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green dot pulleys installed

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I just replaced my cam belt (blue race belt) and decided to install the green dot pulleys while belt was off

the job was not too bad, I did have to fashion a short gear puller to remove all 3 pulleys

I wish I had installed them years ago

everyone says they make such a minor difference so it was low in priority

however, they make the car more driveable when there is no boost

the engine always seemed breathless until the turbo kicked in

the best way I can describe thier effect

would be to say that the engine seems more like a 2.4 L with the pulleys than a 2.2

driving around town with no boost

much more pleasurable

if any have not done it, the cam belt change is the time to do it and only $250

well worth it



just because I don't CARE doesn't mean I don't UNDERDSTAND

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Chris Yes I have a concept for an autotensioner, but needed to finish the belt first to ensure the loadings are correct. That is nearly done but I now need an engine to play with to get the Autotens

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Two questions i have to ask

1.what is a blue race belt ? is it a special cam belt . you think the difference is not as much the cam gears as maybe you were always a tooth out (before)?

a picture or two would be nice

Technically sound ...Theoretically poked !

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Good move on green dots... these set the timing to 104/104 instead of 100/110 which is a retarded setting for the cams. The design profile setting for these cams is 104 so it will always run better because the cam timimg in now correct..... I went one step further and put on adjustable pulleys to make sure they were set spot on. The overlap on the valves on the rock is much stronger and allows a cleaner charge of fuel as so better ignition , hence the better low down performance. You may find the exhaust note a little more poppy on back off depending on your system.

Your next move should be induction, standard system throttles it . best fit ram air system this allows the turbo to work much better, it won't have to suck so hard to get the air to blow. result...... quicker spool up , better and smoother all around perfomance.

Well done


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yes, set TDC on crank and dots on cam pulleys facing each other

i needed a small flat gear puller, one with adjustable (slotted) holes to grab the cam pulley. I used small bolts and big fender washers

through the holes in pulleys.

pretty easy

blue race belt is made by Gates for lots of cars. JAE in the USA sells them for Esprit $200. Gates says you can double the change period under normal driving

JAE also sells the green dot cam pulleys. one is required at $250. there is already one on the aux shaft (oil pump). just swap with one of the cam pulleys

the cam alignment was correct before the change. and pretty much perfect after the change. not sure why some people need an adjustable pulley...?

Travis has a nice Word doc with plenty of pics for the belt change

post-144-002887100 1288833324.jpg

post-144-020123100 1288833978.jpg

Edited by ragingfool35



just because I don't CARE doesn't mean I don't UNDERDSTAND

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JAE implied that they have Gates make the belt only for them. I believe it since Esprit is such a low volume niche vehicle.

some of my buddies do the Jap tuner car thing and all use the blue race belts in their Hondas and such

even though there is a much higher volume in that area, the cost of the belt is the same

you may be able to special order or otherwise obtain the belt for the Esprit through that venue

Gates supplies the standard belt for the Esprit, so try ordering Gates T188 in Blue Race

JAE gives outstanding support to Esprit owners at a reasonable price, so I always choose to support them by ordering from them

just found: (good ole Tim!)


I wrote the original Lotus message that was quoted in part in Msg #42. I'm in the USA, but that message is scattered all over the Lotus community. I'm not surprised someone found it on a UK site.

The basic belt is an industry standard HTD spec with a 0.375" tooth pitch and 133 teeth. When they're made, they're laid-up in very wide bands on a drum mandrel, and then narrow loops are sliced off in whatever width is required for a given application.

Belt technology has evolved over time, and continues to do so. The basic dimensions of the .375 pitch HTD have remained the same, but the materials and lay-up have improved.

