Replacing the Rotor on an Alpha Twin-Spark 164

Editor's Note: CR4 would like to thank JohnDG for blogging about repairs he made to his 1989 Alpha Romeo 164, a car whose Twin Spark engine had a two-stage valve timing system before Honda's more famous VTEC came along. Cheers, John!

Back in 2000, I was running an '89 Alfa Twin-Spark 164. On a drive back from Cumbria to Reading (about 350 miles), up across the Kirkstone Pass (not stopping!), it started missing, and was struggling up some of the 20% gradients. I pushed on down to the M6 motorway, then sat at about 70 mph for the next 200-odd miles. The engine was alternately trying to race, then losing power. It was gradually getting worse, so I finally pulled into a service area, and called Green Flag (I used to be OK with my old Ford, but I mostly left the T-Spark to the pros!). The guy found that the rotor arm in one of the distributors was completely shot – only the central sleeve was still there. He couldn't replace it, so recovered us the last 40 miles to Reading.

Next morning, I checked out the listed rotor arms at Halfords, but couldn't find one for the T164. I called an Alfa dealer, and was told that the rotor arms where not replaceable, and I'd need a new distributor (about £200 + labour). I checked out the other distributor, and sure enough, the rotor arm was bonded onto the shaft. The kit was Bosch – and it occurred to me that German engineers wouldn't be daft enough to produce distributors which had to be junked because of rotor arm failure. I guessed it was bonded on because it was a "high-performance" version.

I got the part number off the distributor cap, memorized the shape of the intact rotor arm, and went back to Halfords. Trawling through the lists, I found the cap listed, and cross-referenced it to the arms that appeared to work with it. I picked the one which looked most like the one I had, and bought it (about £2-ish). I took it back, and eye-balled it against the intact one – it looked like a good match.

I then cleaned off the remains of the broken rotor, which seemed to be something like GRP, epoxy bonded to the distributor shaft. I chiseled most of it off (with old blunt woodworking tools), cleared out the keyway with a small screwdriver, and rubbed off the remaining bits with wet'n'dry. Offering up the new rotor, it was a perfect fit on the shaft.

After replacing the cap, it started up first "kick", and as far as I know (last heard about 6 months ago from the guy I sold it to), it's still running fine.

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