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> Jensen Healey & Jensen GT Tech > Engine & Transmission > Need to change out the Timing Belt Tensioner |
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> Jensen Healey & Jensen GT Tech > Engine & Transmission > Need to change out the Timing Belt Tensioner |
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| Need to change out the Timing Belt Tensioner | Rate Topic |
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| Posted: 05-23-2019 04:05 pm |
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1st Post |
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cjwilson Member
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Starting to get an intermittent bearing noise from the front of the engine. Have found it's the tensioner for the timing belt. Is there a good writeup anywhere? I have the older style which apparently needs a thin wrench squeezed between the pulley and the block to capture it in order to loosen. Is there a good source for the bearings?
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| Posted: 05-23-2019 05:16 pm |
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2nd Post |
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Esprit2 Member
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cjwilson, Have you replaced timing belts before? The 907 is an interference engine, which means that if the timing is off, or if the belt jumps timing (too loose), the pistons will hit the valves and bend them all. Things get expensive in a heartbeat. The 907 isn't a good engine on which to learn. It's not especially difficult, it's just not forgiving of mistakes. To remove the tensioner, you'll just need standard tools. The special thin wrench is only required for adjusting the tension during installation. But you WILL need it before your job is complete, and I don't have a source for you. Check with Delta Motorsports, or maybe someone else on this forum can point you toward an over-the counter bent wrench. Options would be to start with a thin bicycle wrench, and have a shop bend it for you. Or start with a crowsfoot wrench, and have it cut down to the appropriate thickness. The bearings in that early tensioner are just standard 6005 ball bearings... available through industrial bearing distributors 'everywhere'. Or, contact any Jensen-Healey parts specialist. JHPS has a tech article about replacing those bearings, here: http://www.jensenhealey.com/tech/bearing/bearing.html An alternative to rebuilding would be to replace the old tensioner with the later style tensioner that uses the dedicated tensioner bearing. A purpose-built, double-row bearing in which the outer race is the tensioner's roller. The main advantages of that type of tensioner are: 1) Both the tension adjusting hex head and the retainer nut are on the front of the tensioner. Access is much easier, and no special bent wrench is required. 2) No need to rebuild the old tensioner. Just replace the one-piece, combined bearing/ tensioner roller. 3) The later bearing/ tensioner roller is more durable. Back in the Fall of 2017, Pieter Van Ruth, qwerty on JHPS, machined up a custom batch of the later-style tensioners, specifically dimensioned to be a drop-in replacement for the early tensioners. He sold them to J-H owners on sort of a group buy basis. You might try touching base with him to see if he's still selling them. Enter "qwerty" in the JHPS forum's search function, or go to this thread: http://www.jensenhealey.com/forums/view_topic.php?id=2356&forum_id=2&page=1 Regards, Tim Engel Last edited on 03-23-2023 04:22 am by Esprit2 |
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| Posted: 05-24-2019 07:39 pm |
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3rd Post |
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cjwilson Member
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Thanks Tim. I've ordered 2 good quality SKF 6005 rubber sealed bearings. I've done a couple of timing chains so not overly concerned. I'll go slow and careful. I'll try to bend a wrench out of the old wrench pile.
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| Posted: 05-25-2019 07:13 pm |
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4th Post |
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Esprit2 Member
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Chris, A 'thin' wrench is easier to bend, and easier to use in the tight space. And torque capacity isn't a factor for simply turning the eccentric to tension the belt. It's not like tightening the retaining nut to 25-30 lbf-ft, which requires more of a 'real' wrench. A 'service' wrench, or a bicycle wrench is a good starting point for a 'bent' wrench. Turn the eccentric COUNTER-clockwise to tension the belt, and the tensioner will hold it's setting in service. If you erroneously turn it clockwise to tension the belt, then there is a real risk that it will back off in service. Clockwise & counter-clockwise are as viewed from the front, looking back at the front of the engine. As the retaining nut is tightened to 25-30 lbf-ft, friction will drag the eccentric along with it, changing the tension setting a little. Set & tighten once, then check the tension and note how much it changed. The re-set the tension higher than you intended by that 'change' amount, and re-tighten. That should put the end result pretty close to where you want it to be. Stray Note: If you remove-replace the cam or auxiliary sprockets, torque-tighten them to 25 lbf-ft. *~*~*~*~* The standard BLACK belts (early HCR & later HSN rubber) should be tensioned to: For Installing a NEW belt: 97-100 if you have a Burroughs gauge (BT-33-86J, or BT-33-73F) 53 - 55 if you have a Krikit KR-1 (use the POUNDS scale). For Re-Tensioning a USED belt: 95 if you have a Burroughs gauge (BT-33-86J, or BT-33-73F) 52 if you have a Krikit KR-1 (use the POUNDS scale). New black belts stretch initially. Proper procedure is to monitor a NEW belt's tension frequently over the first 1000-1500 miles (until the tension stabilizes), re-adjusting it as required. That's a bit of a pain in the butt. An alternative that works is to set a NEW belt's initial tension a little higher than spec. Then continue to 'check' the tension periodically over the first 1000-1500 miles... but you shouldn't have to re-adjust it. Typically, as the belt does it's initial stretch, the tension will settle down to the target 'used' setting. Long term, 95 Burroughs or 52 Krikit KR-1 (pounds scale) is what you want. The NEW-belt 'high' settings are just an expedient to eliminate the potential PITA work of re-adjusting the tension during the first 1000-1500 miles. When you periodically check the black belt's tension... 