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ImaPseudonym 10-28-2002 08:36 AM

351 Cleavland valve seals
I have a '73 Mach I with a 351 Cleavland engine with relatively low miles (51,000). It runs great, but smokes on startup. I've heard that it is possible to change the valve seals without removing the heads. Does anyone have any suggestions on doing this or is it even possible? Thanks

Biggarmike 10-28-2002 09:56 AM

There is an adaptor for an air fitting to sparkplug hole. Set cylinder to TDC one at a time and pressurize the cylinder. (be careful) there is a tool available to compress the springs and remove the keepers. The air holds the valves shut so that you can replace the seals and re install the springs and locks. I personally havent used that method in at least 20 years, but many swear by it. 10-28-2002 02:33 PM

you have to set the piston at bottom dead center not top, if it is at top the piston will travel to the bottom when you turn on the air and startle the sh****t out of you. make sure all the pushrods are out. and give the valve spring retainer a sharp tap at an angle to the valve to loosen the set that it takes after running a few thousand miles. don't let the air pressure fall while you have the spring off. you can buy the overcenter tool to compress the spring at any well stocked parts store they are sold for chevys but with some minor mods can be used on many other motors.

BstMech 10-28-2002 02:48 PM

You can also jam a bunch of 1/4-5/16" rope into the plug hole (with piston in a lower position) After you have a lot of rope (at least a couple of feet) jammed into the cyl. (make sure to leave some hanging out so it can be removed later <img src="graemlins/drunk.gif" border="0" alt="[drunk]" /> ) Turn the crank to bring the piston up, pushing the rope against the valves. Try it, you'll get good at it quick, and best of all, you'll never lose a valve because of a loss of air etc. :) Oh yeah, make sure the rockers are off (both valves closed or you might bend a valve) :eek:

[ October 28, 2002: Message edited by: BstMech ]</p>

slider 10-28-2002 03:08 PM

I like that rope trick Best Mechanic. Having had the engine take off with the air pressure is exciting to say the least. At best you won't bleed when you hit your noggin on the hood so you can get a beer down quick. Last time I looked KD made the valve spring compressors for most everything, even some universals. :cool:

BstMech 10-28-2002 03:36 PM

K-D is what I use now (with the screw and fingers), they are strong enough to smack with your palm to break the keepers. Those cheap ones (Auto Zone brand) aren't worth a crap unless you're very careful with'em. :)

dmorris1200 10-28-2002 03:43 PM

I used the air method on an old 302 I had. I never set the engine to top dead anything. Took off the valve covers, removed one spark plug at a time each time screwing in an adapter from an old compression gauge I had, and with an air line connected with a regulator keeping the pressure to about 50 psi or so (don't remember exact amount-been a few years) backed off the rockers and removed the springs. Worked my way around the whole engine in no time and ran that puppy smoke free for a few years after that. Not a bad idea to remove the oil pan when done if you can. I found a few valves with nothing left of the old seals, guess where those pesky little pieces of the old seals went to :D .

[ October 28, 2002: Message edited by: dmorris1200 ]</p>

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