Valve Adjustment, Part 3

Dan Sarandrea (Phila)

Waitin' On Parts...
Continued from Valve Adjustment, Part Two-B:
https://xwebforums.com/forum/index.php?threads/valve-adjustment-part-two-b.34270/#post-291964


In this last Valve Adjustment segment, you'll learn how to calculate the shim size needed and how to install the shims.

Up to this point, we've removed the cam box cover, measured and recorded the existing valve clearances, removed the existing shims and measured and recorded their thicknesses. Now we are ready to calculate the thickness of the shim needed to bring our valve clearances back into spec.

The calculation is:
(Existing shim thickness + existing valve clearance) - target valve clearance**** = required shim thickness.

So let's walk thru cylinder one Intake:
Existing shim thickness 3.90
+
Existing valve clearance .203
=
4.103
-
Target value clearance .32 (center of .28-.36mm range)
=
Required shim thickness 3.783 ~ 3.80

Makes perfect sense...the valve clearance was too small, meaning the shim (which sits between the valve and the cam) was too fat, so we had to choose a thinner shim.

Let's walk thru cylinder one exhaust:
Existing shim thickness 3.90
+
Existing valve clearance .356
=
4.256
-
Target value clearance .42 (center of .38-.46mm range)
=
Required shim thickness 3.835 ~ 3.85


You can also try one of the several valve clearance shim calculators on the internet (most of these seem to be for motorcycles), or do a search in the Store for your phone platform for valve shim clearance calculator app.

Now that you know what shim sizes you need, where to get them? Of course, our regular supportive vendors carry whatever shim sizes you need.

Another option is The Mirafiori Shim Exchange, a mutually supported cooperative started by the FIAT and Lancia enthusiasts who have been participating in the forum at Mirafiori.com for many, many years.

Here's how it works:
1. Make a list of the shims you need.
2. Email the list to the Curator of the Exchange, along with your contact information and mailing address. In your email note that you are a member of XWeb!
3. The Curator will send you the available shims by mail.
4. Remove old shims, install the replacements you got from the Curator.
5. At your expense, mail the removed shims back to the Curator, along with a donation that covers at the very least the to-you postage costs.


Mirafiori member Alvon Elrod is now the Curator of the Mirafiori Shim Exchange. Alvon has authorized me to post this information here on XWeb.

Email Alvon: ventura underscore ace at juno dot com (no spaces)
Call Alvon: eight zero 5, three three eight, one 7 six 7

Alvon also says to encourage those that aren't already participating at mirafiori.com to drop in and chime in.


Now to the task of installing the replacement shim. If you can read the printed size marking on the shim, most reference material will tell you to place that side of the shim facing the shim bucket and away from the cam lobe. Carefully lay the shim into or onto the recessed area at the top of the bucket. Get it as centered as possible over the shim bucket. Depending upon the individual replacement shims you have, the fit of the shim into the recess at the top of the bucket may be a drop-in fit, or a fit so tight that it will need the valve spring's pressure to pop it back into position. If the latter, once you have carefully positioned the shim on the bucket, drape shop rags over the cam box, one on each side of the bucket depression tool's handle, covering the bucket in question. Now rotate the bucket depression (aka valve adjusting) tool to release pressure on the bucket. With tight fitting shims, you will hear a loud "snap" sound as the shim is forced into the bucket. If you correctly positioned your shop rags, you won't be the victim of the oil spray:).

Once the shim snaps into place, CAREFULLY do a visual inspection to ensure the shim popped fair and square into the shim bucket. A displaced shim at this point would be major issue. Once you are satisfied that the shim dropped in where it is supposed to, squirt a bit of oil onto that bucket and shim, then exercise the valvetrain by rotating the engine with the right rear tire. Assuming no issues, after several cam revolutions, recheck the valve clearance on the just changed valve with the feeler gauge. If now within spec, you are DONE! If not within spec, try again!

Now that you've checked and replaced shims as necessary and confirmed that all valve clearances are now where you want them, it's time for a final visual and magnetic check. Using your best glasses and brightest shop light, put your nose in there closely and look for any dirt or debris that may have fallen into the cam box. Be especially on the lookout for tiny slivers of metal that may have been left behind by pick tools, screwdrivers, etc. Use your stick magnet and drag it thru the nooks and crannies of the cam box to help pick up any metallic debris.

Once you've gone thru all of the valves and done your final visual and magnet check, squirt or drizzle more clean engine oil over the cam to make sure it's nice and lubed, place your new gasket (so little pressure up here that a gasket sealer is probably unnecessary), and button up the cam box cover. FI peeps, make sure those FI harness grounds are good, clean, and tight. Accelerator linkage maintenance is a safety item, so please be sure to check for good operation of your return springs and do use anti-seize or a judicious dab of white grease on the two linkage ball joints. Replace the air intake hose, taking care to match the hose clamps up to the indentations in the FI intake hose that are there from years of set.

Start up, warm up, and then test drive to check for possible issues such as oil seepage or air intake hose vacuum leaks.

****Now some thoughts on the target valve clearance. Most folks would probably do well to establish their target valve clearance as the center of the OEM specified range. The argument for setting clearances at the wide or big end of the range would be that such a setting affords the longest run time before you have to set the clearances again, as normal valvetrain wear on the SOHC is always the narrowing or lessening of the clearance. The obvious downside to a wide setting is increased valvetrain noise. The argument for setting clearances at the narrow or small end of the range would be that such a setting would increase performance (how much this increase would be is debatable) due to the thicker shim allowing the cam lobe to push the valve away from its seat that much more, increasing valve lift. The obvious downside to a narrow setting is that readjustments are going to be more frequent.
 
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This might not be for the meek but I have ground shims to proper thickness on a grinding wheel, using a micrometer and an old shim bucket as a holder. You have to go slow and constantly mic the shim all the way round. Never had any problems and my valve adjustments were dead on.
 
Thanks!

Dan -- as always, REALLY appreciate your instructional posts with clear steps, descriptions and annotated photos. Not sure if/when I will choose to tackle a job like this, but posts like this help me to better understand how my engine operates. AND certainly paves the way for anyone to do the job if they want to. So thanks very much!
 
This might not be for the meek but I have ground shims to proper thickness on a grinding wheel, using a micrometer and an old shim bucket as a holder. You have to go slow and constantly mic the shim all the way round. Never had any problems and my valve adjustments were dead on.

And the ground face goes down when you install the shim, right?

The 2-valve Ferrari 308 uses the same shims and buckets, and this a common practice there.
 
And the ground face goes down when you install the shim, right?

The 2-valve Ferrari 308 uses the same shims and buckets, and this a common practice there.

Yes. If anyone tries it be sure to polish the ground side a bit so the puck can smoothly rotate in the socket. Also make it a point not to scuff the hard shiny side that goes against the cam lobe. By the way this is a very informative piece Dan. Even though I have done several valve adjusts on fiats I still find your write up interesting.
 
Great stuff Dan. Does Alvon have a Shim-Tool to loan?

If not... tell him to get back to me and I'll donate one of mine to the cause... that Brian so graciously gave me for the use of my original.
 
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