I recently put a new Fastburn 385 crate engine into my 66 coupe. Upon firing it up, it has a semi-serious vibration problem. The car did not vibrate like this before the swap (eliminating the driveshaft, axles, etc.), it vibrates while not rolling (eliminating the transmission, which was also worked on) and it does it with the March serpentine pulley system disconnected (eliminating power steering, water pump, idler pulley, etc.). It has a GM nodular iron flywheel and a brand new Centerforce II clutch setup. I am suspect of either the flywheel or the clutch at this point.

The vibration isn't too bad at low RPM but by 4500 it is bad enough that the rear view mirror shakes itself right out of adjustment.

Has anyone had a similar experience, and in general, what is the sentiment regarding the Centerforce product? Any quality control issues that others have encountered? I really like the feel of the unit, and if I'm going to pull the drivetrain out and replace the flywheel, clutch and pressure plate on a fishing expedition, I'd like to have some confidence that my situation is an anomoly, because some might reason that replacing a potentially defective clutch with another from the same manufacturer might be, in fact, an act of lunacy. Thank you.

 

what about your harm.damp. is it correct

 

Yes, it was part of the crate engine direct from Chevy. In fact, I was suspicious about the March pulley, because I chose to use the decorative cover for the crank pulley, which is a pretty sizable chunk of billet aluminum. I could see some evidence that the balancer was working hard (cracked paint around the rubber ring) so I in fact purchased a new damper from Chevy and installed it, and ditched the March pulley cover. Unfortunately, that was not the problem.

 

Looks like you are on the right track.

To be really simplistic, the problem has to originate in one of three basic areas. The Motor, the transmission, Unions for lack of a better term (where they come together)

Engine and causes for vibrations not listed in any special order, just basics:

ENGINE
1. Missfire, ignition or valve related. Possible high RPM ignition missfire or RPM related valve component failure. Valve scenario seems unlikely as I don't think one cylinder no matter what it were doing would likely generate a vibration with the severity you mention.

2. Dampener, Sufficient mass but very small diameter, so simplistic unless it were catastrophically damaged I don't think you would notice a vibration. It would probably just eat bearings over time. Keyed and bolted, not something that is likely to become intermittently loose either.

3. Flywheel, the flywheel definetly has some variables. It has sufficient mass and a large circumference compounding any minor defect.
a) Assuming it didn't come with the motor and all the aftermarket cranks about, is it possible you have a balance issue (internal vs external).

b) I once encountered a hang up where the flywheel I installed had been turned a bunch of times resulting in the pressure plate mounting bolts bottoming out before snugging the pressure plate all the way down. Given it tightens against a spring and was REAL close I never noticed. Didn't have a vibration however clutch was was weak and I can see how potentially this scenarion could introduce a vibration.

c) The ring could have been whacked by the starter or for some other reason just be coming loose? As the flywheel pretty much always stops in the same place everytime you shutdown the motor I would think it conceivable you have a bad ring gear and not know. Being on the very outside of the flywheel I think it potential but unlikely possibility.

Transmission
1. Pressure plate, If it were to have a balance problem (heavy sucker) you would certainly now about it. Other than the engine reciprocating assembly (crank and pistons) it has got to be the largest, heaviest and most complicated of the suspect potential components given shifting weights, springs etc. I would however be surprised if it would pass their technical inspection as to be out of balance I think springs and components would likely have to be missuing. The pieces are big, visible and strong. Not a fragile thing where some critical component may fall off prio to assembly. I have had very good results with the Centerforce units and found them to be quality components given nothing I ever owned previously could withstand my abuse. Someone may disagree and the next person to read this post if not yourself may understand more than I care to know of the design and others better than myself, I am simply relaying what has repeatedly been a great product FOR ME where as others failed miserably in the past causing me a lot of trouble, time and frustration when I really had to depend on the car.

Mounts (pieces where the motor and tranny join and then all attach to the chassis
1)I have heard of a pilot bearing (or lack thereof) creating vibration issues. Having not experienced this I can't speak to what it would actually feel like but perhaps someone on tge forum may. I think it more likely it would be left out rather than installed incorrectly. I had one go bad once and it just got noisy in an irritating brake squeal kind of way.

