Engine Vibration - 1965 Riviera 401

[dbaker9323]

I recently purchased a very nice 1965 Riviera. It went through a complete restoration, including engine rebuild, in 2010, and has been driven  only a couple thousand miles since then.  I noted when I inspected and drove the car that there was a minor vibration in the car (I would call it a 2 or 3 on a scale of 1-10), which I assumed was either related to wheels or tires.  However, those items have all been checked  by 2 different mechanics, wheels replaced with different ones, new tires purchased and balanced twice, suspension inspected (and all proper and intact), and the vibration persists.   As added info for my question, the car runs and performs beautifully at all speeds and is extremely powerful.  Both mechanics concluded that it is related to the engine.  The vibration can be felt at all speeds above Idle;  it is constant in that it is always there, but it does vary according to RPM;  at higher ends of each gear it gets smoother, then when it shifts it becomes more pronounced, presumably due to lower, momentary  RPM.  They checked the harmonic balancer, and state that is not the cause;   they checked the driveshaft and state that is in perfect balance.  That said, their only suggestion for a possible cause is that the engine is out of balanced internally and would have to be torn down to correct it.

 

Any suggestions for other checks or causes, or should I expect that the engine will need to be torn down to correct this?  Both mechanics state that I should just put up with it since the car runs perfectly and is very nice otherwise; .  That is not acceptable to me, although it seems practical!

 

Thanks.

 

David Baker

[Seafoam65]

                The flex plate on the 65 nailhead must be put on the correct way or the engine is thrown out of balance. Most

people don't know that the flex plate must be indexed correctly. Odds are extremely high that this is your problem. Refer to the service manual

for correct placement of the flex plate on the crank shaft. Also if the crank was balanced without the flex plate attached, the engine

will be out of balance even with the flex plate correctly installed.

Edited November 30, 2017 by Seafoam65 (see edit history)

[1965rivgs]

When looking at the flex plate  there is an extra hole which looks like a bolt should be there but is not. If the flexplate is correctly indexed, the hub of the crank should look like someone tried to run a drill bit thru the hole and started drilling into the hub of the crank. This is the "mark" on the hub of the crank which is used to index the flexplate. If one looks thru the indexing hole and just sees a flat surface behind it the flexplate is incorrectly indexed. Your mechanic can see this with the engine in the proper place of rotation from underneath the car without any special tools. These days it is common for a shop to have a boroscope which would give a clearer, more easily seen perspective.

  Tom Mooney

[Seafoam65]

                    Another thing you need to check immediately is the torque on the harmonic balancer bolt at the front nose of

the crankshaft. Most Chevy rebuilders that try to rebuild a nailhead Buick are not aware that the harmonic balancer bolt must

be torqued to 250 foot lbs. If not torqued properly, the bolt will back off and the balancer will start wobbling on the nose of the crank.

The crankshaft can be damaged by this...the balancer is always ruined when this happens. Also this usually happens about 1500 miles after

it is put together improperly, so in your case it is a strong possibility. What usually happens is that the balancer cracks along the key

way slot. The same is true with Pontiac V-8s as well.

Edited November 30, 2017 by Seafoam65 (see edit history)

[dbaker9323]

Thanks for your helpful replies, gents!  I will use these approaches with the Mechanic.

[DualQuadDave]

Hard to believe, but I have seen a few times including on my own Riv, but if the valve springs are weak/pushrods bent or incorrect length, it will cause a weird low rpm shudder/vibration in the motor. Might pull the valve covers/rocker arms and have a look.  Any rebuilt Nail should have adj pushrods or measure and order specific length rods for proper lifter preload.

Edited December 22, 2017 by DualQuadDave (see edit history)

[dr914]

so it vibrates at a standstill with the engine running?  If so certainly the engine, (like has already been stated, harmonic balancer, torque convertor, flex plate, if not the driveline, maybe the drive shaft

[TKRIV]

Before pulling the engine, disconnect all belts and pull back the torque convertor so as to completely isolate the engine.

Other possible (but unlikely) reasons for vibration are collapsed engine mounts, exhaust pipes mounted with no give. Crack(s) in flex plate. 

[TKRIV]

I had a engine vibration very similar to the above. Vibration at all RPM but most noticeable above 1600RPM

After eliminating all the obvious culprits (H Balancer, Torque conv. Dizzy...) the engine was pulled, balanced and rebuilt including new flexplate,

Lifters, Rods...  The Vibration was still there!!!

Lots more investigates by many good old school mechanics. Pulled engine again and found #5 Pot was clean.

Cylinder was not working at all. We knew we had Spark, Air/Fuel and Compression but no combustion. Engine rebuilt and the only modification we made was to block the exhaust cross-over ports which run through the inlet manifold.

Bingo! No more vibration.

One of the tech's told me that he has come across this problem before where the inlet casting between the exhaust and inlet passage is very thin

& can be porous. Some of the exhaust gases leak into the inlet port passage which reduces the oxygen level below the explosion limit. Would love to see if anyone else has had this vibration & fix.

A long and extremely frustrating saga has come to a end.

Tom Kunek

ROA3845

 

[johnrex]

Also check the transmission mount for separation.

[lrlforfun]

OK Riviera People: Internet diagnoses?  NOT HAPPY.  1. Isolate every component. pick a starting point. It could be anything. I had a 65 Riv mimic the same vibration and it was a bum center support bearing/driveshaft issue.  Without isolating each component in the system, who the hell knows.  Isolate each component, eliminate it then move on.  Transmission might  eventually have to  come apart from the motor to isolate that section. .  Mitch

[TKRIV]

Yes we isolated each component one by one and yes even pulled back the trans. Replaced Trans mount and engine mounts.

