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no compression after head change
Posted: Tue Mar 12, 2013 1:00 pm
by stuart8862
Hi I have just changed the head of my 1098cc to unleaded with a new Head Gasket, but when i try and start the engine turns withought firing. I have used a compression guage to test compression but there doesnt appear to be any compression, can anyone pls help.......
Re: no compression after head change
Posted: Tue Mar 12, 2013 1:08 pm
by aupickup
well first why did you change the head
have you torqued the head down properly then retorqued after first heat cycle
i take it the spark plugs are in place
Re: no compression after head change
Posted: Tue Mar 12, 2013 1:11 pm
by stuart8862
Hi
I changed the head due to head gasket failure and thought i'd kill to birds with one stone!
I have torqued head down, but cant get the first heat cycle as it wont start.
Re: no compression after head change
Posted: Tue Mar 12, 2013 1:18 pm
by aupickup
plugs in the right order 1342
valves gaps correct
gasket on the right way
have you checked to see if there is a spark at the spark plug
Re: no compression after head change
Posted: Tue Mar 12, 2013 1:22 pm
by stuart8862
Maybe im being a little dumb, but is there a wrong way to put the gasket on??
Do i need to set the valve gaps on a new head?
Re: no compression after head change
Posted: Tue Mar 12, 2013 1:24 pm
by aupickup
thegasket would have had top front stamped on thegasket
and yes you will need to set the valve gaps
Re: no compression after head change
Posted: Tue Mar 12, 2013 1:30 pm
by brucek
Yes you do - in removing the head you will have had to remove the rocker assembly. On reassembly, no matter how accurate the torque setting is, the valve gaps will need to be reset. It is easy enough if you have not done it before - just let us know and we'll tell you how. Alternatively, check the procedure in the workshop manual if you have one. If not, I know a few people have them as a pdf file so will be able to send you one via e mail or private message(pm).

Re: no compression after head change
Posted: Tue Mar 12, 2013 1:42 pm
by stuart8862
Hi
Many many thanks, guess i best start again!!
Thanks for your help on this, I do have a manual, so i will start again, do you recommend new head studs??
Re: no compression after head change
Posted: Tue Mar 12, 2013 1:44 pm
by aupickup
only if yours are stretched or threads stripped but many use the same studs
Re: no compression after head change
Posted: Tue Mar 12, 2013 2:04 pm
by brucek
Agree with aupickup - only need to change studs and/or nuts if they are damaged. Make sure everything is scrupulously clean - esp on the block and cylinder head faces that meet together. If possible, use the copper faced head gasket rather than the fibre type - whilst they are both fine, the fibre type does tend to leave more of itself attached to both faces if you have to remove them again at a later stage. Some suggest a light smear of grease on both gasket faces too. Follow the torque sequence and then follow the sequence for setting up the valve gaps. If you have done this, and you have a spark, and the plug leads are on and in the right order, and you have fuel getting through, the engine should fire up. Allow the engine to get warm and then don't forget to retorque after the first heat cycle.

Good luck
Re: no compression after head change
Posted: Tue Mar 12, 2013 5:35 pm
by bmcecosse
It is obviously the valve gaps! OF COURSE you need to reset them.....12 thou inlets and 15 thou exhausts...... And yes - retorque after the first heat cycle and then reset the valave gaps. Studs will be fine - torque to 44 ft.lbf in steps round the head.
Re: no compression after head change
Posted: Tue Mar 12, 2013 5:39 pm
by aupickup
we all said the same
perhaps some one else will be along to say the same thing

Re: no compression after head change
Posted: Tue Mar 12, 2013 5:42 pm
by Bazzalucas
One would think that there would be SOME compression, on at least one cylinder, just by dumb luck...
Re: no compression after head change
Posted: Tue Mar 12, 2013 5:54 pm
by brucek
Well, we all have to start somewhere

let's face it, we all learned how to do it right
AFTER we did it wrong

my guess is that once the head is back on and the correct sequence is followed, our new friend will know next time he needs to do it. As Yoda says "In a dark place we find ourselves, and a little more knowledge lights our way." Sorry - more Star Wars there

Re: no compression after head change
Posted: Tue Mar 12, 2013 6:07 pm
by beero
Assuming your compression gauge may be at fault...... can you feel any compression when turning it with the handle?
Oh, and welcome to the forum.
Re: no compression after head change
Posted: Tue Mar 12, 2013 6:09 pm
by lambrettalad
makes one wonder which manual or did it have pages missing?