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cam timing query
This is frustrating. I timed the cams and triple checked them - ie 3 x 720 deg on each bank, at least. To make sure the results were repeatable and close to each other - less than 0.05mm. Torqued the cam bolts up and bolted up and install engine. Fired first kick of starter but sounds 'off'. After diagnosing every other option, check cam timing again. It has shifted. By 1.5mm on 1 bank and about 0.4 mm on other bank. This is the second time this has happened to me. After doing several cam timings which are right first time and stay right. I can't figure it.
Not sure how sensitive it is to chain tension, but this time I used the engine tensioner on one side and special tensioner tool on other side. But they were definitely timed with tension on. Any ideas why it is moving after triple checking? So I have re timed the cams with engine in the car. But I am not sure whether to have any faith in that timing either - since I don't know why they are not stable. Thanks Alan
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83 SC, 82 930 (track) - Stock except for RarlyL8 race headers, RarlyL8 Zork, K27-7006, 22/28 T bars, 007 Fuel head, short 3&4 gears, NGK AFR, Greddy EBC (on the slippery slope), Wevo engine mounts, ERP rear camber adjust and mono balls, Tarret front monoball camber adjust, Elgin cams, 38mm ported heads, 964 IC. 380rwhp @ 0.8bar Apart from above, bone stock:-) |
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02-26-2016, 10:48 AM
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Join Date: Mar 2004
Location: Windsor, CT
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Do you check timing before you torque the cam bolt?
If so the fit between the cam, woodruff key, inner sprocket, pin, and sprocket is pretty loose. I would only check after the bolt was torqued. |
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02-26-2016, 10:54 AM
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Right - maybe an issue there. I check/set before torquing the bolt. Since the bolt is such a PITA to torque. I just nip it up - or finger tight. It maybe the play between the bits you mention.
Regards Alan
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83 SC, 82 930 (track) - Stock except for RarlyL8 race headers, RarlyL8 Zork, K27-7006, 22/28 T bars, 007 Fuel head, short 3&4 gears, NGK AFR, Greddy EBC (on the slippery slope), Wevo engine mounts, ERP rear camber adjust and mono balls, Tarret front monoball camber adjust, Elgin cams, 38mm ported heads, 964 IC. 380rwhp @ 0.8bar Apart from above, bone stock:-) |
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02-26-2016, 11:34 AM
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Join Date: Oct 2008
Location: Nash County, NC.
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I try to set the number against the rotation. The first setting to the left gives you the number you'll work with?
The right side doesn't always come in to match. Occasionally, I have to pull the cam gear and rotate it inside the chain to give new locators. I watched the Stompski Racing degree wheel with the tools for holding the cam and it appears he dials in his number then with the holder, runs the impact on the bolt. That way he would get the number he wants but doesn't load the pin against rotation. Bruce |
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02-26-2016, 01:45 PM
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Cam timing woes.....
Quote:
Alan, I experienced a major setback when I failed to tighten the cam bolts during cam timing. You were aware of my problem and was corrected after I applied enough torque to tighten them. An impact wrench would be sufficient to keep the sprocket in place during cam timing process. Then apply the 89 ft. lb. torque when completely satisfied with the values. But I never use the hydraulic tensioner when setting cam timing. Always with the mechanical or solid tensioner. Unless you have the degree wheel like those made by Stromski, getting consistent reading is both an art and science. Tony |
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02-26-2016, 06:54 PM
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Yes - I think I have unconsciously changed the way I do it. I suspect in early days I was tightening the cam bolt as I was checking settings. I have varied my method several times - as I read the threads I always a find a new twist/shortcut.
