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| Strange Misfire | Rate Topic |
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| Posted: 05-09-2021 01:37 am |
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1st Post |
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BrandonDN Member
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So my Jensen Healey I just got running and it’s driving now (around the block because of a lack of turn signals and plates for now). But it sounds like it misfires until you push the gas and accelerate a bit. However, if you accelerate too much then it makes a sound like it’s misfiring again. We’re sure that the spark plugs are good and my dad thinks it’s timing, which brings me to the question of what is the correct position for the distributor because we struggled finding the correct answer for the timing. But when you put the choke on a bit, it sounds great other than running a slightly higher RPM than it should (12). Anything will help please and thank you.
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| Posted: 05-09-2021 08:36 am |
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2nd Post |
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discogodfather Member 
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What carbs do you have and what's the engine like (stock, modified, condition, ignition setup, etc)? How long was it sitting?
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| Posted: 05-09-2021 03:17 pm |
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3rd Post |
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BrandonDN Member
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It’s a stock four speed. I’m using two stromberg carbs. The engine’s condition is actually pretty good more or less. The distributor is brand new as are the spark plugs.
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| Posted: 05-09-2021 03:17 pm |
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4th Post |
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BrandonDN Member
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It’s a stock four speed. I’m using two stromberg carbs. The engine’s condition is actually pretty good more or less. The distributor is brand new as are the spark plugs.
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| Posted: 05-09-2021 03:30 pm |
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5th Post |
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noomg Member
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Brandon, First things first, if you don't have a workshop manual, get one, it has the numbers you need. The manual shows 3 to 5 degrees BTDC. You should certainly check to see your timing is correct, but I suspect that's not where your problem lies. I think the first area I'd look at would be coil, points and condenser.
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| Posted: 05-09-2021 04:02 pm |
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6th Post |
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BrandonDN Member
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It’s just difficult to find a manual. Also there aren’t points anymore because it’s an electric distributor and the coil is also brand new. Almost certain I have it wired all correctly too
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| Posted: 05-09-2021 04:44 pm |
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7th Post |
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Dakota123 Member
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Mine acted the same way when one of the carb dampers was hanging up in its bore. Fueling was only more or less correct over a narrow rpm range.
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| Posted: 05-09-2021 06:57 pm |
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8th Post |
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BrandonDN Member
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Okay that’s curious. One of the carbs was acting strange. How did you fix that
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| Posted: 05-09-2021 08:49 pm |
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9th Post |
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noomg Member
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Pull the tops off, clean and lube the pistons, reassemble. It can happen to Zeniths when they've sat for a while.
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| Posted: 05-09-2021 08:54 pm |
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10th Post |
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BrandonDN Member
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Sounds like a plan. Thank you all very much for the answers on all my various questions. I’ll post more if it comes up on this issue. Thank you again!
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| Posted: 05-10-2021 03:31 am |
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11th Post |
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Tom Bradley Member
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Idling is where everything tends to be most finicky: timing air-fuel ratio, etc. According to my manual, idle or static timing for Strombergs is 8 deg BTDC. Generally speaking, the more advanced the better as long as you don't get any detonation. 12 BTDC is supposed to be optimum for these engines, but that can depend on what octane gas you can get. Lower octane burns faster so requires less advance. When you engage the choke you are doing two things: enrichening the air-fuel ratio and increasing the idle speed. Either one could be what is fixing your problem. From what I have read many people find 1200 RPM works best for them. Mine idles more-or-less OK down to 800 RPM but smooths out much better at 1000, so that is where I keep it. Do you have a manual for the Strombergs? They are available on Amazon. You will need one as well as some special tools such as the one for adjusting the fuel mix. There is a Facebook Jensen Healy group that has a ton of files of useful information as well as lots more people contributing helpful information. If possible, you should join.
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