> Jensen Healey & Jensen GT Tech > Engine & Transmission > What cams do I have and is my timing off by a tooth? |
> Jensen Healey & Jensen GT Tech > Engine & Transmission > What cams do I have and is my timing off by a tooth? |
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cjwilson Member
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I have a bearing going out and am laying in the correct supplies and knowledge to tackle the bearing and timing belt change. My reason for this post is two-fold. When I purchased this car years ago, I remember the PO saying something about upgraded cams. I am wondering if I have the 2.2 upgrade? Also, when rotating the crank to TDC, it looks like the exhaust cam is off by a tooth. I would love input from the wise people here on what I have and if I should time it the same or bring the exhaust back by a tooth. The car is running well now! Edit: The pictures attached rotated by 90 degrees and I can't figure out how to fix. The top sprocket in the picture is the intake. Attachment: IMG_0496.jpg (Downloaded 155 times) Last edited on 06-02-2019 03:22 pm by cjwilson |
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cjwilson Member
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Here's the pic of timing notch at TDC Attachment: IMG_0494.jpg (Downloaded 156 times) |
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Esprit2 Member
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cjwilson, In your photo of the crank position, it's a little past TDC. Not a biggie, but accuracy helps when you're trying to judge errors. On the stationary tab that overhangs the pulley, the tops/ peaks of the timing ridges are the timing marks. Not the 'notch' or base of the ridge. The cam pulley timing marks must align "ON" the imaginary centerline between the cams. If they align, but are above or below the centerline, then the cams aren't properly timed. It would help if you were to post another wider-view photo of the cam pulleys that includes the hubs/ centers of both pulleys, if not their full front faces. See the photo I've posted. I marked-up yours, 'guestimating' where the pulley/ cam centers are. Presuming my centerline isn't totally off, it appears that the cams are timed at 115° INtake / 97° EXhaust (ie, 100° EX). "IF" you wish to preserve the early JH 115/115 emissions timing, then yes, the exhaust pulley is one tooth off. But in my feeble little mind, that's a big "IF". For optimal performance, both cams need to be re-timed to 110° / 110°. Read on. 110° / 110° is the design correct timing for the stock JH C-cam. That timing will give the best performance... the engine feels alive. 115° / 115° is the early JH emissions cam timing. It costs about 10 Hp, and the engine feels less than energetic. 100° / 110° is the later JH emissions timing. Combined with neutered ignition and lean carbs, it's the worst, the "Torqueless Wonder". cjwilson wrote: Also, when rotating the crank to TDC, it looks like the exhaust cam is off by a tooth.115° / 97° is where your cams appear to be currently timed (see my mark-up of your photo). Not correct to any JH spec, and not where you want them to be for the best performance. *~*~*~* Not relevant to your photo, but just FYI: With the later 100° / 110° 'emissions' timing... 100° was the intended emissions MOP... ie, the ugly goal. On a dedicated, SINGLE MOP pulley with one blue timing dot per side, 100° is really 100° On a multiple MOP pulley, as shown in your photo, the pulley's geometry/ math doesn't support both 110° (design correct) and 100° (emissions bodge) existing on the same pulley. So the target 100° was 'cheated' to the nearest MOP that did exist on the 110° pulley, which was 97°. Conversationally, both are referred to as, "100° MOP". *~*~*~* In many markets (most USA states) vintage cars older than a certain age no longer have to pass an annual emissions test. If that's the case for your car, and if you want the best performance available, then... Go to the 110° EX timing dot on your intake pulley. Follow that tooth to the back side of the pulley, and you'll find a 110° IN timing dot. Similarly for the exhaust pulley... 110° IN on the front, and 110° EX on the back. For both pulleys, the 110° timing marks you want are on the back sides of the pulleys. Remove the pulleys, flip them over front to back and re-install them. Then align the 110° IN dot on the front of the INtake pulley with the 110° EX on the front of the EXhaust pulley. "IF" your priority is optimal performance (design correct cam timing), then nothing you currently see on the front of your cam pulleys will get you there. Both pulleys need to be flipped over, front to back, before timing the cams. *~*~*~* Whenever you plan to be rotating the cams (playing with timing, or measuring valve clearances), first set the crank to 90° BTDC. That puts all the pistons half way down their bores, far away from all the valves. Then you can rotate the cams without risk of running into pistons and bending valves. When you're done messing with the cams, first align the correct timing dots "ON" the imaginary center line between the cams, then bring the crank back up to TDC. Now the timing belt can be installed and tensioned. Regards, Tim Engel Attachment: cjwilson - Cam Timing - Cam Timing Marks - Notes, 94kb.jpg (Downloaded 151 times) Last edited on 06-02-2019 08:28 pm by Esprit2 |
