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| Cam timing | Rate Topic |
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| Posted: 07-30-2021 11:34 pm |
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1st Post |
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mgfaber53 Member
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Hi all - newbie here, after many years of lusting after a JH, I finally found the right car at the right price. A '74, #19024. Previous owner just rebuilt the engine. Cam timing at 110IN 115EX. I've gone through the forums and the shop manual, and it seems it should be 110/110? Haven't located the engine number yet. Set static timing at about 14 BTDC, seems to run smoothly. Can someone sheds some light on this for me? Last edited on 07-30-2021 11:35 pm by mgfaber53 |
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| Posted: 07-31-2021 12:29 am |
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2nd Post |
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redracer Member
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Sounds like you got yourself a nice one--5spd at that. Many threads have been written on this, but the 110 IN & EX are what you want. Assume you have a workshop manual, but the maximum advance I leave at 30, BTDC. (don't care what the idle is, which will usually be 10-15BTDC). Advise you plug up the vacuum retard capsule(on the dizzy)with a steel ball in the 90 degree elbow coming off the back-center of the intake manifold. keep us posted, bruce
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| Posted: 07-31-2021 01:23 am |
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3rd Post |
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mgfaber53 Member
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Thanks for the info Bruce - just what the doctor ordered. The vacuum line is plugged, but the steel ball is a much better solution. It's a decent car - very straight body, no rust other than the floor pans. Tranny seems good. Fuel replaced gas tank. Lots of work, but I'm semi retired and wanted a project.
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| Posted: 07-31-2021 06:41 pm |
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4th Post |
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Esprit2 Member
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The 110 IN / 110 EX cam timing is what you want for best running/ best performing (emissions not being a consideration). Are both timing marks (110 & 115) on each pulley? As in, does the current 115 EX exhaust pulley also have a second, unused timing dot next to a 110 mark? If yes, then note that on the current front face of the exhaust pulley, there is a 115 EX, and a 110 'IN'. You can NOT time the exhaust cam by an 'IN' timing mark !! You'll bend valves. Instead, follow the tooth the 110 IN timing mark is on to the back side of the pulley. There, on the back side of the same tooth, you will find the 110 EX timing mark you need. So changing the cam timing (for either cam) involves first removing the pulley, flipping it over front-to-back, and re-installing the pulley (torque the bolt to 25 lbs-ft). Then align the 110 EX mark on the exhaust pulley with the 110 IN mark on the intake pulley. *~*~*~* All the above started in the middle of the procedure just to highlight what you need to accomplish. The correct first steps would be... Set the crank to TDC with the cam pulley timing dots aligned on the imaginary centerline between the cams (ie, #1 at TDC). Remove the timng belt. Not 'completely', but slide if off of the two cam pulleys and let if flop down out of the way. Turn the crank back 90 degrees. Don't get too OCD precise about it, just an 'eyeball' 90 degrees. That puts all the pistons halfway down their bores, and well out of the way of the valves. With that done, you can now spin both cams willy-nilly as you work on them, and no valves will collide with anything. When you're done 'flipping', align the "forward facing" cam timing marks "ON" the imaginary centerline between the two cams... 110 IN on the intake pulley with 110 EX on the exhaust pulley. If the timing marks align with one another, but are not on the imaginary centerline, then the cams are "NOT" correctly timed. Once you have the pulleys correctly timed... Turn the crank back to TDC and align the auxiliary pulley, then re-install and tension the timing belt. Torque the tensioner retaining Nyloc nut to 25-30 lbs-ft. The correct tension for the oem BLACK timing belt is 95 on a Burroughs BT-33-86J, or BT-33-73F tension gauge... or OTC 6673 tension gauge (same gauge carrying a corporate syster's brand). If you use an inexpensive (you get what you pay for) Krikit KR1, then set the tension to 52 on the KR1's "Pounds" scale. If you install the Gates Racing Blue trapezoidal tooth belt (T104RB), then the tension should be 82-84 Burroughs, or 34-35 Krikit KR1. The Krikit's scale doesn't go that low, so you'll need to use the 'sharp points' of a caliper to scratch new marks below the end of the existing "Pounds" scale. A proper Borroughs gauge is a worthwhile/ recommended investment if you're going to do your own mechanical work on your Jensen-Healey. Regards, Tim Engel
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| Posted: 07-31-2021 07:40 pm |
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5th Post |
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mgfaber53 Member
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Just so I'm clear - I should be able to back off the timing belt tensioner, remove the belt, remove the exhaust pulley and relocate to 110 EX in line with the intake pulley at 110. Then just reinstall the belt and re-tension. Assumes crank pulley at 0 TDC. Am I on base here? And Bruce, you said you set the static timing at 30 Btdc?
