Help, engine vibration!?
Thread Starter
Melting Slicks
Joined: Dec 2001
Posts: 2,025
Likes: 1
From: Billings MT
Help, engine vibration!?
Just need a quick bit of help.
I just built a new motor for my car (heads,rings,bearings,cam,rollerrockers, pistons)
I have already driven the car 600 miles, and there has always been
a vibration starting at about 60mph (2800 rpm) and it gets a lot softer
at 3200rpm. I thought it was just something in the drivetrain, but
i put the car in neutral and reved it to 2800 and the vibration was the same. Could my blancer possibly be bad? I reused it from the previous motor (i'm using the same crank/rods). Coudl the fan be bent?
Maybe a flexplate? Torque converter?
This vibration during the breakin period didn't damage anything did it?
Any help would be greatly appreciated, its been a lot of work and i want
it to work right.
Thanks :cheers:
I just built a new motor for my car (heads,rings,bearings,cam,rollerrockers, pistons)
I have already driven the car 600 miles, and there has always been
a vibration starting at about 60mph (2800 rpm) and it gets a lot softer
at 3200rpm. I thought it was just something in the drivetrain, but
i put the car in neutral and reved it to 2800 and the vibration was the same. Could my blancer possibly be bad? I reused it from the previous motor (i'm using the same crank/rods). Coudl the fan be bent?
Maybe a flexplate? Torque converter?
This vibration during the breakin period didn't damage anything did it?
Any help would be greatly appreciated, its been a lot of work and i want
it to work right.
Thanks :cheers:
Race Director
Joined: Dec 1999
Posts: 11,091
Likes: 990
From: Sierra Foothills CA
Re: Help, engine vibration!? (VETDRMS)
Just wondering- did you have the rotating assembly balanced? If not, that's a possible source.
However, I'd look at external possibilities first. As silly as it may sound, have you checked the bolts that attach your fan for tightness? I actually had this happen to me once- didn't get them completely tight & had a noticable vibration right after a rebuild which had me pretty worried too. Also, I've seen vibration occur when the bolts attaching the bellhousing to the block weren't fully torqued- symptoms were pretty much as you describe. Just a coupla thoughts....good luck.
However, I'd look at external possibilities first. As silly as it may sound, have you checked the bolts that attach your fan for tightness? I actually had this happen to me once- didn't get them completely tight & had a noticable vibration right after a rebuild which had me pretty worried too. Also, I've seen vibration occur when the bolts attaching the bellhousing to the block weren't fully torqued- symptoms were pretty much as you describe. Just a coupla thoughts....good luck.
Thread Starter
Melting Slicks
Joined: Dec 2001
Posts: 2,025
Likes: 1
From: Billings MT
Re: Help, engine vibration!?
I tightened the fan, a couple bolts were just snug, it seems to be a little
less, but still there. I'm pretty sure the bell housing bolts were tight enough. Thanks.
less, but still there. I'm pretty sure the bell housing bolts were tight enough. Thanks.
Race Director
Joined: Mar 2001
Posts: 11,322
Likes: 1
From: Living in the Hartland
Re: Help, engine vibration!? (VETDRMS)
I have had 3 diff engines in my vette and all had a vibration at 3400-3500 rpm's which goes away when I drop the clutch. My guess is it is coming from the Flowmaster 40's which I see you have. Funny things is when I go for long drives at the rpm range it goes away, I figure they are heating up from constant rpm's which changes the resonance. This just a guess but I can think of no other reason for it. I will be adding dynomax headers and an h-pipe soon and will let you know if it stops or changes rpm ranges.
Thread Starter
Melting Slicks
Joined: Dec 2001
Posts: 2,025
Likes: 1
From: Billings MT
Re: Help, engine vibration!? (Tom Johnson)
Got79Fever The mounts are good, i just replaced them not 2000 miles ago. Although i think the vibration may be something different, the vibration is HORRIBLE at 5100rpm, shakes the entire car. Looking at my crank pulley i notice it doesn't look right and it "bounces" when running, so i think i found my culprit. I've never had the engine reved that high, it scared the hell out of me when it did that. The new engine pulls like a raped ape :D:D I documented the build up and was planning on a very lengthy post soon....
FevreThanks for your input, i have an automatic, your vibration may be caused by teh clutch? I'm running an x-pipe with dynomax headers currently, and the resonance goes away at crusing speeds :D :yesnod:
Stevo Yes, real easy to remove fan (flexi-lite).
Thanks for the helpful input, i think it is the crank pully. will update. :cheers:
[Modified by VETDRMS, 2:09 PM 8/19/2002]
FevreThanks for your input, i have an automatic, your vibration may be caused by teh clutch? I'm running an x-pipe with dynomax headers currently, and the resonance goes away at crusing speeds :D :yesnod:
Stevo Yes, real easy to remove fan (flexi-lite).
Thanks for the helpful input, i think it is the crank pully. will update. :cheers:
[Modified by VETDRMS, 2:09 PM 8/19/2002]
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Race Director
Joined: Mar 2001
Posts: 11,322
Likes: 1
From: Living in the Hartland
Re: Help, engine vibration!? (VETDRMS)
If the vibration gets worse with rpm's then you got something out of balance. Might be drive shaft but if the vibration goes when in nuetral at speed them eliminate from trans back, gotta be engine/flexplate or exhaust.
BTW New clutch on engine 2and 3, same vibration.
BTW New clutch on engine 2and 3, same vibration.
Thread Starter
Melting Slicks
Joined: Dec 2001
Posts: 2,025
Likes: 1
From: Billings MT
Re: Help, engine vibration!? (Fevre)
Fevre I'm thinking it is the crank pulley or balancer. The pulley looks kind of out too far and when running looks out of whack, i am going to pull it apart and see if that's the culprit. Thanks for your input.
