Hi All!

My winter project this year was replacing the valve springs, rockers and valve seals, as well as powder coating some things while I had everything apart. I got started early winter, but since my garage isn’t heated, I got delayed, and just got back to work on it!

Anyway… I started removing the valve springs on the #1 cylinder. I found TDC, and hooked up an air hose to an adapter I threaded into the sparkplug hole. When I did this, I can hear air hissing out somewhere. I think I could feel some air coming through the exhaust, but it might have been my imagination. It could have just been a leaky adapter too. I really couldn’t tell.

My question is… Should I hear this leaking? Where is it leaking from?

I’m guessing this is blowby coming from worn rings. Or could it be bent valves? It’s not a lot of leaking, and the ‘89 does have over 135K on the clock. Is this something I should be worried about?

Thanks!

--- John

 

What you hear is the air escaping from a partially open valve. Turn the engine by hand backward or forward a little and the hissing should stop. Then proceed to remove the springs and replace the seals.
If you have more questions send me an email or PM. Did mine on my 85 and helped another member with his 86.

John

 

pull both rockers when you do each cylinder. It takes the cam out of the picture for the removal of the spring.

 

First remove all the rocker arms and sparkplugs and go down the line with air pressure in each cylinder to replace seals and or springs. It is normal to experience some leakage past valves and rings when you do this but it should not be much. Why not purchase an inexpensive cylinder leakage tester to know for sure the mechanical condition of your engine is within limits? Since you have to apply compressed air to each cylinder before you can disassemble the valve spring retainer locks why not do it through a leakage tester which will report percentage of leakage? An out of limits reading will indicate needed work and where the leakage is heard will pinpoint the cause. For example; air escaping out the exhaust would indicate an excessively worn exhaust valve and or seat; air heard escaping in the crankcase would indicate worn rings. For accuracy you should try to test each cylinder at TDC because cylinder wear if any would be greatest there. The other reason would be so that you don't accidentally allow a valve to drop down in the cylinder if the air supply were interrupted somehow. If you don't have the engine pretty close to TDC for that cylinder when you apply air pressure it will turn the engine to BDC. You should be able to locate a fairly inexpensive cylinder leakage tester with a google search. The one below is $39.99 at harborfreight.com, I am not endorsing this particular tool but rather using it for an example of cost, however this would be better than just guessing with an air hose only.

 

I believe that I did have #1 at TDC, and I did remove both rockers on #1 before applying air.

I don't have a leak tester, but I'll check around for one. Not a bad tool to have!

I know how to find TDC on #1, but how do I find it on each of the rest?

 

Mark the balancer. With #1 tdc and at 12 0'clock, mark the balancer at 3, 6 and 9 o'clock. Then you can do number 1, rotate the cranl 1/4 turn and follow the firing order.

 

That makes sense! Why didn't I think of that?

Thanks!