An old boy rolled up to the shop today in a pretty nice 61 Electra. Said he had a problem and someone had told him I know something about Buicks. Hmmmmm...okay.
He's had the car for quite some time. It ran great but it smoked. So he took it to a shop about 40 miles from his home. He lives about 25 miles from me and I'm not familiar with the shop he spoke of.
Anyway, they did a major rebuild on the engine. He wasn't quite sure exactly what they had done. He thought they "miked the crank" and put in new pistons. When he picked the car up it didn't smoke but it vibrated badly. When he asked about it they told him it was a big powerful engine and it had more compression now so it's normal for it to vibrate. (?????)
He took it to a few places to look at it. A trans shop pulled the tranny back and rotated the convertor to the three possible positions. No change. Another shop put new motor mounts in it. No change. Another shop put a new Edelbrock carb on it and charged him 850 bucks! No change (really???) Another shop put two new (used?) harmonic balancers on it. No change.
There were some other steps and more money spent but I don't remember the whole story except that he has NINE GRAND in the engine rebuild project and it vibrates like heck!
I checked the fan blade and it's okay. This thing has a major balance problem. I don't know if any of you guys have ever experienced an engine with the wrong flexplate/flywheel (internal vs external balance) but that's what this feels like. Serious harmonic resonance through the entire car.
Stand next to it, seems just fine. Runs just fine. But sit in it and it's there! BAD! RPM aggravates it even more.
So where did these guys go wrong? Looking at the 401 damper it tells me this 401 is an externally balanced engine. I have a flexplate off a 59 364 and it appears to be zero balance.
The majority of my Buick V-8 experience is with 322s. I am not well versed on 401. Is it possible that they bought a crank kit from a different year 401 that is internally balanced, or is there no such thing as an internally balanced 401 crank?
If they used the original crank, damper, flexplate, and rods, that only leaves pistons. But even if they are a different weight they would have to be WAY WAY off for it to vibrate like this!
I told the old boy all I can do is tear it down and send everything to the balance shop unless some 401 experts can give me a clue.
I would like to isolate the convertor from the engine but I can't think of any way to spin it up if I do. But considering the power train was smooth before the engine job I can't see what they could have done to the convertor to cause this problem.
You might have better luck with the folks at http://speedtalk.com Go to the forums, and then to the engine forum. It's mostly 'race' but there are some more experienced machinists there that have dealt with, and still deal with the older stuff.
I recently dealt with a cracked flex plate on our Dodge minivan, and it didn't vibrate at all. It was cracked all the way around at the bolts. Sounded like a bucket of bolts being rattled around, but didn't vibrate.
I have no answer to the question, but the owner should be glad you're a good guy. Greg. If you were like the Edelbrock install shop, you would have done a total resto, charged him for it and still left it vibrating.
I am betting there is an interesting story coming when you figure it out.
My uninformed guess is that the engine is going to be opened back up to find the problem.
Greg,
Is it possible that it could be something that only concerns a single cylinder? I would think that that could be isolated with pulling the wires one at a time until the one that makes the greatest difference is isolated. I am thinking maybe a piston weighing significantly more or less from the others.. or perhaps a rod. In any case, unless you get a quick and easy answer for the guy, he is going to have to decide whether or not he wants to pay you to fix the issue...if you decide to take it on. Is there any way he can go back against the original shop?
My 83 mustang i had vibrated from the day i got it. 2yrs later i built a new 306, and figuared i got the vib, but it must have been the convertor or the tranny. I put a different C4 and convertor, no more vib. Just a thought.
ALl the flexplates I've worked on that were cracked made a lot of noise but only a little vibration...
I suppose the people double checked the firing order about 30 times. Plus SOMEONE had to have pulled the plugs and read them to be sure there weren't a couple dead cylinders, or a couple firing out of order which houls definitely cause a vibration...
I'm also pretty sure that the vibration isn't coming from an improperly weighed Rod or Piston, that kind of diffrence in weight would have to be tremendous, and most likely would have been spotted upon assembly, even by a new kid right out of school...
The 2 401's I rebuilt at the machine shop in CA went together smoothly.
I'll check the books on the cranks and or balancing of them this morning if they're still available.
Greg I know the cracked flexplate is an off the wall probability but having seen this just a couple of weeks ago it was fresh on my mind.I also bought an expensive set of pistons recently.One piston was 12 grams heavier than the others.If it was related to the transmission you would think the transmission shop would have caught it.I generally solve problems by the brute force of ignorance method.That being said,I would seperate the engine from the transmission and verify the engine has the vibration.I talked to a machinist with 30 yrs experience this morning but he had 401 specific things to check.sorry
If you want to do a cut and paste and be my representative that's fine with me.
