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How Can I Dial-In the Rotating Balance After Install?
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How Can I Dial-In the Rotating Balance After Install?
I am trying to solve an RPM vibration, worst at 2400 RPM-ish. Newly rebuilt engine, new Summit clutch kit, resurfaced flywheel. All seems fine. Engine makes plenty of power, trans shifts just fine, clutch works very nicely. Everything works as it should.
I am seeking advice on the path of least resistance working my way up to buying a new flywheel or clutch.
I have some experience with this type of vibration long ago. On a pretty much new 1988 Mustang GT. All stock. Engine had this same harshness. revving through the range above 1800 RPM. Idle was also not as smooth as other stock factory 5.0's which were known for their silky smoothness. I tried all kinds of things but after lots of things like a new Centerforce Dual Friction Clutch, I decided to try the flywheel. I bought a McCleod billet and the vibration completely went away. Forever. This car has the same vibration, but a bit worse. So I am focused on the flywheel. One important fact to add, was that when I first got the car, it WAS smooth. Then a shady dealer told me my engine was shot at 58,000 miles and "replaced it under warranty". That's when I noticed the problem.
So I am thinking I did a rebuild on a 1988 5.7 block, used a donor car WC T5 setup (I think it was a 1990 TBI) but it's definitely a WC. I had the flywheel surfaced but that's it. Reused the flywheel bolts. The crank journals were polished, factory rods reused, original rod bolts, and Mahle 0.020 flat top HE pistons put in. I did not have the rotating assembly balanced as I was told it was not necessary. As mentioned, new Summit clutch kit. Pilot bearing did go into the crank.
I am pretty sure I either have a balance problem or a defective part but I am favoring the first one.
I am hoping for some experience and advice here to proceed in the most logical way to fix the problem. I am not aware of flywheel "fine tuning" kits so I am thinking if I index the clutch and/or flywheel, that should do it.
I have already verified the vibration is there with the clutch in and out so I do not believe that transmission side has anything to do with it.
Tentative Plan:
I will first do a runout check - outside of flywheel to bellhousing using a feeler, but I expect that will show just fine.
I will then remove the trans and clutch and rev it up. Depending on what it does I might index the pressure plate or the flywheel. I did not verify that the shop gave me back the correct flywheel, I assumed they did. I am trying to dig around my pics to verify.
Here is the flywheel from the donor car (again, I did not verify I got back the correct flywheel - but am pretty sure I did) and new pistons used:
Re: How Can I Dial-In the Rotating Balance After Install?
I know of no good way to attack a balancing problem on a fully assembled vehicle. You're going to have to take some stuff apart.
Clutches and flywheels are the things most likely to be a problem. You can pop the transmission & BH out, unbolt the clutch and turn it 180° on the flywheel, and see if it makes any difference.
Also, how you assemble a clutch, can make a YUUUUUUUUUJJJJJJJJJJE difference. As you bolt it down, all sorts of parts of it, BEND. If it isn't PERFECTLY centered, and tightened EVENLY, many odd things can happen.
Try doing what I just said. Pay PARTICULAR ATTENTION to holding the clutch up (don't just let it hang there) as you start tightening the bolts, making sure it's centered on the flywheel. Tighten one of the bolts at the bottom first, just until the disc is held in place; then tighten one of the top ones about the same amount; then the other 4. Then tighten them a turn or so, evenly, all the way around. DO NOT just jam the clutch onto the flywheel, run a bolt down, then put the others in.
Also, I'm going to assume you're using ACTUAL clutch bolts. They are NOT standard bolts. They have a sort of shoulder to them between the threads and the head that acts like dowel pins to more accurately locate the clutch on the flywheel. If you aren't using ACTUAL clutch bolts, replace whatever you have with the right thing. Get new; Mr Gasket, ARP, the various clutch companies, etc. all sell em. You can probably find em at AZ and such even, hanging on a card.
If you have access to a balance shop (NOT a regular run-of-the-mill "machine shop") you can take your clutch & flywheel in and have them checked and/or trued up.
Re: How Can I Dial-In the Rotating Balance After Install?
I had about a 1500 RPM vibration with the original 700R in my 86. Indexing the flex-plate and torque converter solved it. This is actually mentioned in the factory service manual. Kind of a PITA with a manual to index the pressure plate but certainly needs to be ruled out. I tried replacing the (original) balancer first. Interestingly, in the subsequent 700R's I have dealt with (two more on that car, and now several more on my Jimmy) I have never run into that again. Nor did I have any issues with replacing the clutch in my 91 Formula T5. Just the original trans/flexplate/converter in my 86 TA (which I personally had never removed or changed the indexing on at the time of this vibration - car was new to me at that point).
