 Valve Adjustment, ...why did I have zero clearance? |
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| tomeric914 |
 Aug 4 2010, 02:18 PM
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#1
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One Lap of America in a 914!  Group: Members Posts: 1,263 Joined: 25-May 08 From: Syracuse, NY Member No.: 9,101 Region Association: North East States 
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I had adjusted the valves to .006" before the last track event I went to in April. It was about a 4 hour drive to the track and probably 40 or 50 degrees F. When I got there, the darn thing wouldn't idle (dual IDF 40's, 2.1L). No matter what adjustments I made, I couldn't get it to idle when hot (right off the track) but it would idle if it sat for a while. So I came home from the event, parked the car and started on the flare installation.
Now 3 months later with flares on and driving it on a regular basis, it still didn't idle. Again, checked the synchronization on the carbs, idle mixture, etc. Still didn't idle. Thinking logically, if it won't idle hot, a valve must be sticking open. So I let the car sit for a day and pulled the valve covers to find that all 4 exhaust valves had ZERO (more like negative) clearance! (IMG:style_emoticons/default/WTF.gif) So what happened? A. The valves all stretched the same length. B. All the seats got mashed evenly C. The valves weren't adjusted at TDC D. It was about 20 deg F in the garage when I adjusted them last A and/or B? I doubt it. D seems the most logical but does the valve grow .006" over 60 degrees? You would think that finding TDC doesn't matter, but I believe it does. Years ago I tried adjusting them with what is now referred to as the "rocking method" using the opposite side valve as a guide with the theory that a valve closed is a valve closed anywhere on the cam. I found when checking the clearance at TDC that the valve did not have the same clearance as measured when using the rocking method. It ended up being too tight at TDC! On my 914, the flywheel is paint marked at the groove for TDC and 28 deg BTDC. If I used the 28 deg BTDC mark, I was on another part of the cam that resulted in a different clearance than at TDC. The result being a valve held open when the engine is hot and no idle. After adjusting the valves at TDC and confirming all adjustment through one rotation, it idles perfectly. |
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| jaxdream |
Aug 8 2010, 06:30 PM
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#2
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Senior Member Group: Members Posts: 974 Joined: 8-July 08 From: North Central Tennessee Member No.: 9,270 Region Association: South East States |
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Posts in this topic
tomeric914 Valve Adjustment Aug 4 2010, 02:18 PM
Vacca Rabite Don't use the TDC mark when adjusting valves.
... Aug 4 2010, 02:40 PM
tomeric914
Don't use the TDC mark when adjusting valves.... Aug 4 2010, 02:48 PM Don M
Don't use the TDC mark when adjusting valves... Aug 7 2010, 06:56 AM jeffdon
[quote name='tomeric914' post='1352154' date='Aug... Aug 9 2010, 02:08 PM ME733
[quote name='tomeric914' post='1352154' date='Au... Aug 9 2010, 05:12 PM tomeric914
Awe hell, i used the lobe method......494 cam, wi... Aug 9 2010, 05:50 PM ME733
Awe hell, i used the lobe method......494 cam, w... Aug 10 2010, 08:53 AM Vacca Rabite
Awe hell, i used the lobe method......494 cam, wi... Aug 10 2010, 09:34 AM ME733
Awe hell, i used the lobe method......494 cam, w... Aug 10 2010, 09:54 AM Vacca Rabite
..................If you are satisfied with getti... Aug 10 2010, 10:45 AM tomeric914
All the folks that claim it does not work have pr... Aug 10 2010, 01:49 PM vsg914 Just curious, why is your flywheel marked at 28btd... Aug 4 2010, 04:09 PM Root_Werks Valve seats letting the valves settle in a little ... Aug 4 2010, 05:20 PM tomeric914
Just curious, why is your flywheel marked at 28bt... Aug 4 2010, 06:24 PM realred914
Just curious, why is your flywheel marked at 28b... Aug 4 2010, 10:56 PM ME733
I had adjusted the valves to .006" before th... Aug 7 2010, 05:17 PM tomeric914
.........................Well you have experience... Aug 7 2010, 05:40 PM ME733
.........................Well you have experienc... Aug 8 2010, 06:17 AM ME733
[quote name='tomeric914' post='1353499' date='Aug... Aug 9 2010, 09:55 AM jaxdream Ok , TDC it is , but is it TDC for every cylinder ... Aug 8 2010, 07:20 AM tomeric914
.................And...when building any engine ... Aug 8 2010, 10:01 AM vsg914 Find the notch in the flywheel with your finger th... Aug 8 2010, 10:34 AM bandjoey :blink: :blink: :blink: :blink: :blink: :blin... Aug 10 2010, 10:23 AM |
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