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Discussion Starter #1
Bought my 355 as an assembled short block with my Fairlane.

Put it together with AFR heads, and with a C351 balancer (28.2 oz) and matching flywheel.

Now that it's running, I get a pretty strong vibration that starts around 2000 rpm and will nearly shake you out of the car.

I did not disassemble the short block to get the entire assembly checked for balance - just put it together with the "recommended" parts.

I don't KNOW that it's the balance issue, but I don't have any dead cylinders, and can't find anything else that might be causing a misfire.

Any suggestions or ideas?

P
 

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Hey there,Could use some more info.
Is the vibration while sitting?
Is the car moving and in gear?
What trans?
By balance... you mean the rotating assembly was "pre-balanced"? and then installed into the block?
 

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Discussion Starter #3
Vibration is "noticeable" when just sitting - dramatically amplified in gear and driving. At first I thought it was the driveshaft (hadn't really noticed the vibration when the car was sitting - big cam - loud pipes) but when I stab the clutch in while rolling along, and hold the rpm to at least 2000, you can still feel it. Trans is T5.

If the rotating assembly was balanced - I don't know. The short block was assembled. When I asked around - everyone told me to get a 28 oz balancer and matched flywheel, so I did, but I don't know if a mismatched balancer could cause this kind of vibration.

Thanks,
 

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What sort of balancer and flywheel did you get for it? Were they factory parts, or aftermarket stuff? If they were aftermarket, I suspect one, or both, of them might be the wrong balance. Last year I rebuilt a 302 and bought a crank for it since mine what somewhat questionable. I ordered a 28 oz balance, but they sent me a 50 oz. I had no idea since theres really no way to differentiate between the two by eye. I installed it with my 28 balancer and flywheel, and that motor shook like a prostitute in church. Eventually took it apart, sent it out to have it balanced and they told me it was a 50 oz crank. I guess the moral of the story is never ever ever cheap out and order from unreputable companies when it comes to balance-related items. That damn motor cost me wayyy more than it should have after buying 2 sets of pistons for it, 2 sets of bearings, and paying for the balance job because the company I ordered the crank from would do nothing for me. Not to mention the time involved.

Good luck,

Will
 

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Discussion Starter #5
The balancer is Ford Performance parts C351, and the flywheel came from Modern Driveline - stamped with a 28.2 oz identifier. I'm just wondering if this is a symptom one would see if the assembly was neutral-balanced, and then I hung 28 oz pieces on there out of ignorance...

Thanks,
 

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Discussion Starter #7
Nope. Short block was assembled when I got it.

Anyone have any experience with "wrong balancer" or "wrong flywheel"? Did it/Would it shake the WHOLE CAR like a wet dog? It just seems like too much of a shake to be the crank balance.
 

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I replaced a clutch on a 302 this year and induced a helluva vibration in the process. It started about 2000 rpm and got scary by 4000 rpm. Turned out to be a bad NEW clutch. By bad I mean the pressure plate was out of balance. I don't remember the manufacturer of the clutch but it had a Made in Mexico sticker on it. The way we were able to ID the problem was by removing the pressure plate and disk and reinstalling the tranny without them. There was no vibration without the pressure plate. We exchanged the new clutch for another new clutch that cost about $50 more and haven't had any vibration problems since. What I think is very interesting about this is that NOBODY involved in this had ever heard of a
new pressure plate that had a balance problem. That includes the shop that supplied the clutch, a local driveline shop and a local shop that balances rotating assemblies. It's a lot of work, but you might try running your motor without the clutch because you COULD have just a bad pressure plate. If that's not it I would bite the bullet and pull it all down and take the whole rotating assembly to a balance shop. This is one of those deals where the longest way is actually the shortest way.
Bruce
 

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Discussion Starter #9
Well, I did some "crude" measuring today, because it looked like the pinion angle was a bit "off." I have about 12 degrees of pinion angle, and about 5 degrees of angle at the back of the trans. Just sitting on the garage floor, the nose of the pumpkin looks like it is pointing at the floor.

I think I'm going to start by getting the pinion angle right, and then think about pulling down the motor.