90 Burroughs / 50 Krikit KR-1 is the normal minimum-limit tension... re-adjust it. *~*~*~*~* For the current HNBR rubber BLUE belt (Gates Racing T104RB): 83-85 with a Burroughs gauge (BT-33-86J, or BT-33-73F) 34-35 with a Krikit KR-1 (use the POUNDS scale). One benefit of the Blue belts is that they're very stable... they don't stretch. Continue to check a new belt's tension periodically, as noted in the service schedule; but once tensioned when new, you'll rarely, if ever have to re-tension a Blue belt... they just don't stretch. Therefore, there's no difference between the tension specs for NEW Vs USED Blue belts. Note that the BLACK-belt tension spec given in the original J-H Workshop Manual is out of date, and too low. Use the above tension specs instead. And the Blue belts ARE different, and require a different tension. Regards, Tim Engel Last edited on 05-25-2019 10:08 pm by Esprit2 |
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| Posted: 05-26-2019 03:09 pm |
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5th Post |
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cjwilson Member
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Thanks Tim! I'll chime back in once I receive the bearings and start to work through this.
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| Posted: 05-26-2019 06:34 pm |
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6th Post |
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Frank Schwartz Member
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Tim..and others: So what is the tension requirements for the blue belt. I do not have a tension measurement tool. Most of us with the black belts use the twisting method..but I have a blue belt I'm going to put on a JH and wonder about this. Also I do have one of those tools for the early type JH idler adjustment. I will be happy to lend it to anyone who needs to use it...on loan, of course. Regards to all, Frank
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| Posted: 05-26-2019 06:38 pm |
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7th Post |
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Frank Schwartz Member
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The Blue belt: I bought this one from the local O'Rielly auto part store. Not in stock, but a special order. No problem doing this. It is not cheap but looks to be very good quality. Frank P.S. I would like to have a belt tension gauge. Can someone suggest a good one and a source??
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| Posted: 05-27-2019 01:45 pm |
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8th Post |
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Brett Gibson JH5 20497 Member
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Frank, this is the one I use, probably less expensive ones out there. Brett. https://www.mcmaster.com/belt-tension-gauges
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| Posted: 05-28-2019 12:27 am |
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9th Post |
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Frank Schwartz Member
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Which one in particular? Seems they are for V belts... Frank
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| Posted: 05-28-2019 04:06 am |
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10th Post |
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Esprit2 Member
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Frank, See message #4, above, for tension to use with the Gates Racing BLUE timing belt (both trapezoidal and round-tooth HTD). Lotus specified the Burroughs BT-33-86J gauge, but it's hard to find and more expensive when you do. The BT-33-73F is commonly available, more reasonably priced, and it's readings are within a pound or two of the 86J. The Burroughs gauge is more expensive, while the Krikit KR-1 is cheap (~$15 at NAPA). But you definitely get what you pay for. The KR-1 has two tension scales... always read the POUNDS scale. Use only the KR-1, "NOT" the KR-2 or KR-3. Note: 34-35 'Krikit' is off the low end of the KR-1's scale. Use the points of a dial caliper to scribe additional lines, extending the scale. Or suck-up and buy a Burroughs. Frequency meters work well, and there are apps for your smart phone. But the only frequency tension spec Lotus ever gave (1997-ish TSB) is for the black, round-tooth HTD belt. It does NOT apply to the trapezoidal belt. 100-110 Hz with the crank set to 30 BTDC... not TDC as with other methods. Regards, Tim Engel Last edited on 05-28-2019 04:17 am by Esprit2 |
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| Posted: 05-28-2019 04:28 am |
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11th Post |
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Esprit2 Member
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Frank Schwartz wrote:Which one in particular? Seems they are for V belts...Frank, Of the various Krikit models, use only the KR-1. And read the POUNDS scale. Yes, it's made for V-belts. But it gives consistent, repeatable readings on the 9XX timing belt. Not the same number values as on the more expensive Burroughs gauge, but they correlate consistently. As stated in Msg #4: Gates Racing Blue Belts, HTD & Trapezoidal On a cold engine, with the crank set to TDC: 83-85 on a Burroughs gauge (BT-33-86J, or BT-33-73F) 34-35 on a Krikit KR-1 (use the POUNDS scale). McMaster-Carr's price for the Burroughs is scary-high. Google Burroughs BT-33-73F. You can do much better. Regards, Tim Engel Last edited on 05-30-2019 08:41 pm by Esprit2 |