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| Posted: 07-31-2021 07:47 pm |
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6th Post |
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mgfaber53 Member
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Tom, I posted my reply before I saw your post. That is great info, I greatly appreciate it I will order a Burroughs tension gauge before I go much further. I haven't done any of this kind of work since the last 66 Mustang I had 45 years ago - and it was much simpler. We'll see if I can still re-learn old tricks. Are there any other members in the Portland OR area?
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| Posted: 07-31-2021 08:40 pm |
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7th Post |
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redracer Member
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mg: the FULL/MAXIMUM advance is 30BTDC. I usually static time it 12-15BTDC and adjust after the engine is running. btw, I use SKYPE quite a bit to do "real-time" help. This would be particularly helpful for a newbie trying to adjust timing. my SKYPE name: RockClimber52
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| Posted: 07-31-2021 09:32 pm |
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8th Post |
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mgfaber53 Member
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That would be a great help. I've got my grandson here now so no more work today. I may reach out in a day or two. Where are you in Georgia? - Mark
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| Posted: 07-31-2021 10:43 pm |
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9th Post |
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redracer Member
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Mark: click on my name/'handle", RedRacer and my profile will open up for you
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| Posted: 07-31-2021 11:13 pm |
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10th Post |
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discogodfather Member 
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It's an art working with the all the marks, lining everything up, then tensioning it correctly and then checking to see if any slack might have entered into the timing (that appears after a few rotations). My process has always been: 1) Line up TDC on the crank to as close to the mark as possible (hopefully this is an accurate TDC mark) 2) Mark the distributor pulley at some point (I usually line it up with the bolt that holds it onto the bracket) just to make sure you will return to a ballpark timing. I always use some red nail polish to mark it. 3) De-tension the belts (replace the belt if needed) and align the pulleys to the correct timing marks 4) The belt slack must be controlled well, it needs to be as tight as possible across the distributor pulley to the two cam pulleys, and then as tight as you can get it (just making sure there is some tension across the teeth of the belt) going down to the crank pulley. If you do not pay attention to this slack, when you tighten the belt things are going to slip out of alignment as the belt is tensioned. 5) Hold the belt across the cam pulleys and down to the crank pulley as you add tension, slowly and in a linear way. Try and make sure the distributor returns to a ballpark area of it's mark, this is difficult to do. 6) The slack should only come out between the crank pulley and the tensioner, minimizing any slip or teeth jumping at any other point. 7) Tension the belt by taking the reading with the Burroughs between the distributor pulley and the intake cam pulley 8) Rotate the engine a few times manually (always clockwise) and verify that the timing marks always return to their correct positions. This is where you loose faith- because a single jump of a tooth or a bit of slack in the wrong place can throw you out by 5-10 degrees. If it's not quite right, just repeat the entire process again. It takes some time to master. 9) Check and adjust the ignition timing. It's been my experience its very hard to get the dizzy back to the original position, and it always requires some adjustment. NEVER rotate the crank and cam pulleys independently of each other by more than a few degrees. This is an interference engine and valves will collide with pistons guaranteed. Always keep things within a few degrees, and only make very small adjustments to the cam pulleys for timing corrections and always keep that crank on it's TDC mark. If you feel any resistance at any time, back off and rethink what's going on. Also it's always helpful for me to remember that it takes TWO rotations of the crank, 720 degrees, to return cams to their correct TDC relative markings, not one rotation. So in other words, you are always going to have to rotate the engine at the crank twice to check if the timing marks all line up.
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| Posted: 08-30-2021 10:01 pm |
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11th Post |
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mgfaber53 Member
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Finally getting back to the timing project. The PO set the cams to 110 IN and 115 OUT, saying that was what the shop manual specified. I see that in the illustration in the manual, but reading the text it seems the 110/110 you recommended should be correct. The car runs - poorly - should it run at all with this setting? And if some am I risking damage by running it with the 110/115 setting?
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| Posted: 08-30-2021 10:43 pm |
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12th Post |
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redracer Member
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The 110 settings are preferred, but it should NOT run "poorly" at the other setting. There is something else "wrong" with your engine
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| Posted: 08-30-2021 10:49 pm |
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13th Post |
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mgfaber53 Member
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I am certain there are other problems, just more involved on to carb adjustment, fuel delivery etc. I was mostly concerned with the possibility of engine damage. I'll take the time to change the cam settings before moving on.
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