The Gates T188 belt is a .375" pitch HTD-spec that's 25.4 mm (1.0") wide, and made to the original mid-1980's technology (circa 1985-86?). The main components being HCR rubber (High-Temp Neoprene/ Chloroprene) and a glass cord body. They're the inexpensive "economy" belts you can still buy. They're not as stable, so check the tension regularly; and they don't last as long so replace them more frequently. The Gates T188 part number works in North America and Australia (elsewhere?). In the UK, the T188 is known as the Gates 5168NS (or the long version: 5168-58133-1-209DS). 5168NS may work in parts of Europe, but there it's also known as the Gates 5206 for the Peugeot MI 16 L4 1.9 DOHC. T188, 5168NS and 5206 all come off the same tooling, they just have different markings printed on them.

The Gates T249 belt is dimensionally the same as the T188, however it uses HSN rubber (Highly Saturated Nitrile) that was introduced a decade later (around 1994-95) and has reinforced teeth. The T249 is significantly more durable, so the belt change interval is much longer. They're the "long life" or "extended service" belts.

The current, modern generation of timing belts uses HNBR rubber, which is another quantum leap forward in durability (HNBR = Hydrogenated Acrylonitrile-Butadiene Rubber... the "N" is for Nitrile, the common nickname for Acrylonitrile). The Gates Racing version of the HNBR belt uses a glass cord body, Kevlar tooth reinforcement and a Nylon tooth jacket that, overall, doubles tooth strength. Unfortunately, I've not found any manufacturer, including Gates, who is bothering to develop HNBR belts for old applications... there are no listings for the old Nissan VG30E, Peugeot MI16, Honda B20a applications.

However, JAE, an independent Lotus parts supplier in Goletta, CA, has worked directly with Gates Racing Products to develop an HNBR version of the .375" pitch HTD for use on the Lotus engines. Gates Racing does low-volume, short-run products for special, high performance racing applications, and operates outside the normal Gates "big business", so they were willing to produce a special belt.

The .375" pitch HTD belt Lotus uses is unique in being a little wider than most at 26.4 mm (1.039"). Most other applications, like the Nissan VG30E V6, Peugeot MI16 L4 1.9 liter DOHC, and the generic Gates T188 and T249 belts are 1 mm narrower at 25.4 mm (1.0") wide. If the wider Lotus belt will fit on your Honda pulleys, then it's otherwise the same pitch, mesh, number of teeth and length.

For my education, what is the Honda B20a OEM belt's width? Which Honda models use that engine/ belt. That would be helpful cross-ref info for Lotus owners.

I'm a Lotus guy, I don't know Honda or the B20a engine (I found this site while searching for other Lotus timing belt cross references), and I don't know if your engines can accept a 1 mm wider belt than the standard Gates T188 / T249. But if you're interested in the HNBR belt upgrade, contact:

JAE, Jeff Robbinson, (805) 967-5767.

I'm new here and the system won't let me post an email address until after I’ve posted 5 messages, so here's Jeff’s email non-address.

Jeff at JAEparts dot com

The HNBR belt is expensive at something north of US$100, but it's better, stronger, more durable. It's also more stable and will have to be re-tensioned less often. The Lotus engine uses a manual tensioner, so that's important to us.

I have no business interest in JAE. I'm just a Lotus owner, and I've found JAE to be a straight-up resource I can trust. However, they don't know Honda, so you'll have to work with them collaboratively if this HNBR belt is to be of any value to the Honda world.

JAE has made the HNBR belt they developed available to other Lotus vendors if they wish to carry it. If the HNBR belt fits Honda applications, I'm certain Jeff would be happy to work with a Honda specialist or two in order to make it more available to Honda owners. But I'll leave that up to you guys to work out if you're interested.



This thread started in Nov, 2005 when Redexcel posted a copy of a message I'd posted on YahooGroups. That's cool, it's all info to be shared. However, that's a file I keep and update from time to time, and the version Redexcel posted is out of date now. Here's the current version... for what it's worth. If you have more to add, let me know as I'm always updating it.

If the forum owner or Redexcel could edit the original message to delete most of the body and refer to this message, it may minimize confusion. I'm the original author of both, so no one should be offended by the deletion (it's not censorship).


