Twin Cam timing chain jammed

[Milcroft]

Hi Guys can anybody help. On resetting my cams clearances I removed the inlet sprocket first and then the Exhaust I held the chain up and the engine a TDC when replacing the exhaust sprockets first and chain was far too short by a mile to go over the inlet.
I tried everything cams bearing housings released Sprockets off and rotated the engine no joy with the chain and it would jamb up giving the impression the chain is wrapped around the Jack shaft.
Having tried everything two people one pulling one turning the engine there was no joy the chain tensioner is fully back.
Does anybody have any suggestions on how to resolve the problem. Is it worth removing the tensioner sprocket to get better access.
Pete

[JohnMorin]

Hi Pete

I know exactly what you mean. The way I did it, several times, was with the engine at TDC and camshaft marks aligned gradually loosen the the inlet camshaft bearing caps in sequence until you can lift the No 4 end of the camshaft to get the chain over the sprocket. Then carefully and again in sequence tighten the camshaft bearing caps again. Be very careful and tighten the bearing caps a little bit at a time or you could snap the camshaft.

Regards

John

[rgh0]

Hi Guys can anybody help. On resetting my cams clearances I removed the inlet sprocket first and then the Exhaust I held the chain up and the engine a TDC when replacing the exhaust sprockets first and chain was far too short by a mile to go over the inlet.
I tried everything cams bearing housings released Sprockets off and rotated the engine no joy with the chain and it would jamb up giving the impression the chain is wrapped around the Jack shaft.
Having tried everything two people one pulling one turning the engine there was no joy the chain tensioner is fully back.
Does anybody have any suggestions on how to resolve the problem. Is it worth removing the tensioner sprocket to get better access.
Pete

Is your engine a standard 1500 block and a 120 link chain or something else. ?

cheers
Rohan

[Milcroft]

Hi John
a very simple solution to what appears to be a timing chain which is too short. Many thanks for the idea I will give it a go.
Peter.

[alan.barker]

Imho when you turn the Engine it isn't the Chain that's jamming it's the Valves on the Pistons. Be careful.
Have you released the Chain Tensioner.
DO NOT FORCE the rotation or you'll be looking at bent Valves
Alan
P.s. have you done this job before?

[Milcroft]

Hi Alan thanks for that I had leases all of the bearing housings when rotating the engine so there was no contact with the valves. I have now removed the tensioner which as allowed me enable the chain is making correct contact with the crank sprocket creating more length of chain.
Thanks for your comment.
Peter

[rgh0]

I always put the sump on last when building an engine as it enables yuou to ensure the chain is seated correctly when setting the timing. It also enables you to retrieve anything you drop down the timing chain cover when setting up the cams

cheers
Rohan

[Milcroft]

Hi Rohan
Thanks for your response on the chain fitting correctly on the crank sprocket It may well be possible if it is not fitted correctly. Just a note the chain fitted ok before I adjusted the cam clearances.
I will do a trial to remove both cams and rotate the engine back wards to see if I can release the jammed chain it will also ensure the crank sprocket is correctly engaged.
Thanks to all for your advice
Peter

[Milcroft]

Hi All
Having removed both cams to ensure the valves are not in the way I tried rotating the crank in reverse while pullin the chain on the right side of the head to see if I can un jam the chain all that happens when you hit resistance the pull bolt I rotating comes loose or the chain jumps of the crank sprocket. The only way forward is to remove the front cover to see where it jammed.
Can I loosen the front cover without disturbing the head. Or does anybody have any ideas what I can try next..
Thanks Peter

[Craven]

If you can remove the oil pump the chain has enough slack so that it will drop down away from the engine sprocket, then the chain can be pulled around just rotating the distributor. This should happen at fairly low pull hopefully by more pull you will engage the engine sprocket correctly and prove by spanner on the pulley to continue rotation. Hope you get the idea.

[Milcroft]

Thanks for the suggestion of using the distributor to rotate the jack shaft.
Well after weeks of trying to un trap the timing chain from the jack shaft I got a very long flat bladed screwdriver located it on the jack shaft sprocket and with a hammer tapped it in reverse direction and bingo the timing chain un jammed giving an extra two inches in length of the chain problem solved.
Many thanks to you all for each of the ideas lead to a result.
Peter it