Thanks, all
 

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You didn't say what year your block and crank are. I am sure there are guys that can let you know what year Ford went to a 50oz ballance. I THINK the earlier 302 engines were a 28 oz balance. The HO's were 50oz. No knowing what you have in the bottom end can cause lots of vibration.

I am dealing with a vibration issue myself. It starts about 2200 and really is shaking at 3800. After doing some patch work (new SFI damper and Centerforce billitt flyweel and dual friction clutch) I am tearing the engine down and taking it to a local engine bulder for a complete ballance. That includes, damper, crank, rods, pistons, flywheel, and clutch. ... but I digress. Best bet may to bite the bullet and do what I am doing. Hope this helps.
 

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My Falcon has a poorly balanced clutch, but since I must remove it and sent it out to get rebuilt and that leaves me without a car, so I just live with it for the time being, it behaves exactly as you are describing, but I can make mine self balance if I revv it high enough or dump the clutch at a certain point, but it alway's comes back after I use the clutch again. :)

FE
 

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302/5.0L balance changed in 1982, early 28oz. and later 50oz. 351W/5.8L is 28oz.

TECH NOTE:

Small block reciprocating assemblies have some balance. The compact lightweight crankshaft itself does not carry enough counterweights to achieve zero balance. Extra counterweight is cast into the flywheel and harmonic balancer bringing the entire assembly into neutral balance. Early engines use 28.2 oz.-in. external balance, while 1982 and later engines use 50 oz.-in. flywheel and 34 oz.-in. damper external balance.

All 351W engines use the early style 28.2 oz.-in. external balance.
What is a 355? Is it an overbore 351W?
 

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A motor not ballanced to the correct flywheel will shake the car to death the more rpms you put to motor . A fly wheel that has the weight in the wrong place will shake a car till in time the motor will blow being out of ballance . There is a easy way to fix this problem I know you gona think I am nuts but I have done it . In simple ways to exsplain like a putting up a new ceiling fan in your house . When you turn it on the blades wobble so bad no way can you turn it to high for you will shake your whole house . A simple way to ballance a car fly wheel will work like that fan somewhat . In the fan box there comes a metal weight that will stick to the fan blades . Put it on a blade and it wobbles worse or better when you turn it on . Stop it , move the weight to another spot , it fan wobbles less keep going in that dirrection till the wobble is gone and the fan likes where you placed the weight . You can do this with a car fly wheel , sounds silly but alittle free time and no money add a weight to the fly wheel under the car say a automatic you see fly wheel when dust cover is removed . After weight on fly wheel crank car . If it shakes less move it around a bit till car runs smooth . I have seen this done many times a very cheep fix and it will work . I am sure again I may sound nuts , your problem maybe else where . Thats just my 2 cents worth on a motor built and builder didnot ballance fly wheel to the crank , rods and pistons . Ok now go ahead and throw it at me lol.
 

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I am just trying to help but I kinda dummy now so donot throw nuttin at me again . I have seen new motors and trannys come into the shop vibrating to death . Knowing the motor was ballanced to zero to the crank and flywheel had to be something else . One thing was the input shaft on the front of the tranny was too short . Took tanny out added say 3/8s inch to exstend the small shafter in front of the spline , replaced tranny and runs smoth . I bought a liberty 4 speed top loader from a man he swore it came out from a 428cj . Maybe so but all looked new so no problem I thought . Took to speed shop finding a 4 speed . Shop owner looked at it saying may have come from behind a 428 but the car no way will work cause someone welded the shaft longer like a small block . Cut it back off and then it will work . Now am I a dummy here by hearing this because I build homes for a living and always just threw a motor together . I had them shake as well , ran her till she blowed . I am just trying to help and wana know myself . I turn my car 9700 out the lights and something must be right cause she runs smooth as silk ...Ok my last post here before I sound dummer than I already do .
 

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Just got my 347 back in the car. This after the aformentioned ballance job. WOW what a differnece. This baby purs like a kitten. No hint of any vibration (other than the rumble from my Crane roller cam of course!) I can't over emphesize the importancce the absolute need to have a ballance job with ALL of your parts. Don't trust that your engine builder can do a good ballance job using some of his mock up parts vs your build parts.
 
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