GD
Last edited by GeneralDisorder; 03-09-2020 at 11:45 AM.
Re: How Can I Dial-In the Rotating Balance After Install?
Not likely a runout problem if it is rpm specific, indexing can werk if you know what part is causing the problem and is usually quite effective for any rotating part (including wheels and tires). You have a new rebuild, what parts were carried over? If it's rpm specific, anything attached to the rotating assembly can cause this.
Re: How Can I Dial-In the Rotating Balance After Install?
So I reused everything except the pistons and rod bolts. The machine shop prepped the block, crank and pistons and I assembled the short block with my sons (teaching moment!). I went with the Mahle OE replacement pistons mentioned above and used ARP rod bolts. That's it. Mahle iron rings, ring kit, etc. Everything mic'd out when I assembled the short block. Excellent tolerances, clearances, etc. Engine makes healthy oil pressure and plenty of power with no funny business so I think it is fine.
I am going to dive in and index it. While I'm at it I will replace the flywheel and pressure plate bolts with new for good measure. I'll fire up the engine with the bell housing off to try different index points. I agree, I will probably get it nice and smooth. Maybe I'll splurge and finally get the quick jacks. <<evil thoughts ensue>>
Last edited by Tootie Pang; 03-09-2020 at 05:33 PM.
Re: How Can I Dial-In the Rotating Balance After Install?
Originally Posted by Tootie Pang
..... I am thinking if I index the clutch and/or flywheel, that should do it.
Tootie, if this is the correct flywheel for your engine, it CANNOT be indexed.
See in your pic above - from 5:30 to 8:00 o'clock there is a raised area - a weight. That needs to be in the correct position.
Re: How Can I Dial-In the Rotating Balance After Install?
Who was it that told you the internal rotating assembly didn't need to be balanced? and did they say why? anytime you have a multitude of parts bolted together and then they move - especially rotationally, they should be checked for weight.... if you were told that unless yer revving to 10000 you don't need it, that's incorrect. You can have vibrations in an engine from idle on up. If that's where it's from, I really hope you can externally dial out some of that imbalance... sounds like you have a great package there.
Re: How Can I Dial-In the Rotating Balance After Install?
Originally Posted by 427seven
Who was it that told you the internal rotating assembly didn't need to be balanced? and did they say why? anytime you have a multitude of parts bolted together and then they move - especially rotationally, they should be checked for weight.... if you were told that unless yer revving to 10000 you don't need it, that's incorrect. You can have vibrations in an engine from idle on up. If that's where it's from, I really hope you can externally dial out some of that imbalance... sounds like you have a great package there.
Yep that sounds like my machine shop. Not revving to 10,000 so it shouldn't matter. I agreed. The pistons and pins are sold as stock replacements so I assumed they would weigh the same as OEM pistons but I did not check. Now I will check. Crank journals not turned, just cleaned up. I just realized I did not use ARP rod bolts - I used the stock rod bolts intentionally just for preserving balance. I'll correct my original post. I used ARP on the mains and head bolts.
Re: How Can I Dial-In the Rotating Balance After Install?
Call me crazy, but if you change pistons, you changed the weight. Also since you changed the pistons, the rods should have been reconditioned, which would have changed the weight of the rods. At that point the crank/pistons/rods, etc should have been balanced. That's how you get a quick an simple rebuild that balloons into stupid money, and why I pretty much always tell people to just throw the old engine away or sell it as a core and buy a crate engine. You usually will spend as much or more money rebuilding an engine than just buying one that's already done, and in the case of GM the chances are above average they'll build the engine right. The local machine shop that rebuilds whatever happens to walk in off the street, and doesn't put a warranty on anything, is a lot more likely to make mistakes and cut corners. Rebuilding an engine is a learning experience, sometimes you learn not to waste time having a local shop do machine work and trying to assemble everything just right when you can get new parts from a major manufacturer. I hope it works out for you, but there are so many possibilities, who can tell you where to start trying to resolve the problem?
Re: How Can I Dial-In the Rotating Balance After Install?
If the crank didn't have the dowel pin in place, need to at least line up the dowel pin holes. NoEmisssions84TA mentioned this. Otherwise the rotating assembly is out of balance. Here is a post that describes fixing an engine vibration via slugs in the flywheel:
Re: How Can I Dial-In the Rotating Balance After Install?
Yes, I verified crank still had the dowel pin so the flywheel should be lined up.
