Need some help, please! - Team Camaro Tech
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post #1 of 7 (permalink) Old Nov 16th, 05, 10:38 PM Thread Starter
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Need some help, please!

I have a vibration that comes in at 3200 rpm then smooths out by 3600 then comes back about 5200 and gone again at about 5600 or so. The engine has just been torn down, sent the rotating assembly for balancing, put everything back together and it is still there. I put in a smaller cam just for the heck of it and the vibration is still there but moved down in the rpm range. I have left the car in neutral (4 speed manual) and while not as noticeable as when driving the vibs are still there. I'm thinking of taking my fluid damper off and trying the TCI rattlesnake but that's a pretty expensive test. By the way the engine is a 383. Any suggestions?

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post #2 of 7 (permalink) Old Nov 17th, 05, 06:34 AM
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Re: Need some help, please!

Buddy up the street found his header was hitting the bolt for the upper A-arm and caused his vibration during acceleration . (383,67Camaro)

You can also use the search button up top... long list, was gone over many times.

68 Camaro~LSx ~all motor
1.54 60'--6.95 @ 98.45 660'--10.96 @ 121.53
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post #3 of 7 (permalink) Old Nov 17th, 05, 06:46 AM
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Re: Need some help, please!

Have you checked your U-Joints? Pull the drive shaft and see if they both move freely each way.
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post #4 of 7 (permalink) Old Nov 17th, 05, 06:50 AM
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Re: Need some help, please!

Boooyah, you hit my tender spot with this post! I have vibration similar to yours. Started about 6 years ago. I bought a used (but freshly rebuilt) 454 to swap into my 350 '68 SS. I put engine in and got vibration as you described. I rebuilt engine, had it balanced, still vibrated, but at different rpm range. So i took engine back to machine shop. They re-balanced the assembly, but it STILL had a shake. So I took it back a third time; this time saying that I wanted to be there while they balanced it. They thought I was crazy and that the balance would be perfect. So, we set up the crank and bobweights, flywheel and damper (external balance); put it on the balancer and it shook all over the place! It took over 100g of added material to correct the balance.

Anyway, it STILL did not seem smooth enough for me, so I built a new 454, using a block I had laying around. This time I used Callies forged crank and had it internal balanced (by a different shop). Balance job cost me $1,200 (Mallory metal is expensive). So I put the engine in and it's pretty good, but nowhere near perfect. I ripped out this engine and had balance checked by still another shop, who said that the crank assembly was good, but it shook as soon as they put flywheel on!!!!!!!! So, I'm curious to see how the engine feels after this latest tear-down.

But it's only after I joined this forum that I learned I was using wrong crossmember, so that could be a big part of my problem. Plus I bought new GM motor mounts and will use them instead of poly mounts. Hopefully, I'll get a smooth running car for next Spring................

But your vibration could be something else too (hopefully something simple as mentioned above). I got a fabulous Camaro vibrations document from garymac69 on this forum, who (like me) spent years tracking down a vibration. I converted it to .pdf and you can download it at my server:

Dave F. in Rhode Island
'68 Camaro SS Accel DFI 454 (SOLD - I'm a boring Corvette owner now)
Bought my first big-block Chevy in 1970

Last edited by Chevy-SS; Nov 17th, 05 at 07:37 AM.
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post #5 of 7 (permalink) Old Nov 22nd, 05, 06:47 PM
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Re: Need some help, please!

I had the same problem last year with my engine. It would vibrate at about 3200 RPM and then go away at about 3600 RPM. This is what I changed last year to fix the problem. I built a new engine with new Scat crank, Speed pro flat top pistons and an aluminum balancer from Romac, and had the whole assembly balanced. I only paid $200 for balancing. The Machine shop told me that my crank was REALLY good so good in fact they only had to take metal out of it to balance it. No Mallory here. Anyways the only other thing I did was add a new pilot bearing to the new crank. The flywheel was also resurfaced. I used the roller type pilot bearing from GM. OH YES most importantly after a tear down of the 350 I found that I had 2 busted cylinder rings (primaries). This could be the final culprit as the engine comes up in RPM the cylinder probably couldn’t hold pressure and would make the engine feel out of balance (The Vibration) . Oh yea now it works perfectly now. Feels great at all RPMs.
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post #6 of 7 (permalink) Old Nov 26th, 05, 12:42 AM Thread Starter
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Re: Need some help, please!

Thanks for all the suggestions guys. Fastbowtie, could I tell if I had a busted cylinder ring by checking the cranking compression on all cylinders?
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post #7 of 7 (permalink) Old Nov 29th, 05, 06:43 PM
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Re: Need some help, please!

I would perform a leak down test. I find that compression tests are not very reliable. If you had the primary ring busted like mine it might pump up fine with cranking speed but underload might be a diffrent story. My 406 one had a piece of the ring land gone and was still with in 10% of the other cylinders.


<NOTE This is not the 350 I just told you about.>
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