914 1.7 Knocking Sound -- New Here, First Post, Horrible knocking coming from the motor |
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914 1.7 Knocking Sound -- New Here, First Post, Horrible knocking coming from the motor |
UberElectricEagle |
Sep 20 2009, 07:20 PM
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#1
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atomic Group: Members Posts: 43 Joined: 10-August 09 Member No.: 10,659 Region Association: None |
Greetings. I am new to the Porsche world and I purchased a 1972 914 1.7 about a month ago. It's a pretty nice car over all, but I think the motor, or part of the motor, might be toast.
When I purchased it, it badly needed a muffler. The knocking noise was harder to notice and sounded more like an exhaust leak over the horrible sound of the lack of a working muffler. The car seemed to run decent even with the poor exhaust and the price was good so I bought it. I just wanted a decent car over all that I could drive around for fun on sunny days before the winter gets here. It came with stainless heat exchangers I installed and I installed a really nice dual muffler from Dave at Triad. When I fired it up with the new muffler, I really noticed the knocking when I drove it since the all the exhaust leaks were now sealed up and I wasn't wearing ear plugs. At idle it's not too bad, but once I get going, the knocking is very noticeable. It's odd too, because it's not real consistent under power in motion. To me it sounds like the noise is coming from the #1 cylinder. I think the cylinder is providing no power, because when I take the wire off the cap, there is really no change in performance. (I put a video link of the horrible sound below.) Any advice on where to go from here would be great. My gut feeling is telling me the motor is going to have to come out. If I'm going to do all that, I might as well put a 2.0 liter in or ????? I'd even settle for just a solid running motor with some minor upgrades to make it a little quicker. Any advice on what route to take on a good used motor would be great. I guess A motor that runs on 4 cylinders would be an upgrade. Thanks for your help, a mildly depressed Sam http://www.youtube.com/watch?v=a5JhEd7SUH4...re=channel_page |
VaccaRabite |
Sep 24 2009, 07:29 PM
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#2
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En Garde! Group: Admin Posts: 13,465 Joined: 15-December 03 From: Dallastown, PA Member No.: 1,435 Region Association: MidAtlantic Region |
D'oh. You have exceeded my knowledge area. I heard dual carbs and assumed IDF, which was silly of me. I'm glad no one asked me to back up my bet with cash.
For shits and giggles.... Start the engine and then pull the #1 and #2 spark plug wires. See if there is any change to the engine. You want to see if it is running on just 3&4. Go to the store and get a more modern compression tester. You want the kind that threads in. They are not expensive. And see if they will loan or rent you a leak down tester. Do you have a carb sync? Looks like this: (IMG:http://www.peekperformance.com/shop/images/carb%20sync.jpg) or the older crappier kind looks like this: (IMG:http://www.356registry.org/Tech/images/solex/unisyn.jpg). If so, are your carbs drawing the same at idle? Is your linkage balanced right? I am looking at the Weber Tech Manual (get a copy if you don't have one - you WILL use it. ) and there is still an idle jet that is worth pulling and blowing out with compressed air. You have checked valves. timing has to be close if it is running, but have you checked it? Do you know where your engine is timed? you have spark Your variables unknown are fuel and compression. Zach |
UberElectricEagle |
Sep 24 2009, 09:09 PM
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#3
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atomic Group: Members Posts: 43 Joined: 10-August 09 Member No.: 10,659 Region Association: None |
D'oh. You have exceeded my knowledge area. I heard dual carbs and assumed IDF, which was silly of me. I'm glad no one asked me to back up my bet with cash. For shits and giggles.... Start the engine and then pull the #1 and #2 spark plug wires. See if there is any change to the engine. You want to see if it is running on just 3&4. Go to the store and get a more modern compression tester. You want the kind that threads in. They are not expensive. And see if they will loan or rent you a leak down tester. Do you have a carb sync? Looks like this: (IMG:http://www.peekperformance.com/shop/images/carb%20sync.jpg) or the older crappier kind looks like this: (IMG:http://www.356registry.org/Tech/images/solex/unisyn.jpg). If so, are your carbs drawing the same at idle? Is your linkage balanced right? I am looking at the Weber Tech Manual (get a copy if you don't have one - you WILL use it. ) and there is still an idle jet that is worth pulling and blowing out with compressed air. You have checked valves. timing has to be close if it is running, but have you checked it? Do you know where your engine is timed? you have spark Your variables unknown are fuel and compression. Zach Ok, here comes a lot of words. Thanks for the pics. I've already done the pull the wire thing and I have a change when I pull #2 and no change at idle with #1. I also have a change when I pull # 3 and # 4. I did notice today, I pulled #1 wire while I revved it at about 3 grand steady and I noticed some change, so It must be firing somewhat. I think I'm on about 3 and a half power. (that doesn't make sense) I also checked the spark again and compared it to the # 2 cylinder sparking and it appears the same. It actually runs pretty well considering and idles pretty evenly, but it has that horrible noise. I know (claim to know) it's not firing on #1 at idle, or not at it's full potential. The new plug is already black. I think there's so much oil in the combustion chamber that it can't fire properly or get a proper fuel air mixture. There's fuel because #2 is firing well and I can look down the carb and see the fuel going in. Maybe the left side carb is running lean? Can anyone explain why the idle on the driver's side carb increased with carb cleaner sprayed in and the passenger side carb bogged down when cleaner was sprayed? I could probably assume the carbs are not synched up properly. One more thing---it appears this engine likes to leak a lot of oil even when parked. When I ran it today for about 3 to 5 minutes, it dropped the standard oil leaks on the ground which are pretty clean and clear. It also dropped some black oil, almost like it was forced out of somewhere on the driver's half of the motor where there is carbon build up. Like left middle. Can oil be forced out of where the push rod tubes meet the case? Or where the heads meet the cylinders? I don't know If I'm saying what I mean. (leak pics below) Could it be forcing the combustion chamber air out of where the head meets the cylinder? Sometimes the noise sounds like a loud slap like you can have in an exhaust leak. Getting close to just driving the crap out of it until I reach catastrophic failure. Anybody in or around Seattle have a cheap running motor they don't need around. Also, What's a fair price to pay for a running stock 2.0 liter. ? |
Gint |
Sep 25 2009, 08:20 AM
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#4
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Mike Ginter Group: Admin Posts: 16,083 Joined: 26-December 02 From: Denver CO. Member No.: 20 Region Association: Rocky Mountains |
Can anyone explain why the idle on the driver's side carb increased with carb cleaner sprayed in and the passenger side carb bogged down when cleaner was sprayed? I could probably assume the carbs are not synched up properly. More likely that the driver's side carb or carb to manifold has a leak. When you squirt carb cleaner in/on the carb it temporarily seals the leak and the engine runs differently for that brief moment. I'd get a couple of kits and rebuild the carbs before going any further. It's cheap and easy enough to do. Then I'd drive it for a while. Don't thrash it, but get it driving off the idle circuit and see if you can clear out that #1 cylinder a bit. (IMG:style_emoticons/default/welcome.png) |
Spoke |
Sep 25 2009, 11:17 AM
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#5
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Jerry Group: Members Posts: 6,992 Joined: 29-October 04 From: Allentown, PA Member No.: 3,031 Region Association: None |
More likely that the driver's side carb or carb to manifold has a leak. When you squirt carb cleaner in/on the carb it temporarily seals the leak and the engine runs differently for that brief moment. I was thinking of this too. Spray the carb cleaner on the outside of the carbs by all the gaskets: the ones from the carb to runner and from the runner to head. There should be no change in engine tune when you do this. If there is, then you have a vacuum leak and must fix it. |
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