Engine vibration - what is it?

[CliffyC]

Recently rebuilt my engine. Have lots of "go fast stuff" - Champion iron heads, GT3161 turbo, Precision intercooler, etc. Have been carefull to break it in properly. Has about 600 miles on it now and only really got on it a couple of times. At first engine ran nice and smooth (has 208 cam) but now it's developed a bit of a vibration I feel through the steering wheel. Seems to be all the time, even at idle, and most noticable at crusing speed 25 to 45 mph. Engine still runs very strong, no real miss or bad idle, just this annoying vibration like one of those massage things. Not real strong, just there. Engine was balanced and all machine work done by reliable shop. Have changed plugs but no difference. Any ideas? Help would be much appreciated. Thanks.

 

[QUIP'6']

Recently rebuilt my engine. Have lots of "go fast stuff" - Champion iron heads, GT3161 turbo, Precision intercooler, etc. Have been carefull to break it in properly. Has about 600 miles on it now and only really got on it a couple of times. At first engine ran nice and smooth (has 208 cam) but now it's developed a bit of a vibration I feel through the steering wheel. Seems to be all the time, even at idle, and most noticable at crusing speed 25 to 45 mph. Engine still runs very strong, no real miss or bad idle, just this annoying vibration like one of those massage things. Not real strong, just there. Engine was balanced and all machine work done by reliable shop. Have changed plugs but no difference. Any ideas? Help would be much appreciated. Thanks.

poly mounts? and engine strap too tight? torque convertor bolts and balancer bolt loose

 

[87natl]

2 things come to mind. Flywheel damaged or loose, or exhaust pipe hitting the frame. Downpipe, crossover, etc. Take a good look at those.

 

[CliffyC]

Thanks, I'll check those things out. Anything else?

 

[FastRegalWE2]

hows your driveshaft? siezed ujoint...out of balance?

 

[CliffyC]

Dought if it's the drive shaft. Seems to vibrate with RPM of engine - even slightly at idle when stopped. Wouldn't hurt to check it out anyway, thanks for the input.

 

[Clark6]

this is pretty close to what mine was doing remember you said vibrate at idle, could be the motor mounts but mine was at rpm increase , & it was the rod bearings i think i was told to pull ea. spark plug to see if vibes go away on ea. cylinder check if it does rod bearing hopefully not your case i'll have mine pulled out by the weekend to know for sure but check your convertor , trans & engine mounts like every one suggested.

 

[FastRegalWE2]

so being on this subject, how bout this,
vibration at 1500 rpm, light at 30 mph or so. Same vibration at 1500 rpm but more harsh at hiway speeds. Speed up a little, or slow down a bit, and the vibration will all but go away. Back to 1500 rpm, same intensity at, light at 30 mph, harsher at hiway speeds...
1 poly mount, drivers side
wasnt there until about 800 or so miles on a new engine, but there was a drivesahft swap at the same time as the engine

 

[QUIP'6']

so being on this subject, how bout this,
vibration at 1500 rpm, light at 30 mph or so. Same vibration at 1500 rpm but more harsh at hiway speeds. Speed up a little, or slow down a bit, and the vibration will all but go away. Back to 1500 rpm, same intensity at, light at 30 mph, harsher at hiway speeds...
1 poly mount, drivers side
wasnt there until about 800 or so miles on a new engine, but there was a drivesahft swap at the same time as the engine

but there was a drivesahft swap at the same time as the engine
check into new u joints cheap and good insurance and peace of mind also see if it eliminates the problem

 

[FastRegalWE2]

but there was a drivesahft swap at the same time as the engine
check into new u joints cheap and good insurance and peace of mind also see if it eliminates the problem

i was leaning toward unbalanced driveshaft or bad ujoint since it seems to vary more with speed and rpm than just rpm. The guy I gave my old steel driveshaft to is going to let me use it to see if it goes away.

So, on the rod bearings on the original poster, what would haen to it to make the vibration?

 

[turbobose13]

I WOULD check the exhaust like someone said before.it will cause a nasty vibration, ask me how i know.

 

[mlabrecque]

Did you ever figure this problem out? Very curious as I have the exact same problem. Mine does it in park however so I can rule out u-joints or driveshaft. It isn't noticeable at idle, but as soon as I start to apply the gas, there it is. Not noticeable under acceleration, but very annoyng at cruising speed. I've already changed the flywheel thinking that was it... no cigar.

 

[xcessiv6]

check tensioner and AC, Alternator bolts make sure every thing is tight