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Location: Argyle TX
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Is The Chain Too loose
Getting ready for a chain tensioner upgrade on my 80SC. I just replaced the chain ramps and noticed that on the left side the lower chain is loose. I can easily lift it off the ramp a 1/2 inch with no effort. What are your thoughts?
Do I need to replace the chain or will the new tensioner fix this. Also the top of the chain is very tight as well as the right side. Thanks  
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Brad W 1980 911 SC 1982 928 Auto 1982 928 5spd Comp PKG 2005 SLK 350 w/ AMG Pkg 2007 Hummer H3 |
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02-13-2008, 04:46 PM
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Location: Rio Rancho, New Mexico
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Brad W,
Yes the chain is worn out. The pictures don't clearly show the condition of the cam and idle sprocket. Some on this board advocate replacing all sprockets, (including splitting the case and replacing the intermediate sprockets). I however carefully examine the sprockets then determine whether to replace or just go with new chain. Better pictures of the cam and idle sprocket will help to determine what to do.
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DOUG '76 911S 2.7, webers, solex cams, JE pistons, '74 exhaust, 23 & 28 torsion bars, 930 calipers & rotors, Hoosiers on 8's & 9's. '85 911 Carrera, stock, just painted, Orient Red |
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02-13-2008, 06:22 PM
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We can't tell if the chain is worn out from those pictures. Slack in the chain doesn't mean it's worn out. The tensioner might not be tensioning. You need to look at or show us the top of the tensioner. If the piston is close to all the way out or the arm on the idler wheel is close to the chain housing then most likely your chains are worn out.
-Andy
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72 Carrera RS replica, Spec 911 racer |
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02-13-2008, 08:00 PM
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The tensioner doesn't "tension" the chain as much as it dampens it. The spring in the tensioner is actually very soft, but the hydralic dampening is very stiff.
The tensioner isn't powerfull enough to keep the chain tight on the otherside of the cam gear. Edit: Disclamer: I'm no expert, this is just my conclusions from when I changed my chains and rebuilt my tensioners.
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Magnus 911 Silver Targa -77, 3.2 -84 with custom ITBs and EFI. 911T Coupe -69, 3.6, G50, "RSR", track day. 924 -79 Rat Rod EFI/Turbo 375whp@1.85bar. 931 -79 under total restoration. |
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02-14-2008, 03:53 AM
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abit off center
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Is the idler gear arm hitting or close to the chain box?
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______________________ Craig G2Performance Twinplug, head work, case savers, rockers arms, etc. |
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02-14-2008, 04:52 AM
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Location: So. Calif.
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Did you rotate the engine in the correct direction?
I believe you're lifting the "pull" side of the cam drive system. As such, there should be no slack here since the crank rotates the cam sprocket via the intermediate shaft and chain. The idler arm removes slack from the trailing side of the cam sprocket. Rotate the engine one revolution in the clockwise direction, then recheck. Sherwood |
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02-14-2008, 09:58 AM
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I second that ^ If the chain is tight on the tentioner side but not on the skid side
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02-14-2008, 01:55 PM
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I spun the engine around in the clockwise direction and the chain is now tight. Just in case I have a pic of the tensioner.
 
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Brad W 1980 911 SC 1982 928 Auto 1982 928 5spd Comp PKG 2005 SLK 350 w/ AMG Pkg 2007 Hummer H3 |
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02-14-2008, 02:58 PM
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Brad,
What's going on? The right side is clean and the left side is not. The chain tensioners both are about half extended indicating the chains still have some life left. The position of the idler sprocket from the first picture looked as if there was little room left for takeup. The left side indicates a long time between oil changes. My opinion.
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DOUG '76 911S 2.7, webers, solex cams, JE pistons, '74 exhaust, 23 & 28 torsion bars, 930 calipers & rotors, Hoosiers on 8's & 9's. '85 911 Carrera, stock, just painted, Orient Red |
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02-14-2008, 04:50 PM
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Doug,
My opinion is that the cat is on that side and the heat from the converter keeps that side cooking. Inside the valve covers everything is clean and uniform. So, if thats not the answer then I am stumped.
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Brad W 1980 911 SC 1982 928 Auto 1982 928 5spd Comp PKG 2005 SLK 350 w/ AMG Pkg 2007 Hummer H3 |
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02-14-2008, 06:30 PM
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Brad,
Something is going on that I had not noticed before. This is a pic of my 2.7 race engine when I had it out last summer. I've run synthetic oil in it for the last ten years. '74 exhaust manifold, no cat on the left. I really noticed it after commenting on your engine. Not the contrast of yours, but definitely the same. I'm with you, stumped. Dirty on the left, clean on the right. 
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DOUG '76 911S 2.7, webers, solex cams, JE pistons, '74 exhaust, 23 & 28 torsion bars, 930 calipers & rotors, Hoosiers on 8's & 9's. '85 911 Carrera, stock, just painted, Orient Red |
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02-14-2008, 08:38 PM
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Could be that oil gets slung up there from the taught end of the chain being lower on the LH side?
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Ed Hughes 2015 981 Cayman GTS 6 speed,Racing Yellow Past:1984 911 Targa (Ruby), 1995 993C2 (Sapphire), 1991 928S4 |
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02-15-2008, 04:21 AM
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1977 Porsche 911 Targa 2.7s
1969 and 1986 Porsche Targa and Coupe 1720cc and 3
Porsche
1972 porsche 914
1984 Porsche 911 Targa 3.4L
Sapphire