Lotus 9XX Timing Belt Cross-Reference Guide

by Tim Engel, Lotus Owners Oftha North, USA -- Revised 30 Oct 2008

Lotus OEM 9XX timing belts are unique in that they are 26.4mm (1.0394”) wide. Other manufacturers' engines (like Nissan VG30E 3.0 liter V6 and Peugeot 405, 1991 1.9L DOHC) use a similar 133 tooth belt, but narrower at 25.4mm (1.0”) wide. Some Lotus owners are using such belts either as a matter of convenience (local availability) or price. While it may be that less expensive belts can be found, the Lotus OEM belt isn’t unreasonably expensive, and it is the proper width.

If your 9XX is equipped with HTD pulleys, I strongly recommend buying a timing belt which is made using HSN rubber (ie, the later, B-prefix Lotus belt).

More important than the 1mm difference in width is proper tension, regular maintenance, and on-time replacement. The 9XX engine is not a clearance engine, which means that if the timing belt breaks, or jumps timing sufficiently, then the pistons will strike the valves. In which case, things get very expensive, very quickly. The timing belt is not the place to go cheap, or to get lazy about maintenance.

Lotus 9XX Timing Belts:

TRAPEZOIDAL, ~SQUARE Tooth Timing Belt, HCR Rubber (High-Temp Neoprene/ Chloroprene).

Prior to 1986 Model Year, all 9XX

A907E0191Z, trapezoidal tooth, 133 teeth, 910, 911 and 912 LC (Low Compression)

A907E0191ZE, trapezoidal tooth, 133 teeth, 907 (Z and ZE suffixes interchangeable)

B907E1050FL, trapezoidal tooth, 137 teeth, 907 (Federal Elite/Éclat with air injection pump).

The Lotus OEM belts are 26.4mm (1.03937”) wide. The following cross-reference belts are all narrower at 25.4mm (1.0") wide, have 133 trapezoidal teeth, are specified for use on earlier 3.0 litre Nissan VG30E engines and fit the 9XX as well… if you accept that they are 1mm narrower.

* Gates T104

* Gates 5146

* Dayco 95104

* Flennor 41133

* Goodyear 40104

Lotus Change Interval: 24,000 miles / 24 months (street logic = 12,000 miles/ 24 mo).

HTD, ROUND Tooth Timing Belt, HCR Rubber (High-Temp Neoprene/ Chloroprene).

HTD = High Torque Drive

1986 Model Year Onward , all 9XX

A912E6697F, HTD round tooth, 133 teeth, 910 HC, 910 HCi, 912 HC (high compression).

* Gates T188 in the US, Canada, Australia and New Zealand (others?),

* Gates 5168NS in the UK (or the long version: 5168-58133-1-209DS),

* Gates 5206, (Peugeot 405 X-ref). and

* Dayco 95188

The following cross-reference belts are all 25.4mm (1.0") wide, 133 teeth, and are similar to the original Lotus HCR round tooth belt (A-Prefix / pre-HSN)... but again, 1mm narrower. They will fit, but they shouldn't be run as long between changes as the wider Lotus belt.

Lotus Change Interval: 37,500 miles / 36 months

* Peugeot 405, 1991 1.9L DOHC

* Nissan VG30E SOHC V6 engine variants with HTD belt (ie, after Aug 1994)

The Gates T188, 5168 and 5206 are all basically the same Gates belt. The differences are in proprietary markings for specific engine applications, markings that don't apply to the Lotus engine anyway. Get down to the basic Gates belt, and the T188 = 5168 = 5206. What you order will have more to do with which part number works in your part of the world.

Gates Catalog data for the T188, HCR Rubber, HTD belt:

Profile Type: ... Curvilinear (HTD, or High Torque Drive)

Product ID:...... 85950084

Part #:........... T188

UPC Code:....... 072053384888

No of Teeth:.... 133

Pitch (In.)........ 0.375” (9.5 mm)

Pitch Length... 49.875” (1267 mm)

Top Width:...... 1.000” (25.4 mm)

Material:......... HCR (Hi Temp Neoprene)

HTD, ROUND Tooth Timing Belt, HSN Rubber (Highly Saturated Nitrile)

1995 Onward, 910 Esprit S4s and standard HTD service replacement hence forth.

B912E6697F, HTD round tooth, 133 teeth, 912, 910 - 1995 on, California requirement.

