Back to the Back Side method ?

[Don LaVance]

I am all for change but need some clarification on two points before I mess things up.
1. do I use the .025 (0.63mm) for the go clearance feeler gauge?
and the .030 (0.75mm) as the no go clearance feeler gauge ?

Or, is it ment to use the much smaller .003 0.08mm as a no go?

or something else entirely.
I understand that the normal clearance on the tappet/valve stem approach would be .004 or 0.10mm.

Also am I going to need longer feeler gages to do it the backside procedure.
Thanks in advance. I don't want to do this and worry about it later.

[AVDCAV]

If you go to the pp home page on the left are the tech
Articles . Under 911 scroll down you" ll see the entire guide.

Or do you just have guage questions?

[Bob Kontak]

Believe you need regular feeler gauges. I have tried the backside method but have not spent enough time to understand it fully. I double checked with the standard method as it seemed weird to me. It clearly can be used successfully as many swear by it.

[K Sykes]

Your option 1 is correct.

[JAR0023]

.0025 for the go and .003 for the no-go.

I"m collecting tools and parts for my first valve adjust. I want to try both front side and back side methods.

You can buy Starrett 1/2" wide by 12" long feeler guages from Amazon (w/ Prime) for about $2 each. I did not see that our host carries them. -J


ETA - Cut and Paste from Pelican tech article.

Why do we use a .0025" feeler?

Simple math. The ratio of the rocker as it sits against the base circle of the cam is 1.4 to1.

This means the .004" gap at the rocker swivel foot and valve stem is 1.4 times greater than the gap at the point where the other end of the rocker contacts the base circle of the cam.

So if we divide .004" by 1.4 we get .00286". Actually .00285714286",

So .00286" is a rounded off number. Plenty close for what we are doing.

To answer the question why a .0025" feeler?

Since it is smaller than .00286" it will slip easily into the rocker/cam gap.

We now have a GO gauge, .0025".

As a Go gauge it will slip into the rocker/cam gap unless the gap at the other end of the rocker is less than .0035".

Now the NO-GO gauge .003". This should not slip into a properly set gap.

[snbush67]

Don,

To make things easy when I first started using this method, I took a two Popsicle sticks, black electrical tape and the two gauges. I taped a gauge in-between each end of the Popsicle sticks which gave me a handle and some additional length to work with.

This little tool saved me a bunch of time as all I had to do was simply flip the tool. Also the Popsicle stick with the shortened gauge on the ends provided a firmness that you don't normally get from the regular length of gauge. Without the firmness of the Popsicle stick the thin gauge has a tendency to fold or bend when it should slide in.

After some experimentation I managed to create a better tool using some scrap steel and small set screws.

[Don LaVance]

Good tip on the popsicle stick holder mod.
I believe I understand both front and back procedures I am just having some trouble with the suggested feeler gauge sizes.
.003 is much different than .030.
.030 is equal to 0.75 mm.
.003 is way smaller.
From the replys I am thinking
.025 or (0.63mm) for the go size. .030 or (0.75mm) as the no go size, Correct?
Thanks to all.

[K Sykes]

Sorry, posted wrong before. .003 and .0025 are right. A bit less than the .004 for the conventional method, due to the geometry explained above.

[dhagood]

Originally Posted by Don LaVance

From the replys I am thinking
.025 or (0.63mm) for the go size. .030 or (0.75mm) as the no go size, Correct?
Thanks to all.

you are an order of magnitude off. the gauge sizes are .003 and .0025

the gauge sizes are not .03 and .025

[Don LaVance]

I guess my confusion was that I can't seem to find a .0025 feeler gage but have many .003 which is the same as a 0.08mm one.
What would the .0025 be in mm perhaps I can find one of those.
I appreciate all of your patience and understanding.

[47silver]

i tried this back side go no go,, seemed more difficult then using the correcct tool.
i bought 4 tools from a fellow pelican who had a ton of them with fresh feeler gauges and away you go

[JAR0023]

Originally Posted by Don LaVance

I guess my confusion was that I can't seem to find a .0025 feeler gage but have many .003 which is the same as a 0.08mm one.
What would the .0025 be in mm perhaps I can find one of those.
I appreciate all of your patience and understanding.

Starrett 667-2 1/2 Steel Thickness Feeler Gage,0.0025" Thickness,1/2" Width,12" Length: Amazon.com: Industrial & Scientific


Starrett Steel Thickness Feeler Gage,Inch,1/2" Width,12" Length: Amazon.com: Industrial & Scientific

[Don LaVance]

Hello and thank you Jaroo23.
I will order one. tomorrow. It is just what I need.
Don

[Ronnie's.930]

Originally Posted by 47silver

i tried this back side go no go,, seemed more difficult then using the correcct tool.
i bought 4 tools from a fellow pelican who had a ton of them with fresh feeler gauges and away you go

My experience was the polar opposite - I found the backside method to be my easier/quicker . . .

[NOLAsc]

Originally Posted by Ronnie's.930

I found the backside method to be my easier/quicker . . .

Me too. Worked nicely for me on my first adjustment. I also tried the traditional method. I have a little cable tie holding the two feelers together.

It's about time to check the valves again.

[47silver]

i have to reread that post,, maybe i did it incorrectly, i was not comfortable with my results when i checked a few with the traditional method.

[kodioneill]

The go no go method is the only way I adjust valves. It gives you definitive answer while adjusting. The standard method is inaccurate because you can tighten the adjusting screw down and pull the gauge out even though the adjustment was to tight. With the g n g method you can't force the feeler in under the rocker and over compensate or under compensate and you get a genuine feel for the clearance. I love the Popsicle stick idea to stabilize the feelers. All the VW's I worked on in the 70's and 80's had shims in buckets and the only method used was such.

[AVDCAV]

Ooohhhh Noooooo. Let the comments begin
We all know very well. Pelicanites don't like words like
Inaccurate or standard. We're a twisted bunch so we need words like
Optional , available and our favorite " possible

This should be a poll because it comes up so much.

[Don LaVance]

Anyone in the S.F. Bay area contemplating trying this method and willing to have the various aspects documentated/ photographed for viewing here. PM me.
This forum has been good to me. Time to payback.
Don

[Bob Kontak]

After reading the link info JAR0023 posted, the backside makes sense now and I will try it next time. Wish I would have understood it fully in the past as it is an excellent double check for guys that do adjustments only once every couple of years on their own cars.

I don't think I would do it as the only check first time through but experience is a good teacher. I swore by a dial indicator until I was instructed (well, batch-slapped) and experienced the standard feeler gauge method. Dial indicator was a huge and needless time soak.