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Valve lash adjustments and feeler gauges

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TomChar Avatar
TomChar Silver Member Tom Coulter
Springfield, PA, USA   USA
I've been driving my car all the time this summer, and started to notice a bit of a tick from one of the valves when idling. So I went to adjust the valves and noticed there was a lot of play using the new 0.010" Lisle feeler gauge I bought just for this purpose. Previously, since 2012, I had been using a feeler gauge set that's at least 50 years old, and had been sitting in the bottom of a rusty toolbox since the last time I needed it, back in the late 80's. So anyway, after I was done, the tick was certainly gone, but the car ran like crap. At speed it was okay, but it would hardly idle. So I checked the new gauge and the 0.010" gauge checks out at 0.0075" on my calibrated micrometer.

Haven't gone back in yet to readjust using the old gauge, but just thought I'd point this out in case anyone else gets a new set. The 0.010" gauge is a brass gauge in this particular set. I can only guess that it's not letting the valves properly seat and at idle I'm losing compression.



Tom
1974 TR6 CF24871UO. Dual Weber MCHH carbs.



Edited 1 time(s). Last edit at 2017-10-11 11:35 AM by TomChar.

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dicta dick Taylor
Downey, Callifornia, USA   USA
In reply to # 1491380 by TomChar I've been driving my car all the time this summer, and started to notice a bit of a tick from one of the valves when idling. So I went to adjust the valves and noticed there was a lot of play using the new 0.010" Lisle feeler gauge I bought just for this purpose. Previously, since 2012, I had been using a feeler gauge set that's at least 50 years old, and had been sitting in the bottom of a rusty toolbox since the last time I needed it, back in the late 80's. So anyway, after I was done, the tick was certainly gone, but the car ran like crap. At speed it was okay, but it would hardly idle. So I checked the new gauge and the 0.010" gauge checks out at 0.0075" on my calibrated micrometer.

Haven't gone back in yet to readjust using the old gauge, but just thought I'd point this out in case anyone else gets a new set. The 0.010" gauge is a brass gauge in this particular set. I can only guess that it's not letting the valves properly seat and at idle I'm losing compression.

Tom --- Something else is amiss here. The valve(s) should still close when the lash is at .007. We need further explanation of "ran like crap". Misfire? Lope? Vacuum signal bounce?

Dick

TomChar Avatar
TomChar Silver Member Tom Coulter
Springfield, PA, USA   USA
It just doesn't idle well at all. Giving it a bit of gas helps, but pulling the choke out slightly doesn't - unless you really pull it out then it idles around 1200. Otherwise it seems like it's trying to idle very slow, but it just stalls. But as I said, it was running fine before. I All I did was let it sit for about an hour after driving to my garage, removed the valve cover, made the adjustments, put the VC back on and took it for a spin. From the very start the idle was noticeably wrong. I agree that at 0.0075" the valves should still seat, but it was such a drastic change. Also, I have dual Weber MCHH carbs, an MCHH being essentially half a DCOE.

Still haven't gone back in to readjust it, but mostly the post to let folks know that a reputable tool can be so off.



Tom
1974 TR6 CF24871UO. Dual Weber MCHH carbs.

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TR3driver Randall Y
Confusion, Los Angeles, USA   USA
Setting the lash too tight can have a significant effect on valve timing, making it act (kind of) like a more radical cam. The intake valve opens sooner, which lets exhaust gas flow backwards into the intake at very low rpm.

So, as long as it runs OK once you reset the gap, I wouldn't worry about it.



Randall
56 TR3 TS13571L daily driver
71 Stag LE1473L awaiting engine rebuild
7? Stag awaiting gearbox rebuild



Edited 1 time(s). Last edit at 2017-10-23 03:40 PM by TR3driver.

frostr6 Avatar
frostr6 Bill Connell
St. Paul, Minnesota, USA   USA
Just a thought, if the car only sat for an hour after driving, it may not have been cold enough to set the valves accurately.

TomChar Avatar
TomChar Silver Member Tom Coulter
Springfield, PA, USA   USA
Finally getting back to resolving this issue. So yesterday I dove under the valve covers, and I couldn't squeeze a 0.007 feeler gauge under any of the rockers. I reset everything using another 0.010" gauge, one that checked out to be between 0.010-0.015 or so at various grabs with the micrometer. While there, I also checked the plugs and wires, and all seemed good. So with the rockers reset, it runs great again, and idles around 600. Although now I'm concerned about the accuracy of the tach. It's a little bouncy, and I don't have an external tach to compare it to.



Tom
1974 TR6 CF24871UO. Dual Weber MCHH carbs.

dicta dick Taylor
Downey, Callifornia, USA   USA
In reply to # 1493461 by TomChar Finally getting back to resolving this issue. So yesterday I dove under the valve covers, and I couldn't squeeze a 0.007 feeler gauge under any of the rockers. I reset everything using another 0.010" gauge, one that checked out to be between 0.010-0.015 or so at various grabs with the micrometer. While there, I also checked the plugs and wires, and all seemed good. So with the rockers reset, it runs great again, and idles around 600. Although now I'm concerned about the accuracy of the tach. It's a little bouncy, and I don't have an external tach to compare it to.

You may be able to get some relief from the bouncy tach needle by removing thinner tach cable, and lightly smearing it with grease. If this doesn't help, a new tach cable could be needed.
A feeler blade shouldn't produce a reading of between .010 and .015.( Is that a misprint?) No matter, so long as the engine is happy. Even at 600 rpm!

Dick

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TomChar Avatar
TomChar Silver Member Tom Coulter
Springfield, PA, USA   USA
You're right, typo. I meant 0.010" to 0.0105". The micrometer readings vary, but this is probably due to the feeler gauge in question being older than me, and having a hard life stored in a completely inappropriate rusty steel toolbox spending inordinate amounts of time in various wet basements, musty garage attics, and old GM car trunks traveling around the country during my stint in the Navy. But it's still better than the new 0.010 that reads 0.075.



Tom
1974 TR6 CF24871UO. Dual Weber MCHH carbs.

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