no engine compression

[tutilee]

Re: no engine compression

So than my next step should be remove the valve cover and what, see if they travel what up and down. Is that correct? please let me know. thx.

 

[havasuboatman]

Re: no engine compression

YES! Check if the valve stems are moving up and down. If they are, the valves are adjusted too tight.
If they are not, the valves are either adjusted too loose, or your hydralic lifters have bled down.

 

[Maclin]

Re: no engine compression

It almost has to be a valve lash or a valves sticking in the guides or bent valves not sealing issue. If the lifters bled down the valves will not open as soon or reach as high of a lift as they should but this would not cause a compression problem if the lash was correct and the valves are not bent and/or sticking in the guides. I think.

 

[havasuboatman]

Re: no engine compression

Oh, contraire, flat lifters can cause no lift and therefore no compression what so ever.
Furthermore, I doubt that his valves are stuck open, since he has not mentioned any backfiring or carb fires.
Even if both valves are not closing, some air/fuel mixture is gonna make it within range of the sparkplugs.

 

[Bondo]

Re: no engine compression

So than my next step should be remove the valve cover

Ayuh,... You had the head Off,.. Right,..??
Did you adjust the Valves when you reinstalled the head,..??

Furthermore, I doubt that his valves are stuck open, since he has not mentioned any backfiring or carb fires.
Even if both valves are not closing, some air/fuel mixture is gonna make it within range of the sparkplugs.

Ayuh,... If he just tightened the rockers, instead of Adjusting them,...
There'll be No Compression,+ hence No fire, No Backfires, No carb fires...

 

[Maclin]

Re: no engine compression

Oh, contraire, flat lifters can cause no lift and therefore no compression what so ever.

I apologize, but you have to explain this one to me. No lift, so the valves do not open, how do closed valves cause no compression?

 

[havasuboatman]

Re: no engine compression

Oh, that's an easy one.
If the pistion is on the intake stroke, it draws A/F into the cylinder thru the intake valve, right? now the cylinder has all this mixture in it. The intake valve closes, pistion comes back up pressure builds, we have compression. right?
Well, if both valves are closed on the intake stroke, nothing is drawn into the cylinder. In fact, what happens is a vacuum occurs. If he were to hook up a vacuum gauge instead of a compression gauge, he would get a nice increasing reading until the piston bottomed out, then the reading would decrease back to 0 when the piston reached TDC.
Imagine an irrigation syringe. You put your finger over the hole at the tip, then pull the plunger down. It's hard, but you can do it. When it goes back up, does it push air out the hole in the end? Of course not, because nothing was drawn in. It just returns to neutral pressure

 

[Maclin]

Re: no engine compression

Very good explanation, forgot about nothing in nothing to compress except what got trapped when he put the head back on, thanks! :redface:

 

[Lyle29464]

Re: no engine compression

Ayuh,... You had the head Off,.. Right,..??
Did you adjust the Valves when you reinstalled the head,..??



Ayuh,... If he just tightened the rockers, instead of Adjusting them,...
There'll be No Compression,+ hence No fire, No Backfires, No carb fires...

Bondo knows what is wrong.

I would stop turning engine over
remove valve cover
look at number of threads showing on #4 rocker arms

My guess it it is about 4 or 5
set all the rest like it is maybe not that tight

start engine and back off each rocker till it taps loud
then tighten it down till it is quite and add one full turn.

It will be hard at first till you get rid of some of the noise.

read book. it might call for 1 and 1/2 turn after zero lash.

 

[tutilee]

Re: no engine compression

Hi. thank you all for the good technical help, and especially to btdoctur. The problem turned out to be over tightening of the rockers on my part. Loosened
them and readjusted all rockers and the engined fired right up and it sounds great.

Again thank you all, tutilee

P.S. I like to also say you people provide a awesome service to guys like me.

Thank you for spearing your time and expertise.

 

[Maclin]

Re: no engine compression

Glad you got it going

 

[Silvertip]

Re: no engine compression

When you removed the cylinder head, did you also remove or loosen each rocker arm? If you did, there is a specific adjustment procedure that needs to be followed. The rocker arm nuts CANNOT be simply turned all the way tight. These are adjustable rocker arms because the valve lifters are hydraulic to maintain zero valve lash. By tightening the rockers you collapse the valve lifters thus preventing the valves from closing and hence the loss of compression.