HSN, used in order to meet California requirement for a 100k mile belt service interval.

Owners without warranty coverage should limit service life to 50,000 miles.

The followint is written on the side of a new B-prefix Lotus OEM HTD belt:

"Gates PowerGrip HTD Made in UK B912E6697F (464DS)". DS = Made in Scotland.

The following cross-reference belts are all the HSN version of the HTD belt, but in the narrower 25.4mm (1.0") width. They fit, they work, but being narrower you should back off from the Lotus-spec replacement interval.

* Gates T249,

* Dayco 95249

* Goodyear 40249

Lotus Change Interval: 50,000 miles excluding California, 100k in Calif by law, not by choice.

Nissan Change Interval: 60k to 105k, depending upon engine variant & application.

Gates Catalog data for the T249, HSN Rubber, HTD belt:

Profile Type: ... Curvilinear (HTD, or High Torque Drive)

Product ID 85950350

Part #:........... T249

UPC Code:....... 072053081435

No of Teeth:.... 133

Pitch (In.)........ 0.375” (9.5 mm)

Pitch Length... 49.875” (1267 mm)

Top Width:...... 1.000” (25.4 mm)

Material:......... HSN, Highly Saturated Nitrile

The B-prefix version of the Lotus HTD belt is made with HSN rubber (Highly Saturated Nitrile rubber). That's a very tough, wear resistant rubber, and Lotus specified the longest service interval with that belt. It was introduced in 1995 in response to California's requirement for timing belts to last 100k miles, and henceforth it became Lotus’ default service replacement HTD timing belt. If you want the best belt for your 1986 or later HC engine with HTD pulleys, then the HSN HTD is the one you want. You can get an B-prefix, HSN, HTD timing belt in the correct Lotus width from any Lotus dealer or from most independent Lotus parts suppliers.

To the best of my knowledge, the trapezoidal belt is not available in HSN rubber, either for the Lotus applications, or for any of the noted cross-references.

By law, California cars from 1995 onward (HSN belts) were required to go 100k miles before replacing the timing belt. That was mandated by California law and Lotus had to comply if they wished to sell cars in California. The extended service interval was NOT a result of some superior construction used on those engines. For the rest of the world, Lotus recommended 50k mile change intervals for the same B-prefix, HSN timing belts. That should tell you something.

If the warranty has timed out and "you're paying the bills", I would strongly suggest staying with the shorter service intervals.

The latest (2007) belt technology uses HNBR rubber for the new, more stringent, mandated service life of 150,000 miles (HNBR = Hydrogenated Acrylonitrile-Butadiene Rubber... acrylonitrile is commonly referred to as just Nitrile). Gates HNBR belts are blue, so there shouldn’t be any mistaking them.

Lotus Cars has not developed HNBR OEM belts for it’s old, out of production engines, nor made service interval recommendations for them; but the specified replacement interval for older Lotus belts generally went about half the life expectancy of normal "civilian" automotive applications. The new HNBR is supposed to be the belt to meet the US government mandated 150k service interval, so I'm thinking 75k in the 9XX 4-cylinder engines. For a typical Lotus, that will be a long time. Just my thoughts, use your own judgment, your mileage may vary, yada-yada-yada.

JAE is working with Gates to make HNBR belts available in Lotus sizes (as well as Cosworth race engine sizes). The HNBR belts are in stock for the 918 V8, will be in stock for the HTD 4-cylinder applications soon (today is 30 Oct 2008), and HNBR versions are under consideration for the trapezoidal 4-cylinder applications. They’re not cheap (approx US$168), but they will approximately double the belt change interval.

If your parts guy finds a basic belt for you, then ask him if there's a newer HSN or HNBR cross-reference available. Better yet, just call JAE. Either way, buy the best you can get.

Change interval synopsis:

Trapezoidal (original, old technology) - 24,000 miles/ 24 months (street logic = 12,000 miles).

