on here to see if anyone has dealt with this or has any ideas

gassman wrote:I totally understand your position. All the probes are identical. I only posted on here to see if anyone has dealt with this or has any ideas

So, are you saying that NONE of the probes works? Or just that all the probes look alike? What he suggested is to switch to a different probe into that cylinder.

MTV

The other three probes work fine and they are all the same. For some reason this cylinder bottoms out just as the threads catch. I know this because the tip of the probe is scuffed and clearly came into contact with the end of the cht well. Also confirmed with a depth gage. Need about 1/8" more depth. Lycon did get back with me tonight and discouraged drilling any deeper for fear of going into the combustion chamber.

Why not just use a spark plug bayonet sensor and be done with it,,,Sounds like you got a mis drilled head...is it worth pulling a jug to set the sensor...? Perhaps worth checking when installing a new jug...small item but obviously important

The hobby machinist in me says measure the depth of the other three cylinders and see how deep they are and if they are all the same depth. If those three are the same depth it would be a good indication that the manufacture intended for the wells to be that depth and also that when drilled to that depth there was sufficient thickness of the cylinder head remaining. I would not want to drill that hole without a hard stop on the drill bit to prevent inadvertently drilling deeper than intended. Our you could go the safer route of asking the cylinder manufacture for a warranty replacement as it is clearly a manufacturing defect. The manufacturer would know the design depth of the hole and an error of this type would represent a failure of their FAA quality control program so you would think that they would like to have the opportunity to correct it.

Tim

Can you put a shim (washer) under the head of the CHT probe to space it up?

Or get a buddy with a lathe to build you a small standoff.

You may want to consider a different probe type. We manufacture a quick release (spring loaded) version of our CHT probes (P-101). If you'd like to try one out, I'm happy to send the adapter (see pic) to you in the mail at no charge. This is the piece that threads into the cylinder well. If it works in the suspect cylinder, the P-101 probes could be a simple alternative.

After further thought I think you would want to proceed with caution before drilling. The hole may go to the specified point in the cylinder head but the face the prob tightens against may be cut deeper than normal, be it just a flat face or a counter bore. Even though the cylinder is 4 years old I would expect my engine shop to help me with a claim with the supplier/manufacture as the problem is definitely a manufacturing defect. I do understand that none of use wants to remove a cylinder but that may be the safest thing to do. If there are enough threads on the probe I think the posted idea of a couple of washers is a good solution. Copper washers would be good.

Tim

Thanks for all the replies and ideas. I think im going to try the adapter before anything else. Ill report back