Engine Vibration 2500-3000 RPM - Team Camaro Tech
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post #1 of 24 (permalink) Old May 20th, 10, 08:01 AM Thread Starter
Matt
 
Join Date: Feb 2006
Location: South Jersey
Posts: 27
Engine Vibration 2500-3000 RPM

I have been chasing this vibration down for almost a year now. I have done countless searches and done everything suggested in those posts but cannot seem to find this vibration. A little background, the engine is the 290hp GM Performance Parts 350ci and it is showing this vibration between 2500 and 3000 RPM in park, so that eliminates the trans and remaining driveline. So far, I have replaced all pulleys, bought and installed a new ATI balancer, checked the runout on the crank snout, pulled plugs while engine was at vibration rpm and all plugs caused a drop in rpm. This vibration happens while accelerating and decelerating, so I'm hoping this can eliminate timing/carburetor issues. So I have now moved to the rear of the engine and removed the transmission and clutch and am still getting the vibration. Does anyone have any suggestions on what I could do next? The flywheel is stamped GM and 3973456N which looks like a neutral balanced flywheel (per Google) and there are no weights on it. Can a flywheel go out of balance?

Matt

1967 Camaro RS
GMPP 350 c.i. (soon to be aluminum head 355 when the machine shop is done!)
M-20 Muncie 4-spd
12-bolt 3.55s (4.10s were too much)
Hugger Orange w/Black Z/28 stripes
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post #2 of 24 (permalink) Old May 20th, 10, 08:29 AM
Luigi
 
Join Date: May 2010
Location: Connecticut
Posts: 21
Re: Engine Vibration 2500-3000 RPM

Yes, an unbalanced flywheel will cause a slight disturbing vibration. Nothing exaggerating though, kind of like it would make any loose change (coins) in the ashtray chatter a bit. That is what I had found in my RX-7 back in the mid 80's. The flywheel had no weights drilled in it and it made my engine vibrate. Very annoying. You have checked everything else. Engine would shake if the crank was not balanced.
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post #3 of 24 (permalink) Old May 20th, 10, 09:15 AM Thread Starter
Matt
 
Join Date: Feb 2006
Location: South Jersey
Posts: 27
Re: Engine Vibration 2500-3000 RPM

Yeah, thats the vibration I'm getting. Its not jarring, but enough to be really annoying. I'm also worried that a vibration is going to cause some sort of damage to the engine. I'll see if I can get it balanced to see if that fixes the problem. The last quote I got was $110 which seemed a little high considering its a neutral balanced flywheel...

Matt

1967 Camaro RS
GMPP 350 c.i. (soon to be aluminum head 355 when the machine shop is done!)
M-20 Muncie 4-spd
12-bolt 3.55s (4.10s were too much)
Hugger Orange w/Black Z/28 stripes
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post #4 of 24 (permalink) Old May 20th, 10, 10:17 AM
Luigi
 
Join Date: May 2010
Location: Connecticut
Posts: 21
Re: Engine Vibration 2500-3000 RPM

All things considered, that price doesn't seem too high. Hopefully someone else can comment on this thread. I don't believe a bad front balancer damper would cause slight vibrations. It is definitely a weight distribution issue. Take the flywheel off and see or feel ?? The vibration will indeed cause more problems in the future. Good luck
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post #5 of 24 (permalink) Old May 20th, 10, 10:24 AM
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Dave
 
Join Date: Jun 2009
Location: Nocal
Posts: 37
Re: Engine Vibration 2500-3000 RPM

Does your engine have a 1pc rear main seal? If so, you need the weighted flywheel since there are no weights on the crank end.
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post #6 of 24 (permalink) Old May 20th, 10, 11:01 AM
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Paul
 
Join Date: Jan 2006
Location: Pearl,Ms
Posts: 403
Re: Engine Vibration 2500-3000 RPM

Quote:
Originally Posted by stratrex View Post
Does your engine have a 1pc rear main seal? If so, you need the weighted flywheel since there are no weights on the crank end.
The 350/290 HP engine is internally balanced and requires no balance weights on either the flywheel/flexplate or
the harmonic balancer. ( Copied from GM website, specs on 350/290 crate engine)
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post #7 of 24 (permalink) Old May 20th, 10, 11:09 AM Thread Starter
Matt
 
