Classic Alfa UK

Alfa Romeo brake system overhaul, Part 2

RichardReina Alfa Romeo GT 1300 Jr., Events, Repair sessions , ,

As you read in Part 1 of the Alfa Romeo brake system overhaul, the new front calipers I had purchased, through no one’s fault, didn’t get the job done. It was just as well; in an attempt to get my car ready to drive to the AROC Convention in Pittsburgh, I was hurrying through the job, which is no way to work on a braking system. If anything, the inability to make the car roadworthy gave me just the excuse I needed to do the right thing.

 

I had purchased this car in 2013 from my friend Pete. He bought it in 1968, drove it for perhaps five years, mothballed it for over 20 years, then took it out of long-term storage. After refreshing various systems, including the brakes, Pete enjoyed the car for about 10 years before handing over the keys. In my mind, this Alfa had been “recently” refurbished. However, once I added up the years and the miles, I realized my own miscalculation. At best, Pete worked on the brakes around the year 2003, meaning, the brake fluid alone was now 16 years old. Shame on me! Since I loved driving the car, I wanted 100% confidence in its brakes, so The Right Thing meant a complete overhaul: rebuilt calipers, new or rebuilt master cylinder, and new lines and hoses. I got all 4 wheels up off the ground, drained what little fluid remained, and brought both front calipers to the workbench.

Caliper with piston, dust boot and spring in place before removal

First, the dust boots and their retaining springs had to be removed. The springs were so rusty that it was difficult to see them against the boots, but with a little urging from a dental pick, they popped off. The boot for the seized piston looked like it had been on fire (it almost was), and this early discovery reinforced that this overhaul was necessary and overdue.

 

Dust boot and rusty old spring on their way off

 

This dust boot is ready for the trash can

 

I’ve rebuilt calipers before, as a Volvo tech, but it wasn’t a job we did very frequently. All 4 of my car’s calipers are of the two-piston fixed type, and research from my Alfa library led me to conclude that there was no need to split the calipers. The pistons could be removed with compressed air, and the bores cleaned up as necessary.

 

This 2-piston caliper has 1 piston behind each pad. It is “fixed”: the two halves are bolted together.

Starting with the seized right front unit, my technique was to start by pushing the pistons back into their bores with a piston compression tool. The reasoning is that any movement is good movement. Once they were fully retracted, I hit the fluid passage with compressed air, and both pistons moved outward a few millimeters. The cycle was repeated: retract pistons, apply air; retract pistons, apply air. Finally, one piston popped free.

At the start, piston retraction tool was used to push pistons all the way back

 

Compressed air is good stuff

 

But now I had a problem: the compressed air escaped from the now-empty bore, and did nothing to move the piston still in place. I reinstalled the removed piston, but the same thing happened: one piston came out, and one stayed in. I needed a way to block the fluid passages without fully reinstalling the first piston. Stuffing rags into the bore did nothing.

C-clamp is employed to hold 1st piston while compressed air dislodges 2nd one

Here’s how I did that: lubing up the piston with brake fluid, I reinserted it just a few millimeters back into its bore, enough to block air flow, but not so much that I couldn’t pull it out by hand. I held this piston in place with a C-clamp, so the force of the air would blow out the 2nd piston. It worked! The 2nd piston shot out, and once I removed the C-clamp, the 1st piston could be worked out with my fingers. With the pistons out, the inner seals were easily coaxed out with a dental pick.

Removal of the inner seal

A close examination of the pistons revealed that one had a mark along its surface. My local Ace Hardware store had 3M brand emery cloth which I bought in medium, fine, and super fine grit. While I couldn’t completely remove the nick, I smoothed it out so that it couldn’t be felt. The front lips of the pistons showed marks from pliers or Vice-Grips, so someone (not me) got aggressive with a prior piston removal attempt. Thankfully, the marks would not affect the braking performance.

The bores themselves showed some minor corrosion along the outer edges, but the insides (below the inner seals) weren’t bad, and the super-fine emery cloth made them even better. While this was going on, the rear calipers were unbolted and disassembled so that I could measure the piston diameter. According to my supplier, Classic Alfa, this generation Giulia used either 30mm or 36mm rear pistons, and of course, one needed to know before ordering parts. It turned out that my car has 30mm pistons. I placed my order with my favorite Alfa supplier, knowing that I’d have the parts within 48 hours or so.

 

 

Pistons before (left) and after (right) emery cloth treatment

 

Nick in surface could not be removed, but was minimized. Note pliers marks.

 

Rear caliper piston confirmed as 30mm

 

… to be continued …

 

All photographs copyright © 2019 Richard A. Reina. Photos may not be copied or reproduced without express written permission.

 

 

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Alfa Romeo Valve Adjustment, Part 1

RichardReina Alfa Romeo GT 1300 Jr., Events, Repair sessions , , , ,

The owner’s manual for my 1967 Alfa Romeo GT 1300 Junior calls for the engine valve clearances to be checked every 18,000 kilometers. According to Google Calculator (before Google Calculator I would have used my slide rule), that’s every 11,185 miles. Coincidentally, I’ve put almost exactly 11,000 miles on the Alfa since purchasing it in March 2013. So in part to prepare for what is anticipated to be a very busy 2019 driving season, and in part because I really don’t know when this was last done, I decided to check all 8 valve clearances (4-cylinder engine, 2 valves per cylinder equals 8 valves).

