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View Full Version : Change valve seals with heads installed?



handfulz28
07-15-2011, 02:03 PM
'93 Chevy 305 TBI over 200k miles is burning/smoking more each day. It's the beater/mule/Sanford & Son junk truck we bought for $500, so it doesn't go far but all that oil can't be good for the pistons/valves. Gotta love when $10 in parts will take hours of labor to replace. Not to mention what I'll find/break when I pull the valve covers; I can see the sludge through the oil filler.

So - worth the effort? Pull the heads? Let it smoke like a diesel?

gcarter
07-15-2011, 02:28 PM
There're a number of compression testers that can be adapted to putting air into the spark plug holes.
Once sufficient pressure is in the cylinders, you can break down the retainer and springs, and of course, the seals.

joseph m. hahnl
07-15-2011, 02:29 PM
I've been contemplating this also. I think it can be done by putting the piston at top dead center and doing one cylinder at a time. You would need to block off the oil drain holes to prevent a dropped valve keeper from falling down the hole into the oil pan.



http://lh3.googleusercontent.com/public/KY46P-T_O5D8JEXEBD3-9W9zyVy6HQyVtTx0iHFuA8Slr_JidTZaraI0czwhM-6RttFMkz6qTzfTgWKX2NBR4zB2vItzVYDAig988zwbejGThjog E33eHQn63E3r_LAw9vhymKtU5As7Gwr8f9rFZIhPFfD15UIkCc 3OLxIUv9bl0u7Lu9J307OS

silverghost
07-15-2011, 03:07 PM
I've been contemplating this also. I think it can be done by putting the piston at top dead center and doing one cylinder at a time. You would need to block off the oil drain holes to prevent a dropped valve keeper from falling down the hole into the oil pan.


KD, New Britton makes this jaw style heads-on sping compressor as well as a simple lever arm type of sping compressor.

http://lh3.googleusercontent.com/public/KY46P-T_O5D8JEXEBD3-9W9zyVy6HQyVtTx0iHFuA8Slr_JidTZaraI0czwhM-6RttFMkz6qTzfTgWKX2NBR4zB2vItzVYDAig988zwbejGThjog E33eHQn63E3r_LAw9vhymKtU5As7Gwr8f9rFZIhPFfD15UIkCc 3OLxIUv9bl0u7Lu9J307OS


Any good auto store sells them.

dsparis
07-15-2011, 03:37 PM
Theres an L shaped tool thats makes compressing the spring easier, it bolts to the rocker stud. Don't need to have cyl. at tdc because rockers will be off. Not a bad idea though if you run into trouble the valve won't drop as deep. Old timers used to stuff rope in through the plug hole to hold the valve up.

mrfixxall
07-15-2011, 03:53 PM
Theres an L shaped tool thats makes compressing the spring easier, it bolts to the rocker stud. Don't need to have cyl. at tdc because rockers will be off. Not a bad idea though if you run into trouble the valve won't drop as deep. Old timers used to stuff rope in through the plug hole to hold the valve up.


+1 old timer....

i use the same method except i use a regulator to regulate the air down to 100 psi,,dont want to blow a gasket by putting too much air in a cylinder,,did that once and and got coolent shot in my face from the puke tank..

also just having sludge around the valve springs will trap oil and will leak around the valve stems then gets burned,,best to clean the sludge from around them..

dsparis
07-15-2011, 04:35 PM
Hey Fixx,
Do you know if his 305 uses o-rings or are the stud bosses machined or cast to accept the good seals. If not he can always use umbrellas.

mrfixxall
07-15-2011, 05:39 PM
Hey Fixx,
Do you know if his 305 uses o-rings or are the stud bosses machined or cast to accept the good seals. If not he can always use umbrellas.


most likely they are orings..i have also seen umbrellas on the intakes and orings on the exhaust..

