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Barthol Member
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Hi I noticed that my Cam Shaft wheels looks like they have been worn down. Unfortunately I did not notice wheter they looked like this when I changed my cam belt. Is this normal wear or normal design. My Cambelt is still tight ( If I twist it right over the termostat housing I can twist it 45 deg) Is this ok for tightness ? It runs without any noise . Any suggestions on what I should do? Best regards Kim Attachment: cam wheel wear.jpg (Downloaded 424 times) |
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Art DeKneef Member
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The cam wheels on one of my cars and a set from a parts car look the same. Based on this I am hoping it is normal and they came this way. My cam belt was adjusted to the same 45 degrees. It runs but I haven't been able to drive it on the street yet. Still have a few things to do yet. Art |
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Jim Ketcham Member
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The cam sprockets do not come this way. These are worn. |
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Brett Gibson JH5 20497 Member
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If they are shinny on the surface and have a bit of a lip on the tooth one edge or the other they are worn. |
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Jensen Healey Super Moderator 
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I used pulleys in this condition for several years before ordering some anodized pulleys from Mike at http://www.Lotusbits.com It sure would be a shame to lose an engine to belt slippage. Kurt |
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Barthol Member
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Hi I agree with Kurt. Loosing an Engine would be a shame. I´ve got a set Of E-cam Sprockets which are MOP 107. will they work with my C-cams? or do I need to find a new 110 MOP set. Is the wear caused by a too tight Cam belt or is it normal wear and tear whiz will come over the years? Best regards Kim |
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Brett Gibson JH5 20497 Member
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Usaully to tight a belt is the culprit. |
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Esprit2 Member
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Kim, The pulleys in your photo are worn and should be replaced. A timing belt that's too tight might aggrevate the situation, but it's not the primary cause. The early J-H pulleys were not hard anodized, have a shiny appearance on the wear surface (like yours), and tend to wear relatively rapidly just because they're too soft for the task. Later J-H pulleys, and all Lotus pulleys were hard anodized for anti-wear protection, have a dark muddy-gray-green color (almost black), and provide long service without noticeable wear. Note that not all anodizing is hard anodizing. Bright colors are not hard anodizing and offer little wear protection. Do NOT use your E-cam or 107 MOP pulleys with your C-Cams. Nothing bad will happen if you do, but the engine will not run at it’s best. The E-cam used a 102.5 MOP (Yellow dot) pulley. There is no 107 MOP pulley! But there is a 107 camshaft that seems to be popular with J-H owners, and it uses a 104 MOP (green dot) pulley. The "104" in a PULLEY name refers to the valve timing MOP (Maximum Opening Point) that the position of the keyway in it's bore produces. The "107" in the CAMSHAFT name refers to the last three digits in it's Lotus part number. At some time, Lotus revised the part number format for camshafts. Originally, all cams had the same part number, and each cam was identified by a different prefix letter. The C-cam was C907E0351Z. With the new format, the C-cam was given the part number F907E0101G, and should have been called the "101" cam. However, the "C-cam" name stuck, and is still it's street-name to this day. Same with the D-cam (102) and E-cam (103). The 104 and 107 cams missed all that fun, and never had prefix part numbers/ names. It's just coincidental that a 104 camshaft also uses a 104 MOP pulley. Don't get confused by the similar number naming. The 100 MOP (blue dot) pulley is really 97 MOP. For some reason (??) they rounded that one off, but all the other pulleys are accurate as marked. If you are ever trying to degree a blue dot pulley, use 97 degrees in order to get the math to work out. In any case, don't use your E-cam pulleys or 107 pulleys (whichever you have) with the stock J-H C-Cam. Buy replacement 110 MOP pulleys to make the engine that run better & stronger than stock. Or, if your engine originally came with 115 MOP pulleys and 'must' still pass an annual emissions check, then buy replacement 115 MOP pulleys. But buy HARD anodized pulleys. All Lotus OEM pulleys are hard anodized. *~*~* The stock J-H C-cams are designed to run with 110 MOP (red dot) pulleys. The 115 MOP pulleys that were stock on early J-H 907s are for reduced emissions. They reduced the valve timing overlap, reduced the power output by about 10 Hp, and marginally reduced emissions. The later 100 Intake (blue dot) / 110 Exhaust (red dot) set-up was also for reduced emissions, but took a different approach. The ignition timing was also severely retarded, and the fuel mixture was very lean. This set-up is the original "Torqueless Wonder". A design-correct 110 Intake/ 110 Exhaust engine easily passed the 1972 Federal emissions standards; however, the Federal gov't had already published the new, more strict standards for 1974. The 110/110 set-up would also pass the '74 standards, but just barely. So, the original 115/115 cam timing was used in order to provide a larger margin for wear and mis-adjustment. Lotus didn't wish to go through the expensive Federal Certification any more often then absolutely necessary, so the 115 Int / 115 Exh set-up was used from the very beginning of production... even though the 1972-73 cars didn't need it. *~*~* The tensioner has enough adjustment