Re: Valve Grinding and Guides

Posted by carla on Sep. 19, 1998 at 10:35:50

In Reply to: Valve Grinding and Guides
posted by Glenn Spyksma on Sep. 17, 1998 at 19:36:12

: I am currently rebuilding a 1929 model A engine.I have a reciprocating valve grinder that I will use to grind the valves as described in Jim Schild's repair manual.

: Jim describes that the valve should have been numbered by the orignial valve grinder.

: If I am installing new guides do they need to be fitted to the valves?Is there any work required for the valve guides?Or is Jim saying that since each guide alignemnt is slightly different, once the seat is cut, the guide and valve should be numbered to the bore?

: I searched for info on this site but no one has asked this quesiton before.

: Thanks for your help, all advice is welcome.
: Glenn
: .

hello, glenn,

much depends on whether you are just making your engine run as cheaply as might be, or whether you would like to make a nice job of your valves.----- the old ford two-piece guides and mushroom-foot valves are a bit of work to set up properly.

best is to borrow or rent a hard-seat grinding set and do the seats properly, that is, use a roughing, then finish stone of 45 deg for the seat angle, then narrow the seat with 30 deg and 60 deg stones until the seat is 1/16 wide, fitting the valve in the centre of its 45 deg working surface--- use dykem dye to make the grind diameters easier to see--- set a small divider to the diameter for each narrowing cut, grind and check until the seating will show up as a 1/16 band around the valve face, using prussian blue.

be certain to number each valve and guide once fitted.

then use the "reciprocating grinder" to lap each valve to its seat with fine compound.

grind the "mushroom foot" for tappet-clearance as usual.

i don't know whether this is worthwhile on the four cyl fords, but on the 'flat-head" V8's, we commonly fitted hard seat rings to the exhausts, to keep the seats from cracking.

seats narrowed and fit up correctly will last far longer in service without burning the valves, and will have much less chance of local over-heat and seat cracking.

carla




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