BUIZILLA
07-15-2011, 07:18 PM
I made a MUCH easier tool, give me a day to find it..

also, it's probably the guides worn out and not the seals

handfulz28
07-15-2011, 07:45 PM
I made a MUCH easier tool, give me a day to find it..
also, it's probably the guides worn out and not the seals

Doh, that's not what I want to hear. Guides = pull heads I bet? But you're probably right since the occasional bottle of "stop smoke" doesn't work so well anymore. And thanks again for letting me distract you for a while the other day! :cool:

Anybody know off hand how a set of 333882 (1.94/1.50 ~76cc) heads compare to my stock 305 TBI heads? Just happened to come across a set that look fresh. Actually, I have to take a look but I think they're early pieces with no accessory holes...bugger.

BUIZILLA
07-15-2011, 07:47 PM
call Richard at Auto Motive Machine, he's right off I95 and I think 125st exit

he'll do ya right

joseph m. hahnl
07-16-2011, 07:53 AM
Theres an L shaped tool thats makes compressing the spring easier, it bolts to the rocker stud. Don't need to have cyl. at tdc because rockers will be off. Not a bad idea though if you run into trouble the valve won't drop as deep. Old timers used to stuff rope in through the plug hole to hold the valve up.


That's why I said it.

zelatore
07-16-2011, 03:49 PM
I've done spring/seal changes on small block fords with the heads on using the air pressure trick, but it's a PITA.

Given that your project is growing and you're now thinking about pulling the heads for replacement, you might find it easier to just swapt the motor for another junk yard take-out. I'm betting you can buy a running 305 for $500 or so.

Carl C
07-16-2011, 04:12 PM
I brazed a nut to the tool in post #4 so I can use a 3/8 drive air ratchet on it. Put piston at TDC, You can find TDC by feeling the piston with a screwdriver in the plug hole. The engine is easy to turn by hand with plugs out and rockers off. Put in about 80 PSI air, lightly tap the retainer with a brass hammer to free up the split keeper. Compress spring, remove keepers, retainer and spring. If the seals are at fault they will probably have hardened and broken apart, IOW they will be gone. Use vaseline to hold the keepers in place on reassembly. If all of the o-rings are in place then you know you need to look deeper. I've done lots of these and it's a simple job.

Donzi_Dude
07-16-2011, 06:28 PM
not to start a flame fest but does this thing burn all the time or just when you start it?

Phil S
07-17-2011, 12:04 AM
Just curious....smoking either way...what is your suggested path forward ?

Donzi_Dude
07-17-2011, 06:02 AM
Doh, that's not what I want to hear. Guides = pull heads I bet? But you're probably right since the occasional bottle of "stop smoke" doesn't work so well anymore. And thanks again for letting me distract you for a while the other day! :cool:

Anybody know off hand how a set of 333882 (1.94/1.50 ~76cc) heads compare to my stock 305 TBI heads? Just happened to come across a set that look fresh. Actually, I have to take a look but I think they're early pieces with no accessory holes...bugger.



Just curious....smoking either way...what is your suggested path forward ?


well that depends on the OP. seems to me if it only smoked when it started we wouldnt be here.

as the great BUIZILLA stated if thats the case its unlikely a $10 part will help.

as for 882's, ya, they are better heads but i cant help with fitment because im not a chevy guy. :yes:

i would start with compression and vacum readings.

handfulz28
07-18-2011, 12:40 PM
Now that I've been watching more closely, it's only real bad with blips of throttle. I was backing a trailer up an incline last week, so I had to work the pedal a bit...it's a stick. With little breeze all the smoke hung around giving the impression of more oil burning.
At this point I'm inclined to leave it alone and check oil level. Running 20/50 and it's only burning about a quart per thousand. GM would say that's "within spec". LOL

dsparis
07-18-2011, 01:33 PM
Pull a valve cover and check the oil returns at the back of the head. If its sludged up the returns may be blocked. That would explain why its worse when on a slant.