valve guides

[Michael_e]

Hope this is in the right place. I want to rebuild a 283 for my 1950 panel truck and I want to do as much as possible of the work myself. I got a set of sbc heads that I've disassembled and car wash cleaned. They look to be in decent shape except the valves are a little loose. I believe a new set of guides are in order. I will probably have a machine shop install the guides but I would like to ream them myself. The valves are 11/32 dia or .3437. How much clearance should I use? Maybe ream the guides to .3447?

Thanks,
Mike

[Speedbumpauto]

11/32 is a nominal size. Did you measure those valves? Most chevy new valves measure about .3415" The guide is usually reamed or honed to about .343 to get the .0015" clearance, sometimes .3435 on the exhaust to get .002' on them. BUT some exhaust valve stems are only .341 so they have the extra clearance built in. Unless you have access to a good mic, reaming the guides yourself is a bad idea and the shop isn't going to give you much off since the set-up to do the guides is a lot of the work/time. No offense meant and if you're a machinist/engine builder/gearhead type, please disregard the above as you will know where you're going.

[Michael_e]

Thanks for the info Speedbumpauto. I'm a home hobbyist type of machinist and want to learn and do just as much of the rebuilding as possible. My next adventure will probably be building some sort of jig setup to get everything in alignment so I can bore and install the guides myself.
Thanks,
Mike

[Speedbumpauto]

If you're really going to do it, spend your money on guide liner installation stuff, not the .500 replaceable type guides. It's a lot cheaper to get started and will let you learn good stuff about what guides are about. The bare bones setup can be done by hand with a drill and an air hammer. As you get more experience and money, you can upgrade to a vertical mill or guide and seat type machine and the stuff you have will be adaptable. Regardless of what you do, IMO, you need to get some quality measuring tools. They are the heart of a quality job because they are repeatable in measurements. It doesn't do any good to machine something if you can't ACCURATELY measure what you did.

[magicoolbus]

Trying not to be flippant, but doing your own guides is not a good idea as previously stated. New guides always means you need a new valve job. To do a valve job properly, you will need to reface the valves and reface the stems. I have provided what you will need to do this properly. I am sure you could find them cheaper, but it is a starting point. Or you could pony up the 300 bux and let the machine shop do a proper valve job.

I worked in an auto machine shop in AZ for many years and the work you are requesting would be turned away. If I ever did this type of request, the work would most certainly come back, with the customer looking for a warranty because the valves will not seat.

The alternative may be to have the guides knurled if they haven't been done before. This restores the guide I.D. You will still need to ream the guides to fit the valve stem. The valves should still seat with a good lapping. This is shade tree mechanic stuff and should be avoided.

[Michael_e]

I appreciate all of your concerns. Maybe some background would help here; Always been interested in machining, I worked in the local Fxxd parts dept as a young kid and was always delivering or picking up parts at the nearby machine shop, I always stayed a few extra minutes if they were running the crankshaft grinder, fast forward about 45 years, finally took some evening classes at the community college on machine shop operations, finally got my chance to make some chips, few more years pass and I just stumbled into an unbelieveable deal on Bridgeport in almost new condition, and all along the way I've been investing in quality measuring tools and a few tools for the BP.
So, I'm not totally in the dark about machine operations, just don't have much in the way of experience. I've been thinking about checking around to see if anyone local might have some junk/cracked, or otherwise broken heads that I can practice on before I actually do MY first set. I wasn't trying to hide anything here, just didn't know how much info you all would want. I'm still playing with 283s and 327s and carbs. But recently, a good friend wanted to know if I might be interested in converting his 48 GMC over to a newer
5.3/4l60 drivetrain. YIKES...computers and wiring.

Mike