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HELP!!! Head change dramas...

6K views 53 replies 14 participants last post by  Thanatos 
#1 ·
Hey guys,

I'm currently putting a new head on my EA and i've run into a bit of a problem.

Basically, the timing chain seems too loose... (See attached pics).


We are sure the timing tensioner is working, so this isn't the problem.


One theory we have, is that due to the increased compression (head has been decked 40 thou, and using AU head gasket), is that the tensioner can no longer take up the slack in the chain. Could this be the case??


Everything was fine with my old head, yet as soon as we put the new one on, the problem started straight away.

If it is just a case of the tensioner not being able to make up the slack, then we were thinking we could just pack it out a bit with some spacers. Can anyone see a reason why this wouldn't work?


Cheers,
Dave
 

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#8 ·
Doesn't the tensioner work off oil pressure, maybe it'll tighten when you start it? Although, I wouldn't be game to start it with the chain that loose either!! 60 thou is only 1.5mm, as others have said the tensioner should take that up easily!
 
#9 ·
Thanks for the replies guys.

My theories have actually changed now...

I'm thinking the chain may have skipped a tooth on the crank gear.

Does this make sense to anyone else??

I'm 99% sure it isn't tensioner, as it is actually the other side that is slack (i.e. the non-tensioner side). The side that the tensioner is on is actually nicely tensioned.


Cheers,
Dave
 
#10 ·
i was working with thanatos on his car today. The tensioner is in perfect nick, and is putting plenty of tension on the chain, the problem is that when you turn the engine over, the chain become slack on the opposite side. ???

We were thinking that maybe the chain had skipped a tooth on the bottom cog while we put the new head on? Is this possible?? I wouldn't have thought so, but it seems to be the only logical explanation we can come up with, as their seems to be "too much chain" on the right hand side as shown in the pics, while there is plenty of tension on the opposite side. Were ruling out a stretched chain as it is fairly new and it was fine up until we put the new head on...
 
#11 ·
Could be. If the tensioner is pushing its side tight, but the chain has slipped and now there is slack on the other side. The tensioner would not be able to pull the crank or cap around. so one side would be tight and the other loose.
 
#12 ·
Rmyers said:
i was working with thanatos on his car today. The tensioner is in perfect nick, and is putting plenty of tension on the chain, the problem is that when you turn the engine over, the chain become slack on the opposite side. ???

We were thinking that maybe the chain had skipped a tooth on the bottom cog while we put the new head on? Is this possible?? I wouldn't have thought so, but it seems to be the only logical explanation we can come up with, as their seems to be "too much chain" on the right hand side as shown in the pics, while there is plenty of tension on the opposite side. Were ruling out a stretched chain as it is fairly new and it was fine up until we put the new head on...
what you described there sounds like the chain guide on that side. as for skipping a tooth, i dont think that it would make it slack on one side. the best way to find out would be to pull the timing cover off and see whats happening. just hope that the auxiliry shaft hole hasnt slogged out but i dont think it would give it that much slack if it did.

EDIT- did you cable the the chain onto the cam gear?
 
#13 ·
John_xr6 said:
what you described there sounds like the chain guide on that side. as for skipping a tooth, i dont think that it would make it slack on one side. the best way to find out would be to pull the timing cover off and see whats happening. just hope that the auxiliry shaft hole hasnt slogged out but i dont think it would give it that much slack if it did.

EDIT- did you cable the the chain onto the cam gear?
We'll be taking the timing cover off tomorrow to have look inside. hopefully we'll know more by then...

I doubt it's a case of anything being excessively worn, as this probably would have showed up with the old head as well.

And yes, we cable tied the cam gear to the chain...


Cheers,
Dave
 
#14 ·
before you do it.... the chain can not skip a tooth.....
turn the motor over this will pull the chain tight, then at tighest spot reaslease tensioner. its not posible to have slack chain on that side of the cam. the tensioner doesnt affect the chain on that side... even with no tensioner the chain will be tight on that side.. check for broken guide, with torch... fuk pulling the timing cover off. it just looks like the motor has t urend a lil, trust me just turn it till chain is tight even without rockers if you want to be safe.... then resease tensior, make sure u turn it the right way to
 
#15 ·
THere is no way even a skipped tooth will ause the chain to be slack.... its simple either the chain is stereched.... or when you wind it over the pulling side of the chaine passenger side, should and will be tight, relase the chain and away ya go...


****** we had a speed way engine it had decked block 150 pluss of the head u head gasket and we had to take a link out**** You know the ridge at the front of the head ner the timing cover this was razor sharp thats how much it had off
 
#17 ·
Thanatos said:
Thanks for the replies guys.