I read the thread RBob linked above. My long block is from a 1988 350 TPI but the flywheel and trans I used is from a 91 RS 5.0. Would this have anything to do with the crank having a that dogbone weight and now I've got twice the balance weight?
And regardless, that balancing procedure in the FSM seems easy. Take the inspection cover off and have at it. I gotta find where to get those weights!
I looked a bit. No mention if them anywhere. Hmmmm.
Last edited by Tootie Pang; 03-09-2020 at 10:37 PM.
Re: How Can I Dial-In the Rotating Balance After Install?
Would this have anything to do with the crank having a that dogbone weight and now I've got twice the balance weight?
No...
Any flywheel that fits your crank will be the "correct" balance for it. At least, to the extent that the factory considers "correct". Just like, if you look up the flex plate (which contains the same balancing function) for a L03 and a L98, you'll find they're the same.
Your problem isn't parts selection. It's that something has changed along the way, like one side of the flywheel getting more metal taken off if it when resurfaced; or the clutch not being centered.
Never heard of any "balancing" procedure in the FSM. But I haven't read the whole thing.
Re: How Can I Dial-In the Rotating Balance After Install?
One important fact to add, was that when I first got the car, it WAS smooth. Then a shady dealer told me my engine was shot at 58,000 miles and "replaced it under warranty". That's when I noticed the problem.
So I get the timeline,......... You bought the car & it was OK. Dealer told you about 58000 mile engine swap, then you first notice a balance problem, then you rebuild engine and convert to stick ?? The vibration is still occurring even after the engine rebuild and tranny conversion.
Do both Engine Mounts and the tranny mount check out ?? ( Checked with pipe/leverage, not by eye. )
Re: How Can I Dial-In the Rotating Balance After Install?
[QUOTE=John in RI;6358569]So I get the timeline,......... You bought the car & it was OK. Dealer told you about 58000 mile engine swap, then you first notice a balance problem, then you rebuild engine and convert to stick ?? The vibration is still occurring even after the engine rebuild and tranny conversion.
I think the 58000 miler was his first car, a 5.0 ferd
Re: How Can I Dial-In the Rotating Balance After Install?
Interesting. I have previously noted the procedure for rotating the torque converter and that did solve my 1500 RPM vibration that the car came to me with.
I hadn't seen that procedure for the MT flywheel weights. I wonder where one might find those....
Re: How Can I Dial-In the Rotating Balance After Install?
Originally Posted by GeneralDisorder
Interesting. I have previously noted the procedure for rotating the torque converter and that did solve my 1500 RPM vibration that the car came to me with.
I hadn't seen that procedure for the MT flywheel weights. I wonder where one might find those....
Re: How Can I Dial-In the Rotating Balance After Install?
Originally Posted by Drew
Call me crazy, but if you change pistons, you changed the weight. Also since you changed the pistons, the rods should have been reconditioned, which would have changed the weight of the rods. At that point the crank/pistons/rods, etc should have been balanced.
Re: How Can I Dial-In the Rotating Balance After Install?
So this investigation is sounding like I could have more internal balance problems than an indexed clutch pressure plate and fine tuning. I will go to the shop and verify that he did not balance the setup. If he did not I will ask if he verified the weights matched. These replacement pistons/pins are sold as OEM replacements. This shop owner knows his stuff so I would not be surprised if he accounted for the new pistons and rings in whatever balancing determination he made.
Regardless, I will hold out hope that I can try the flywheel balance weights to get it to feel right. I would love to know where to get those wieghts and if not, what they are like so I might just make some. I wonder if they are just threaded holes for bolts?
Last edited by Tootie Pang; 03-10-2020 at 01:30 PM.
Re: How Can I Dial-In the Rotating Balance After Install?
I think John was up late! L
Yup,...... was up for 3 days on about 7 hours sleep. The 5 hours I got today was the most sleep in 1-shot I've gotten in a week. Strange days. Sorry I wasn't 'on the ball' Steve !!
Re: How Can I Dial-In the Rotating Balance After Install?
Originally Posted by John in RI
Yup,...... was up for 3 days on about 7 hours sleep. The 5 hours I got today was the most sleep in 1-shot I've gotten in a week. Strange days. Sorry I wasn't 'on the ball' Steve !!
LOL! I fall off that ball more and more the older I get!
So I went to the shop at lunch and he said he never balances on these V8s even when replacing pistons with stock replacements and has not had a complaint.
I may be making more of this than its worth. I'd say the vibration is medium-light in intensity. I just want to get it very smooth. I will track down flywheel weights, mess with it and report back.
