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

[OrrieG]

283 and 327's are my favorite engines, with a strong lean toward the 283. I found that rebuild parts like pistons are very expensive ( in my world). the numbers matching engine for my 64 Chevelle can be rebuilt without decking so the serial number stays intact, but needs .030 over pistons. last time I priced them they were north of $50 EACH. I ended up buying a 283 short block with good .030 over pistons for $75, my machinist said it will be easy to match the pistons to my block. I like the idea of old junk heads to practice on, if you can find them, but who knows there are lots of old SB sitting out behind barns that have not been scrapped yet. I have three sets setting around "just in case" the Chevelle decides to suck a valve somewhere along the line.

[Speedbumpauto]

alrighty then! Assuming the mill is a 9x42 or so, the first thing you need is a head fixture to mount to the table. You might look at CP motorwords stand. Pricey but the best I've seen. It will allow you to do guides, valve seats and surface as your tooling grows. Then you need to settle on a guide pilot size. .375 seems to be where everyone is going. You can start with a couple in the 11/32 range, a .343 being the most common. A .342 and a .344 will cover most of that range heads you get. Then you need a quality level that will fit on your pilot top so you can level the head(guide) to the machine. Then you need to buy a core drill or so. Core drill/reamer combinations are pretty nice and most common is a .343 or so pilot, drills to about .490 and reams to exactly .500. they guides you buy will be .501. This is for the set up I told you not to buy, which is the .501 thin wall guides. You can buy the same tooling for the K-line and others guide liners which is where many shops are going. The last thing you need is an air hammer to install the guides and you're in the guide business. Then you need to do the seats. You use the same pilot but different cutters that are available for your machine.
Go online to the Goodson catalog and look at all the stuff available for guides and seats. Most will talk about a guide and seat machine but it's all adaptable to your Bridgeport. You can have a good experience doing this stuff. I build street rod engines in my retirement in a shop in my back yard and find that it keeps me out of the tavern... a little. Good luck.

[Michael_e]

Thanks for the replies!
OrrieG - Did you ever find the skirts on used pistons to be a little fragile? I was taking apart a 283 and had a plastic trash barrel with a pillow in the bottom to catch the piston/rod as it came out and still ended up with one broken skirt.
Speedbumpauto - Yes, it's a 9 X 42 table and has variable speed control. I would really like to add a DRO system to it, but other things are after my dollars currently. Thanks for the Goodson lead.

I have a small shop and currently working on converting a 52 Chevy from a 3 window to a 5 window for a customer. I really like working with metal in just about all forms. My personal favorite things to work on are building vintage speedsters. I've been working on my own 1930 Chevy speedster. I'll see if I can get a pic of it sometime this weekend.

Mike