valve problems

[m240]

I have a 71 engine that i am having problems with. Its valve timing was way off and I over revves it causing a rocker to come off on the #3 cylinder at an angle, the valve lashpad to come off, and 1 valve keeper to come off. (At first I thought I only had to replace the lash pad). I tried to put air in the cylinder to hold up the valve but it doesn't want to hold any pressure(I am using a hand pump). I try to compress the spring but when I do there isn't any room to get to the top of the valve to put the other keeper in ( and the valve goes down because the cylinder is'nt holding air pressure). Is there some trick to this? Do you think I broke the valve and that is why it won't hold air pressure? Is it time to think about swapping the head with one from my parts car? Is there any other gaskets that I need to get besides the head gasket? I would rather keep this head on the engine if I can because swapping them looks like quite the project. Thanks again for any advice!

Mark

[smg1404]

I have heard of doing this... but have never tried it... I do not think you can succeed with out an air compressor or tank with plenty of reserve... anyway, if you think there is any chance that the valve contacted the top of the piston, take the head off. there is almost certain to be some damage. If you put it back together and something is screwed up the damage, and ultimate price of repair will increase dramatically.

[2ManyZs]

It sounds as if you may have "soft' valve springs on the head you are using now. The way you describe the problem because you over-rev'd it might suggest your valve springs are well used up. Of course, if your vavlve timing is way off the way you describe you may have slapped a piston and bent the valve. I think the best thing to do is to take the head off and check it over thoroughly for any damage it may have received or if it needs any further attention.

If you want to, you will need to make sure both valves are closed before you hook up air to the cylinder. You will probably need at least a portable air tank to give you a supply of air to hold the valve in place while you are working on the valve. One "old timers" way of doing it is to take a soft cotton rope and feed a long length of it into the cylinder, and then raise the piston to top dead center to hold the valve in place. I don't like this method myself, because of the risk of a piece of the rope being caught in the valve and being left in the cylinder when you fire it up.

You will need a top end gasket kit or what parts people call a head gasket replacement set. It will have all the necessary gaskets to do the job, Head gasket, intake gasket, valve cover gasket, thermo housing gasket and the like.

Next question is why is the valve timing off? You will need to correct this or all your repair work may be pointless. If you have a stetched chain ort a bad tensioner you may as well take off the front cover while you have the head off and replace the timingchain and tensioner at the same time and correct your valve timing issue.

[Ed]

Measure the valve height of other valves and compare it to your problem valve. This might tell you if you bent the valve. You do need to use a compressor to fill the cylinder with enough air to be able to compress the spring without the valve going down. You can also use a piece of 1/4" fuel line, feed it through the spark plug hole towards the culprit valve. Raise the piston to create some resistance. This should work. After you get the valve keeper off, remove the spring. Lower the piston, and manually grab the valve stem, give it a spin and check for binding. If it feels tight or it won't rotate then you probably did bend it. Raise the piston against the fuel line to re-install the springs & keepers. Don't forget to adjust your valves. By the way did you ever find the lost lash pad, not to mention the other keeper?

[m240]

I did find the lash pad and the other keeper. I'm going to try the fuel line in the cylinder to see if that will keep the valve up. I hope it does because after looking at the head it does not look like an easy job to swap them . It wouldn't be to bad except for all the other stuff attached to it. Before this happened the engine ran pretty smooth but wouldn't rev past about 2800rpm. Thats why I think the valve timing caused this problem. I bought the car in april and have been working on it little by little. I guees I should have checked the valve clearance and timing earlier. Thanks for the advice.

Mark

[Ed]

Definately check the timing. An engine that won't rev over 2800 has to have something really out of whack.