HTD - old HCR A-prefix belt...... - 37,500 miles/ 36 mo.

HTD - HSN black B-prefix belt... - 50,000 miles (no time ref.).

HTD - HNBR blue belt.............. - ?? ~75,000 miles?? Just my guess.

If you choose to run one of the narrower belts, I would suggest not going the full interval between changes. How much less? Your guess is as good as mine and I'd prefer you be responsible for your engine since you’re making the choice to run the narrow belt.

Just my humble opinion: I prefer to service and replace the 9XX timing belt much more often than specified. For trapezoidal toothed belts, I use 12,000 miles or 2 years, whichever comes first. For HCR HTD, 25,000 miles or 3 years. For HSN HTD, 36,000 miles or 4 years. In each case, that's less than the Lotus manuals specify.


UK-owners have reported getting no where when asking for a Gates T-188 (the old HCR / pre-HSN HTD), but advise asking for a 5168NS works (NS = Non Standard). The belt that's delivered often shows up with this long part number: 5168-58133-1-209DS. "5168" is the main identifier portion of the number. DS on end of part number indicates Made in Scotland. In the overall Gates world, it's a T-188.

Others in the UK and continental Europe have had success ordering belt number 5206, the Peugeot Mi16 1.9 liter belt.


The Nissan Maxima belt reference is for the VG30E SOHC engine as used in Maxima, Pathfinder, some? Pickup Truck, 87-88 200SX and 84-94 300ZX non-turbo. It uses a 133 tooth timing belt that will also fit on Lotus 9XX engines. However, like the Lotus engines, the Nissan went through an evolution of timing belts. So which one will fit your Lotus depends upon the year.

The earliest versions of the Nissan VG30E engine used a trapezoidal toothed belt that will also fit early Lotus 9XX engines (pre-1986).

Later versions of the VG30E went through a series of different round-toothed timing belt styless. Don't make the mistake of assuming all round tooth timing belts are created equal and put just any round tooth Nissan belt on your 9XX.

Nissan round tooth belts:

*Pre – July 1993 = Shallow Groove, round tooth, 60k miles? No, don't use.

*Jul 93 - Aug 94 = DEEP Groove, round tooth, 60k miles. No, don't use.

*Aug 94 Onward = HTD (Gates T188), 105k miles <<<< Use this one !

Lotus HTD owners should use the last version of the round-tooth Nissan VG30E timing belt (Aug 94 onward - Gates T188 HTD belt).

For the US market, Ford used a variation on the same Nissan engine in the joint-developed Villager/Quest mini-van. However Ford insisted the engine be re-designed for a clearance valve train (pistons don’t hit the valves if the timing belt breaks). The result was the V40 engine = Villager/Quest mini-van. But I'm not certain the Ford-spec version used the same T-188 timing belt ?? Something else to check out.


Okay, now I'm just rambling on…

Servicing the timing belt:

HTD, ROUND tooth timing belt service intervals

6,000, Check tension. Re-tension only if required.

12,500, Check/ Adjust Timing Belt Tension

12,500, Inspect Timing Belt condition

12,500, Inspect Tensioner Bearing condition

12,500, Inspect valve timing (dot alignment on pulleys)

12,500, Check valve clearances, recommended

37.5k or 36 mo, Check / Adjust valve clearances, required

37.5k or 36 mo, Renew Timing Belt, required -- A-Prefix HCR (Pre-HSN) A912E6697F

50.0k, Renew Timing Belt, required -- B-Prefix HSN (Pre-HSN) B912E6697F

Miles or Months

Tensioning the timing belt:

Lotus originally recommended the Burroughs gauge for tensioning the timing belt, then the expensive Clavis Frequency meter. If you don’t have access to either of them, then….

The Krikit KR-1 is manufactured by HMC International and sold private labeled by many retailers. Gates carries it so you can ask any Gates retailer to order it for you. NAPA carries it also. The counter guy won't know what you're talking about, but work with him.