2) A small vibration can be getting exacerbated in a situation where the moter and or tranny are not held down tight.

To preface this appropriately, I am not a mechanic or anything along those lines, just an enthusiast who has blown a lot of pieces up and enjoy's trying to put them back together. To summarize, I think one of the above has got to be the issue. Unfortunately much of the investigation will require dissaembly. I don't remember if it is possible but it would be nice to seperate the tranny from the motor, (slide it back out of the way)start the engine and see if has issues without the tranny. This would greatly reduce the mystery.

Good luck
-Andre

 

good imput

 

Andre:

Thank you very much for the input--it is appreciated. All that you have said pretty much lines up with where my head has been on the subject.... Just to clarify, everything on the engine was new--I am using GM's nodular iron flywheel and Centerforce II pressure plate, so the ring gear is good.

The thing bugging me is that I trust GM and I trust Centerforce so I don't know how a product that was unbalanced could make it through the pipeline.... I really like the feel of the CF product so I'm probably going to go ahead and order up another one, and will be paying a visit to my Chevy dealer this afternoon for another flywheel....

I have installed a Moroso needle bearing pilot bushing, and I agree with your assessment that it would be unlikely to be the cause of the problem....

With regard to engine misfire, while I wouldn't put it past me to mis-diagnose what that feels like, I think that I've had enough experience to be able to feel that...but oftentimes right when I convince myself that I know what I am doing is usually the time that I am proven wrong.... But I had the car put on a scope after I got the engine running and they didn't see any evidence of a misfire. In fact, it was the 34-year-veteran mechanic at the Chevy dealer who told me that it felt to him like a clutch/flywheel problem. He said that "sometimes you just need to take it apart and turn the pressure plate one bolt or two and put it back together and it is fine"--but I don't have the patience or the facilities to keep trying that until I get a smooth ride...

I did convert the car over to using urethane motor and transmission mounts, but I can't believe that could be a cause--this vibration just feels "mechanical," and I can't explain it any better than that.

Again, thank you for your comments and the time you spent on your reply. It is appreciated.

 

When I read your post I instantly felt your pain having been there myself a few times and am no expert at any of this. These kinds of problems really suck when you just can't see what's going on. It's not so much a matter of trust but rather "sh-%$ happens" although I REALLY don't like the comment the mechanic made of how it sometimes just a matter of turning the assembly a bolt hole or two and it goes away??? Comment makes no sense at all. I would bet dollars to donuts that whenever this happened the pressure plate either wasn't tightened all the way or was bound on the bolts preventing a sqaure fit to the flywheel and the second time through 1 minute more was spent looking at it and it seated correctly. I read a quote from Caroll Shelby's book where he says something to the effect of "parts don't fail people do".

The clutch, pressure plate and flywheel simply have to be taken to a reputable independant machine shop to be evaluated and balanced. Should cost peanuts. I have always been told that even when buying a new flywheel it should be turned and in fact just paid to have a brand spanking new $400+ billett titanium shatterproof whatever flywheel turned for my new engine. Never questioned the expense when I saw it on the bill.

Good luck and sorry it is such a PITA but it MUST be fixed or other components will take a beating not to mention it is simply no fun to drive just knowing something isn't right. If you didn't put in the pilot bearing yourself I would be looking for it as well. Too small of an item in a big procedure that can easily be overlooked. The good part of it all is I'll bet nothing is damaged yet or broken but rather misaligned, improperly attached or omitted thus it will be a low dollar fix but a troublesome one nonetheless.

 

I just had a hayes steel SFI flywheel and centerforce ll clutch sent in to be balanced with my rotating assembley. They were far enough off that it could have caused a problem. I was suprised that what was supposed to be quality stuff was that far off.

 

I love my CenterForce clutch feels as easy as a stock clutch but it can handle some power. I heard one forum member say that he had to send one back as it was not balanced properly, wish I could remember more but
it could have had somthing to do with the wieghts that are supposed to add more clamping force as they spin faster. You might just want to just pull the clutch first and take a look to see if the weights are in a uniform pattern.