The Alfa engine, before any disassembly

Accessing the valves and followers is the simple part. This overhead-cam engine has its two camshafts at the very top. The valve cover can be removed once the spark plug leads, air hose, and the top of the intake plenum are out of the way, which is a 10-minute affair. The valve cover is held in place by 6 large Allen screws along the top, and two bolts at the front. I had never had the valve cover off this engine before, and my first reaction was one of pleasant surprise at how clean the engine looked.

Valve cover removed

My first task was to find the camshaft part numbers, to verify that these were Alfa Romeo cams and not some hot aftermarket replacements (in which case the clearance specs would be different). A prior conversation with Pete, the family friend who sold me the car, revealed that he wasn’t sure what cams were in it. The part numbers of both cams were readily visible, and verifying them against my technical literature confirmed that these are indeed the factory cams.

This is the correct part number for a 105-platform 1300 Junior engine (105020320001)

Now it was onto the actual clearances. To rotate the engine, I first tried getting a socket on the crank pulley bolt, but the fan shroud blocked that. The next-easiest way to spin the engine was via the nut on the front of the alternator. Popping out the plugs provided less compression resistance, and some moderate thumb pressure on the alternator belt was all that was needed to get the crank and cams to spin.

Paper and pencil at the ready, the valve clearances were checked in firing-order order (1-3-4-2) and recorded. While my owner’s manual provides specs in both millimeters and inches, I decided to stick with the metric measurements – I have metric feeler gauges, and the needed shims are sold in metric sizes.

The spec for the intake valves is 0.475-0.500 mm, and the exhaust spec is 0.525-0.550 mm. Six of the eight valves were out of spec: all 4 intakes and 2 exhausts, and, all 6 showed too little clearance, meaning the valves were not seating completely, subjecting them to less cooling since they were not making full contact with the valve seats.

The worst measurement was #4 intake: 0.350 mm, meaning it was 0.150 mm too tight compared to a correct outer range of 0.500 mm. Yes, we’re talking fractions of a millimeter, but specs are specs, and I felt that the clearances should be corrected.

Here is where it got interesting. My Alfa engine was originally designed in the early 1950s. It’s a very sophisticated layout, with not only overhead cams, but all-aluminum block, wet cylinder liners, hemispherical combustion chambers, etc. However, like most other OHC engines of its time, adjusting the valves requires removing the cams to allow access to the followers (buckets) and shims which are under the buckets. Most friends to whom I mentioned this procedure looked at me with a combination of horror and pity. “It’s really easier than it sounds” I would retort, which did nothing to alleviate their sympathy for me.

(As a complete aside, the first OHC engine to incorporate a valve design which allowed for adjustments with cams in place was the Fiat twin-cam engine, introduced in 1966. My 1970 Fiat 124 Coupe used this design, although I never did adjust those valves!)

The timing chain’s master link is to the left of center

The official Alfa procedure calls for locating the timing chain’s master link, disconnecting it, and swinging the two chain ends out of the way. This method opens the possibility that the cam timing would need to be adjusted at reassembly. Of course, some very clever people have devised a work-around. One of the service books I own is the Alfa Romeo Owner’s Bible, written by the late Alfa expert Pat Braden. He describes a method that does not involve unhooking the chain. Instead, he suggests loosening the chain tensioner, pushing the tensioner all the way IN (making for a loose chain), locking the tensioner in this position, and then lifting the cams toward the center of the engine without disturbing the cam sprocket/chain connection. In this way, on reassembly, the cam timing does not change at all. Ideally, this is done with both cam timing marks lined up with the bearing cap marks.

This is exactly what I did. With the tension off the timing chain, I started on the intake side and removed the 3 cam bearing caps (Alfa thoughtfully numbers the caps 1 through 6, and I documented everything with photos before turning the first nut). The intake cam was lifted and placed over the spark plug holes (which were protected with clean rags). The chain remained on the cam sprocket.

Cam bearing cap #3 – cap nuts were loosened gradually

 

Intake cam lying over spark plug holes- note timing chain still on cam sprocket

The next trick was getting the buckets out, as they were oil-covered and lacking a way to grab them. I realized that a magnet might do the trick, and it did. The bucket came out, and under it was the shim, which was also removed.

These slippery guys were tricky to remove!

Working on just one cylinder at a time so as not to mix up any of the locations, I measured each shim with a digital metric micrometer. The value was recorded on the same sheet of paper as the clearances. I started on the #1 intake valve, went down the line to the #4 intake valve, then did the same thing on the exhaust side. Once all these measurements were taken, the shims and buckets were back in place on the engine. I gently placed the valve cover on top of the engine, lowered the hood, and took my measurements inside so that the ‘new’ shim sizes could be calculated.

Bucket/follower (top) and shim (left) pose with micrometer

 

Starrett No. 216 records a shim value of 2.15 mm

I knew that all the out-of-adjustment valves were tight, so I needed greater clearance, so all the new shims needed to be thinner than the current shims. I found an online “Alfa shim calculator” someone built in Excel, and I used it, but I also checked all my numbers two more times. I aimed for the higher end of the spec, figuring that if the valves are tightening up over time, I had best start by providing the maximum clearance while remaining in spec.

 

Documentation of initial clearances and shim thicknesses

My go-to Alfa supplier, Classic Alfa in the UK, sells shims in increments of 0.125 mm, so it was a fairly easy task to calculate my needed shim sizes. The order was placed, and now I just needed to wait for the shims to show up. But it certainly felt like the hard work was behind me!

 

All photographs and video recordings copyright © 2019 Richard A. Reina. Photos may not be copied or reproduced without express written permission.