Valve Guides and Seals

by Kevin Faughnan

Originally published in the Austin-Healey Magazine, December 1973

All of our Healeys have reached the point where mechanical repairs are a fact of life. Generally one of the first jobs encountered is a valve job. Whether you do the work yourself or have a machine shop do it, one important item often overlooked is valve guide wear. Excessive wear will prevent a good valve job, allow the valves to wander off their seats, increase oil consumption, etc. This last item is particularly troublesome if the rocker shaft or bushings are worn. That extra oil vapor finds its way into the combustion chamber and onto the plugs, fouling them up in the process.

Valve stem-guide clearance is not a difficult spec to check. Factory specs for 4- and 6-cylinder Healeys are .0015 - .0025 inches intake and .001 - .002 inches exhaust. These figures are quite common to American engines as well. Motor’s manual and Glenn’s Auto Engine and Maintenance—a very good book—say when the clearance is .002 1nches or more in excess of factory specs, replace the valve or guide as necessary.

The factory manual gives good, clear instructions on removing and installing guides, so I won’t try to improve on that. Any good machine shop can do the entire job at no more that $1.00 per guide. If you want to check the wear yourself--and most Healey owners would probably prefer to—expensive tools are not absolutely required. First clean the guides and stems thoroughly with solvent. With the valve springs off, raise the valve to its full lift position (approximately). Rock the valve in the plane of the rocker, i.e. ii the width direction of the cylinder head. The greatest wear will be in this plane. If you can actually see the wobble, the clearance is excessive and new guides or valves are in order. F.G. Draper in England has the intake and exhaust. Guides at 25p and 30p respectively. If you can only feel the wobble but see no perceptible motion, the clearance is OK (Less than .004 inches). Of course if you have access to a mic’ and telescope gauge, use them. You can verify the above procedure works as I have. If you believe that the wear is borderline and can't afford the new guides, TRW has come to the rescue. They put out a set of neoprene rubber valve seals similar to the high quality Teflon seals Perfect Circle markets. However, these TRW seals (48VP24) require no machining of the guide bosses. The price is $7.80 a set as of Dec. 1973 and are on my B38 now. Other Healey models may require a different size; so check, as I didn’t think of it at the time. The seals are actually for a Chevy truck arid my machinist just was lucky in finding them. Perfect Circle probably also has a suitable set if you can cross-reference the TRW ones. The seals don’t interfere with the inner valve springs and are a tremendous improvement over the stock 0 rings. The seals are a nice extra and should be considered when that next valve job comes up.

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