Head


#1

my car 95 corsica 3.1 was running very rough took it in guy said no compression on the front head and said i need new one when i took old head off the far right cylinder was to the top of the hole and the other two were farther down at the same level is this normal thanks


#2

Yes that is normal. The pistons move up and down to perform the combustion cycle. If you are concerned about the connectivity of the pistons to the crankshaft, turn the crankshaft over using the front crankshaft pulley.


#3

thanks alot man i was worried ill try that thanks again


#4

The pistons are intentionally staggered in order to create a continuous sequential firing of the cylinders. Each moves up to the top twice in its cyles, once to compress fuel and the second time to push exhaust out. The downstroke of the first upward cycle is the power stroke, the downstroke of the other is the intake stroke.

As Researcher said, they’re all safely and solidly connected to the crankshaft. If one did break free you’d have a “broken connecting rod” and the noises would be far more severe than just a rough idle. And the damage would be severe.

What you’re seeing is normal.


#5

you have eased my mind considerable and you sound like a gear head too thanks again


#6

You should not remove cylinder heads if you have no idea what is underneath them…


#7

Usually true, but it’s a 95 Corsica after all. Perfect car for the situation.


#8

while i had the front head off i also took cover for the 6 lifters off and noticed that there were two that were up higher then the others is that normal also? and i turned the crankshaft and all three did move


#9

Are you SURE that your mechanical skills and automotive knowledge are adequate for this task?


#10

o yes i have all bolts and parts laid out and all in order i have another car and taking my time and doing it right im just waiting for my new head to come in


#11

Did you order the gasket, and do you have a torque wrench to set the correct torque when you reattach the head?


#12

i have all that


#13

You need to get a Haynes or Chilton manual for this from a bookstore or parts store.


#14

Yes, the valves (tappets, rockers, and everything related) will be in various positions, typically some opened and some closed. And yes, they should move when you turn the crank. As the crank turns it opens and closes the valves. The intake valves should open on the intake stroke and the exhaust valves on the exhaust stroke.

I admire your courage and your willingness to learn. A good book on the fundamentals of gas engines from the bookstore might help you understand what you’re seeing. A good book on engine rebuilding, beyond the repair manual, might help too.

By the way, it isn’y generally kosher to put new heads on a high mileage block…but is it really the head gaskets he wqas alluding to rather than the head?


#15

i took the car in to get looked at and the guy said i had no compression at all on the front head and it needs replaced he wanted 1000.00 he said either its a bad valve or a bad injector. it was ticking real bad before it started running rough then i had rough idle and the ticking but i said i can do the work instead so thats what i am doing just waiting for the head to get here also cause its a new head should i pour oil on new valves before i close valve cover thanks again


#16

I have no idea why this guy would claim that no compression would be caused by a valve (possible) or a bad injector (no way). An injector has nothing to do with compression unless it’s stuck open and gasoline has washed the piston rings out of it.

You did not state exactly how thorough a diagnosis was done, but I hope you don’t install the head and discover you still have compression problems. Piston rings (except in a very rare and fluky circumstance) won’t cause no compression at all but can lead to low compression. In this case, install a new head and you still have a major problem.

A compression test, both dry and wet, should have been performed on all cylinders.
Hopefully this was done, bu the bad injector comment is odd assuming there is no misinterpretation.


#17

The ticking you hear could be from a worn camshaft and lifters.
The compression can be low because the valves are not seating good (worn, or bent), and/or because the piston rings are leaking a lot.
You REALLY need a mechanic to evaluate the engine while it’s apart.


#18

And I should have added that if a valve, or valves, in a cylinder head are bad enough to cause a “no compression” problem then you should be able to look at them and see the problem with the naked eye.

Turn the old head upside down with the valve heads facing up and the spark plugs in place. Pour a little gas or whatever in there. If the valves are causing no compression then the liquid should run out past the valve faces almost instantly.
If not…


#19

I agree (as usual) with ok4450. The reasons that the OP was given for “no compression” make only partial sense or no sense, and a more complete diagnosis would be a good idea before the OP begins surgery on this engine.

It is very possible that after replacing the head & head gasket, the problem will remain. As mountainbike stated, putting new heads on an old engine may be an exercise in futility. I suspect that this engine needs much more than a new cylinder head, and I believe that mountainbike has similar suspicions.


#20

just to let all know that i put the new head on friday and the car runs better than when i first got it runs so smooth no leaks no nothing while i had head off i replaced those six lifters too