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Re: TIMING CHAIN HELP - MGA 1600

To: Rick Brown <mgrick@mgcars.org.uk>, mglist <mgs@autox.team.net>
Subject: Re: TIMING CHAIN HELP - MGA 1600
From: Barney Gaylord <barneymg@ntsource.com>
Date: Sat, 22 Jun 2002 01:28:45 -0500
At 06:40 PM 6/21/02 -0400, Rick Brown wrote:
>I put a new timing chain, tensioner and camshaft plate on the engine - I 
>now find that it is very hard to turn the engine at least a LOT harder 
>than it was before. Is this normal or did I do something wrong?

The tensioner has an anti-push-back mechanism.  During installation you 
need to remove a small threaded plug in the tail of the cylinder part 
(opposite side from the rubbing block), insert the appropriate size hex key 
and turn it to rotate a cylindrical cam inside to retract the rubbing 
block.  Failure to do this can result in forceful interference between the 
rubbing block and the timing chain.  Do remember to reinstall the plug 
after installation.

When the engine is running, pressurized oil is fed into the tensioner 
causing it to press forwards against the timing chain, as well as feeding 
oil through a small hole in the rubbing block for lubrication of the 
rubbing face.  As the tensioner block moves forward the cylindrical cam 
inside rotates a bit to present a notched helical cam slot that prevents 
the rubbing block from backing off (much) in the absence of oil 
pressure.  If it gets too far forward during assembly it won't back up 
without some help from your friendly hey key.

>.... The two sprockets seem to line up correctly - without shims - there 
>were none when I took them off.

Place a straight edge across the face of the sprockets.  Hold a bright 
light on one side and sight through from the other side.  If you can see a 
gap behind the straight edge at either sprocket you need to adjust the 
shims behind the crankshaft sprocket.  There are usually two to four thin 
shims installed there (but it is possible that it could line up with no shims).

Barney Gaylord
1958 MGA with an attitude
http://www.ntsource.com/~barneymg

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