The Krikit KR-1 comes in two versions. The 91107 (common in the USA) reads in pounds & kilograms, and the other one (P/N - ???) reads in pounds & something else (?). In either case, read the pounds scale and the following will apply.

Tim Engel's Krikit KR-1 Guidelines - all caveats apply, YMMV, yada, yada, yada.

Burroughs......Krikit KR-1 ranges (my judgment, not Lotus - tim engel).

.............80 = 44 Park it... proceed at your own risk.

.............90 = 50 Normal minimum (okay, but schedule adjustment)

.............95 = 52 My routine used belt target tension when adjusting.

...........100 = 55 New belts to allow for stretch (just me, YMMV).

...........105 = 58 Too tight, IMHO.

Burroughs......Krikit KR-1

PROCEDURE for Checking Timing Belt tension: (Lotus Workshop Manuals & Service Notes)

1) Cold engine, before it's been started for the first time that day.

2) Do NOT attempt to tension a hot engine.

3) 15° - 25° C (59° - 77° F) ambient temperature.

4) Rotate the crankshaft a minimum of one turn clockwise.

5) Set crankshaft TDC with the timing dots on the cam pulley rims aligned.

6) Check belt tension at a point midway between the INTAKE camshaft

.... pulley and the AUXILIARY pulley. Do NOT check tension at any

.... other point !

7) Take three readings at 120°crankshaft degree intervals.

.... (0° TDC, 120° & 240°)

Average the three readings for a final tension value.

That's the official procedure. But I've never found a significant difference between the average of three readings and the reading taken at TDC. I usually just take one reading at TDC and call it good. Readings are not very repeatable and there's as much variation between successive readings at any one point as there is between readings at the three different positions.

The engine expands as it heats up, stretching the timing belt more. A belt properly tensioned to Burroughs 95 cold will increase in tension to approximately 125 at full operating temperature. All tension readings taken on a hot engine are bogus unless you have some sort of temp Vs tension conversion chart (none exists). So, simply do not attempt to check or set the tension at anything other than the conditions given in steps 1-3 above.

Later (1997 ??), Lotus specified using the Clavis Frequency Meter for tensioning the timing belts. It's important to note that the new procedure specifies measuring the frequency response with the crank set to 30 BTDC, NOT TDC as with the previous Borroughs/ pounds specs. That's a significant point of difference... don't mix up the two crank positions.


Tim Engel

Lotus Owners Oftha North

Edited by ragingfool35



just because I don't CARE doesn't mean I don't UNDERDSTAND

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Good info.

The HNBR belt drives that go to 150K miles tend to have auto tensioners. It gives much better control of the tension on the belt and reduces the damage to the belt caused by over or under tension. The HNBR has been around now for some time. I used it ten years ago to develop the first 150K mile production belt drive and have since refined it further to allow it to run in oil. This has also been successfully in production for the last 3.5 years in a mass produced engine and many other mainstream car companies are working hard to include this technology on new models as it has should significant benefits over some chain drives, again it is signed of for 150K miles. I actually run engines for twice that distance and it was the engine that finally expired not the belt.

With regard to long life belts, I have already had some 133 tooth belts produced for me not only using HBNR, but I have also been playing with the fabrics and coatings to not only get the wear reduction, but also to lower friction. I also developed this some time ago (13 years ago). A couple of these are on test, unfortunately in cars rather than on Dynos, but the extensive testing I have already done to develop this technology into powertrains means that I am confident that doubling of the service life should not be an issue. On some of the more recent ideas I have worked on, 250K miles + could be achieved. Unfortunately this would mean a massive tearup to the front of the Esprit engines so is probably not viable. I am also trying to finalise an autotensioner design that could be retro fitted so I can extend the limit further. As a matter of interest, when I have used the technology I have made the belts from, on mileage accumulation fleets, I have seen the belt life go from 30K miles in some cases, to in excess of 150K miles and still with plenty of life left (Autotensioners also fitted)

Hopefully this will be available soon, currently wrestling with the commercial issues. Price will be cheaper than the $200 you quote.



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[the cam alignment was correct before the change. and pretty much perfect after the change. not sure why some people need an adjustable pulley...?