We did every conceivable isolation or replacement with new or known working parts before pulling motor.

After complete rebuild still the same vibration. Absolutely no change. 

So we think that somehow we have the crankshaft balancing wrong as every other component again checked out OK.

 

Stripping the motor the second time we could see that one pot was clean (no combustion)

So the only item between the pot and the carby is the inlet manifold. The only thing we did differently in the second rebuild

was block off the cross-over exhaust ports.

I totally understand that there must be nailhead mechanics out there that find this fix for the vibration implausible.

TomK

 

[RockinRiviDad]

On 11/30/2017 at 6:01 AM, Seafoam65 said:

harmonic balancer bolt must

be torqued to 250 foot lbs. 

 

Not to hijack but I just did this last night. Finally getting my car together & service manual calls for 200 ft lbs 

 

Am I missing something?

Edited April 8, 2018 by RockinRiviDad (see edit history)

[SwedeDownUnderR63]

2 hours ago, RockinRiviDad said:

 

Not to hijack but I just did this last night. Finally getting my car together & service manual calls for 200 ft lbs 

 

Am I missing something?

220 seems to be the recommended torque. See http://centervilleautorepair.com/tech-info/264-322-364-401-425-bolt-torque-specs

 

[1965rivgs]

7 hours ago, TKRIV said:

Yes we isolated each component one by one and yes even pulled back the trans. Replaced Trans mount and engine mounts.

We did every conceivable isolation or replacement with new or known working parts before pulling motor.

After complete rebuild still the same vibration. Absolutely no change. 

So we think that somehow we have the crankshaft balancing wrong as every other component again checked out OK.

 

Stripping the motor the second time we could see that one pot was clean (no combustion)

So the only item between the pot and the carby is the inlet manifold. The only thing we did differently in the second rebuild

was block off the cross-over exhaust ports.

I totally understand that there must be nailhead mechanics out there that find this fix for the vibration implausible.

TomK

 

Tom,

  Great to hear you acheived good results. But what puzzles me is that a pro tech would miss the fact a cylinder was carrying no power while running and choose to rebalance a motor? Surely such a cylinder presented itself as a profound "miss" which can very easily be detected by anyone with a minimum of experience? Doesnt make much sense to me? What am I missing?

Tom

[pyntre]

Are those heat cross over plugs custom made , or are they available somewhere ,,,, never seen something like that before ,,, 

are they epoxied into place ??? 

Amazing amount of detective work to get it figured out ,,,KUDOS !

[RivNut]

7 hours ago, SwedeDownUnderR63 said:

220 seems to be the recommended torque. See http://centervilleautorepair.com/tech-info/264-322-364-401-425-bolt-torque-specs

 

You NEED to have a chassis manual for your car.   The 220 ft. lb. of torque comes from the manual which also gives you the correct torque for EVERY bolt on the engine.  (Where do you think Russ came up with the numbers? ?)

 

If you don't have one, you're missing the most important tool in your shop!

 

Ed

[SwedeDownUnderR63]

4 hours ago, RivNut said:

You NEED to have a chassis manual for your car.   The 220 ft. lb. of torque comes from the manual which also gives you the correct torque for EVERY bolt on the engine.  (Where do you think Russ came up with the numbers? ?)

 

If you don't have one, you're missing the most important tool in your shop!

 

Ed

Ed,

it might be worth noting that the chassis manual have a range for most if not all bolts. That is 200 to 220 in this case. I can only assume that Russ prefer the higher value based on experience, maybe to be absolutely certain that one doesn’t run into a harmonic balancer getting loose as a torque wrench could be slightly off.

It is even more “fun” if one starts to use stainless steel bolts (not for this case) as the torque then is likely to be different from what is in the chassis manual.

Edited April 8, 2018 by SwedeDownUnderR63 (see edit history)

[RivNut]

My 65 chassis manual says "200 min." for the balancer bolt, it gives a range for all others. 

 

All I'm saying is that without a chassis manual, you're on a treasure hunt at night without a flashlight. 

 

I wonder just how many guys assemble an engine by using the "that's about right" feeling on their box end wrench when tightening things like distributor hold down bolts, rocker arm cover bolts, valley cover bolts, etc.witout using a torque wrench. If there wasn't a torqe setting needed, they wouldnt be in the manual.

 

So many questions asked on automotive forums could be answered immediately with a chassis manual rather than waiting and hoping,  while the project just sits there, that someone else can answer the question.

 

The chassis manuals are available, they're not that expensive, and they're invaluable. EVERYONE needs one if they're committed to doing it properly.  

[TKRIV]

Machine shop made the plugs for the inlet manifold. 

When you don't live in a cold climate there is just no need to heat the Carby.

We just don't have the cold winters that you have in Nth America.

I agree with you TomM that the diagnosis of the vibration was perplexing as all the  "pro techs" saw it as

an out-of-balance issue rather then a non rotating actor. 

We got there in the end and at least I have a nailhead built that runs super smooth.

[pyntre]

??????

[RockinRiviDad]

Just a thought: I bought a new heavy duty fan clutch. It came with a brass collar/sleeve that slips over the water pump snot to take up any slop in certain applications. My old one didn’t have this. The instructions state that if this collar/sleeve is not used to take up said slop then a serious vibration may occur. 

 

Hope your issue is that simple. 

[slosteve]

On ‎4‎/‎8‎/‎2018 at 6:53 PM, TKRIV said:

 When you don't live in a cold climate there is just no need to heat the Carby.

We just don't have the cold winters that you have in Nth America.

 

So where is it that you live with such intolerable conditions, TKRIV?

[1965rivgs]

Australia

  Tom