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 |
ME733 |
Sep 24 2009, 12:46 AM
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#2
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Senior Member Group: Members Posts: 842 Joined: 25-June 08 From: Atlanta Ga. Member No.: 9,209 Region Association: South East States |
Well...140 psi does not indicate a blown piston, or dropped seat,or valve. YOU MAY have an easy fix.,,BUT DID YOU REPLACE or absolutely make sure THAT spark plug wire is good. SET spark plug gap to .028 ths. check and recheck that the valve lash is properly set to .006 ths.when you know all this is right do the following......Flash back to maybe its an easy fix...what could have happened is that the P.O. previous owner had a bad plug, it fouled , and that cylinder went dead....but the dumb ass kept driving the car....SO the rings and oil control rings have just gotten "loaded up" with oil, and, with so much oil on the cylinder wall have become "unseated"....get some extra spark plugs.(for the bad cylinder.) DO NOT DRIVE THE CAR. start it and let it idle at a high idle it should be higher IF the plug is firing, as compared to before...do not let it run with a misfiring plug. if its firing you should detect blue smoke from the exhaust..white if it has synthetic oil. ( thats why you got spare plugs .Eventually the oil will burn out and it could get back to normal...but keep the rps low. ...CONFERM that the cylinder is getting fuel at IDLE.(no fuel allows oil to foul plug.) adjust idle jet to about where it should be...(1- to 1.5 turns out from seated is a good general rule...IDLE increase?...No=turn it out somemore. IF this does not work. you may have a plugged/or clogged idle jet. (probably need carbs rebuilt.) HOWEVER you may have water in the float boal...remove carb. dump it out .check butterflys for equal operation-opening ..reinstall. try that.
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