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Tech Q&A Special Edition: V6 Timing Belt Tensioner Installation
Article and Photos by Rex Chalmers

Judging by the number and content of your questions of late, it appears that there has been much debate over the relative merits, proper installation procedures, and adjustment techniques for the mechanical timing belt tensioner fitted to Alfa V-6 engines. As to the merits of the mechanical tensioner, the subject has been argued ad nauseam. Personally, I prefer using a modified hydraulic tensioner, but that is fodder for another article at another time. This article will concentrate on the installation and adjustment of the mechanical tensioner.

All of the photos for this article were taken while converting a freshly rebuilt '85 GTV/6 engine to a mechanical tensioner. The text of this article borrows heavily from Alfa Romeo Technical Bulletin #01.93.04 and from the tech bulletin published by our friends at Centerline Alfa parts. The full text of the Centerline article is available at Or, for the digitally challenged, phone 888-750-2532.

Once you get the radiator, hoses, belts, and timing belt covers removed, it is essential to find Top Dead Center #1(TDC). First remove the sparkplugs and rotate the engine clockwise until the pointer is aligned with the line next to the “P” on the crank pulley (See Photo 1). Now remove the distributor cap and verify that the ignition rotor is pointing at the #1 post on the distributor cap. At this point it is a good idea to mark the position of the ignition rotor relative to the distributor housing and camshaft pulley referencing a point on the cylinder head. I generally use paint to mark the distributor housing, one tooth on the pulley and a reference point on the cylinder head.

Now remove belt and the old style tensioner. Save the thick flat washer, as you will need it to properly install the mechanical tensioner. If you already have a mechanical tensioner installed, now is a good time to check the back of tensioner body and make certain that the springs are not broken or corroded. I recommend changing the tensioner when you change the belt, it can be a very cost effective move. You guys and/or gals with the mechanical tensioner already installed may now skip to the belt installation section. The front of the engine should now look like this with the hydraulic tensioner removed (See Photo 2). Next, remove the hollow oil feed stud with either a stud remover or by double nutting the threads on the end of the stud (See Photo 3).

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It’s time to tap the oil feed-back hole. First put a dab of grease on a small piece of shop rag and insert it about .75” into the hole. (See Photo 4). The next step is to drill out the hole. Install a piece of tape .5” from the end of the drill so that you only drill .5” into the hole. You will note that the hole is machined into the block at an angle, this is normal, just follow the angle with your drilling and tapping. First use a 1/4” drill and enlarge the hole .5” deep. Now do the same with a 17/64” drill. Vacuum the drilling slag out of the out the hole, making sure to leave the greased rag in place. Spray the hole out with brake clean. Apply aluminum taping fluid to the hole and to an 8X1.25mm. tap. Proceed to tap the hole about .5” into the hole (See Photo 5). Now clean out the hole again and remove the greased piece of rag and use a vacuum to clean. Use a light and a mirror to make certain that all debris from the drilling and tapping have been removed (See Photo 6). Now install the 8x1.25mm. Plug that Alfa provides. Note that the end of the plug must be below the surface of the block to allow for proper seating and movement of the tensioner. Be sure to use thread locker on the plug (See Photo 7).

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Now install the Conversion stud (See Photo 8) into the hole that the oil feed stud used to occupy by double nutting the 8mm end of the stud (See Photo 9). Again, be sure to use thread locker on the 10mm end of the conversion stud. We are now ready to mount the mechanical tensioner (See Photo 10 and 11). Next, install the tensioner on the studs (See Photo 12), using the OE thick washer you took off when you removed the hydraulic tensioner on the lower stud. Use a new nut and washer for top stud. Snug the nuts down but do not tighten at this time (See Photo 13).

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Neither, it's publisher, FORZA Modern Media, LLC., or the individual article authors makes any warranties, expressed or implied, that the techniques, modifications, and procedures outlined in these stories are free of errors and omissions, meet applicable safety standards, or are suitable for the purposes described. The publisher and authors also expressly disclaim all liability for damages that may arise from the use of information presented in these articles.

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