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Daved 07-25-2003 11:21 AM

Hitting Valves
 
Hi Guys,

Anyone who remembers my other threads, Stuck Valve or Removing Heads may remember that I have just pulled a head from my 350 SBC, to find that one exhaust valve was stuck open and had been hitting the piston. I had that head overhauled by a machine shop, and a new valve put in.
Today I have just pulled the other side, and although the valves aren't stuck open like before, mark on the pistons show that two of this sides valves have also been hitting.

Can anyone suggest why this maybe? Could it been explained by valve float?

Thanks

Daved

CJ2AWILLY 07-25-2003 11:31 AM

Improper cam timing. in another words, the valves are open when the piston gets to top dead center or too much lift via the cam or rocker arm ratio. If you do not have a "High Lift" cam and are using stock rocker arm ratio then you need to pull tha timing cover off and check that the timing marks are properly aligned.

You may want to also check your connecting rods to ensure that they are not bent. I had a customer install a HP timeing set incorrectly and destroyed the lower end because of a bent rod.

gt2betubbed 07-25-2003 11:50 AM

It can really bend a connecting rod? I can see a push rod or a valve, but never heard of a connecting rod. I guess that's cuz I'm still a greenhorn with not that much experience...Still worth checking though.

Daved 07-25-2003 12:51 PM

Thanks, I had thought it might be that.
Just wondering, why would only three vavle be hitting pistons?
Also, is it possible for the timing chain to slip? I have no reason to think that it has ever been taken off, and so should be in the right place.

Thanks

Daved

woodz428 07-25-2003 01:08 PM

One other thing to consider and I thought about it in your first post,fuel supply. One of my longtime customers had a similar problem on a '66 7 Litre Galaxy, either the fuel had gone stale (varnished) or someone had sugared his tank. When he pulled the heads and brought them to me there was a caramel like substance that had caused several to hang open. He hadn't driven it in a year or so and keeps all his vehicles (builds show quality early Mustangs) in a climate controlled garage and it was fine the first day he drove it after storage and the next morning he bent a pushrod which lead to the head removal. Some of the valves had to be heated with a propane torch to soften the goo enough to get the valves out. Because of his storage situation he was sure it wasn't tampered with, so I insisted he drain the tank or the problem was likely to re-appear. He drained it while I was working the heads and said that it was very stale and he flushed it and put in fresh and hasn't had the problem since. Although I encounter gummed up carbs regularly since the reformulation of fuel this is the first and hopefully the last that has had such a serious side effect.

Daved 07-25-2003 01:14 PM

Thanks Woodz,

I keep meaning to replace the fuel, it could well have sat there for a year. The only thing is that fuel is so expensive over here I keep putting it off.

I have had the two latest problem valves off, and they are very free moving. I'm going to get that head overhauled anyway, just for piece of mind.

Thanks

Daved

malc 07-25-2003 01:48 PM

Will it have been worth it to get those heads done,plus the the other problems you´ve had, and fuel price is an issue .Fuel
has to be used or it deteriorates and gets moisture,which settles at the bottom of the tank.Did you look at the valve seals?
probably burned oil gumming it all up.I changed the heads on mine as the originals were shot and it was cheaper to get a new set,then the oil problem came up from below,past the rings.It
seems you get one thing done and along comes the next,
but don´t we love it!


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