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| Moderated by: Greg Fletcher |
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| Cams and Cam pulleys | Rating: 
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| Posted: 03-27-2014 10:20 pm |
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1st Post |
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thatmak1 Member
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I have a 1974 Jensen Healey with a stock engine, I believe, and I have been reading a lot about the cams and carburetors. The car has a single Weber 32/36 DGEV. I have a hard time getting a smooth idle, the car takes a long time to warm up and hesitates when I put it to the floor at almost all rpm's. But at steady speed or slight increases it runs smooth above 2000 rpm. Obviously I have a carb issue, vacuum or possible valve leakage. I am trying to determine which cams I have and what the 110in and 115 ex on the C cam pulley means. I also have an ignition switch problem and would like to change it or change to a more reliable. Any suffestions? Can anyone help.
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| Posted: 03-28-2014 06:35 am |
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2nd Post |
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Tom Bradley Member
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I had a problem with my ignition switch as well. It was not making reliable contact so the engine would misfire sometimes. The switch has two screws holding it to the mechanical switch, so it comes off fairly easily. I took mine apart and cleaned up the contacts and got a couple more years use out of it, but ultimately ended up replacing it with a homemade electronic switch similar to what is used on new cars which do not have key switches any more. If you understand electronics are good enough with a soldering iron, I could provide the details (it is a simple circuit). Keep in mind, though, that the reliability of a custom circuit depends on how well it is assembled and installed. You might check with Delta to see if they still can get replacements or try to get a used one from British masters which is in better shape than the one you have.
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| Posted: 03-28-2014 12:51 pm |
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3rd Post |
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thatmak1 Member
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Thanks Tom, I am interested in your fix if you good provide the details it would be greatly appreciated. Thanks.
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| Posted: 03-29-2014 05:37 pm |
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4th Post |
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Tom Bradley Member
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Attached should be the circuit I used to replace my ignition switch. This gets rid of the steering column switch entirely and replaces it with some switches installed on the dashboard. An alternative circuit is to still use the steering column switch to control the MOSFET's. This reduces the current through the steering column switch to a few milli-amps instead of amps, so it should last just about forever. The transistors I used were actually IRF4905's, but these do not seem to be readily available any more, so for this drawing I put in some others which have the same characteristics. Two of these in parallel have an on resistance of about 10 milli-ohms which gives minimal voltage drop as well as have low enough power dissipation so the transistors will not heat up much even under a fault condition before the fuses blow. I put this circuit in my JH back in the mid 1980's and it has been working with no problems for almost 100K miles so far. Hope this is of some use. Attachment: JH ignition switch replacement.jpg (Downloaded 68 times)
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| > Jensen Healey & Jensen GT Tech > Carburetors > Cams and Cam pulleys | Top |