 

Thanks again for the input. I was slightly concerned about the centerforce weights, too, but they are supposed to be "self-aligning" and they seemed to be able to move around freely when they were installed. I've decided to bend over one more time and try another Centerforce. At least if this one doesn't solve the problem, I'll be so expert at yanking the drivetrain that the sucker will come out and be back in a box heading back to Summit so fast it'll make your head spin! Thanks again for the opinions; in a few weeks (or months) when I schedule my clutch & flywheel thrash weekend, I'll update the group and let you know if I'm enjoying the smooth sailing of my Fastburn or whether I'm looking for a short pier somewhere.

Steve

 

First off, I personally have had fantastic luck with Centerforce Dual Friction clutches. I've heard stories of weights getting stuck and causing an imbalance, but not sure how accurate they are. They aren't really that heavy and they are pretty close to the center. But it's possible.


My gut keeps pointing to the flywheel. What you describe is a pretty big vibration. GM uses several variations of flywheels on the newer motors with counterweights. Old stuff was all internally balanced except for 400's. New stuff uses weight on flywheels. I would really double check that you actually have the correct one for that motor.

Not sure if the holes on carank allow for it to be installed wrong, but if the there was no dowel and you installed it in wrong position it would be a mess. I haven't worked on enough new small blocks to answe it completely, but I'd sure verify that first.


Good luck....let us know how it turns out.



JIM

 

Thanks, Jim. The flywheel that I'm using is the GM "lightweight nodular iron" flywheel for later small blocks with the one-piece rear main seal. It is in fact listed in the document that came with the Fastburn as an acceptable flywheel for the engine. It does have a hole for the dowel pin so I don't think that I could have screwed that up too badly....

Andre, do you know if an automotive machine shop would be able to evaluate and balance the flywheel, pressure plate and clutch disk by themselves (without the crankshaft, rods, pistons, etc.)? I've been WAY out of touch with machine shop services so I was unaware that this might be a standard service from them. And speaking of which, can anyone recommend a top machinist in the San Jose, CA area? Since I've got the new clutch and flywheel sitting in a box, it wouldn't hurt to take them in, get the flywheel lightly surfaced, and the whole thing balanced--if this can be done.... Thanks.

 

I have to talk to my machinest tomorrow anyway so I will ask how it is done. When my motor was balanced all the components were required to be together at once to make them match and function together. In the case of the pressure plate and flywheel I believe they are bolted together and balanced as a unit. I may be wrong on this but will confirm. It would fix your problemj but not neccesarily then tell you which one was out the most if not equally out.

This may be a situation where each part (the flywheel and pressure plate) are each within tolerance however given unique characteristics where they they are individually physically imbalanced may be a dreadful match for the other compounding the overall imbalance? If luck were on our side (never is) and they were instead imbalanced on opposite sides you instead would have had better balanced assembly.

I'll post tomorrow with the procedure as I am speculating on how I think or understood it to be done.

-Andre

 

Gromm cylinder heads also does balancing. They are very good. Head work is very slow to get through their shop, but the balance work is fast. They are in the phone book, I don't have the number handy.

 

2many: Thanks for the tip on Gromm. I just got off of the phone with them and I liked what they had to say. Because I have the original flexplate that came with my motor, he said that they are able to do a "transfer balance," using the new flywheel and pressure plate, and get me right into the balance that I need to be. The peace of mind will be worth it! Steve

 

I learned some things about balancing today as well. Interestingly enough the Centerforce pressure plate is apparently self balancing unlike other brands because of how the weights work although they must hit a certain RPM before they align. Builder said that yes he can balance a flywheel alone but usually does so with the pressure plate attached except in the event of a Centerforce! In a situation where you are using an externally balanced flywheel unless he has the crank as well as the balancer etc he can only match the flywheel to factory external balance spec instead of "zeroing it out" with the crank and front balancer.

