I'm installing a VDO CHT gauge. I've read that in order to make changing spark plugs easy, some amount of material needs to be removed from the head in order for the sender to clear it. I'm looking for a good photo showing this before I break out the Dremel tool and start grinding. A picture showing how you bent the sender ring would also help.

Also, I've read that the sender ring replaces the spark plug's crush washer. Is this accurate?

Yes, it replaces the washer. I don't think you should remove metal from the head. I'd think that this would place a stress riser on the Cyl 3 spark plug hole, which is prone to cracking as it is all ready.

Zach

http://www.pelicanparts.com/catalog/images...temp_sensor.JPG

Damn, I guess I'm stupid. I just put it under the plug and bent the tab on the ring.

Since the "ring" is not a crush washer, I can't see how placing it under the crush washer would cause any problems.

Yeh, mine works both on the 4 and the 6.

I just removed the crush ring from the spark plug and the cht sender is the new gasket. works great for me! better than dicking with the heads!

It's much easier to change plugs if you notch the head. This needs to be done with the head on a work bench. I use a 3/8 egg carbide burr. Remove material that is between the vertical webs and work down until you are very close to the crush washer seal surface, but don't nick it. One must be very careful! When done correctly the sensor will lay in the head and stay in position during plug changes. We do all of our race heads this way. Unfortunately I have no photos.
We remove the crush washer, though it wouldn't be the end of the world if you left it in place.

Does putting the VDO sender under the stock sender work?

No, head temp always measured under #3 spark plug. The stock sender location is for the fuel injection only and won't be giving you accurate temp. readings.

Anyone have a picture of a CHT installed? To my newbie's eyes, the picture Jim linked to and the other descriptions almost sound counter intuitive. Does the CHT mount in the #3 spark plug hole and the spark plug into the CHT?

Thanks!

there IS a thread on this, i just can't find it...

I would prefer not to remove the head in order to make a notch. My thought was to find a bolt to fit the spark plug hole or just use from electrical tape to cover the hole to prevent metal from getting in the combustion chamber.

The prblem with doing this notching with the head on the engine, in the car, is that this operation requires precision work. Getting in the correct position would be tough. Sticking a bolt in the plug opening will prevent you from being able to notch low enough to make a difference.

If you don't want to remove the head I would just bend the tab and run it as is. A failed attempt at this operation could open a can of worms that would force you to remove the head.

Placing the sensor anywhere but under the plug will not give you a meaningfull reading.

This is the state of my engine currently, so I have great access to the head. It would seem that the sender ring would get in the way of the spark plug socket.

Click to view attachment

dude, just put the vdo CHT ring under your #3 plug after removing the crush washer and be done with it.

What he said

Ron, which cylinder did you use on the six?