My theories have actually changed now...

I'm thinking the chain may have skipped a tooth on the crank gear.

Does this make sense to anyone else??

I'm 99% sure it isn't tensioner, as it is actually the other side that is slack (i.e. the non-tensioner side). The side that the tensioner is on is actually nicely tensioned.


Cheers,
Dave
DAMM ...thats what it must be....tensioned on one side..not on the other.If you release the tensioner androtate it gently by hand anit clockwise the tooth may go back in.Then find tdc ..line up the timing mark onthe crank and mark on cam 3 degrees above the cylinder head and voila
 
#18 ·
Thanks heaps for the help, guys...

We tried turning it over by hand until the chain was tight. As soon as we cranked the motor it went slack again.


We've now taken the timing cover off, and the first thing i noticed is that the bottom guide had dislodged at some stage, (obviously long before the head change, as the chain seems to have been running along the timing case slightly).

This doesn't fully explain the problem, as if this was the only cause for the slackness, then it would have been like that with the old head as well.

Therefore, this makes me think that the guide not being there has allowed the chain to skip back a tooth on the crank gear, resulting in an excess of chain between the crank gear and the cam gear. Due to the nature of chain driven gears, the slack probably won't be able to move around to the tensionor side and get taken up.

Does that theory make sense to anyone else?


What i'll be trying today is to line up the timing marks, and move the chain around until it is tight on the non-tensioner side. Then i'll put the timing case back on, re-tension the chain, and crank her over. *hopefully* that should see the problem solved. If it doesn't then i'm gonna torch the bitch! lol.


Cheers,
Dave
 
#19 ·
Ok, guys, we've put the guide back in place, and tensioned it up properly...

BUT what's happening is the chain keeps going from tight to slack repeatedly. The chain was 100% tight when i set it this morning, but turning it over a few times, and every now and then it just goes slack again.

Any ideas???


I've already had to miss a day of work when money is really tight, and i can't really afford to have the car off the road much longer. :(


Cheers,
Dave
 
#21 ·
Hmmm, i didn't think of that...


I doubt it very much, though, as they were fine before. So it doesn't seem to make sense that they would suddenly start now...

I'll check it in the morning anyway, though.


Any other ideas??? Keep 'em coming people!


Thanks heaps, guys.

Cheers,
Dave
 
#23 ·
It sounds like a tensioner problem to me too.
Though if you feel you have it spot on, I can only trust that it is.

What happens is that before the engine is actually started and had oil pressure build, the tensioner is only relying on a spring to keep the tension on the chain, this spring is not very strong as it's merely an aid when assembling. So, if you are turning the engine over by hand or just by the starter, though without actually running the engine, the chain will have some slack in it as the adjuster is designed to have some slack in it and release a few mm. Without oil pressure this slack can easily be shown, and is perhaps what you are seeing.

Does the tensioner feel like it is releasing all the way when letting it out? You should be able to get an idea by taking note of how far in degrees you have to wind it out before it takes up the slack

Rick.
 
#25 ·
INJECTED250 said:
key way on the bottom gear on the crank chewed out
How exactly would I go about checking this?


Soxx said:
It sounds like a tensioner problem to me too.
Though if you feel you have it spot on, I can only trust that it is.

What happens is that before the engine is actually started and had oil pressure build, the tensioner is only relying on a spring to keep the tension on the chain, this spring is not very strong as it's merely an aid when assembling. So, if you are turning the engine over by hand or just by the starter, though without actually running the engine, the chain will have some slack in it as the adjuster is designed to have some slack in it and release a few mm. Without oil pressure this slack can easily be shown, and is perhaps what you are seeing.

Does the tensioner feel like it is releasing all the way when letting it out? You should be able to get an idea by taking note of how far in degrees you have to wind it out before it takes up the slack

Rick.
So could the lack of oil pressure explain the kind of slack that is shown in the pictures at the start of the thread???

The tensioner is definately releasing fully.


Cheers guys,
Dave
 
#26 ·
Thanatos said:
How exactly would I go about checking this?
Remove the harmonic balancer, it's pretty unlikey that this is the problem however.
So could the lack of oil pressure explain the kind of slack that is shown in the pictures at the start of the thread???
Definately, it is only the oil pressure which keeps the chain tight, the spring is simply to locate the tensioner when assembling.
The tensioner is definately releasing fully.
When you say 'fully', do you mean it is at the limits of it's ultimate travel, or at it's limits within the assembled engine and pushing against the chain?

There is a difference, as it shouldn't extend to it's absolute maximum travel in the engine, as there is extra travel in the tensioner for wear in the guides, chain, etc.

Rick.
 
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