lotus timing belt issue

[andydclements]

I have resorted to removing the panel that surrounds the engine on my Turbo Esprit. With that removed it has approximately the same space as the S1 & S2 but die to more components, slightly less space. It's also an absolute pig to get off (grind out riv-nuts that have started spinning) and similarly awful to re-fit.

[molemot]

Once it IS off, though, things become easier...and when I did finally take mine off (after 20 years of ownership!) I dealt with the duff rivnuts by replacing them with real nuts welded to strips of steel, mounted to the car by pop rivets. Access to the fasteners themselves - I replaced mine with stainless - is easiest using 1/4" drive socket stuff...I bought some brilliant "wobbly end" extensions from eBay for very little, five or six different lengths in a red plastic tray. If one fits a socket to the end of the extensions and adds a bit of thin card or similar into the end of the socket, it will grip the head of the bolt and enables the bolt to be unscrewed and (with care!) withdrawn or replaced from it's inaccessible location. I also have a 1/4" drive extension which includes a screwdriver handle around the outside of the chrome vanadium steel centre...so one can attach a ratchet to the string of extensions and then, when loosened, undo the fastener in a civilised manner. Copper grease fights corrosion, and the next time it's a breeze.... I do tend to forget how awful it all was to start with; once the original designed in rust points have been done away with, then life is far more pleasant.

[scottmgibb]

I dealt with the duff rivnuts by replacing them with real nuts welded to strips of steel, mounted to the car by pop rivets.

That's exactly what I did (on both my Esprits) - works a treat! 5min job to take the boot floor and shroud off and away you go...

[MrDangerUS]

Here is an engine oil additive (blue bottle, LUBEGARD BIO/TECH ENGINE PROTECTANT, MOTOR OIL TREATMENT ADDITIVE , 30902), which increases lubricity of the oil and reduces the friction between all rotating parts, especially cam lobes and followers, therefore it helps increasing longevity of the belt. I use it combined with 8 oz of ZDDP per oil change.

http://www.ebay.com/...f4e0f17&vxp=mtr

Edited June 20, 2012 by MrDangerUS

[PilotSteve]

mine not done many miles but is 2.5 years old ,reading the service notes it needs a special tool for tensioning,does this mean that everyone cept me has such a device ? or is there a secret

[ramjet]

The special tool is a Burroughs gauge. Mechanical.

No, not everyone has one.

A lot of people are using a freeware program called TuneIt with a mic and are getting quite good repeatable results. Sonic.

[Sir Paolo]

There are usually three methods that are supposed to be complimentary to each other -

1) Burroughs Gauge

2) Krikit Gauge (made by Gates) pn 91107(?)

3) Hand twist method

All a bit cheaper than the sonic type

[910Esprit]

??? sonic type is free. Just did mine last weekend. Just need a laptop and microphone. Hand twist method is not a method! imho

[Vulcan Grey]

Acoustic method should only be used on the round tooth HTD type belts...

[910Esprit]

Well it works for me - I guess I'm just lucky. As Hz/Tension is based on a mathematical formula that can be applied to any drive belt, It may be more accurate to state that Lotus have not provided calibrations for the trapeziod belt? To avoid me passing on any more duff info, please can you direct me to the Lotus advice that it should not be used on a trapeziod belt? ta

Edited June 21, 2012 by 910Esprit

[Vulcan Grey]

Yes, of course the method will work on any belt, or rubber band, or wire, or steel cable, or even a bridge... But as you said, Lotus has not provided the specification for the trapezoidal belt...

Lotus does say

In order for these benefits to be applied to the Lotus 4-cylinder 912/910/920 engines, the following belt tensioning should be used on all such engines equipped with the 'HTD' (round tooth profile) type cam belt

https://docs.google.com/open?id=0B2nifoCpaFSfOGJkMjQxMDUtNzk1YS00YjEyLTgyZTAtYmI5NjE4MjgxMmRm&authkey=CO_S1NoE

[molemot]

Thinking from first principles...the fundamental frequency should only vary with the length between supports and the tension. My guitar strings are different thicknesses and materials depending on what their intended tuned frequency is....but, given the same length and tension, the frequencies should be the same. So....HTD belt or trapezoidal, shouldn't make any difference at all. It will affect the timbre of the note produced...what it sounds like, by changing the overtones and harmonics produced (that may be a tautology!) but you ought to get the same base frequency for the same length (fixed by the "pulley" wheel spacing) and tension...what you're trying to adjust.

[sailorbob]

Somewhere on the forum the frequency is given for the early belt, either calculated or confirmed by Ralph IIRC.

