(NEW) Engine Vibration

[luke-ao]

I did buy a Harmonic balancer for a 1971 302 any way to verify I got the correct one?

[luke-ao]

So I checked the driveline and its was indeed out of phase. I corrected that and it definitely helped but I still have the vibration but it seemed to settle down to spesific points now instead of spread out like it was.

Now the vibration rises and gets strongest as the RPMs increase just before shifting from 1st to 2nd then 2nd to 3rd. Also in park when when gassing it to higher RPM the shake comes in.

Is there any chance the brand new harmonic balancer is bad?

[sargentrs]

It's always possible a new part could be bad. Quality isn't what it should be anymore. As long as we're just playing around, would it be possible to add weight to the balancer and move it around the perimeter to see if it changes anything? I wouldn't rev it up or anything but just idling. Wouldn't want to sling anything through the radiator or something. Maybe a heavy magnet? Did you replace your torque converter or flex plate?

[luke-ao]

Man I've been round and round with this, all suggestions here have been checked and double checked. Motor and trans mounts are new and tight. Firing order is correct. Driveline is phased correctly. New harmonic balancer. New flex plate. Engine actually runs excellent but with a vibration.

I dont know of any internal mistakes I could have made with the build that would cause this(?) I used all the recommenced parts based off the heads I had, cam, intake, carb, exhaust, etc like I said it runs good.

It really seems like it's the harmonic balancer or maybe the Flexplate, both are new and the HB looks identical to the one I removed which leaves the flexplate. Is there anyway to identify the flexplate as being a 28 ounce imbalance part with it installed and through the inspection cover opening?

I wonder how bad the vibration would be with the correct harmonic balancer but the incorrect flex plate?

EDIT: I found some good pictures of the 28/50oz imbalance harmonic balancers of the exact brand I purchased and I do indeed have the correct one so the unknown at the point is whether or not I was sent the correct flexplate.

[luke-ao]

So to answer my own question on the flexplates, I can count the teeth, 164 tooth for the 28 oz imbalance application...

[luke-ao]

I counted the flexplate teeth and it is 164 tooth.

The only thing I can think of now is to pull the plugs see if there's something off there...

[71cc]

If possible slide transmission back on long bolts so you can run engine without converter. I chased a similar deal and turned out to be converter once. In another instance I got a badly balanced pressure plate. Same symptoms. I guess you're confident it's not a light miss from vacuum leak ? Sounds like the rotating assembly is the culprit. If it wasn't balanced you have no idea if it's " right"

[luke-ao]

71cc, I'll keep this all in mind, but the transmission/converter was fine before the engine swap. Its been my daily driver for several years and the vibration problem showed up with the new engine.

[luke-ao]

Problem solved! Swapped out the flex plate and she's purring like a kitten.

[DuckRyder]

Glad you got it worked out... were they different of the old new one just not build properly?

[luke-ao]

Well the "OLD" one was actually brand new and it was a 28oz imbalance flexplate and based on this video>>
https://www.youtube.com/watch?v=LxxAwxzlQFo
It was for a C6 (I'm running a C4) apparently I was sold the wrong one. The two flexplates shown in the video just happened to be the two FP's I have. I didn't know that going in, so it's just a coincidence.

I was pretty sure it was a 'rotating assembly' problem as 71cc suggested because that's what it felt like from the vibration feedback but I wasn't certain either way because I've never ran into that before. I just had the rule out the easy stuff first.

As soon as I fire it up and rapped on it once I knew it was fixed. It's smooth as butter now and I'm as giddy as a school girl.

[jp2005]

Well the "OLD" one was actually brand new and it was a 28oz imbalance flexplate and based on this video>>
https://www.youtube.com/watch?v=LxxAwxzlQFo
It was for a C6 (I'm running a C4) apparently I was sold the wrong one. The two flexplates shown in the video just happened to be the two FP's I have. I didn't know that going in, so it's just a coincidence.

I was pretty sure it was a 'rotating assembly' problem as 71cc suggested because that's what it felt like from the vibration feedback but I wasn't certain either way because I've never ran into that before. I just had the rule out the easy stuff first.

As soon as I fire it up and rapped on it once I knew it was fixed. It's smooth as butter now and I'm as giddy as a school girl.

That's great news! Love when things work out.