vibration.........from where????? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

vectorit · 10-07-2009, 11:59 PM

The tach sounds as though it has a loose connection to the coil.

What kind of fan are you running? If it's a clutch fan, it could be bad. That and check all the blades, and make sure they are solid.

The mis could be causing one hole to not fire long enough to cause some funny business, especially if it is happening on either cyl # 5 or 7. But I'm guessing not. What kind of distributer?

Check everything that rotates off the crank.

**americanmusc1e** · 10-08-2009, 10:25 AM

alright, when I did the compression test I left a spark plug wire disconnected,

the engine runs better, and the tach doesn't jump as bad, but....... the tach still jumps around a little after 3000, the engine still has a miss to it, and the vibration is still there.

I would be working on the truck right now, but I have a paper for college that I need to start and finish today, and I shouldn't even be on here right now.

**Classic Heartbeat** · 10-08-2009, 12:37 PM

My first Blazer had a vibration when I purchased it because it had a small block 400 in it and the previouse owner installed a 350 harmonic ballancer.
The second time it happened I was down on the Cowletz river on an icy cold winter day steelhead fishing. I drove down there without issues, but when I started it up to return home all hell broke loose!! My engine was vibrating so bad I thought it was going to jump out of the engine compartment!!! I revved the engine up a couple of times seeing if it would clear up and when it didn't I figured I was in for a large tow bill. I went out to see if I could figure out what happened. I popped open the hood and to my suprize there was what looked like bits and pieces of spider webs under my hood, only the web had color to it. It smelled realy bad too!! I scratched my head while I was looking at all this stuff all under my hood, when I looked up toward my fan (witch was hidden by the shroud of coarse) there was a cat woven in and out of my fan blades!! I'll spare you the goary details, but let me tell you it wasn't easy relieving my fan of it.

The third time it happened it turned out to be the flywheel. It had cracked and at certain rpms would vibrate the engine. WES

mikajo39 · 10-08-2009, 06:43 PM

Quote:

Originally Posted by Classic Heartbeat

My first Blazer had a vibration when I purchased it that turned out to be because it had a small block 400 in it and the previouse owner installed a 350 harmonic ballancer.
The second time it happened I was down on the Cowletz river on an icy cold winter day steelhead fishing. I drove down there without issues, but when I started it up to return home all hell broke loose!! My engine was vibrating so bad I thought it was going to jump out of the engine compartment!!! I revved the engine up a couple of times seeing if it would clear up and when it didn't I figured I was in for a large tow bill. I went out to see if I could figure out what happened. I popped open the hood and to my suprize there was what looked like bits and pieces of spider webs under my hood, only the web had color to it. It smelled realy bad too!! I scratched my head while I was looking at all this stuff all under my hood, when I looked up toward my fan (witch was hidden by the shroud of coarse) there was a cat woven in and out of my fan blades!! I'll spare you the goary details, but let me tell you it wasn't easy relieving my fan of it.

The third time it happened it turned out to be the flywheel. It had cracked and at certain rpms would vibrate the engine. WES

That happened to my dad, darned cats! his galaxie 500 turned it into Cat suey!

jay6891 · 10-08-2009, 08:01 PM

Has this been doing this since the engine was new. Sounds to me like the wrong balancer or bad flywheel. But not a new engine... out on timing?

**americanmusc1e** · 10-08-2009, 11:37 PM

Quote:

Originally Posted by jay6891

Has this been doing this since the engine was new. Sounds to me like the wrong balancer or bad flywheel. But not a new engine... out on timing?

been running the motor for a while now, the vibration just started, although it did do it once before.