Re: How Can I Dial-In the Rotating Balance After Install?
Found an ebay auction for this pins. They are clearly not threaded. So looks like wrong part. L98 Vette used that weird german 6 speed...... different clutch entirely.
Re: How Can I Dial-In the Rotating Balance After Install?
Yep. I will be messing around. I did order three of those Vette pins. They are about 3g each. Probably won't fit but hey, this a R&D budget. I may try to bottom tap those holes for bolts.
Re: How Can I Dial-In the Rotating Balance After Install?
Guessing a flywheel balancing weight is probably going to be tungsten to pack the most weight into the smallest space possible. Steel would be a poor substitute.
Re: How Can I Dial-In the Rotating Balance After Install?
Originally Posted by 8Mike9
Any chance you have an accessory issue? Maybe pull the belt(s) and give it a try.
Curious you should say that. I was just getting ready to post this update.
So the vibration has been reduced considerably. Two things have happened. One, I got a another tune iteration from Scott and the car drives amazingly well. And the vibration is much less. He says the BLMs are now in line and that we are almost there.
However, before I put the latest chip in and ran it, my serpentine belt broke. The belt was not old (maybe three years, and with few miles so it was unexpected. It split down the length of the belt before half of it tore off and broke in two. The other half, by length, remained on the pulleys and under tension from the tensioner. Strange.
I expected to find an accessory bound up but all were fine. New PS pump, new water pump, new tensioner, new smog pump, recent AC compressor. I replaced it with a high end Continental belt and off I went like nothing happened.
So either the vibration is partially caused by a tune that is off or by a failing accessory belt. Or just coincidence.
I will still play with flywheel weights once I get a chance, and report back.
Re: How Can I Dial-In the Rotating Balance After Install?
THe engine that was the replacement...couldnt have been one of those that was int balanced with the ext balance on the FW? think some C4s were like that or maybe the LT1s cant remember
I believe it all matters, even took the FW and clutch to the machinist and had him balance it, super picky about that stuff.
Last engine shook so bad it was embarassing. Turned out to be a cam that wasnt straight.
Hope you get it figured out
Re: How Can I Dial-In the Rotating Balance After Install?
350s are ALL "internally" balanced.
However... 86-up (1-pc rear main seal ones) have the rearmost INTERNAL balance weight, located on the flywheel or flex plate.
Older motors had a funky shaped crank flange that acted as the balance weight. Looked like this.
The 86-up motors moved that last little bit of INTERNAL weight on the flange, to the flywheel, so that they could accommodate slipping the seal over the rear of the crank. Which obviously would have been impossible with the stuff in the photo. That DOES NOT make them anything other than "internally" balanced.
Your 350, and the 305 you took out, came with the same balance setup (internal with the "batwing" weight on the flywheel) and therefore properly set up 305 parts SHOULD, assuming your "new" 350 is STOCK balance, be just fine. Far be it from me to "***-u-me" anything at all, except that, it would have taken time / cost money to have changed that particular feature. Therefore I doubt anything was done to it, at least, deliberately.
How did the clutch indexing experiment work out? What did you learn? Did anything change?
Re: How Can I Dial-In the Rotating Balance After Install?
Ok, I have an update and an unexpected turn. I got the weights but haven't messed with that yet. It turns out, I believe most of the culprit (most of the RPM range) was the exhaust.
I have factory manifolds, a MAC Y-Pipe, factory Cat, Magnaflow muffler, and factory tailpipes. Professionally installed (i.e. not kluged), and all on factory hangers.
First thing I noticed was that, as mentioned, with each successive engine tune iteration (it took eleven), the vibration got "better". In other words, when I first fired the engine after rebuild, the vibration was more pronounced.
I would not have thought a tune would be able to do that. Then I thought about the exhaust. The factory Y-Pipe is HEAVY. Heavy wall. It is stiff. The MAC Y-Pipe, though very strong as well, is significantly lighter. That Y-Pipe and the cat are held up by the exhaust manifolds and the hanger at the back of the transmission, that's it. It's a long run and significant weight between support points.
After the final tune, the vibration was minor, so I looked underneath at the hanging point. Although the T5 hanger was fine, rubber all intact, I could tell it was old and the rubber kind of soft. I pulled the rubber up with two heavy tie wraps just to help out and "tension" the hanger better.
Hello!
What is the diameter of the balance pin GM 3890192?
I have the 153t 16lb flywheel for externally balanced motor GM 14088646. Holes for balance pins are 0.253".
03-09-2020, 10:53 AM