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Esprit2 Member
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Attachment: cjwilson - Cam Timing - Crank Timing Marks - Notes, 94kb.jpg (Downloaded 149 times) Last edited on 06-02-2019 05:33 pm by Esprit2 |
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Esprit2 Member
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cjwilson wrote:When I purchased this car years ago, I remember the PO saying something about upgraded cams. I am wondering if I have the 2.2 upgrade?The 2.2 liter 912LC used 107-cams on both the intake and exhaust. The later 912HC (high compression) used a mix of the street-hot 104 cam on the intake, and the 107 cam on the exhaust. Both of those cams required the use of Lotus' 104° MOP pulleys (green timing dots). 104° MOP doesn't co-exist with any other Lotus MOP on any pulley... there's just one green cam timing dot per side. Since your photo of the pulleys shows multiple timing dots, then they're the 110°/ 115°/ 97° pulleys ('ALL' other Lotus pulleys are single MOP). Taken on faith that someone knew what they were doing, that would indicate the cams are not 107s, or 104s. Yours are probably stock C-cams, but they could be Lotus D-cams, which were also designed to run at 110° MOP. When Lotus started using the 907 in their own cars, Federal emissions models got the C-cam (same as the JH), and all other markets got the D-cam. There isn't a big difference. C-cam . . . D-cam 0.340" . . . 0.350" . . . Lift 26° . . . . . 25°. . . . . . In. Opens, BTDC 66° . . . . . 65°. . . . . . In. Closes, ABDC 66° . . . . . 65°. . . . . . Ex Opens, BBDC 26° . . . . . 25°. . . . . . Ex. Closes, ATDC 52° . . . . . 50°. . . . . . Overlap 272° . . . . 270° . . . . . Duration 110° . . . . 110° . . . . . MOP, Design Correct OEM Lotus cams are marked on the bit of exposed cam between the front of the cam carrier and the back of the pulley. C-cam = no mark D-Cam = one groove cut all the way around E-cam = two grooves cut all the way around 107-cam = 7777777... stamped all the way around 104-cam = 4444444... stamped all the way around. Aftermarket copies or alternate cams don't follow that ID convention. They may not even be marked. All 'stock' JH 907s, in all markets, have the C-cam. A numbered cam name (104, 107, etc) refers to the last three digits of the Lotus part number. A numbered pulley name (100, 104, 110, 115, etc) refers to it's MOP timing. It's only a coincidence that a 104 cam requires a 104 pulley. Don't read too much into that. Regards, Tim Engel Last edited on 06-02-2019 06:59 pm by Esprit2 |
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cjwilson Member
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I've rotated it back around an posted another picture of the cam pulleys. Attachment: InkedIMG_0505b_LI.jpg (Downloaded 145 times) Last edited on 06-03-2019 05:27 pm by cjwilson |
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Esprit2 Member
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cjwilson, Draw in the imaginary centerline between the pulleys, and that photo pretty much confirms that, "IF" you wish to preserve the Original JH 115° IN / 115° EX emissions timing, then... 1) The intake pulley is correct, and... 2) The exhaust pulley is off by one tooth, counter-clockwise (retard). The 115° EX 'emissions' timing advanced the exhaust cam 5° to start with, and each whole tooth increment equals 18° crankshaft degrees; so your exhaust cam is currently retarded 18° - advanced 5° = 13° retarded compared to the design-correct 110° IN / 110° EX. "IF" you would like to take the opportunity to pick-up a little free horsepower, then re-time both cams to the design-correct 110° IN / 110° EX. As mentioned in post #3, that will require removing both pulleys, flipping them over, front-to-back, and re-installing them. A minor task. Then follow-up by re-timing the ignition's static advance to 12°-14° BTDC, and re-tuning the carbs for best running (richer) instead of emissions lean (too lean). Regards, Tim Engel Attached Image (viewed 0 times): Attachment: cjwilson - Cam Timing - Cam Timing Mark, Wide - Notes, 95kb.jpg (Downloaded 141 times) Last edited on 06-04-2019 12:13 am by Esprit2 |
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cjwilson Member
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Got your answer Tim. Thanks. So, I definitely will go to the 110/110 timing by flipping over the cam pulleys. I'll follow the write-up you wrote and put on face-book, but in that write up, you said set to TDC and start disassembly. Should I set to 90 BTDC so the pistons are down, remove belt, flip cams pulleys and set to 110/110, then rotate crank to TDC, then reinstall belt? |
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Esprit2 Member
