valve lash opinions - LotusTalk - The Lotus Cars Community
 
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post #1 of 10 (permalink) Old 03-05-2018, 01:50 PM Thread Starter
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valve lash opinions

Based on this thread https://www.lotustalk.com/forums/f25/...fusion-133786/ and using the "cellica" technique of measuring at the valve cap/lifter interface, I took the following readings

Intake Large: .012/.010/.011/.012
Intake Small: .011/.011/.013/.008
Exh Large: .018/018/019/018
Exh Small: .018/.018/.018/.019

The lash was set after the valve seats had been redone (2nd time for this head, once by prev owner of head, once by a machinist when I got it before putting it on). The guy who assembled it and set the lash had difficulty getting as much lash as he wanted and reportedly had the machinist shave one or more shims ... I'm guessing that is the .008...

I know the machinist told us to be on the loose side because the valves might "seat in" but now it's been through 6 auto crosses with multiple trips to the rev limiter, so probably whatever was going to tighten up did.

Given that I see claims some folks have taken to running 011-013 intentionally to avoid cam wipe, the only thing that worries me is the .004 difference between the one pair of intake valves, and I worry slightly about the .019 exhaust valves.

It's kind of a lot of work to re-shim this, and I do have after market cams (piper stage 3) which should be more durable.

What do folks think?

The other vauge worry (unrelated to valve lash) that I have is that the entire timing chain seems to have been re-installed exactly one link off counter clock wise so that the colored links never quite line up with the marks (I used the 0 degree mark/notch and the dots on the sprockets to position the engine for lash measurement, ignoring the links).

Since it's already had close to an hour at speed, I'm pretty sure if there were an actual problem with the chain position, I'd have a bucket of engine parts already, and it probably wouldn't have dynoed/tuned to 195whp (N/A)... That's an even bigger pain to fix, so I hope nobody is going to tell me it's a real problem.

Note: The head actually was installed/removed/reinstalled due to a problem with the installation when the valve lash was set the first installer caused the chain issue, which was pointed out to me by the second installer who fixed the problems with the first install. I only just realized when I opened things up that he kept the chain where it was rather than re-positioning it (I did not specify that, and it seems to have been fine, so I'm not faulting him).

2005 Lotus Elise, Starlight Black # 111 SSM NER SCCA Solo - 1835lbs up to 1.65 Lat [email protected]~55mph (asphalt) 193whp 142wtq Normally Aspirated.

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post #2 of 10 (permalink) Old 03-05-2018, 05:02 PM
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Check the crank marking in reference to the cams to make sure that it really is off one link.
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post #3 of 10 (permalink) Old 03-05-2018, 06:54 PM Thread Starter
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Originally Posted by Nessal View Post
Check the crank marking in reference to the cams to make sure that it really is off one link.
Just prior to the first half of the measurements I took thse photos, and had rotated the crank a total of 8 times before deciding this was as good as it was going to get:
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2005 Lotus Elise, Starlight Black # 111 SSM NER SCCA Solo - 1835lbs up to 1.65 Lat [email protected]~55mph (asphalt) 193whp 142wtq Normally Aspirated.

http://www.the111shift.com/p/the-build.html

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post #4 of 10 (permalink) Old 03-05-2018, 08:57 PM
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Looks like you are off two teeth. It's actually quite easy to fix after removing the tensioner. For extra clearance, you can remove the exhaust cam or the exhaust cam sprocket and then move the chain to the correct markings then tighten everything down again. It's easier to just remove the sprocket but you will need a crowsfoot. I'm surprised your car is running as good as you say!
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post #5 of 10 (permalink) Old 03-06-2018, 04:34 AM Thread Starter
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Originally Posted by Nessal View Post
I'm surprised your car is running as good as you say!
I'm pretty sure there's a gear down in the chain cover too, and the number of links between that and the top two determine the timing. My hypothesis is that with everything (including the lower gear that I would have to take the timing chain cover off to access) off by 1 link (2 teeth) the timing is still correct. The only actual problem is if at some later date someone who doesn't know this takes apart the engine and puts it back and lines up the marks like they are supposed to, then I'll have an "issue".