[Mr_John111]

IIRC

Trapezoidal belt is 114 Hz

John

[ramjet]

There are usually three methods that are supposed to be complimentary to each other -

1) Burroughs Gauge

2) Krikit Gauge (made by Gates) pn 91107(?)

3) Hand twist method

All a bit cheaper than the sonic type

Of those, I would only trust #1. I know people on here have used Krikit gauges, but Krikit maintain themselves that the Krikit should not be used on timing belts.

The hand twist method is worthless.

[Sparky]

I beg to differ. I used the twist method (and plenty of common sense) on hundreds of cars across a 20 year period and never had a belt fail within its service period. It's not perfect, but it'll get you to within a forgiving few percent of specification.

I've worked in a number of garages, and am yet to find a belt tensioner gauge of any description in any of their toolkits. Don't assume you're getting it done properly just because you're paying good money for it! Lotus excepted, of course. :-)

[ramjet]

But you can't use the hand twist method unless you have a tensioned belt to start with to understand the feel that a particular tensioned belt requires. It may be relevant for someone that does timebelts every day. For Joe Citizen, I would not recommend it.

If you can walk up to a car, cold and without any knowledge other than what is written in the specs, and hand twist a belt to tension, you're a MUCH better man than me Sparky.

[Mike6]

I started a thread some time ago before dismantling my engine - Burroughs or Krikit - which covered most of this discussion. I gave up getting hold of a burroughs and someone very kindly sold me a Krikit which I must say looks very basic but I know these are used extensively in the US and are made by Gates.

Last week I got to the stage of fitting the cambelt having replaced these on other cars without problem in the distant past. Mostly it is common sense, a loose belt might jump a cog whereas an overtight belt will squeel and could end up knocking out your main bearings, if it doesn't snap first. Using this approach I tensioned the belt using a new tensioner and noting the correct positioning so it cannot loosen in use.

It felt about right and roughly the same as before I stripped the engine. I then rotated the engine and rechecked. Not unsurprisingly the belt was looser so I retightened rotated the engine a few turns and checked again, all by hand and using twist method. Another tweak on the tensioner was need. I then tried the Krikit at same location (between inlet cam and auxiliary) but with engine at different points btc. There was a small difference on the reading but I was almost spot on according to the Krikit and the twist method. Although I have yet to restart the car I am fairly content that everything is OK.

It took me a long time to get this right (hopefully) and this was time that you just would not get in a garage, as Sparky says earlier and as I have found out on other jobs on my car garages cut corners and simply do not deliver what you think you are getting.

Apply common sense when fitting and I bet you will avoid all those problems associated with getting it done at a garage.

[Tony K]

I own two Borroughs gauges and two Krikkit gauges for Esprit timing belts. The Krikkits are more consistent than the Borroughs, and the Krikkits are consistent with each other. After you do it enough times on a particular engine, you can tell quickly by the feel and sound if you have it right. I think the safest and most sensible route is to use the gauges along with your common sense.

As for the Krikkit, yes, it says not for timing belts. The Krikkit has a flange along one side of the short end that you are supposed to line up along the edge of the V-belt to make sure it is located properly. Because of the timing belt's width, this puts the Krikkit off to the side of the belt, thus making it seem more slack than it is (pushing on the Krikkit begins to twist the belt). The key to success with the Krikkit on a timing belt is to be consistent in where and how you place the gauge on the belt. Same point of distance between the two sprockets, make sure it is perfectly straight, in the middle of the belt not to either side, and press down on the short end in a manner so you don't tip it toward the long end. Every time.

It only takes an extra minute or two to take half a dozen or more readings. It only takes a few more minutes to rotate the engine around again and take a few more. Spending an extra fifteen minutes to check it an extra few times is a no-brainer.

Just my .02 . . . .

[Sir Paolo]

Gents, I'm sure we've all read Lotus Guru Tim Engels detailed methodology about checking cam belts with Borrough's/Krikit and Hand.

But as has been mentioned, I'm sure experience will tell you when something is right.

BTW - I was fortunate enough to get hold of a BNIB Borroughs gauge. However, the leaflet inside states that you have to callibrate it by hanging a known weight off it, and moving the dial sticker if necessary.

Have any Borroughs owners callibrated their own gauges?

[910Esprit]

Yes, by suspending an old cambet (cut into a straight piece) from the garage ceiling and attaching a known weight from the end (If I recall, a spare TR6 overdrive gearbox I had was exactly the correct weight).

However, I sold the Burroughs gauge and now only use the 'controvertial' Tune-it method on a trap. belt