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Discussion Starter #1 (Edited)
So per one of my other threads, I am concerned about the tension on my recently serviced (by professional Esprit experts) timing belts. I'm in the planning stages of checking the tension, so I have been reading through manuals and online instructions. I have some questions on making the process no more difficult than it needs to be to get a good tension readings.

Here's what I have come up with for a process from everything that I have read. For those that have done lots of these, what do you think?

1) Prop truck up with broom sticks after disconnecting the struts to give more room to work.
2) Remove top cam covers with 2 screws, and only having to temporarily remove one air box line to the driver's side plenum to get that side out.
3) Remove at least 1 observation screws for the positioning pins on the cam shaft.
4) Remove all 8 spark plugs to make it easier to turn the engine.
5) Jack up the car on the driver’s side, remove left rear wheel, block the right side rear to keep tire from turning, put the car in 5th gear, and remove the parking break.
6) Rotate the wheel using the hub nut and a big wrench until the cam shaft hole lines up. Use a drill bit to confirm it’s very closely lined up.
7) Get under the car and confirm that the mark on the cranks lines up with the cam sensor (which it better, or you’re screwed)
8) Stick on a printed-out-from-the-web timing disk onto the crank pulley and screw in a pointer to the oil pan so it shows 10deg BTDC on cylinder 2. Permanently mark crank pulley positions if possible to make it easier next time.
9) Mount iPhone with Tango video conferencing app to look at the pointer and the timing disk position, and watch the position on iPad from above the car.
10) Rotate rear wheel until at 80 deg ATDC. Check the left hand tension with Tune It on (another) iPhone for 120-135Hz (new belt <500 miles for me)
11) If adjustment is necessary, rotate engine twice and check again after making the adjustment.
12) Repeat the 10 and 11 for the right hand side at 120 ATDC.
13) Put it all back together.

Of course this procedure would not be anywhere close to ok for changing the timing belt, but it seems like a complete way to check the tension correctly while minimizing the pain.

What do you think?

There are no special tools required (given you have lots of iPhones and iPads), and it would involve a lot less time under the car and removing extra parts from the car.
 

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I would not do it that way.

You are basing the position of the crankshaft on the alignment of the cam timing pins. Your eyes will not be able to seen the small misalignment of the crankshaft to set the base line starting point. Also trying to rotate the engine via the drive train is not very precise. Buy or borrow the crankshaft alignment tool and use the crankshaft damper nut to rotate the engine. Plugs can stay in and you don't need to see the cam alignment holes to set belt tension, only to check for belt strech, which is a good idea if you like to push the life of the belts.
 

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Wayne is right, you will not be able to see the cam dot alignment. Be careful.

For accuracy, buy 4 drill bits and the size is 4.2mm (metric) for the intake cam. Buy 4 drill bits and the size is 4.7mm (metric) for exhaust cam @ 10 degrees TDC #2 cyl at the firing strokes. Oh, the hole of the intake is smaller than the exhaust. So, the drill bit if not exact is very close to the measurement.

I made my own (machined) crankshaft timing tools but someone borrowed it from Denmark, he's not done with his project.
http://img194.imageshack.us/img194/4025/timingtools002.jpg
 

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Discussion Starter #4 (Edited)
Thanks for the wisdom.

I want to make sure I understand, and not offend.

Again, I am not trying to change the belts here. The tension check instructions say to use a pretty inaccurate stuck-on-with-putty disk with a rudimentary pointer sticking out of the oil pan to find the 80 and 120 deg ATDC to make a tension check.

So if I can see the holes line up in the cam shafts, why do I need to lock down the crank? And how close am I if the camshaft holes lines up pretty darn close?

It seems excessive for just a tension check given the inaccuracy of the disk/pointer to be too worried about the crank and cam locking pins.

And I could see where turning the wheel hub to get close and then turning the crank itself for fine tuning would make sense -- especially when you need to turn the engine twice to get another measurement since that's a lot of under the car cranking with not a lot of room to turn a wrench (no lift in my garage).

And if you don't *need* to remove the plugs, how much easier does it make to turn the engine without having to fight the compression? Given that the tension adjustment process is trial and error and you have 2 tensioners and you have to turn the engine twice after each change, that could be a lot of turning.
 

