Our Cars: Valve Adjustment for the308GTB QV

By Pete Vack

In which we tell you what we are doing, (not how you should do it), why it must be done, parts sources, good and bad, and how much it costs.

Currently off the road, the 308 is now in so many peices we wonder if it will ever be all together again.

OHC Valve Lash Adjustment Methods
The history of the overhead cam engine has been the history of a variety of interesting methods of valve adjustment. Alfa had a remarkably easy method of adjusting valves by a notched ring and threads. Expensive and a little noisy, but the cam itself did not have to be removed to adjust valves. This was before they decided to convert to an inverted bucket, with the pad sitting inside on the valve stem, which was introduced with the Giulietta models in 1954. Cheaper, but now the cams had to be removed to adjust the valves.

At left, the Lampredi method, with a hardened shim sitting on top of the inverted bucket. At right, the inverted bucket with inside shim, used on 1300-2000 Alfas .

The Ferrari V-12s did not have to worry about this as the Columbo and Lampredi V -12s did not use overhead camshafts directly over the valve. To make a short story long, many DOHC designs use a "finger" between the cam and valve, and while increasing complexity and reciprocal weight, it makes valve adjustment easier. The Ferrari Dino engines used the Alfa Romeo method of inverted bucket with inside shims.

Origin of the species
After a famous stint with Ferrari, Aurelio Lampredi went to Fiat in charge of engine design. For the new 124 Fiat twin cam in 1966, Lampredi still made use of the inverted bucket directly over the valve, but put a hardened adjustment pad (or shim) on the top (or bottom) of the bucket rather than beneath it. A tool depressed the bucket to provide clearance between the camlobe, allowing the shim to be replaced without entailing the removal of the camshafts. Notably, the Fiat TC was one of the first applications of toothed belts to drive the camshafts, another innovation carried over to the Ferrari V-8.

Two Ways to Skin a Horse
Hence, there are two ways of adjusting valves on a 308. If you have to remove the camshafts to replace the camshaft seals (which is always a good idea), valve adjustment is easy. Simply measure the clearance before the cams are removed, pop out the shims from the buckets, measure the appropriate pad thickness and do the numbers. The shims are easily removed while the cam is out of the way. Place the new shims into the buckets and replace the cams.

This is an image of the rear bank, cylinder 1. One of the easiest to access, note the very limited working space. Compressed air is blown into the slots on the side of the bucket to remove the shims.

The second method is more difficult primarily because of the very limited room available, particularly on the QVs, and particularly on the front bank. In addition to the cam being in the way, you must be able to manipulate the two shim removal tools, then blow compressed air into the bucket to get the shims to come out, while holding a light to be able to see what your are doing. Then rotate the engine to align the next set of valves in the fully closed position and start the procedure again.

Tools are 90% of the Job

From the Ferrari manual, the offical tools needed to depress the valve bucket and the holding device. Note that the manual illustrates the tools as applied to a two valve 308, with two less valves in the same space.

But first the proper removal tools must be acquired or fabricated. The Ferrari part numbers are A105 and A106. Similar tools can be ordered from T.Rutlands (1-800-638-1444) for $105--and be sure to tell Rutlands if it's a two or four valve car. In my case, I fabricated similar tools, but it took time and patience as the measurements are critical if the tools are to work properly and safely. Simply, the first tool (AS 9560) depresses the valve bucket by prying against the camshaft. The second tool (AS 9560 A) is a semi circular ring, which by resting on the side edge of the bucket, keeps the bucket depressed while allowing clearance for the shim to be removed. Note here that the bucket must be depressed all the way, flush with the surrounding well, in order to provide enough clearance for the pad to make its way between the camshaft and the bucket itself. Using screwdrivers in place of these tools is not recommended.

With the engine out and plenty of light and room, this is fairly simple. In-car adjustment is a different matter entirely.

