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| Re: [GMCnet] test on timing chain? [message #138754 is a reply to message #138737] |
Fri, 12 August 2011 19:18   |
klassic kampers
Messages: 93
Registered: July 2008
Location: greer,s.c./ellijay,ga
Karma: 0
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Steve, its easy to test in the motor home......with the engine cool, take a socket and pull bar on the harmonic balancer bolt, rotate the engine counterclockwise until you feel the crankshaft pull the cam against the valve spring pressure......mark a reference mark on the harmonic balancer and the lower part of the timing cover......then gently rotate the engine clockwise until you feel the valve spring pressure again......mark the timing cover aligning with the mark you previously made on the balancer....the distance between the two marks on the timing cover is the "slack" in the timing chain .....on a somewhat fresh engine you might have 10-12mm distance between the marks but I have seen 100k engines that run well with slightly over 25mm of slack...........if you are new to this you may pull about 4 spark plugs to get a better "feel" of the valve spring resistance........it probably does not matter if you check clockwise or counterclockwise but I like to pull against the natural engine rotation...........hope this helps....
Mike Stewart
1973 GMC 26' Canyonlands /
1973 B.S.A. B50 street tracker-----
Greer,S.C/Ellijay,Ga
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| Re: [GMCnet] test on timing chain? [message #138756 is a reply to message #138737] |
Fri, 12 August 2011 19:37 |
chasingsummer
Messages: 434
Registered: May 2011
Location: asheboro, nc
Karma: 0
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klassic kampers
your post , i think it made my light bulb flicker,
pulling the plugs, how does that effect the feel of this?
also, once my light bulb is at full power, and i am trying this, what would be the "slack measurement" which would indicate chain being on borrowed time?
thanks bgk
brian
asheboro, nc
75 eleganza, 74 build
119k miles and counting,
DOG HOUSE
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| Re: [GMCnet] test on timing chain? [message #138760 is a reply to message #138756] |
Fri, 12 August 2011 19:49 |
LNelson
Messages: 335
Registered: December 2008
Location: Springfield, MO
Karma: 0
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By pulling the plugs, you would not be fighting compression. You are trying to feel what the innards are doing inside there. With the plugs gone, it will be easier to feel the valve train doing it's thing.
Larry Nelson Springfield, MO
Ex GMC'er, then GM Busnut
now '77 Eleganza ARS WB0JOT
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| Re: [GMCnet] test on timing chain? [message #138815 is a reply to message #138756] |
Sat, 13 August 2011 04:38 |
klassic kampers
Messages: 93
Registered: July 2008
Location: greer,s.c./ellijay,ga
Karma: 0
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| chasingsummer wrote on Fri, 12 August 2011 19:37 |
klassic kampers
your post , i think it made my light bulb flicker,
pulling the plugs, how does that effect the feel of this?
also, once my light bulb is at full power, and i am trying this, what would be the "slack measurement" which would indicate chain being on borrowed time?
thanks bgk
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in my opinion, anything over 25mm(one inch) would be on the edge of having enough slack to "jump" a tooth or two....a badly worn timing chain will cause the engine to be lazy at low RPM but may run fine at higher speed .......
removing the plugs insures you are pulling against the valve spring pressure and not against cylinder pressure....also with the plugs removed you have a lesser chance of loosening the harmonic balancer bolt when rotating the engine counter clockwise...
be careful if using "watch the rotor" method....play in the camshaft/dist gear area and any play in the dist shaft/dist gear will show more chain wear than actually there......
here, I pop the LH valve cover and use a dial indicator on a valve retainer.........
if you get confused call me on the tele.....
as usual----disclaimer on file........
good luck
Mike Stewart
1973 GMC 26' Canyonlands /
1973 B.S.A. B50 street tracker-----
Greer,S.C/Ellijay,Ga
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| Re: [GMCnet] test on timing chain? [message #138860 is a reply to message #138737] |
Sat, 13 August 2011 10:29 |
George Beckman
Messages: 1085
Registered: October 2008
Location: Colfax, CA
Karma: 11
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| Steve Phillips wrote on Fri, 12 August 2011 15:01 |
Hi All
Earlier post on the web someone said there is a way of testing the
timing chain still in the coach. Any help . Also is there a web site for
replacing the chain I Realty hope I don't have to replace it.
Thanks
Steve
Helena
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Steve,
I had a rebuilt engine put in this spring at Miguel's in Southern Cal. When my engine was out Miguel had me reach in the fuel pump port and hit the chain with my finger. If had 1/2 inch of play in it. The new engine was like putting your finger against the block; no play. The old engine, with 40 lbs on one cylinder, 60 on the next, going up to 120 was still getting nine mpg. As Jim Bounds said, "They will run broke for quite a while."
'74 Eleganza, SE, Howell + EBL
Best Wishes,
George
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