range that the belt can usually be tightened to spec even with worn pulleys; however, the depth of tooth engagement is reduced by tooth wear. Since the engagement depth with new pulleys is pretty marginal to begin with, the loss of any engagement due to wear increases the risk of jumping timing, and isn't acceptable. Replace the worn pulleys. *~*~* The twist test is a workable way of checking the timing belt tension, "IF" you have the experience required to know what it's supposed to feel like. The big problem with it is that results vary widely with an individual's hand strength and experience. It is far better to invest in an inexpensive Krikit KR-1 tension gauge from any Gates Rubber dealer/ parts store. In North America, NAPA stores carry the Krikit KR-1. If it's not in stock at a local store, they can order it from their central warehouse. I have a NAPA receipt from my last purchase and the line-entry reads: Qty .. Part No . Line . Descrip.. Price ... Net ..... Total .. Code .1 .... KR-1 ..... NBH . Gauge .. 10.89 .. 10.89 .. 10.89 . T6N Krikit on NAPA Online (under US$15.00). http://www.napaonline.com/Catalog/CatalogItemDetail.aspx/Belt-Tension-Gauge/_/R-NBHKR1_0006447252 … Or … https://napaonline.com/Catalog/Result.aspx then search for “KR1“ in the “Find a Part” dialog box … Or … http://tinyurl.com/odau6c3 Krikit on Gates Rubber Website http://www.gates.com/europe/brochure.cfm?brochure=2505&location_id=2976 None of the various tension gauges directly measure belt tension. The Krikit KR-1, Kent-Moore KM-128 and the Burroughs BT-33-86J each measure different attributes, and then relate that back to belt tension. For the same belt tension, they each produce different number values. Don't get caught-up in the exact 'numbers'. Burroughs 95 is NOT the same as Krikit 95! For the Krikit KR-1 on the J-H/ Lotus 907, use these values: 44 Too loose. Don't drive it. 50 Normal minimum before requiring adjustment. 52 Used belt – target for re-tensioning a used belt. 55 New belts – set a little tight the first time to allow for initial stretch. 58 Too tight (do not exceed 100 Burroughs / 55 Krikit). Krikits have two scales... be sure to read the POUNDS scale ! Use at your own risk. Lotus doesn't recognize the Krikit KR-1 or the tension values given above. This is a grassroots alternative, and the tension values were obtained by direct comparison to results produced by the Burroughs gauge that Lotus specifies. Last edited on 05-05-2014 04:42 am by Esprit2 |
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pbahr Member 
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Tim, Is the tension the same for the rectangular and the later Lotus half-moon belts? YELODOG |
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Frank Schwartz Member
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After looking at my cams etc. I can see they are worn, too. I know I can get a set of Lotus half moon ones for close to six hundred dollars, but someone told me that there were anodized regular ones out there that last a long time. Does anyone have these, or a good set of these..or??? Thanks, Frank Schwartz 1110/18299 73 JH |
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Jensen Healey Super Moderator
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Hi Frank, contact Mike at http://www.lotusbits.com He probably has the anodized 110 pulleys (sprockets, cam wheels) in stock. They are listed on his website for 15 pounds, about $25 each. Shipping will generally double the cost but he can't control international shipping prices. Kurt |
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John Finch Member
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Hello Barthol & Frank, how many miles on your cars? |
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Barthol Member
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Hi John, Mine is 79300 miles. I do not know the service history as it is a US import . br Kim |
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Frank Schwartz Member
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Without looking, I guess about 75 thousand or more Frank |
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Esprit2 Member
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pbahr wrote:Is the tension the same for the rectangular and the later Lotus half-moon belts?Pete, Sorry about keeping you waiting... I'm not a regular here. Short answer: Yes, for all practical purposes, but it's not apples to apples. The official Lotus gauge was the Burroughs BT-33-86J, which is sensitive to belt thickness. Thicker belts give higher readings, and the HTD/ round-tooth belt is thicker than the trapezoidal tooth belt. As Lotus gained experience with the trapezoidal tooth belt, they kept playing with the tension spec... 90 Burroughs to begin with, then 95-105 (100+ is too high), then finally 90-95. 95 is in the middle of all that, and the value I have used with satisfactory results for decades. When Lotus switched to the HTD belt, they didn't issue a new gauge, or re-calibrate the old one for the new thickness. They recommended tensioning the HTD to 95 on the old gauge, but the result would have really been something a bit lower... in the 90+ range somewhere. So both belt types are playing in the same general tension area. After playing with both belt styles for a lot of years, I've settled on the same tension for both: 100 for a new belt to allow for initial stretch. 