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Posted by: Cevan Nov 29 2007, 08:03 AM

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?

Posted by: Vacca Rabite Nov 29 2007, 08:26 AM

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

Posted by: jimkelly Nov 29 2007, 09:23 AM

http://www.pelicanparts.com/catalog/images/new_images1/914_head_temp_sensor.JPG

Posted by: SLITS Nov 29 2007, 10:05 AM

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.

Posted by: purple Nov 29 2007, 10:30 AM

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!

Posted by: HAM Inc Nov 29 2007, 03:34 PM

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.

Posted by: chris914 Nov 30 2007, 12:08 AM

Does putting the VDO sender under the stock sender work?

Posted by: Hammy Nov 30 2007, 02:26 AM

QUOTE(chris914 @ Nov 29 2007, 10:08 PM)

Posted by: HalM Nov 30 2007, 07:07 AM

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!

Posted by: lotus_65 Nov 30 2007, 07:48 AM

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

Posted by: Cevan Nov 30 2007, 08:21 AM

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.

Posted by: HAM Inc Nov 30 2007, 08:26 AM

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.

Posted by: Cevan Nov 30 2007, 09:13 AM

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.

Posted by: purple Nov 30 2007, 07:36 PM

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

Posted by: Elliot Cannon Nov 30 2007, 07:40 PM

What he said

Posted by: Elliot Cannon Nov 30 2007, 07:43 PM

QUOTE(SLITS @ Nov 29 2007, 08:05 AM)

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.