If you have the original flexplate they should be able to match that flywheel perfectly to your engine given it should have been balanced to the crank already. I mentioned your problem and he was pretty adamant your issue was likely that you needed an externally balanced flywheel and balancer and likely had internal balanced assemblies or at least one. Interesting how it all works, the longer throws cranks require external balancing on the flywheel and dampner given there is not enough space within the block to offset the weight of the crank throw. Good stuff though, glad you found a good shop and be sure and post the findings.

Cheers
-Andre

 

I just picked up my "transfer balanced" flywheel and balanced pressure plate assembly from the machine shop today. They indexed the flywheel and the pressure plate so that I can put them back together in the same configuration as they had it for balancing. For those curious, it was $100 to do the transfer balance and $45 to do the pressure plate. It will be money well spent if it makes my sweet Fastburn 385 purr like I was expecting it to!

My "remediation weekend" isn't happening for another month so hopefully my thread won't wither and die off before I can report the results. Thanks for the help and support from the board.

Andre, one comment. From what the gentleman at Gromm told me on the phone, the current crop of externally balanced small blocks is only balanced through the flywheel or the flexplate, unlike the older externally balanced 400 CI small blocks, which were balanced by both the flywheel/flexplate AND the harmonic balancer. The only thing on the new engines that is not "neutrally balanced" (that is, perfectly balanced in-and-of-itself) would be the flywheel or flexplate.

 

Greetings:

Just wanted to give an update on the engine vibration problem: it is GONE! After having my brother and a couple of buddies over, we extracted the engine/tranny, swapped in the new, balanced flywheel, clutch and pressure plate, and slapped it all back together. After a trip on the flatbed to the muffler shop (I took the opportunity to install the new, ceramic-coated "D" shape Hedman headers that have been in the box for the 2 years since I started this project), AND after figuring out that I had the distributor in 180 degrees out of phase (I hate to see a nice new carburetor on fire!), it was time to get the engine going and take her for a test drive. As I puttered around the neighborhood for the first few minutes (didn't want to get any farther away from home that I was willing to push, fearing an errant belt or a hose that might let go), I was feeling as if the car had smoothed out but I was reluctant to believe it. Finally, getting slightly more bold, I found a long block on a 4-lane road where I could encourage the tach needle up into what had been vibration territory before.... Man, it was beautiful! It just tached up like it was supposed to, no vibration or hesitation at all.

In the end, I'll never know if it was the pressure plate or the flywheel, but I'm not so concerned to find out. I just want to actually drive my car some!

Thanks again for the support and suggestions.

Steve

 

Hate to say it Steve but if your distributor has been 180 out this whole time it was most likely the cause of your vibrating woes.... Most of the time getting the distributor lined up wrong means the thing won't run but many moons ago I have managed to fire one up 180 out and she ran like $#!*@#, felt like the motor wanted to jump out of the car but for some reason it failed to backfire through the carb. and I had a time trouble shooting that! Thought the balance was off, or had a bad flywheel/damper... tore it down the and started again only to figure out later that I was a numb skull and lined up the distributor backwards... man that makes you feel dumb but as soon as I figured it out the bad vibes went away and the motor started running like it was supposed to.

But hey that's what makes Hotrodding fun right? The live and learn stories you can look back at and laugh as you share.

 

Oh my goodness! That would have been an ugly situation! In my defense, I only installed the distributor backwards a few weekends ago when I was putting everything back together after the work weekend--it hadn't been that way all along! Luckily, I wasn't able to get mine started! I wouldn't have even been messing with it if it wasn't for the trip to the muffler shop. On the return trip, the tow driver wasn't comfortable maneuvering his rig so that he could deposit the car right into my garage. So he dropped it in the street and we tried to push it up the driveway into the garage, where I was prepared to work on getting the car started at my leisure. "Tried to push it" being the operative words. Got it about halfway up and that was all she wrote. So I was hoping to just get it to turn over so I could drive it into the garage for further refining. Luckily the son-in-law is considerably stronger than the tow driver; he and I were able to get it pushed in, and then I went about getting the engine running with a little more dignity and class.