Access to the front bank is limited only by your ability to be double jointed. The alternative, removing the entire engine, is not an option until all else fails.

Once you get the hang of it, getting the pads out goes well enough, but the front bank is not much fun. Practice on the rear bank first, then brace yourself for the acrobatics needed to get to the rest. Light is also a problem for no matter where it is it is never enough and placing the holding tool is critical. I used a rubber hose on an air compressor gun to reach the buckets, and it is easier if you thin out the oil which provides a suction between the shim and the bucket. Think a wet glass on a table. Worse with 50 weight oil. Spray Brakeclean between the bucket and shim first, and the compressed air will take care of the rest. Clean out all oil reside from the head or the compressed air will create a mist of oil. A small magnet helps to withdraw the shim.

Doing the Numbers
With the shim removed, measure it and figure the size of the new shim. Allen S. Bishop, author of "Ferrari Guide to Performance", advises to "replace any poker chip that has scoring or any odd-appearing wear pattern, even if the lash is within specs," further adding to "remember that modern synthetic oils are thin and runny. On cars such as Ferraris that are not driven daily, the synthetic oil cools down and drains into the crankcase, leaving the valve train quite dry after the engine has been shut down for a week or so."

While most feeler gauges now also have metric numbers as well as inches, my micrometers still read only in inches. Measuring the thickness of the shim requires multiplication by 25.4 to give you millimeters. Here's an example of the way to figure out new shim thickness:

Current valve lash (.35mm)
Desired valve lash (.030mm)
Difference is .05mm
Size of current shim (4.0mm)
Size of new shim (4.5mm)
Shims come in .05mm graduations.

At this point, the idea is to walk over to the bench where you will have a complete set of shims in a kit, ready to insert into each cam bucket. We’ll bet that you will not be in possession of such a kit. Therefore you will have to order new shims. In the meantime, it is best to put the old shims back into the buckets. Then, when the new shims arrive, you can go through the procedure again! Remember to thoroughly oil the valve gear and camshafts prior to replacing the cam covers. Allen Bishop also warns that you must be very sure that the shims, whenever re-inserted into the buckets, are in correctly. They have a way of getting 'cocked' and damage can result to the cam or bucket or shim if the shim is not seated fully into the bucket. After you’ve done 64 valve shim removals and inserts, you and your back will have wished you had removed the cams and did it the easy way. But removing the cams means you will probably want to replace the camshaft seals near the pulleys, ($140 for all four). It also means you'll go through the timing belt routine again. In both instances you will also need new cam cover gaskets, ($94.00) including the distributor and cam cover gaskets ($17 for all four). Shims are $4.50 each, and if you need all thirty two, add another $144.

Adding it up, and assuming all valves need adjusting, and you do it with cams in place, it will be $255. This does not include the cost of the Ferrari tools (I’m afraid to ask) or fabrication of a similar set of depression and hold down tools. If you remove the cams and replace the cam seals, total is $395. Compare that to adjusting the valves on a 350 c.i. Chevy V-8. The valve cover gaskets may have to be replaced at a cost of less than $10. Are you screaming yet?

Either way, valve adjustment is not an easy or inexpensive task. It takes time, the correct tools, some means of air compression (it is possible but even more difficult to remove the shims without air), and access is poor at best. You’ll have to order the pads after you remove and measure the existing shims, so that will take three days or more unless you can visit your friendly Ferrari dealer (and pay more of course).

There is a bright side. Once set, valves should be checked (per the owner’s manual) every 15,000 miles, and of course, unlike timing belts, is not time sensitive. Ferrari restorer Bishop agrees. "Once an engine is "run-in" and the valve clearance rectified, the sort of driving we do in the US will ensure that the lightweight 4-valve train will remain in adjustment for a loooong time."

And of course, valve adjustment could be much worse. On the early DB Aston Martins, the valves were adjusted by grinding the tops of the valve stems. So thank God for Mr. Lampredi.