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Discussion Starter #6
Step 0; disconnect battery?
Not a difficult step, but I don't know why it would be necessary since the ignition will be off for the entire procedure.


1998 Lotus Esprit V8
 

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It seems excessive for just a tension check given the inaccuracy of the disk/pointer to be too worried about the crank and cam locking pins.

If that's the case why not simply tighten the adjuster and be done?

If it's me, I will check the accuracy of the timing. Lotus used the pins for accuracy...missing a tooth is a no no....but you go ahead, do whatever you need to do.
 

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Done this a couple of times.
I always use the 4 tolerance pins and the crank lock tool to hold the engine's crank and cams in position when the belts are off.
The transmission is always in neutral. Don't want to be banging away at the tires if the trannys in gear with any of the locking gear installed.
That said, I just tension the belts per the tech notes.
I use the newer tension numbers.
It is my preference to have fresh oil circulated in the engine before working on the belts.
Modified a small degree wheel from Summit racing (put colored notches on the edge and hogged out the center) affixed with sticky tape, and use a bent piece of coat hanger for the pointer.
My frequency checker is a commercial laser device. $$$
You have to be a bit careful and deliberate about all of this, hard to do sometimes as it's a bit crowded up top--and bottom.
 

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For the cam alignment tools there are checking pins and alignment pins and there is the crank pin. Does anyone have or can get the exact measurements of these? I would like to make myself a set. It would be great if someone could stick sketches of them into the files section. I agree it would be difficult to set these by eye especially considering for the cam tools there are two different sizes.
David Teitelbaum
 

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For the cam alignment tools there are checking pins and alignment pins and there is the crank pin. Does anyone have or can get the exact measurements of these? I would like to make myself a set. It would be great if someone could stick sketches of them into the files section. I agree it would be difficult to set these by eye especially considering for the cam tools there are two different sizes.
David Teitelbaum
I think the crank locking tool is the most important, as you need to set the crank to "zero" so you can line up the degree wheel properly.

Seems to me I modeled up the crank locking pin on CATIA awhile back.
Let me check and see if it's still floating around in one of my files.
Found a pic of it, looks like an old V4 model...
 

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Discussion Starter #11 (Edited)
Well, I did it!

I used the procedure in my first message with only a few minor changes, and all I have to say is that I feel sorry for all you guys that have been doing it the old fashion way all these years! :wallbang:

One of the changes: I used the crank locking pin and all 4 tolerance pins to make sure the engine cam timing is correct before I started.

But I never once turned the engine from the crankshaft. I put the gearbox in 5th gear, took the left rear wheel off, and chocked the right rear wheel with wood to keep it from spinning.

I had a buddy turn the wheel hub counter clockwise (turns the engine clockwise) until I could set the crankshaft pin. All the tolerance pins went right on the first try (a 50/50 proposition). That was the last of his help that I needed.

I set up my timing wheel, which I have to thank Luis big time for sending me. See attached. I had to print it out on something like 75% size for it to fit right, and then I spray glued it to some cardboard from the back of a note pad. Then I used double stick tape to hold it on the crank pulley.

I used a sheet of galvanized thin metal to cut out a pointer. I just cut a slot in the end the width of the oil pan screw so that I didn't even need to remove that bolt, just loosen and tighten it back on with the pointer.

Then I set up my iPhone with a video conference app (Tango) to show me the position of the crank to the pointer.

I was able to confirm that I had great control over the position of the pointer by constantly reconfirming 10deg before top dead center for #2 with the tolerance pins. After a while, I just started using a tooth pick to check that I was in the right place since the toothpick will go in about 1/2" less if the engine wasn't at 10deg BTDC #2.

Every 1 turn of the engine crank equates to 3/4" of the wheel hub in 5th gear, so I was able to control the crank position much better than other replies on this forum would lead you to believe.

What I can tell you if you haven't done this before, is that this job is a major pain in the you know what because it's just a guessing game to get the tension set right. When you adjust the tension, you have no idea what you are going to get for a final result until you spin the engine and then check. There is no consistent relationship to what tension you have when you make the adjustment until you spin again. Sometimes I would set it at 120hz, and then it would come out 160hz. Other times, I would set it to 110hz and it would come out to 105hz.

So if I had to go back under the car and crank that engine with no room to move the 50 times I had to set and reset the tension last night, I would be dead right now! Don't do it!