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The main point is to stay focused while working, and be aware of where the pistons are before independently rotating the cams. Which includes accidentally rotating them while attempting to loosen or tighten the bolts that retain the pulleys. If you will be removing any T-belt pulleys, or the crank V-belt pulley, loosen those bolts while the timing belt is still on and tensioned. That way, if you accidently rotate the engine while wrenching on something, everything will still move together like they're supposed to. No valves get bent. Just crack the bolts loose, don't remove them yet. Then, as far as which one to put where first (crank or cams)... either way works, "IF" the timing belt is still installed and tensioned. I choose to set the crank to TDC first, because I'm lazy. That one action simultaneously puts both cams in their 'timed' positions, where you want them. Plus, more often than not, I'm just replacing a timing belt, and it's a convenience to have both cams close to their timed positions when you start. In your case, the exhaust cam will be one tooth off, but that's minor. Then, after the timing belt is removed, the FIRST STEP is to turn the crank back to 90°, putting all the pistons half way down their bores. The alternative is to set the crank to 90° first. Then, after the timing belt is removed, the FIRST STEP is to rotate both cams to their 'timed' positions. It's six of one, and half a dozen of the other... as long as you're thoughtful, and know where the pistons are before you rotate any cams. Again, more often than not, I'll just be replacing a timing belt, so having the cam pulleys start out where they need to be is a convenience. Since you'll be doing more disassembly, you'll have to re-position the cams after flipping the pulleys over anyway, so there's no advantage to following my preferred way. Use the method that makes you the most comfortable. *~*~*~* Both TDC and BDC put the valves at risk of being bent. At TDC, pistons #1 & #4 are at the tops of their strokes. At BDC, pistons #2 & #3 are at the tops of their strokes. Setting the crank to 90°, at either BTDC or ATDC, puts all pistons halfway down their bores, far from the valves. Once the timing belt is off, NEVER rotate the crank 'through' either TDC or BDC. Just go to the nearest 90° position by the most direct route without passing through TDC/ BDC. With the crank is set to a safe 90° position (BTDC or ATDC), you can spin the cams at will. The angles of the valves and diameters of their heads are such that even if two adjacent valves are fully opened simultaneously, they can't touch each other. So you can go nutz spinning the cams and not have to worry... once the pistons are out of the way. The wildest Lotus cam's valve lift is well less than 1/2" / 12.7mm, so the pistons don't really have to be half way down their bores in order for the valves to be safe. Don't get paranoid about setting the crank to exactly 90°... just eyeball close is good enough. 1) While the belt is still installed and tensioned, loosen all the bolts you will be removing. For the bolt retaining the crank's V-belt pulley, have a helper get into the car, select top gear (4th or 5th, whatever you have), release the clutch, and 'stand' on the brakes hard. That should hold the crank still while you apply torque to loosen the bolt. 2) Set the crank to TDC, or to 90° BTDC / ATDC, whichever is the most direct route to 90° without passing through either TDC or BDC. Both TDC and BDC are were valves get bent... stay away from both. 3) Remove the timing belt. A utility knife makes short work of that task. 4a) If the crank is at TDC, move it back to 90° BTDC by the shortest route. 4b) If the crank is at 90°, move both cams to their timed postions. Now everthing is in a safe place, and you can get to work. *~*~*~* Don't forget that the auxiliary pulley must also be timed. It drives the distributor, and if you just randomly change it's position during all your 'cam' & timing belt work, the ignition timing will be changed by a similar amount. Hold a straight edge between the centers of the aux pulley and crank's V-belt pulley. Place a white paint mark where that straight edge passes the lower rim of the aux pulley. When installing the timing belt, make sure the aux pulley is rotated as required to put that paint mark back were it's supposed to be. Rotate the tensioner's eccentric hub counter-clockwise to tension the belt. Yes, the eccentric will tension the belt in either direction. But if you rotate it clockwise to tension the belt, it will tend to back off in service. If you rotate it counter-clockwise, it will tend to stay where you put it. Regards, Tim Engel Attachment: 9XX Timing Belt - Routing & Tensioner Direction - 98kb.jpg (Downloaded 133 times) Last edited on 06-03-2019 11:35 pm by Esprit2 |
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cjwilson Member
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Hey Tim and the rest of the forum. I am back at the JH today. In the interim, my daughter bought a car and it needed a bit of work. Timing belt is back installed. It took a bit of fiddling to get marks to align once belt was tensioned, but overall a pretty simple job. I was wondering if there is a write up anywhere on how to correctly time the aux pulley? I think I have it correct from removal, but would like to read then verify. |
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Esprit2 Member