If I do what you said, the number of links between the bottom gear and the top 2 will change, and that *would* change the timing.

2005 Lotus Elise, Starlight Black # 111 SSM NER SCCA Solo - 1835lbs up to 1.65 Lat [email protected]~55mph (asphalt) 193whp 142wtq Normally Aspirated.

http://www.the111shift.com/p/the-build.html

https://www.youtube.com/c/the111shift
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post #6 of 10 (permalink) Old 03-06-2018, 01:34 PM
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The one low speed cam with 0.008" lash is still within the safe zone. I see no worries with any of the other lash values.

The 2zz timing chain repeats every 9 revolutions. I think one more revolution should get you to the picture below. If not, you've got a hackish build there!
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post #7 of 10 (permalink) Old 03-07-2018, 07:26 AM
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Can you get a borescope camera down to the sprocket on the crankshaft to confirm if the chain is or is not aligning with the timing mark on the crankshaft?

Regarding your valve lash measurements, I don't understand the large vs small measurements. Is this referring to the camshaft lobes? If it is I am confused as I think you stated you are measuring between the valve caps and lifter, not the lifter to the cam lobes.

If your measurements are between the camshaft and the lifter you will want to address the difference between your big/small lash. If I remember correctly, the Toyota engine shop manual provides a maximum discrepancy between the two valves under each lifter.
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post #8 of 10 (permalink) Old 03-07-2018, 07:37 AM Thread Starter
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Originally Posted by +TSRAGR View Post
The one low speed cam with 0.008" lash is still within the safe zone. I see no worries with any of the other lash values.

The 2zz timing chain repeats every 9 revolutions. I think one more revolution should get you to the picture below. If not, you've got a hackish build there!
revolution of the entire chain?

2005 Lotus Elise, Starlight Black # 111 SSM NER SCCA Solo - 1835lbs up to 1.65 Lat [email protected]~55mph (asphalt) 193whp 142wtq Normally Aspirated.

http://www.the111shift.com/p/the-build.html

https://www.youtube.com/c/the111shift
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post #9 of 10 (permalink) Old 03-07-2018, 07:54 AM Thread Starter
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Originally Posted by TedR View Post
Can you get a borescope camera down to the sprocket on the crankshaft to confirm if the chain is or is not aligning with the timing mark on the crankshaft?

Regarding your valve lash measurements, I don't understand the large vs small measurements. Is this referring to the camshaft lobes? If it is I am confused as I think you stated you are measuring between the valve caps and lifter, not the lifter to the cam lobes.

If your measurements are between the camshaft and the lifter you will want to address the difference between your big/small lash. If I remember correctly, the Toyota engine shop manual provides a maximum discrepancy between the two valves under each lifter.
Borescope is an interesting idea.

I'm labeling the measurement of the valve under the large lobe vs the valve under the small lobe side as a positional reference only. Measurements correspond to the maximum thickness gauge that would fit between the valve+cap and the rocker. I'd be very interested to know the discrepancy spec, I don't see it in the (cellica) manual I have.

2005 Lotus Elise, Starlight Black # 111 SSM NER SCCA Solo - 1835lbs up to 1.65 Lat [email protected]~55mph (asphalt) 193whp 142wtq Normally Aspirated.

http://www.the111shift.com/p/the-build.html

https://www.youtube.com/c/the111shift
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2005 Lotus Elise, Starlight Black # 111 SSM NER SCCA Solo - 1835lbs up to 1.65 Lat [email protected]~55mph (asphalt) 193whp 142wtq Normally Aspirated.

http://www.the111shift.com/p/the-build.html

https://www.youtube.com/c/the111shift

Last edited by fsparv; 03-08-2018 at 02:14 PM. Reason: un-thread jacking my own thread...
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