95 when re-tensioning a used belt that's broken in. Experience showed that a new belt would lose about 3-5 lbs of tension in about the first 1000-1500 miles... after the initial stretch settles down. Rather than have to re-tension every new belt at that point, I just dialed in that much extra to begin with. I still check every new belt's tension in 500 mile increments until it's tension settles down, but it rarely requires adjustment if I start at 100 Burroughs/ 55 Krikit. The Krikit conversion factor came about over time by tensioning many belts with a Burroughs, then cross-checking it with a Krikit. The KR1 always produced number values that are about 55% of the Burroughs values. The rest of the values I posted near the end of the 8th post, above, are based upon my experience/ opinion, and are not Lotus specs. The J-H tension spec (3 1/2 on the KM-128 = 35 Kilopond = 77.2 lbs-force) may be low, and I don't recommend following it until that can be confirmed. I don't know exactly what characteristic the KM-128 measures, or if 77.2 on the KM is anything like 95 on the Burroughs. I won't even crank a 907 over if the belt tension is under 80 Burroughs; and as a number, 77 just makes my skin crawl when used in the same sentence with, "907 timing belt". But again, I don't know how number values correlate between the KM-128 and Burroughs BT-33-86J (I don't own a KM-128). Having said all that about low tension values, JAE has worked with Gates Racing to develop an HTD belt that uses current technology HNBR rubber. The belt is BLUE, thicker yet, stiffer, and responds differently to all of the factory specified gauges. At 95 Burroughs, it whines, a sign that a belt is too tight. The tension has to be dropped down to 80 Burroughs before the whine subsides. At that point there's still a slight whisper, but I give in to my old bias and won't go below 80. Call it superstition. Last edited on 05-28-2014 08:43 pm by Esprit2 |
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Barthol Member
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Hi Just replaced my cam pulleys. As you can see the belt now moved towards the engine and is flush with the rear of the pulleys. Is this normal, or is there a way to control that the belt stays in the center? I guess that the wear on the old ones dictated the belt to stay in the center?? BR kim Attachment: cam wheels.jpg (Downloaded 261 times) |
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Frank Schwartz Member
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Where did you source the pulley set? Frank |
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Barthol Member
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got them from Lotusbits in the UK. Br Kim |
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Frank Schwartz Member
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And the cost? And all four or only the two cam wheels? |
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Barthol Member
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I only bought 2 pcs , and I think they were around 15 GBP each plus PP You can see the prices on his homage http://www.lotusbits.com Br Kim |
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Esprit2 Member
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Barthol wrote:As you can see the belt now moved towards the engine and is flush with the rear of the pulleys.Kim, There is no adjustment that will move where the timing belt tracks. It is what it is. Ideally, the belt should run in the center of the pulley, but it rarely ends up being ideal. I understand you purchased pulleys from Lotusbits, but are they J-H, Lotus, or aftermarket replacement pulleys? Even though they might "fit" (as in, bolt on), not all pulleys have the outer rim centered on the hub in exactly the same way; so it may be that the pulley rim moved, not the belt. For example, in around 1979 (?) Lotus re-drew their own pulleys in order to "metricate", and took the opportunity to slightly change the hub to rim relationship. With all else remaining the same, and in perfect condition, simply switching from older to newer production Lotus pulleys will slightly change were the belt 'appears' to track on the pulley... but it will be the pulley that moved. Having said all that, it's not normal for any Lotus 9XX belt to run on the edge as shown in your photo. I suspect something else is at play there. If everything about the engine is straight, parallel and per the design drawings, then the belt will track in plane with the small drive sprocket down on the crankshaft. The belt won't move with the cam pulleys if the pulley offset changes. So that begs the question, when you replaced the pulleys, did the belt move, or did the pulley rims move? *~*~* On the other hand, if the main bearing bore, block deck, head or cam carriers are machined out of alignment such that the crank and cams aren't parallel when assembled, then the belt will track off the cone of the non-parallel center lines. The most frequent cause is having the head skimmed to flatten the bottom surface. When the head warps, the whole thing warps like a banana, not just the bottom. If only the head's bottom is skimmed independent of everything else, then the bottom may be flat, but is it still parallel to the camshaft... wherever the camshaft moved to during the warping. If not, then the cam will no longer be parallel to the crank, and the belt will track toward the convergence of the crank & cam center lines. Similar but different, if the stud that mounts the timing belt tensioner pulley is bent or it's mounting hole is drilled out of parallel with the crank & cams, then the belt will walk off the resulting taper. All working axis must be parallel. If not, the belt will walk out of alignment with the drive sprocket on the crank. If your belt isn't wandering back and forth as the engine runs, then there's no cause for concern if it runs off center. At least as long as it's not hanging over the edge of the pulley, and stays were it is without wandering. Last edited on 05-28-2014 08:51 pm by Esprit2 |
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Schorse Member 
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I just realised that I still have the federal cam timing (115-115) and I was going to change it back to european spec (110-110) Do I have to adjust the ignition and carburettor set up after changing timing? |
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Jensen Healey Super Moderator
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The ignition timing should be checked if the belt is removed from the auxiliary sprocket. The carburetors should be fine but it never hurts to balance them. |
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