Join Date: Feb 2006
Location: South Jersey
Posts: 27
Re: Engine Vibration 2500-3000 RPM

Its a two-piece rear main seal

Matt

1967 Camaro RS
GMPP 350 c.i. (soon to be aluminum head 355 when the machine shop is done!)
M-20 Muncie 4-spd
12-bolt 3.55s (4.10s were too much)
Hugger Orange w/Black Z/28 stripes
ozzie1982 is offline  
post #8 of 24 (permalink) Old May 20th, 10, 11:13 AM
Luigi
 
Join Date: May 2010
Location: Connecticut
Posts: 21
Re: Engine Vibration 2500-3000 RPM

ok, ok, ok ....DON'T TAKE THE FLYWHEEL OFF!!!!. I gaffed like Joe Biden there a bit. I forgot he did mention the engine type he has which is the one piece seal.
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post #9 of 24 (permalink) Old May 20th, 10, 11:23 AM Thread Starter
Matt
 
Join Date: Feb 2006
Location: South Jersey
Posts: 27
Re: Engine Vibration 2500-3000 RPM

It would be kind of hard to start it without the flywheel. Maybe some twine around the balancer and I'll pull really hard....

Matt

1967 Camaro RS
GMPP 350 c.i. (soon to be aluminum head 355 when the machine shop is done!)
M-20 Muncie 4-spd
12-bolt 3.55s (4.10s were too much)
Hugger Orange w/Black Z/28 stripes
ozzie1982 is offline  
post #10 of 24 (permalink) Old May 20th, 10, 11:35 AM
Luigi
 
Join Date: May 2010
Location: Connecticut
Posts: 21
Re: Engine Vibration 2500-3000 RPM

two piece? I thought the GMPP 350/290 hp engines were center bolt valve cover kind with the 1 piece rear main seal, oh well....swap a flexplate, Tranny shops sometimes give them away or sell them for almost nothing.
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post #11 of 24 (permalink) Old May 20th, 10, 01:03 PM
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Todd
 
Join Date: Aug 2006
Location: Henderson, NV
Posts: 1,664
Re: Engine Vibration 2500-3000 RPM

What type of motor mounts? If they are poly or solid it may be normal engine harmonics.
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post #12 of 24 (permalink) Old May 20th, 10, 03:59 PM Thread Starter
Matt
 
Join Date: Feb 2006
Location: South Jersey
Posts: 27
Re: Engine Vibration 2500-3000 RPM

I'm pretty sure they're stock but they could be poly. It rattles right through the shifter handle. Definitely not something I would consider normal.

Matt

1967 Camaro RS
GMPP 350 c.i. (soon to be aluminum head 355 when the machine shop is done!)
M-20 Muncie 4-spd
12-bolt 3.55s (4.10s were too much)
Hugger Orange w/Black Z/28 stripes
ozzie1982 is offline  
post #13 of 24 (permalink) Old May 20th, 10, 04:14 PM
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Todd
 
Join Date: Aug 2006
Location: Henderson, NV
Posts: 1,664
Re: Engine Vibration 2500-3000 RPM

Don't discount body, tranny, and engine mounts. They are designed to absorb harmonics. Some vibration throught the shifter is always present. New car engineers spend countless hours with vibration software. That's part of the reason new cars feel so numb, they have to be to please the masses.
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post #14 of 24 (permalink) Old May 20th, 10, 04:23 PM Thread Starter
Matt
 
Join Date: Feb 2006
Location: South Jersey
Posts: 27
Re: Engine Vibration 2500-3000 RPM

I can definitely rule out the tranny mount because the transmission isn't even in the car now. I'm hoping it's the flywheel. I'm in the process of trying to find a used flex plate to swap in to confirm its the flywheel before I spend the money on the flywheel

Matt

1967 Camaro RS
GMPP 350 c.i. (soon to be aluminum head 355 when the machine shop is done!)
M-20 Muncie 4-spd
12-bolt 3.55s (4.10s were too much)
Hugger Orange w/Black Z/28 stripes
ozzie1982 is offline  
post #15 of 24 (permalink) Old May 20th, 10, 04:58 PM
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Todd
 
Join Date: Aug 2006
Location: Henderson, NV
Posts: 1,664
Re: Engine Vibration 2500-3000 RPM

Any decent machine shop can balance a flywheel.
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