10-07-2009, 11:59 PM	#1
vectorit What? Join Date: Jun 2007 Location: Southern California Posts: 7,617	Re: vibration.........from where????? The tach sounds as though it has a loose connection to the coil. What kind of fan are you running? If it's a clutch fan, it could be bad. That and check all the blades, and make sure they are solid. The mis could be causing one hole to not fire long enough to cause some funny business, especially if it is happening on either cyl # 5 or 7. But I'm guessing not. What kind of distributer? Check everything that rotates off the crank. __________________ Chris 1968 K20 Suburban 1972 K10 LWB PU

10-08-2009, 10:25 AM	#2
americanmusc1e Senior Member Join Date: Jan 2009 Location: Austin, TX Posts: 1,079	Re: vibration.........from where????? alright, when I did the compression test I left a spark plug wire disconnected, the engine runs better, and the tach doesn't jump as bad, but....... the tach still jumps around a little after 3000, the engine still has a miss to it, and the vibration is still there. I would be working on the truck right now, but I have a paper for college that I need to start and finish today, and I shouldn't even be on here right now. __________________ -- Josh Instagram: @americanmusc1e OLD SKOOL-- 1970 C10. 454/Th400/3.07 posi Build Thread FARM TRUCK----1949 Chevrolet 3800 Power Wagon Hauler Build Thread 1999 4wd OBS Tahoe - daily. DM me if you can't see photos i posted

10-08-2009, 12:37 PM	#3
Classic Heartbeat Project Junkie! Fishing Poor!! Join Date: Dec 1999 Location: Olympia,Wa. 98512 Posts: 10,766	Re: vibration.........from where????? My first Blazer had a vibration when I purchased it because it had a small block 400 in it and the previouse owner installed a 350 harmonic ballancer. The second time it happened I was down on the Cowletz river on an icy cold winter day steelhead fishing. I drove down there without issues, but when I started it up to return home all hell broke loose!! My engine was vibrating so bad I thought it was going to jump out of the engine compartment!!! I revved the engine up a couple of times seeing if it would clear up and when it didn't I figured I was in for a large tow bill. I went out to see if I could figure out what happened. I popped open the hood and to my suprize there was what looked like bits and pieces of spider webs under my hood, only the web had color to it. It smelled realy bad too!! I scratched my head while I was looking at all this stuff all under my hood, when I looked up toward my fan (witch was hidden by the shroud of coarse) there was a cat woven in and out of my fan blades!! I'll spare you the goary details, but let me tell you it wasn't easy relieving my fan of it. The third time it happened it turned out to be the flywheel. It had cracked and at certain rpms would vibrate the engine. WES __________________ On-line catolog Classic Heartbeat Pickup Parts WEHEPP@comcast.net Call us Toll Free (888) 338-2502 Like Us on Facebook No appointment necessary. 72 BB Chevy Custom Deluxe / Custom Camper 67 I-6 (Soon to be 5.7 LS1) Panel 68 BB Chevy Short Bed 72 6.0 LQ9 Short Bed Chevy 4X4 Olympia's fastest growing truck parts supplier. Olympia's home for Wayward Chevys Last edited by Classic Heartbeat; 10-08-2009 at 06:48 PM.

10-08-2009, 08:01 PM	#5
jay6891 Car Knocker Join Date: May 2001 Location: jefferson,arkansas Posts: 664	Re: vibration.........from where????? Has this been doing this since the engine was new. Sounds to me like the wrong balancer or bad flywheel. But not a new engine... out on timing? __________________ 68 c-10,91 sportside bed,350 .030 over,4 bolt,10-1 comp,2.05 intake/1.94 exhaust,1.6 Harland Sharp roller rockers,edelbrock rpm cam and intake w/750 carb, 700r4, 3.73 gears,Jacabbs Electronic Igntion w/Accel HEI distributer and super coil. ZR-1 roll pan, filled tailights. Blazer tank. Hidden hitch. 2 1/2" Flowmaster 40's. Parts bought but not installed>> ford 9" posi with disc. CCP front and rear lowering kit 4/5. Cab corners,foor boards,rockers, cab braces, Phatom grill, Painless wiring kit.

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