To answer your question :-

The reason people use adjustable pulleys is to make sure the cam timming is perfect . NOT pretty much perfect. And more to the point what the hell is pretty much perfect. Idon't wish to be critical of such a good thread giving so much great info on the cam timming and belt situation. But unless you set your cams up with a DTI you will not know how accurate your set up is. The standard dot pulleys give a very good guide to an approximate possition for cam timming. This is on a factory built engine with the correct head gasket fitted as factory. If an engine has been worked on and head skim carried out , or even just a new gasket fitted. then the timming will vary. Buy using adjustable pulleys you can eliminate these variants . More important they cost not much more than std green dot pulleys. This is why people fit adjustable pulley systems.

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perhaps that came across wrong...

thanks for the clarification

yes they do seem to be utilized after a rebuild (you and Dermot)

they would give perfect static timing at the time when they are set

I wonder how much the timing varies with engine load and belt wear?

to make it worth that extra step

pretty much perfect is probably a half of a degree

belt stretch as the load varies (I have no idea how much) would make the timing operate in a range

I would hazard a guess of 0.5-1 deg, Ralph would probably know

the overall gain might be miniscule

are there any concerns or tradeoffs when using an adjustable pulley?

do they lock enough not to worry about slipping over time?

or do you have to check them periodically?

anyway, now I know the reason!


Edited by ragingfool35



just because I don't CARE doesn't mean I don't UNDERDSTAND

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Thats fine, belt stretch would be insignificant due to design format of said belts and timming would not really be affected. I have had adjustable pullies on all my race engines for as long as i can remember and never had one slip, but i would always add it into a service to check for peace of mind. All the small improvements we make add up, individually the make little differance but collectively,significant gains can be made. keep up the good work!


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Yes I have a concept for an autotensioner, but needed to finish the belt first to ensure the loadings are correct. That is nearly done but I now need an engine to play with to get the Autotensioner in the right place. I dont really want to remove the engine from the Esprit for that purpose, but my Sunbeam is already out and in bits. Problem is that the Esprit get jealous then keeps looking for attention stopping me from getting on with the Sunbeam, but it is moving up the to do list quite fast..

With regard to cam timing error, this will depend on the engine the layout and the belt used. When we set our timing we set it statically. Unfortunately when the engine is running the system becomes dynamic. In our engines, there are torsion inputs coming from the crank, eg after the spark plug fires, pressure builds and subsides in the cylinder causing different rates of angular acceleration during each engine revolution. we also see positive and negative torsional effects from the camshafts as they open and close the valves plus the oil pump is also a source of variation as the oil pressure in each part of the rotors rises and falls as part of the process. When you put all this together at the same time like it or not, each cam will see a plus or minus variation (cam ref crank) from the nominal position it was originally set as the engine cycles. I have seen variations of several degrees on some engines if a system resonance is encountered making it very important to ensure the cam timing is accurate. I have seen on engine that was set up using the correct timing tools which had seen better days (a bit worn) and the valves hit the pistons. There is sometimes as little as 5° or 6° allowable before terminal damage can become reality. Note that once the belt tension drops the potential for dynamic error increases as the magnitude of cam movement can increase. The transition from slack to tight also accelerates the damage to the belt which is why autotensioner work so well, as they limit this.

With regard to the adjustable pullies, they are a good way to set the cam timing to be accurate. The cam, pullies etc are all made to a tolerance so in theory there is a lot of potential variation on the timing in addition to the above. If you set the timing to be accurate using adjustable pullies then some of the variables are reduced



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Oi - My Esprit is still waiting for parts from overseas ,I got the lump out so if you wouid like a Guineapig , I am happy to do it.

I will pay the shipping costs as well.


[email protected]

Technically sound ...Theoretically poked !

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Ralph, Whilst my S4 isnt ready yet from its renovations...I was aiming to take the engine out for service and general overhaul of gaskets etc and the tanks in a couple of months..I dont know whether that would be opportune for you? As with all projects...they get delayed so could set anything in stone just yet



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