If I had to do it again, I would have just used my PC with a USB camera and USB extension to see the marker because the phone video conference did have some problems with the signal when the phone was tucked up in the engine mess.

In the end, I got both belts to read around 135hz (they are still considered new since they are under 500 miles). The LH belt was set too tight by Viking: 160hz, and the RH was set too loose: 107hz. I know now personally how hard it is to get them right, but hey, they are the pros and they should have made the effort to get this right before taking my money.

A couple of notes on checking the frequency: I did some tests, and found it surprising that the freq of the belt did not change much at all whether I was +/-2 deg from the mark like someone else mentioned. Also, it did appear that the iPhone with the iTuneIT app is very consistent with the Clavis gauge. It is much easier to get a good reading with the Clavis design due to its claw-like sensor. I found I could hit the belt just about anywhere, including the side, and even strum it with my thumb and get the same reading consistently. The hard part is holding the sensor still and in the correct position while hitting the belt.

I also changed spark plugs to the denso iridium while I was at it, and I did a compression check to find that all cylinders are all in the 150psi range +/- 5%. I even did a coolant system leak down test, and that came back great, so no liner issues for me.

One scare: After all that work and buttoning up the engine to test it before going to bed, it fired right up, but there was a very distinct loud knocking noise coming from the engine that I clearly did not have 2 days ago. In the end, I guess all the spinning of the engine for the cam adjustment drained the lifters, because the noise went away after a couple of minutes of running, and now it purrs beautifully.

Also, I did not have to remove anything from the front of the engine except the 2 breather hoses from the air box to the plenum. Those were in the way of removing the two plastic cam covers and wrenching. The driver side cam belt cover is tricky to get off and put back on, but it can definitely be done without removing anything other than that breather hose. The manual says you need to remove a bunch of belts and pulleys to do the job, but that’s definitely not true.

Oh, it was a bit tight having room to work at times, but I did not remove the hatch. I did the broom stick method. I thought I could remove the hatch by undoing the 4 bolts for the hinge under the sun roof, but it typical Lotus fashion, the nuts are not captive and they are not accessible without removing a bunch of interior stuff, so I won’t be trying that again anytime soon.

Well that’s a lot of rambling, but hopefully some info in here will help others, At least now I can finally I can drive the car with confidence.

Big thanks to Matt for lending me the tools and Luis for sending them to me and helping over the phone!
 

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Philip,

Congrats for succesfully performing a major task on your V8! :up:

I do have a question though, did you ever determine if you have the Gates
"blue" belts or not? If so, I'm thinking that 135hz may be too tight as those belts are not supposed to stretch like the standard black belt.

The 120-135hz spec you were using for a new belt was spec'd for the standard belt. Lotus also spec'd 95hz - 120hz for a used belt so one would assume that would be the desired optimum tension for the belt over it's lifetime. The blue belts have never been tested by Lotus so it's really a crap shoot with them but 135hz could conceivably be too high if they don't stretch and loosen up...

Just an opinion and I could be totally off base...
 

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Discussion Starter #13
Yes they are the JAE blue belts (Gates). Everyone with blue seems to be following the revised Lotus specs.


1998 Lotus Esprit V8
 

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So once you set the belts correctly and have followed the proper procedure, and are certain that the tension is correct, is there no way to calibrate another method of checking the belts?
Not necessarily for a new install, but as a way to keep an eye on things. Whether it be using a phone app or a mechanical gauge like the Krikit.

It strikes me that if the procedure is so complex that errors are made by the pros, then there is a need for a simpler way to double check.

The goal of timing belt tension is to provide the minimum tension so as not to slip or slop or jump a tooth. Beyond that I'm guessing there is some leeway before the belt is so tight that damage is caused by too much tension.

I'm pretty compulsive, so I am not suggesting sloppy work, just looking for a better way, and an idea of the dangers of over tensioning by say 10-20%.

Randy
 

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Yes they are the JAE blue belts (Gates). Everyone with blue seems to be following the revised Lotus specs.
1998 Lotus Esprit V8
I agree, that's because they have nothing else to go by.