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| Posted: 06-06-2019 04:47 pm |
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12th Post |
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cjwilson Member
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I decided today was the day to tackle this. I got the tensioner off and find that it's the newer style with the adjuster on the front. Bearing is definitely bad. A bit of PB Blaster freed it from being almost completely locked up. My problem is that the 6005 bearings I bought don't fit this type of tensioner. No biggie there. Is there a replacement bearing for this tensioner? Or do I have to buy a new one? Attachment: IMG_0531.jpg (Downloaded 192 times) Last edited on 06-06-2019 04:54 pm by cjwilson |
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| Posted: 06-06-2019 07:23 pm |
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13th Post |
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Esprit2 Member
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That 'IS' the bearing. Unlike the early JH tensioner, there is no outer ring/ roller into which the bearings fit. The belt runs directly on the bearing's wide outer race. The eccentric hub is still a descrete part. Press it out of the old bearing, and into the new one. Contact Delta Motorsports or any of the Lotus parts suppliers for a replacement bearing. It's a standard bearing, and I used to find them at local bearing distributors. But they seem to be less available that way now, and It's just less hassle to simply call your favorite JH/ Lotus parts specialist. SKF. . . - 414871A . . . - Excellent quality, strongly recommended, my personal favorite. Flennor - FS03299 . . . - Now sold by JAE, but they can provide the SKF if you ask for it. INA. . . - 531 0098 20. - ?? In general, INA is a quality brand. Timken - TKR 9841. . . - ?? In general, Timken is a quality brand, but all Timken production is now in China. Ford . . - 1500004 . . . - 1977-1986 Ford Transit Van "Blue Bird" is a brand of Chinese bearing some vendors were selling for use on the 9XX engines. Don't touch it with a ten foot pole. Regards, Tim Engel Last edited on 06-06-2019 07:28 pm by Esprit2 |
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| Posted: 06-06-2019 07:54 pm |
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14th Post |
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cjwilson Member
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I just ordered the Flennor FS 03299 from JAE. Should be here in a few days...
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| Posted: 06-06-2019 11:24 pm |
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15th Post |
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redracer Member
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I suppose I should have responded earlier, but since I read you had ordered a pair for the earlier style tensioner, I did not reply. I, and quite a few others, do not like the later style tensioner for 2 reasons; 1) they are very expensive(they were in the $80 range 20 years ago; have no idea what they cost now, but don't want them anyway). Just ordered SKF bearings on AMAZON for about $18/pair. Takes me 1/2 hour to R&R the bearings, using Loctite 242 (or 620 for worn housings)on the outer surface. 2) they have a flat surface for the back of the belt as opposed to the slightly concave style of the earlier ones that had the safety factor of making sure the belt would stay on the surfaces. We used to retrofit the earlier style to all the '75 & later vehicles. One very important note that I published in the White Lady, issue 62, June 1993, page 11 (I had told Greg Fletcher he was welcome to reprint any of my articles if he wished, but I guess this was not done). The very early outer shafts have a length of 21mm as opposed to the later style ones of 19 mm. The problem arises if you attempt to use the LATER longer style OUTER washer on an earlier hub;the longer washer will NOT compress on the inner hub of the metal bearings, no matter how much torque you place on the locknut. This will OBVIOUSLY lead to the tensioner turning, loosening the tensioner and breaking valves, etc. However, please feel free to follow your own thoughts, but please be aware. best wishes, bruce
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| Posted: 06-07-2019 11:36 am |
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16th Post |
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cjwilson Member
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As a side note, I received a KR-1 belt tension meter in the mail a couple of days ago. Just before I started disassembly I thought I would check my belt tension. More to see how the tool works before having to check tension on an installed belt that will have to be correctly tensioned. It read 38 pounds. Maybe that's why it was off a tooth.
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| Posted: 06-08-2019 12:03 am |
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17th Post |
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Tom Bradley Member
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On problem I have had with getting the marks properly lined up when installing a new belt is getting all the slack out in the long run between the crank and the exhaust cam. What I have had to do is rotate the cam pulley half a tooth or so CW, install the pulley over the cam teeth, then rotate the cam back to where it should be, removing the slack in the belt. Then the marks should stay lined up after the belt is tightened.
