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Discussion Starter · #1 ·
I just picked up a used SBC 383 with performer RPM heads on it. I have pulled the heads to check piston to deck height so I can get the compression where it needs to be to run on 91. While the heads are off I'm going to dissaseble them and cleam them up a bit. My question is how to tell if the seats and valves are good to go. Is it just a visual inspection for errosion? Also how to check for bvalve guide ware? I have a dial indicator on a magnetic base. Not sure if I can get the job done with that. Anything else I should be looking for ?
 

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Quick way to test for guide wear.

Clean both guide and valve. insert valve in guide, lift from seat approx 1/2 " and rock valve. Should just feel movement. Oil stem of valve and re-insert. Should feel no side movement
 

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Also might make sure the springs are up to par with your cam while you have them out, especially if you plan to go roller cam. I'd take them to a good shop and have them checked with a Rimac spring tester. Of course you'll have to know what cam requirements are 1st. Do you have a roller or flat tappet? Are you keeping the same cam it came with and do you know its specs? Do you know how hard the engine was ran and if the valves were floated? Do you plan on turning high rpms? New springs may be the best way to go? I installed beehives(26986-16) on mine for a roller cam and the heads were brand new. I found out later that the stock springs weren't good enough for a roller cam. Of course the beehives need new retainers/locks/seats/shims. Then you'll probably need a mic to set up the spring installed height. It can get into the wallet.
I'd also give the decks a real good inspection for indentation(brinelling) around the chambers from a gasket that had an integral o-ring. Might have to get them surfaced at a shop. You can probably get by without surfacing/milling if you use the same part number gasket.
Are the tips of the valves worn? Are you gonna use the same rockers? If you are, label them and install them on the same stud/valve. Same goes for the push rods. Are the tops of the rocker studs flat or damaged from polylocks?
If it was me, I'd probally get a valve job done just so I'd know that I started fresh. Same goes for the stem seals. How many miles on the heads?
While you have the springs out verify the spring seats aren't damaged, big deal on aluminum heads. They should have at least had shims between the spring & head.
It all depends on how much you want out of the heads and how long you want them to last? (and how anal like me you are)FWIW
ssmonty
Forgive the spelling
 

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I just picked up a used SBC 383 with performer RPM heads on it. I have pulled the heads to check piston to deck height so I can get the compression where it needs to be to run on 91. While the heads are off I'm going to dissaseble them and cleam them up a bit. My question is how to tell if the seats and valves are good to go. Is it just a visual inspection for errosion? Also how to check for bvalve guide ware? I have a dial indicator on a magnetic base. Not sure if I can get the job done with that. Anything else I should be looking for ?
See how thin the valve margins are. If they're thin from wear, it's a good bet the seats are also worn.

If the guides are worn, that can wear the seat, eventually it'll be worn too much and will need recut after replacing the guides. Guides have to be done if they're loose before the seats are cut.
 

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Discussion Starter · #5 ·
See how thin the valve margins are. If they're thin from wear, it's a good bet the seats are also worn.

If the guides are worn, that can wear the seat, eventually it'll be worn too much and will need recut after replacing the guides. Guides have to be done if they're loose before the seats are cut.[/QUOTe

What would be consider a thin margin and what is acceptable?

To wet leak test do you just fill the chamber with a liquid (gas maybe?) And if it holds fluid you are good to go?
 

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are you freshening the engine or just looking and re using?
any machine shop can pressure test the heads and or resurface.
Anytime I assemble an engine I blue print it so it costs a few dollars because Im fussy
 

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Discussion Starter · #9 ·
Thanks Vin. The guy I bought it from said it onlt has about an hour of run time on the bottom end. It does Look pretty good. Lots of croos hatch. When buying a used motor its kind of a crap shoot. I'm hoping for the best.
 

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Plenty easy to "leak test" the heads without a vacuum table. Pour alcohol (or other "thin" liquid) into the ports while the heads are on their side. Fill the port to "above" the valve and watch the chamber side for leaks. If the valve leaks ANYTHING, it isn't sealing 100%, but that's not a big deal if it only "weeps". New springs could fix that.

Also, it may be a good time to LOOK at the valve jpb and see if the seats were done by the head maker or the machine shop that did the build. Mostly, the latter is preferable, IF it's from a forward-looking modern shop. Lapping a "weeping" valve can clear up any leak, too.

Jim
 

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Discussion Starter · #12 · (Edited)
Thnks for the info Jim. When lapping the valves what is the best way to "spin" the valve?? Ivess the little tool that suctioin to the valve and you spin it in your hand. I've also see this done with a drill. Aslo because the heads have been in service, when I remove the valves is it neccasery to pyt the valves back into the same chmaber they came out of??
 
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