Okay, hopefully I am on the home stretch on my running hot issue. On to the next problem. Used 1972 455 installed in a 71 Skylark. Using the TH350 with a aftermarket flex plate. Probably came from China. It has a weight and only fit on one way, at least that is how it seemed. Balancer is rebuilt from the dampener dudes. The thing will shake your teeth at about 1800 RPM. Pulled the belts and it still does it. In gear running down the street or sitting still in the garage. Added an Xpipe with the 455 swap, because I heard it will help with phantom vibrations. Next step is to "clock" the converter. I think it's the flex plate. any other ideas? Engine mounts and frame pads are new from TA Trans mount is also new. TIA John
Oh, I guess you already said it was new. Maybe time to have your rotating assembly balanced on that used motor?
Remove the three bolts between flexplate and converter, slide the converter away from the flexplate, and run the engine. No vibration=trans problem (probably converter) vibration= engine problem
I was planning on that. if the vibration is gone then I was going to turn the coverter 120* and try again. Pulled the car in with a 350 and no vibration. Pulled it out with a shaking 455. Hard to believe it's the converter, but a good excuse for a new stall. John
John, Your vibration may be caused by the flywheel or the harmonic damper. From the factory, the dampers frequently came with weights in one or more holes in the damper. this was done to bring the damper into overall balance, not to balance a particular engine. Some of these damper rebuilding companys remove the weights(not sure if they check the balance) That may be your problem. The 70 Chassis manual describes a procedure to balance a damper on the engine. They advise to use an amount of putty or clay on the inside of the damper pulley and vary it's location until you see a decrease in vibration. When you determine a location, you can make weights out of 7/16" diameter stock(1/2" - 3/4" long) and insert them into the appropriate holes in the damper. I imagine this would be a very time consuming process, but it's something to try. The Chassis manual also describes a procedure to bring the flywheel into balance. GM use to sell special clips for this purpose(not sure if they are still available-YO used to sell them) The manual says to mark the flywheel in 4 places 90* apart. Then put a clip on one of the marks and note vibration. If the vibration increases, remove the clip and locate it 180* If the vibration decreases, put another clip next to the original one. If you notice no change in vibration, move the clip 90* and recheck. Continue this process until you have decreased or eliminated the vibration. Hope that helps.
Vibration You mentioned that the flex plate was form China. I personally saw and handled one of those. I can't think of the brand name at this time, but the thing was a piece of junk. The bolt hole locations were way off. If you tried real hard you might have gotten all six bolts in, but it would have not been easy. Goes to show the overall quality. Also I seem to recall that the ring gear diameter was off by a small amount, when compared to a stock unit. TA offers a stock replacement unit, or an SFI unit made by JW. If you don't race this car, the stock unit would be fine. Bottom line, I would bet good money that the flex plate is your problem. The harmonic balancer could be bad also, but they generally don't supply the degree of BAD virbration you seem to be experiencing. P.S. Just remembered the name of the flex plate, C.A.T.. From my experience, they make very low quality parts. Thanks, Steve
Here is a photo of the weight and balancer. Notice the relationship of the weight to the timing mark. Flexplate lined up with the bolt holes fine, never seeing another one I do not know if it correct or in the right position. John
Yeah, I've been here in Chandler for a little over two years now. There is finally a chill in the air, about time.
You did balance the entire rotating assembly when you put it together, didn't you? If not, you are probably guaruanted an out of balance motor! With externally balanced engines, even if it is already balanced, if you change a part out (flywheel or whatever), that part has to be match balanced before it is installed. You can ask Jim W about that as he is working on rebalacing my engine. It was balanced by a different shop before I sent it to him and there was some vibration when it was on the dyno, even though he match balanced the replacement flexplate I had him install. That being that, the only way to insure it is right is to rebalance the entire rotating assembly. A hassle I am sure, but it is the only way to be sure it is correct! We don't know if the original shop did it right but Jim does quality work and wouldn't have it any other way. I would seriously consider doing that as you may never get rid of the vibration otherwise if it in the motor. If you don't, it will put stress on the bearings on they will wear prematurely. In other words, it will shake itself to death!!! :eek2: Godd luck, hopefully it is the converter. Brian
I went thru this once....same thing 1800. Motor would shake right at 1800. replaced or tried known good: balancer flexplate converter then thought it was a miss: wires compression coil carb had 2 diff mufflers, thought it might be resonance....no sold car: new owner rebuilt trans and distributor he claimed the problem was distribtutor vibration: GONE Bruce BQUICK
Thought I'd throw this one out there. Rebuilt '70 455, 80k miles/ TH400 combo, drive before you buy, $1000. Exchange? or???? Will trade for early Impala Parts????.....
Sorry to say, but I'll bet it is a balance problem. Those idiots Damper Dudes and Damper Doctor... you'd think they'd have half a clue about their job... Yes, they pull all the weights out of the balancer, then rebuild it and ship it back to you without the weights back in it. The result? The balancer is no longer weighted to match the engine. Flex plates can also cause a vibration dut to a balance issue. It is a royal pain, but try to add weight in the balancer to balance it some.
Looks like I need to get some heavy clay and play. If it's the flex plate and I balance the dampener will I cause a front to back problem? John
