Re: Modern-style Valves

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Posted by MikeK on Aug. 31, 2010 at 07:50:43

In Reply to: Modern-style Valves
posted by OTTAWAED on Aug. 30, 2010 at 09:53:03

Ed, The new single piece valve guides are NOT the same as the originals. Originals were split two piece that needed to be installed simultaneously with the old mushroom tipped valves. The new guides are not without problems: 1) The guides can be easily scratched in the stem bore which will cause sticking valves. Carefully de-burr the valve lock grooves and tip with a fine India stone BEFORE trying the fit of any parts right out of the box. 2) There is no stem clearance difference intake/ exhaust in the sets sold by the vendors. Both guide and valve tolerances vary, so you may want to selectively fit your guides to valves before install. Hone if you want more exhaust clearance. 3) You need to be careful not to hammer directly on the top face of the guides during install. Make an inverted cone tool to contact only the top chamfer of the guide. Measure the O.D. of the top and bottom of the guides. Some manufacturers make guides that look symmetrical (no definite top or bottom side), but may have a slight taper. De-burr the leading edges. Do not drive them in dry. I use E.P. grease. 4) There is no 'stop' when you drive them in, so watch to get them all relatively even. 5) If you use a valve seat cutter or stone with a pilot that goes down the new guides, be extremely careful not to scratch or gall the guides. Make sure the pilot is nick free and well lubed. 6) The original split iron guides had flake graphite and pores in the iron, making them superior to steel guides for holding oil and not sticking. Giving the new steel guides a quick swipe with a hone, leaving a cross-hatch like a cylinder bore may be prudent. Remember, the valves are upside down in an 'A' so there is precious little splash oil that gets to the stems. The exhaust stems also have exhaust pressure pushing down the stem clearance, deterring oil from working its way up. I always use graphite or moly oil as an assembly lube on new valve stems. Do NOT ever use any lithium assembly lube on exhaust valve stems!

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