Valve Adjustment Visual Confirmation Trick

[lespaul]

This post is not for pros who have experience doing valve adjustments.

For those new to valve adjustments -- regardless of the method used, this may be helpful. I recently walked someone who had never done a valve adjustment through the process on the phone. He was concerned that the adjustment he had made was off. Besides using a dial gauge and/or feeling for the smallest tick when pulling on the rocker arm once the adjustment is locked down, there is a visual check you can use to confirm you adjustment is correct.

1. At the beginning of the process, firmly finger tighten the valve adjustment screw clockwise until it is bearing against the valve stem. While doing this, jiggle the valve adjustment screw back and forth to ensure you take out as much play as possible since you may have worn rocker arm bushings/shafts. At this point, you have 0 clearance space between the tip of the valve adjustment screw and the valve stem. Your goal is to get that space to 0.10 mm (+/- 0.05 mm). Too tight and you can burn a valve. Too loose and you will have valve clatter and less power. Shoot for perfect -- 0.10 mm.

2. Observe and note the orientation of the slot in the top of the valve adjustment screw using reference to a clock dial. Where is the top of the slot pointing? 1, 2, 3 or some other hour position or between two positions?

3. Adjust the valve using your preferred method and lock the adjustment into place.

4. Now observe the orientation of the slot. It should have moved to the left or counterclockwise 36 degrees or one hour + a smidge on the clock. If it did not move (or for some reason is on the right side of your original orientation!) the valve clearance is too tight and you need to re-adjust. Something went wrong. Besides pulling on the valve adjustment screw to feel the tick, this visual method will give you assurance that you have adjusted the valve correctly.

The theory behind this is simple. A full 360 degree turn of the valve adjustment screw converts to 1.0 mm of axial travel of the foot of the screw. To achieve the desired 0.10 mm adjustment, you need to open the gap by turning the adjustment screw 36 degrees counterclockwise. The 12 one hour marks on a clock are 30 degrees apart (360/12 = 30). Thus, if your initial 0 clearance orientation is at, say 2 o'clock, when you rotate the screw counterclockwise 36 degrees to open a 0.10 mm gap, you will move the orientation to just a little bit (6 degrees) before 1 o'clock.

I have done dozens of valve adjustments and no matter what technique I use (traditional feeler, backside, VAS tool or SNAPGAP), this additional method helps me confirm the adjustment with confidence.

[boyt911sc]

Brad,

I had done the “orientation” last month when I installed the SNAP GAP in a newly rebuilt motor. But I was NOT thinking of the correct adjustment but rather the change of original position/s afterwards.

This additional tip will further boost people’s confidence in using your product. I was one of the earliest recorded non-believer when this product came out. But that quickly changed. As a matter of fact, using a SNAP GAP will be one of the things I will emphasize in the next Engine Rebuilding Classes (2020). Keep up the good work.

NOTE:
I don’t know or have any business relationship with the OP. I’m just simply a convert.

Tony

[Bill Douglas]

In 25 years of 911 ownership, and checking the valves every 12 months, only half a dozen have needed adjusting.

I'd one that was very clicky. It didn't seen right. So I buttoned it back up and gave it a good Italian tune. After I took the valve covers off again it was fine. No adjustment necessary. Be careful, if I had adjusted it for when there was the (obvious) bit of carbon on the valve seat I'd have had a burnt out valve in no time.

[lespaul]

Keep up the good work

Thanks Tony.

[david.avrahami@]

Thanks Brad

[Reiver]

lespaul...I received the upgraded star socket fastener you sent gratis the other day....I appreciate a guy that stands by his products (valve lash system).

Thanks.

[Bill Douglas]

Thanks for doing the maths Brad. I'll print that up for my next valve adjustment and follow the procedure.

A guy on Adventure Rider XR400 forum welded something like a 100 mm nail to the shaft of a screwdriver, so it's like the hand on a clock. So he can move it "back one hour". Or so he can see if it moves (how much it moves) when he tightens the lock nut.

[lespaul]

Bill,

The Adventure Rider's tool sounds like the "VAS" tool, I covered in the following Blog article

https://snapgap.us/blogs/news/the-vas-tool-on-a-964-engine-a-sound-concept-but-still-has-all-the-flaws-of-the-oem-method

As you can see from my article and the accompanying video, in my opinion that tool is hard to use in order to get an accurate adjustment.