Thread: vibration

Tweet

I have a 1973 nova with a 406. I have noticed an intermediate vibration at 2000 rpm and up. I have been having trouble to get it to idle in gear, and the only way it will barely idle is to have the timing set at 22 degrees advance. I was wondering if this much advance would cause the vibration. was also wondering if the trans converter would cause this, have a vega 2800 stall. Is this possible, unhook the converter from flywheel and start engine to see if vibration disappears. Any help would be appreciated..

An obvious point, but do you have the correct flex plate and front hub for your 406? 400's are externally balanced, different from all other SBC's.
Now, having possibly insulted your intelligence, on to the next question. The engine may or may not run without the flywheel action of the converter, some do, some don't. I have had a few shaky converters, mostly cheapie high stall rebuilds.

Originally Posted by allenbass

I have a 1973 nova with a 406. I have noticed an intermediate vibration at 2000 rpm and up. I have been having trouble to get it to idle in gear, and the only way it will barely idle is to have the timing set at 22 degrees advance. I was wondering if this much advance would cause the vibration. was also wondering if the trans converter would cause this, have a vega 2800 stall. Is this possible, unhook the converter from flywheel and start engine to see if vibration disappears. Any help would be appreciated..

don't believe the timing will do that, but that conv. will. take the conv. loose start the motor, and if its gone you'll know its not the motor. you need to find out why it won't idle first. set you're timing around 10 degrees and forget that. you don't set timing to make a car idle. there are other reasons it won't idle. did you just change the cam or something?

The engine was built about 10 yrs ago, noy by me but a circle track engine builder. It has the 400 flex plate and balancer, I dont know the specs of the cam but its pretty lopey. It has 305 heads which the builder reworked the flow of heads and knews valves. As far as the idle in gear I have always had problem with this, tried different carbs,pv,jets,squirters. It is converted from points to hei found out yesterday the the old resister wire was powering the hei, changed that made a hugh diff but still wont idle good in gear. Have a single plane wiend intake,, just purchased a performer rpm, going to install when i recieve it in mail(purchased from ebay first time purchase on ebay hope everything works out ok) but my main concern is the vibration

Originally Posted by allenbass

The engine was built about 10 yrs ago, noy by me but a circle track engine builder. It has the 400 flex plate and balancer, I dont know the specs of the cam but its pretty lopey. It has 305 heads which the builder reworked the flow of heads and knews valves. As far as the idle in gear I have always had problem with this, tried different carbs,pv,jets,squirters. It is converted from points to hei found out yesterday the the old resister wire was powering the hei, changed that made a hugh diff but still wont idle good in gear. Have a single plane wiend intake,, just purchased a performer rpm, going to install when i recieve it in mail(purchased from ebay first time purchase on ebay hope everything works out ok) but my main concern is the vibration

take the conv. loose and see. i never had any luck with the Vega conv. anyway. they didn't last behind some good power.

Sorry, I didnt change the cam

unhooked the converter vibration gone. Must have had to shim conv to flywheel when i installed the trans, took 1 shim out of all three bolts in the conv and vibration disappeared. Runs down hiway pretty smooth, now if I can get the idle in gear solved I'll be happy, hope the new intake cures that

Why did the converter need shims???

the conv wouldnt go all the in the crank, it is a vega stall conv, dont know why it wont go all the way in maybe should grind it to fit?

Originally Posted by allenbass

the conv wouldnt go all the in the crank, it is a vega stall conv, dont know why it wont go all the way in maybe should grind it to fit?

shouldn't need no shims. how thick of skim are you running now? thats a good way to make it vibrate.

the shims are about 3/32, have to shim otherwise will warp flywheel flexplate

Originally Posted by allenbass

the shims are about 3/32, have to shim otherwise will warp flywheel flexplate

it needs to go up without shims. push the conv. as far forward as it will go, and then tap and turn it and see if it will go in a little more. don't hit it hard. you sure there is no pilot bearing still in the end of crankshaft? how long has those shims been in there?

I will try again tommorow. they have been there for ten yrs, I dont know why it didnt vibrate before, all the bolts were still tight. I had about 1/8 " shim in there took that out and pushed the conv all the way to the crank it went in but not far enough to mate with the flywheel. measured the distance (well I try and error with shims) and shimed it and put conv bolts back in, took for a drive and no vibration. I know thats not the way it is suppose to work but until I remove the tranny to figure out whats up it will do for now beings the shims have been there for long, I will take your advise and try to tap the conv in. I am just about positive there was no pilot shaft bearing in there. thanks for the help and will post tomorrow on results.

Originally Posted by allenbass

I will try again tommorow. they have been there for ten yrs, I dont know why it didnt vibrate before, all the bolts were still tight. I had about 1/8 " shim in there took that out and pushed the conv all the way to the crank it went in but not far enough to mate with the flywheel. measured the distance (well I try and error with shims) and shimed it and put conv bolts back in, took for a drive and no vibration. I know thats not the way it is suppose to work but until I remove the tranny to figure out whats up it will do for now beings the shims have been there for long, I will take your advise and try to tap the conv in. I am just about positive there was no pilot shaft bearing in there. thanks for the help and will post tomorrow on results.

i have shimed them before, but didnt like the idea.

The more I think about the more I think the pilot shaft bearing is still in there, as I said previously a circle track engine builder built the motor and he had the block already and they use stick shifts. Probably wont get much sleep tonight thinking about it. thanks again lt1S10