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03-24-2001, 12:10 PM
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#1 |
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Registered User
Join Date: Mar 2001
Location: Medicine Hat, Alberta, Canada
Posts: 1,508
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engine knock and ping
Two questions on my 98 GMC, 350 Vortec. First when I start it after sitting overnite, it has a terriblr knock that sounds like piston slap. A buddy who is a mechanic says his 97 does it too. Neither truck has more than 40 000 miles and one runs synthetic, the other conventional oil. Another buddy had a 96 that did it when he bought it at 35 000 miles. He sold the truck at 110 000 and he never had to do any motor work. Both these guys say ignore it. GM says it's common, but it really bugs me and the mechanic buddy. Anyone else had this problem? What was the fix. I don't wanna tear down a motor for nothing(although it would give me a good excuse to make some more power). Also when the truck was new I could run regular gas with no problems, and good gas when I pulled a trailer. Now I have to run good gas all the time or it pings terribly. Injectors have been flushed regularly. GM again says these motors should ping a bit, but mine seems like it pings alot. any suggestions?
------------------ 71 Sierra 98 Sierra
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98 GMC Sierra Ex Cab, cowl hood, Euro LED lights, 30 bar billet, Whipple Supercharged 350 Vortec: Forged flattops, E-Tec aluminum heads, Comp Cam, Scat crank and rods, Granatelli Mass air flow, Headers, Flowmaster exhaust , Complete MSD Ignition, Custom Tuning, intake spacer , ported throttle body, AC Delco port injection upgrade, Roller Rockers, Power Pulleys. Gear Vendors Overdrive. Soon to hit a dyno. 2/4 drop(for now). 95 Chevy S-10 Ex Cab 4.3 5 Speed 2/3 drop, Euro lights, billet grill, More to come. The Daily Driver |
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03-24-2001, 01:34 PM
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#2 |
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Vortec 350's Suck
Join Date: Nov 2000
Location: Pickardville Alberta Canada
Posts: 544
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My 2000 5.3 Vortec also knocks when it is cold, as does my grandfathers 2000, his 97 did it, and another friends 2000 6.0 liter does it as well. GM has told me too that it is normal for some knocking when it is cold which I do believe is piston slap. However it is not worth tearing down the engine unless it knocks all the time or something more severe. The pinging I am unsure about, almost sounds like the timing is not backing down because the knock sensor will not let it. Some small ping on cheap 87 is normal but unless you have used a Hypertech programmer and even then, the ping should be very minimal.
------------------ 69 CST, 402 steel crank, heavy rods polished ported heads 2.19/1.88 should be 450+ 700R4 373 Posi buckets/console air/tilt/tach 4wheel discs Daily Driver: 92 Chev 4x4 350 Accel filter/cap/rotor/coil Edelbrock intake and headers true duals Helix TBI spacer stock 700R4 for now!
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69 Chev CST 10 reg cab lwb Daily Driver: 92 Chev Reg Cab LWB Silverado 4x4, K.I.A 7:51 AM 04/22/03 Will be resurrected |
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03-25-2001, 12:49 PM
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#3 |
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Registered User
Join Date: Mar 2001
Location: Medicine Hat, Alberta, Canada
Posts: 1,508
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I thought the knock was OK. I concentrated on the ping this morning, and it seems like it might only be there if the converter is locked up and the motor is lugging a bit. I downshifted to 3rd today and as the converter unlocked it seemed like it went away, but as soon as I felt it lock up again, it was back.
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98 GMC Sierra Ex Cab, cowl hood, Euro LED lights, 30 bar billet, Whipple Supercharged 350 Vortec: Forged flattops, E-Tec aluminum heads, Comp Cam, Scat crank and rods, Granatelli Mass air flow, Headers, Flowmaster exhaust , Complete MSD Ignition, Custom Tuning, intake spacer , ported throttle body, AC Delco port injection upgrade, Roller Rockers, Power Pulleys. Gear Vendors Overdrive. Soon to hit a dyno. 2/4 drop(for now). 95 Chevy S-10 Ex Cab 4.3 5 Speed 2/3 drop, Euro lights, billet grill, More to come. The Daily Driver |
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