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What type of ignition system do you have? Stock breaker points, an early electrronic ignition that uses magnets (Pertronix Ignitor) or a light beam (Lumenition)? Or a more modern system that uses a Hall Effect sensor (Pertronix Ignitor II or III)? With points, magnets and a light beam, you can static time the distributor prior to starting the engine. With a Hall Effect sensor, you can NOT static time it, the engine has to be cranking at some minimum rpm before the system works. So, before I go off on some set of instructions, what are we trying to time? One thing for you to start getting your head around now is that the distributor is spring loaded outward. If you simply loosen the distributor clamp, the distributor will pop out of the oil pump housing. Then we'll be having another conversation about how to re-install the distributor. Place your left hand on the end of the distributor cap and apply inward pressure. Loosen the clamp and make whatever adjustments are necessary, all the while maintainiing inward pressure. Do NOT release that inward pressure until after the distributor clamp is tightened again. Re-read that until it's firmly stuck in your head. Regards, Tim Engel |
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cjwilson Member
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I've made that mistake before years ago. When I first bought the JH, I went to adjust the distributor and before I knew it I was standing there with the distributor in my hand saying oops. I didn't have the wisdom of this forum to back me up. It took quite a while to get back in. I'll never make that mistake again! I have standard points and condenser. Is it as simple as getting the crank to TDC, then rotating distributor so cylinder 1 is centered on the rotor. Then it should fire. Start and then adjust to 10 degrees BTDC. |
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Esprit2 Member
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See the file attachment in the previous message, #9. The upper-left view shows the pulleys. There's a dot on the bottom side of the aux pulley, on the rim. That dot is supposed to be on the imaginary centerline between the aux pulley and the crankshaft. "IF" that's the way the pulley was aligned before you took it all apart, and "IF" you put it back in that position, then the ignition timing should be the same as it was before. That could be either right or wrong, depending upon how the ignition was timed before. The distributor shaft and rotor turn with the Aux pulley. Technically, the distibutor doesn't care where the rotor is, you just rotate the body as required to 'time' it to the rotor's position. However, if the distributor has a vacuum capsule, then aligning the dot on the centerline puts the capsule closer to the oil filter than I like... not enough hands-room when you're changing the filter. I prefer to rotate the aux pulley ~2 teeth clockwise from the position shown in the illustration (dot on the centerline). Or, as far as I can to clockwise (toward the carbs) short of having the vac capsule interfere with the carbs or intake. Accurately set the crank to your desired static ignition timing. If your goal is 10 BTDC, then set the crank/ #1 cylinder to 10 BTDC. Remove the distributor cap and note the rotor's location. As you look at the open end of the distributor, the rotor rotates counter-clockwise. The plug wire terminal on the distributor cap that the rotor is 'approaching' is now #1. Connect the plug wire from the front spark plug there, and the rest of the plug wires in 1-3-4-2 order, counter-clockwise around the cap. For a crude 'eyeball' initial timing, loosen the distributor clamp and rotate the body clockwise until the #1 spark plug terminal aligns with the 'leading edge' of the rotor's metal blade terminal. If that's clearly not going to work because the vacuum capsule interferes with something, or one of the distributor cap's snap clips hits the block, or 'something' doesn't like that set-up, then... You can rotate the distributor body 90 degrees at a time, using one of the other plug wire terminals as #1 (remove & re-install the plug wires on the distributor cap). Does that get you to a set-up that satisfies all needs... nothing interferes with anything? If not, then rotate the distributor body to where it wants to be... where nothing interferes. Now you must turn the rotor to bring it into alignment with one of the plug wire terminal's leading edge. But turning the rotor means turning the auxiliary pulley along with it, and that requires removing the timing belt. Technically, any rotor/ aux pulley position that doesn't cuse something to interfere with something can be timed to work. The only 'magic' associated with putting the aux pulley's dot on the centerline between it and the crank is that Lotus determined that position wouldn't cause anything to interfere with anything else. It has nothing to do with making the engine run or not, it's just about making things fit together without interfering. And personally, I like to rotate the aux pulley about two teeth clockwise from there (viewed looking at the front of the engine) just to get the vacuum capsule as far away from the oil filter as possible, freeing up the maximum amount of 'hand space' around the filter. That's optional. So... 1) Set the crank to your target static timing position (like 10 BTDC), 2) Pick your rotor/ distributor's starting position... adjusting the Aux pulley on the T-belt if required. 