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| Posted: 06-08-2019 04:17 am |
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18th Post |
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Esprit2 Member
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cjwilson wrote:It read 38 pounds. Maybe that's why it was off a tooth.The KR-1 has two scales. Are you sure you read 38 on the POUNDS scale. If so, with a black trapezoidal tooth belt, 38 pounds on a KR-1 equates to about 69 lbs on a Burroughs gauge. That's way loose! Count yourself lucky to have only had one pulley jump one tooth. It could have been far worse. Regards, Tim Engel Last edited on 04-22-2023 05:29 am by Esprit2 |
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| Posted: 06-08-2019 05:20 am |
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19th Post |
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Esprit2 Member
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Tom Bradley wrote:What I have had to do is rotate the cam pulley half a tooth or so CW, install the pulley over the cam teeth, then rotate the cam back to where it should be, removing the slack in the belt.Tom. That's correct procedure. All parts in the engine have dimensional tolearances, and in an assembly the tolerances are additive. As a result, it's highly unlikely that with the crank at TDC, and the pulley timing dots perfectly aligned, that the belt's and pulley's teeth will perfectly align and drop together. And then there's the matter of pulling all the slack out by hand... it can be difficult. As you wrote, put a wrench on the exhaust pulley's retaining nut, and turn the pulley clockwise (as viewd from the front) toward the crankshaft 'just' far enough to engage the first available belt tooth. Then turn it back, pulling the slack out of the long run to the crank, and putting a little bit of tension in it... but not enough to pull the crank away from TDC. Then repeat for the intake pulley. The belt is very stiff side to side. If you slide it fully onto the exhaust pulley first, then it's too stiff to make a zig-zag move to align with the intake pulley. Instead, slide the belt onto the exhaust pulley only 3/8 to 1/2 inch... just enough to engage firmly. Then repeat the pulley rotate-hook-pull with the intake, leaving both only partially engaged with the belt. Hold the belt in place with a little tension toward the auxiliary pulley. Then switch to the tensioner-side of the engine. Pull the run of belt from the crank sprocket firmly up and around the tensioner, only partially engaging it. Finally, pull the belt strands from both sides toward the auxiliary pulley. Rotate the auxiliary pulley as required to ensure that the distributor's rotor is where it needs to be for correct ignition timing, then slide the belt loop onto the aux pulley. Only now, with the three sprockets and the tensioner partially engaged, do you go back and push the belt all the way onto them all. Crank some strong tension into the belt, enough to pull out all slack and add some strong tension. Don't sweat 'correct' tension for now, just strong tension. Now, make certain the crank is still at TDC, then double check the cam pulley timing dot alignment on the imaginary centerline between the cams. If the dot alignment is a mis-match, or not on the centerline, then go back and fix it now. When all the pulleys are correctly aligned with the crank at TDC, rotate the crank through two full revolutions, and back to TDC. Have the spark plugs all out so a minimum of force is required to turn the crank. Rotate it with a little mechanical empathy, 'feeling' for the crank to cluck to a stop. That would be a piston hitting a valve... don't force it! Stop immediately and figure out where you went wrong. If you get through two full revolutions without clunking to a stop, and all the timing marks still align, then the belt installation is correct. Now properly tension the timing belt. Use a gauge and the tension values given in message #4. *~*~*~* One more point (I sound like Columbo). Even with the tensioner backed off all the way, there's NOT a lot of slack in the belt loop. It can still be a bit of a struggle to get the belt stretched onto the auxiliary pulley. While the belt is very limp radially, it's very stiff if you try to bend it across it's flat strand width. Use that against it. Pull the loop up onto the auxiliary pulley as far as you can, engaging teeth on either side as far up as you can. More than likely, there will be the last little bit in the middle that will be a bugger to get up onto the pulley. Leaning in over the left fender (wing), facing forward, left hand nearest the intake pulley and right hand nearest the tensioner... lay one hand on the the top/OD of the aux pulley, where that last, obstinant bit of belt loop is, with your fingers extending past the front edge of the pulley by about two knuckles. Bend your fingers, folding the top of the belt loop over, laying the belt flat against the front of the pulley. Bend your fingers at the last (outer) knuckle, hooking the edge of the belt, and pull up firmly. The belt, being stiff the flat way, will slide up the face of the pulley until it's edge just barely passes the diameter of the pulley. Not by a lot, just barely, but it's enough. Now pull/rotate the belt loop back up to a horizontal position, catching the edge of the pulley, and slide the belt back onto the pulley. Do that as one dance move... pull-rotate-slide, and the belt will go right on. Actually, with practice, the whole procedure is 'one move' that takes less than a second... fold-pull-rotate-slide. It goes right on every time. Regards, Tim Engel Last edited on 06-08-2019 05:30 am by Esprit2 |
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| Posted: 06-08-2019 11:57 am |
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20th Post |
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cjwilson Member
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Sure I read it right! I count myself lucky every day.
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