Timing / cam belt replacement on a 1990SE Esprit

[Vulcan Grey]

The spec is at 30BTDC, the tension will vary at any other position due to the valve springs pushing on the cams. No point in measuring anywhere else.

[lotus4s]

And don't bother measuring when it's hot, measurements are only good on a cold belt. When the engine gets hot it expands and makes the belt tighter, so yes the higher readings are normal.

[Mysterae]

The spec is at 30BTDC, the tension will vary at any other position due to the valve springs pushing on the cams. No point in measuring anywhere else.

 

The thing is the service notes make no mention of 30 degrees BTDC or 10 degrees BTDC when measuring the tension of the cam belt.

 

It states "if the camshaft drive has just been reassembled, rotate the engine in the normal direction of rotation (clockwise when viewed from the front) several times before setting at TDC. Use the timing marks and pointer on the flywheel rim and clutch housing aperture viewable after removing the protective rubber grommet in the top of the clutch housing." It then has an image of the pointer at TDC...

 

Then later it says "... obtain a settled reading. Rotate engine 360 degrees and measure again. Repeat the procedure to obtain a third reading and average the results."

 

Where has this 30BTDC came from? Is it an update to service notes or is it drawn from the experience of many a cam belt change? I'd be happy at either . Apologies if this has already been discussed on the forum.

 

 

And don't bother measuring when it's hot, measurements are only good on a cold belt. When the engine gets hot it expands and makes the belt tighter, so yes the higher readings are normal.

 

Yeah, that's the conclusion I made. It would be of little value as there's no way to adjust the tension when the engine is hot/warm, you'd burn yourself trying. The service notes do say to only measure at an engine ambient temperature of between 15 - 25 degrees C.

[910Esprit]

Check the Lotus service notes on Lotus Esprit World.  30degree BTDC for Clavis gauge (hertz) measurement.   And yes, the belts seem to become unfeasibly tight when hot!  -  I siuspect its even more pronounced for you guys with a fixed tentioner....

[Vulcan Grey]

The thing is the service notes make no mention of 30 degrees BTDC or 10 degrees BTDC when measuring the tension of the cam belt.

 

It states "if the camshaft drive has just been reassembled, rotate the engine in the normal direction of rotation (clockwise when viewed from the front) several times before setting at TDC. Use the timing marks and pointer on the flywheel rim and clutch housing aperture viewable after removing the protective rubber grommet in the top of the clutch housing." It then has an image of the pointer at TDC...

 

Then later it says "... obtain a settled reading. Rotate engine 360 degrees and measure again. Repeat the procedure to obtain a third reading and average the results."

 

Where has this 30BTDC came from? Is it an update to service notes or is it drawn from the experience of many a cam belt change? I'd be happy at either . Apologies if this has already been discussed on the forum.

 

 

 

Yeah, that's the conclusion I made. It would be of little value as there's no way to adjust the tension when the engine is hot/warm, you'd burn yourself trying. The service notes do say to only measure at an engine ambient temperature of between 15 - 25 degrees C.

 

The document that I posted (Clavis_Procedure.pdf) several times on this forum states

"1) Remove the 4 spark plugs, and rotate the crankshaft clockwise until the crank pulley notch aligns with the

30° BTDC front cover mark. The timing dots on the inlet and exhaust cam pulleys should be towards the

centre, but not aligned. Rotate the crank a further 360° if necessary."

 

http://www.thelotusforums.com/forums/topic/56697-service-time-oil-filter-and-cambelt/?p=452399

http://www.thelotusforums.com/forums/topic/47403-burroughs-or-krikit-cambelt-meter/

http://www.thelotusforums.com/forums/topic/4193-cambelt-tension/page-2

[Mysterae]

Cheers Steve, found the article on LEW here.

 

Travis, see, if we had a "How to .." I wouldn't have doubted or posted. But where would the fun be in that .

 

Now off to read those threads you posted. Unfortunately it'll be the weekend before I can touch the Esprit again.

 

Just for info, the app I used to measure the frequency was the "Gates Carbon Drive" app for the iphone.

[Vulcan Grey]

Interesting, hadn't seen that app from Gates before....  Course I have Android.

 

It's on android as well

https://play.google.com/store/apps/details?id=com.gates.carbondrivecalculator&hl=en

[Mysterae]

Just read the Beltfest thread....and I was the last to post on it! 

[ragingfool35]

another data point
i get 95 (laptop with external mic) to 97 Hz (phone) (30 BTDC) at a Krikit value of about 40 (TDC) on my blue belt when placing my my finger at exact midpoint between aux and intake sprockets on Krikit
haven't driven it yet but those are the frequency values

for the PC, i used a free program Visual Analyser 2022 which has features to scale to the range desired for better resolution and auto-calibrate out background noise