Thanks.
PS: The engine is running "uniformly" in that it's hitting on all cylinders. This is not a miss or a weak cylinder. It's a serious imbalance problem. If you ever put a 400 flexplate on a 350 Chevy or mixed up the flywheel/flexplate on a 302/5.0 Ford you'll know exactly what I'm talking about.
Is it possible that a piston can be off in weight to cause this? IE 7 holes used cast pistons and one used forged. Or Parts from different manufacturers being used in different holes.
To my way of thinking, it could be any part in the reciprocating and rotating assembly that is out of line weight-wise.
If the flywheel has weights on it, could one have gotten knocked off when the engine was apart?
If I am the owner, I think I insist that the original shop remedy the issue. If it has been too long for him to make a claim, then that is his problem. If the shop will not fix it, I would suggest small claims court.
I have never faced this type of vibration issue. Is it usually a balancer or a flywheel?
It is really cool of you to investigate for him to see if it could be a simple issue.
This message has been edited by dpfalls on Dec 3, 2008 9:37 AM
If its anything like putting a 390 flex plate on a 410/428 - I understand!
December 3 2008, 10:47 AM
Just because something fits, doesn't necessarily make it the right part.
I made that mistake, combination of trying to save a few dollars and with a little help from the local Grand Auto. Built my first 410 (from a 352). Used the same flexplate, heck - it fit, so I figured it was worth saving the cost of a new one.
Anything over idle would cause some vibrations that got worse - until it hit about 4K. I changed to a C-6 around the same time so I figured it was the flexplate, went to the local Grand Auto, they gave me the 'right' one, I installed it - same results? Obviously, I built the engine wrong or the balance was way off (since it was a budget build, I used off the shelf pistons, re-worked factory rods - beam polished at home and sent out for shoot peen). The car was undrivable, after suffering through it for about 6 months, I bit the bullet, pulled the engine and built a 428. Put everything back together, same damn vibration. Luckily the C-6, crapped out on me. Took it to a new shop, had it pulled, put in heavy-duty everything and valve body kit. Got a call from the ol' time mechanic, asked if it really was a 428 in it as I claimed? Then told me that I had the wrong flex plate - being stupid makes a person very suspicious. I thought he was just trying to hit me up for some more money.
He offered to let me buy any flex-plate from anywhere I wanted, as long as it was for the right part. If the vibrations were still there, he would swap mine back for free. I took the deal, ordered a SFI flex plate out of a catalog, when it came in he installed it. I went down picked up the car - Damn! it ran great! No vibration, the new 2700 stall torque converter was roasting the tires; and finally, no more vibrations. After kissing his butt for about 1/2 hour I paid my bill and started my Jihad against Grand Auto, Checker and Auto Zone.
Moral of the story is stupidity and assumptions have no place in diagnostics. Like you have done - "if you don't know something - ask somebody! Sooner or later someone will come up with the right solution.
I think I have it fingered out. Buick REALLY screwed up on this one! The flexplate is actually a triangular "drive plate". It's hard to see but it is "heavy" on one side. That means it's part of the external balance.
Problem is that the flexplate will bolt to the crank in ANY position. The holes are equally spaced unlike most engines where the flywheel/flexplate will only go on one way due to offset bolt pattern.
I looked at the 364 that's on the floor. There are 6 holes for the flywheel bolts. BUT there is one small alignment/indexing hole. The flexplate will go on anywhere but it appears that this small hole MUST be lined up. You'd think they'd have put a dowel pin in there but they didn't!
Just looking at the flexplate I'd say we're looking at a good 8 ounces of offset weight. THAT, my friends, will make her shake!
Gary, I've worked on a lot of engines and a lot of them were Buicks but I had never encountered this before.
Now that I think about it a different guy called me about 6 months ago with the same problem. Rebuilt 1961 401, smooth before, vibration after. I told him to try rotating the torque convertor. Beyond that I didn't have a clue. Now I know!
What REALLY sucks is that I put the flexplate on the 401 in the white 59 convertible. There's a one in six chance that I installed it correctly. It's possible that I may have picked up on the alignment hole, but I can't say. Good chance I just stuck it on there and when the holes lined up the first time I considered myself lucky and slammed her home!
If that one shakes it will be quite a project to fix it since it's a torque tube car...........
I'm sure Greg will respond, but yes, it's a driveshaft in a tube. Chevies had it too and I had one in my '53 Chev. I suppose it was designed to keep driveshaft vibration at bay since the shaft is supported by bearings and I believe it was also called a Torquetube drive. It added weight to the car, but that wasn't much consideration when it was used.
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