3) Rotate the distributor body until the most convenient plug wire terminal aligns with the rotor's leading edge (remember, the rotor turns counter-clockwise). 4) Install the plug wire from the #1 plug on that terminal, and the rest in 1-3-4-2 order, counter-clockwise around the cap. Static Timing: Distributor clockwise (CW) and counter-clockwise (CCW) are defined while looking at the end of the distributor cap... or the open end of the distributor. Auxiliary & cam pulley rotation is defined while looking at the front of the engine, and hence, the opposite direction. When the points are closed, the coil-current goes directly to ground thru the points, so the light sees little current and is dim or off, depending upon the wattage of the blulb. When the points are open, the coil-current's only path to ground is through the bulb, so it turns on or goes from dim to bright. Using a simple continuity light, connect one wire to the coil's (-) terminal, and the other wire to a solid ground, like the engine block or battery (-) terminal. With the crank at your target timing point, switch the ignition 'ON', then loosen the distributor clamp (hold inward pressure). If the light is initially 'OFF', (or 'ON', but dim) rotate CW until the light turns on or goes from dim to bright... the points just opened.. If the continuity light is initially ON and bright, (or BRIGHTER than dim), rotate it CCW until the the light goes from 'on'/ 'bright' to 'off'/ 'dim'... the points just closed. Cleanly off or on doesn't matter... off is just an extreme case of 'dim'. The key pint is to watch for a transition point between bright/ on and dim/ off. Once you have found the on-off point, go CCW from there until the light goes off or dim, then a little more to allow for any slack. Reverse and slowly go CW until the light JUST goes on or bright... stop immediately. If you over-shoot, repeat the process until you successfuly stop JUST as the light turns on or goes bright. Tighten the distributor clamp, and switch off the ignition. Once you switch the ignition 'ON', work quickly to complete the process, then switch off right away. When the engine is running, the points open & close and don't carry full current long enough (duty cycle) to overheat. But if the ignition is 'ON' when the engine isn't running, then the points can be closed full time, overheat, and burn. It's a little like roulette... where will the breaker point be when the engine stops. So make every effort to work quickly and NOT keep the ignition switch 'ON' any longer than necessary. Start the engine. When it has settled down to a steady idle, check the timing with a strobe light. It should be very close to where you set the crank at the beginning of the static timing process. If need be, re-set the timing with a strobe light. If you don't have a strobe, then static setting the timing with a continuity light is more than accurate enough. If you don't have a continuity light, but do have an electric multimeter, then you can use the meter to replace the light. Select either the ammeter or continuity function, and watch for indictaions of On-Off (continuity), or More-Less current (ammeter). Regards, Tim Engel |
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cjwilson Member
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Thanks Tim. Probably won't have a chance to set timing today. I'll let you know how it goes.I think my timing will be correct from the start. My mark on the aux pulley is still there. And I did pull the distributor cap and can see that it's approximately clocked toward the #1 cylinder. It's tough to see down there with any degree of accuracy. Thanks again for all your wise input. |
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cjwilson Member
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Hey Tim, I posted a reply to this on another thread. Cam pulley swap went great. Timing was off by a couple of degrees and I got it dialed in after starting it. Runs beautifully now and has much more horsepower than it ever has since I purchased it several decades ago. Thanks again! |
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Esprit2 Member
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;-) Thanks for the update. I'm glad you like the results. This is probably redundant, but... IMHO, any owner of a stock J-H that no longer has to pass an annual emisions test, and that still has emissions cam timing (ie, anything other than 110 Int / 110 Exh) should take the little extra time required to re-time the cams to the 'design correct' 110 Int / 110 Exh cam timing the next time the timing belt is removed or replaced. Then follow-up by re-setting the static ignition timing to at least 10 BTDC (I use 12-14 BTDC), and re-adjusting the carbs for best running instead of emissions-lean. |
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