I could easily rattle gun the nut. I've had to have so many goes setting it I just finger tight it so the wheel doesn't want to fall off the cam. And if I can get some pre load into the pin/wheels that may help too. Funny but early days I had no issues and just followed Waynes book. But without mechanical tensioners - G clamp/vise grips. Regards Alan
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83 SC, 82 930 (track) - Stock except for RarlyL8 race headers, RarlyL8 Zork, K27-7006, 22/28 T bars, 007 Fuel head, short 3&4 gears, NGK AFR, Greddy EBC (on the slippery slope), Wevo engine mounts, ERP rear camber adjust and mono balls, Tarret front monoball camber adjust, Elgin cams, 38mm ported heads, 964 IC. 380rwhp @ 0.8bar Apart from above, bone stock:-) |
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02-26-2016, 07:33 PM
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Bruce - can you explain that a bit more - I'm not getting it - but want to understand it.
Anything that gets me to the required value without a glitch is much appreciated. Alan
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83 SC, 82 930 (track) - Stock except for RarlyL8 race headers, RarlyL8 Zork, K27-7006, 22/28 T bars, 007 Fuel head, short 3&4 gears, NGK AFR, Greddy EBC (on the slippery slope), Wevo engine mounts, ERP rear camber adjust and mono balls, Tarret front monoball camber adjust, Elgin cams, 38mm ported heads, 964 IC. 380rwhp @ 0.8bar Apart from above, bone stock:-) |
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02-26-2016, 07:35 PM
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Location: Nash County, NC.
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The idea is to locate the pin to the back of rotation. The cam rotates CCW. Each pin hole, when pinned, has a variable of .15mm in the hole you're set in from the front CW to the CCW side.
Pin the left cam and rotate the cam CCW against the pin, lock it there. The right cam, you'll still want to load the pin to the back of the variable. Some times the numbers don't come out where we want them. Pull the cam gear and move it inside the chain to another cog. This will give you all new pin locations. The biggest thing is loading to the back of the variable so when you tighten the bolt or nut the cam doesn't move off the setting. Bruce |
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02-27-2016, 03:40 AM
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So you are pre -loading the pin , ie taking the slop out of the pin location?
Wouldn't rotating the crank CW towards your dial gauge number do same? What I have been doing is rotating crank CW til I get the number I want, then pulling pin and rotating crank to TDC mark. Sometimes this means going CCW with crank, so I overshoot and run CW to the mark. Would that take account of what you are trying to do? I have to say tho that sometimes I have trouble pulling the pin with the pre load on it, and have to slacken the cam slightly. Thanks Alan
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83 SC, 82 930 (track) - Stock except for RarlyL8 race headers, RarlyL8 Zork, K27-7006, 22/28 T bars, 007 Fuel head, short 3&4 gears, NGK AFR, Greddy EBC (on the slippery slope), Wevo engine mounts, ERP rear camber adjust and mono balls, Tarret front monoball camber adjust, Elgin cams, 38mm ported heads, 964 IC. 380rwhp @ 0.8bar Apart from above, bone stock:-) |
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02-27-2016, 08:35 AM
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Location: Nash County, NC.
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Alan, try this. 12 mm bolt with a locknut in the cam. Lock the nut against the cam. Now you should be able to set the crank on Z1 and turn the cam with the locked on nut to any position and set the pin.
The left pin is the easiest to get into the window of spec. Just remember on the right, if it's more than .15 mm choose the next hole on the cam gear. Bruce Last edited by Flat6pac; 02-27-2016 at 10:27 AM.. |
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02-27-2016, 10:00 AM
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OK, thanks.
Hopefully I don't have to re time any time soon. Will check again tomorrow before buttoning everything up. Thanks for the help guys. Regards Alan
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83 SC, 82 930 (track) - Stock except for RarlyL8 race headers, RarlyL8 Zork, K27-7006, 22/28 T bars, 007 Fuel head, short 3&4 gears, NGK AFR, Greddy EBC (on the slippery slope), Wevo engine mounts, ERP rear camber adjust and mono balls, Tarret front monoball camber adjust, Elgin cams, 38mm ported heads, 964 IC. 380rwhp @ 0.8bar Apart from above, bone stock:-) |
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02-27-2016, 03:08 PM
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