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#1 |
Registered User
Join Date: Jun 2013
Location: Lancaster CA
Posts: 15
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Engine Vibration
I have a 70 C-20 350 when the RPM's are between 1200 and 1500 the engine shake and can be felt in the cab and seen in the steering wheel. I have check the fallowing.
spark to all cylinders at these RPM's disconnected from trans removed all moving parts from front of engine including harmonic balancer shaking always the same any ideas |
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#2 |
Registered User
![]() Join Date: Nov 2013
Location: Roseville, CA
Posts: 207
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Re: Engine Vibration
stick or auto ? Many be in tranny. flywheel, pressure plate or internal problem with torque converter. check the bolts to those items.
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#3 |
Senior Member
![]() Join Date: Jan 2013
Location: North Charleston SC
Posts: 504
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Re: Engine Vibration
Did you check the flex plate or flywheel?
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#4 |
BOHICA
Join Date: Mar 2008
Location: Stewartville, MN
Posts: 440
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Re: Engine Vibration
Try unhooking one plug wire at a time to determine which cylinder is not firing or misfiring, assuming the issue is just one cylinder. Pull the valve covers and roll the engine over slowly to verify that all of your valvetrain is operating correctly too.
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Trying to save someone from their own stupidity is like teaching a pig to dance. It is a waste of your time, and it annoys the pig! |
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#5 |
Registered User
Join Date: Jul 2012
Location: Ft Wayne Indiana
Posts: 1,204
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Re: Engine Vibration
Make sure if you try the spark plug method that you wear thick welding gloves or something, 40,000 volts doesn't feel good. Don't ask how I know...
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71 K20 64 GMC mud truck |
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#6 |
Old member
Join Date: Jan 2002
Location: Liberty, & Garden City S.C. , U.S.
Posts: 19,936
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I would check the engine mounts first.
Have U ever seen the chains tieing down a motor? There is a reason for it. The V-8 is a great motor but it has a problem of viberation when running! Why all this about spark plugs when U haven't said anything about it running bad? ![]() ![]()
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1971 LWB Custom, 6.0LS & 4L80E, Speedhut.com GPS speedometer & gauges with A/C. 20" Boss 338's Grey wheels 4 wheel disc brakes. My Driver Seeing the USA in a 71 ![]() Upstate SC GM Truck Club 2013,14 and 2016 Hot Rod Pour Tour http://upstategmtrucks.com/ Get out and drive the truck this summer and have some fun! It sucks not being able to hear! LWB trucks rule, if you don't think so measure your SWB! After talking to tech support at Air Lift I have found out that the kit I need is 60811. Per the measurements I gave them. Ride height of truck inside spring and inside diameter of springs. |
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#7 |
Registered User
Join Date: Apr 2013
Location: South Westerlo, New York
Posts: 1,325
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Re: Engine Vibration
Also something to think about, the exhaust might be resonating a harmonic back pressure at that RPM. I use to drag race many years ago and when I removed the exhaust from the headers I got what seemed like a vibration at a certain RPM.
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Thanks, Joe.. 1969 C/10, 348 C.I., 3X2 bbl. V8, 2004r , LWB. |
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#8 |
Registered User
Join Date: Jan 2010
Location: Here
Posts: 5,492
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Re: Engine Vibration
I had a 454 with a vibration problem once. For over a year I tried to figure it out. The engine ran well gut at 2000 rpm and up it would vibrate. Finally I chsnged tne engine balancer and that was the problem. It had moved on the rubber just enough to untrue the balance. It was hard to time properly as well due to this.
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#9 |
Registered User
![]() Join Date: Nov 2013
Location: Roseville, CA
Posts: 207
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Re: Engine Vibration
Clutch Fan ??, usually Vibs in steering wheel means front rims,tires,balance, Ect.
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#10 |
Registered User
Join Date: Oct 2005
Location: Overland Park, Ks.
Posts: 5,217
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Re: Engine Vibration
Its probably a mismatch of parts. You may have a harmonic balancer or flywheel from a small block 400. Or the truck has a 400 engine in it with the balancer &/or flywheel from a 350.
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#11 | |
BOHICA
Join Date: Mar 2008
Location: Stewartville, MN
Posts: 440
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Re: Engine Vibration
Quote:
__________________
Trying to save someone from their own stupidity is like teaching a pig to dance. It is a waste of your time, and it annoys the pig! |
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#12 | |
Registered User
![]() Join Date: May 2013
Location: WEST PALM FLORIDA
Posts: 1,174
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Re: Engine Vibration
Quote:
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