It would be interesting to see what your belt tension is after 1000 miles or so of driving. If you could be so persuaded to go through part of the agony again it would be a great service to the rest of the V8 community...:D

Lotus only spec'd 135hz for a new belt because it became a known fact that the standard belt would stretch within a given parameter. That was actually a revision from the original spec of 95-120hz which is now the spec for a belt that has been run in...

So, we need you V8 guys who have some mechanical aptitude to provide some continuing R&D for the new belt technology. :up:

And to what Randy posted about tension, there are many schools of thought of course, but I've had many discussions with Tim E about belt tension and it is generally accepted that for us 4 cyl guys anyway, to get the belt as tight as possible without introducing any belt whine when the engine is hot. I don't know that the same philosophy can be applied to the V8's though as the whole system is so much different and Lotus was much more specific about the tension parameters and measuring for the V8 engine.

Jim
 

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Discussion Starter #16
I'll definitely be checking the tension regularly, and I will report back.




1998 Lotus Esprit V8
 

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Discussion Starter #17
I am thinking there is a way to mark the cam pulleys for the current belt to make checking easier.

The old 4's have dots to line up. You can't make permanent marks on the V8 pulleys because of the design, but you should be able to make temp marks with a paint pen for a given belt.

It would have been good to mark the 10deg btdc and the check points for the left and right hand checks.

Oh well, next time. If I can skip doing all that pointer and timing disc stuff for annual checks before a belt change, it would almost make checking the tension a pleasure.

So once you set the belts correctly and have followed the proper procedure, and are certain that the tension is correct, is there no way to calibrate another method of checking the belts?
Not necessarily for a new install, but as a way to keep an eye on things. Whether it be using a phone app or a mechanical gauge like the Krikit.

It strikes me that if the procedure is so complex that errors are made by the pros, then there is a need for a simpler way to double check.

The goal of timing belt tension is to provide the minimum tension so as not to slip or slop or jump a tooth. Beyond that I'm guessing there is some leeway before the belt is so tight that damage is caused by too much tension.

I'm pretty compulsive, so I am not suggesting sloppy work, just looking for a better way, and an idea of the dangers of over tensioning by say 10-20%.

Randy



1998 Lotus Esprit V8
 

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Guitar Center is offering a tuner for $9. Is it worth trying to use it to tune the belts or is TuneIT! the way to go? I don't think you really need to use the cam checking pins except to make sure the cams are in tolerance. After that you only really need the crank pin to check the tension. Just don't forget to remove it BEFORE trying to move the crank! The tension on the V-8 is a lot more critical than on the I4. The motor expands more when hot. It will be interesting to see if and how the tension changes over time now that you have it set.
David Teitelbaum
 

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Discussion Starter #19
ITuneIt was reading very close to the Clavis, but it's a little harder to get a good reading since it doesn't stradle the belt like the Clavis. But you know when you have a bad reading because it's something ridiculous.

I wanted to make sure my engine was set up right, so that's why I used the 4 tolerance pins at first. And since you have to turn the engine twice every time, I was checking the 10deg btdc on a regular basis using a toothpick to make sure I wasn't off by a turn of the engine.
 

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Discussion Starter #20
I'm thinking I can further refine this process to the point that I can re-tension the belts without ever getting underneath the car, and needing only the special tensioner pulley spanner from Lotus.

What if you used a webcam on a stick to dip down to watch for the white painted mark on the crank pulley lining up to the crank sensor, and then checked with a toothpick if you hit the right cycle for 10deg BTDC?

Then you could confirm you have it exact with a drill bit that measures the same as a tolerance pins. Once you have 10deg BTDC, print up a reduced-size timing disc and attach it to the camshaft pulley instead of the crankshaft pulley and put a pointer to the 10deg BTDC.

Then you just need to move to 40 deg ATDC and 60 ATDC for each side of the engine (since the camshaft pulleys turn at half speed than the crank). Once you get those locations, use a paint marker to make a record for future tensioning, and remember to scratch them off when you change belts and re-do them.

By doing it this way, you would only need to jack up one side of the rear, pull off the wheel, and then lower the car back down to normal ride height since you don’t have to do anything under the engine. That way you don’t have to reach so far to work on the belts and still be able to turn the crank in-between adjustments.

I would use my iPhone for the freq, drill bits for the tolerance pins, and no need for the crank locking tool – only for checking and setting tension, of course.

Thoughts? Any ideas to make it even easier and quicker?
 
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