351W Harmonic Balance problems

[fatboy4211]

I have a 351W with a bad vibration at higher speeds. It purrs like a kitten at idle. Chased down all possible causes and im down to the harmonic balancer.
Problem is I ordered a new one and it wasn't even close to the same
Not sure how to post pics since I haven't had to in many years. Im about as much a mechanic as I am a computer guy.
Suggestions?

 

[Jdgephar]

Just high speed, or high engine rpm in any gear? Could be driveshaft or ujoint related.

351 should be 28oz. There are lots of different balancers. The one that came with my 351 didn't line up with the pulleys. I had to use the new one I bought for an old 302.

Sent from my SM-G981U using Tapatalk

 

[fatboy4211]

I finally figured out the pic application problem

Chased down the degree angle of rear axle due to 2" lift. NOPE
Removed front drive shaft NOPE
Moved exhaust away from contact on oil pan NOPE
Adjusted carb...which helped a wee bit NAAA

Vibration is minimal at low speeds and is crazy annoying at 50-60mph. a heavy drone like sound with vibration. We think the balancer went out of wack.
This engine has approx. 200 miles on it. ran just fine but the bronco has always had a very light drone that was mostly unnoticible

 

[DirtDonk]

What application did you use for your new damper? And what is the engine out of originally?
Later model obviously, due to the serpentine belt setup. Or it could have been swapped on to the engine as well as the engine swapping into the Bronco.

Paul

 

[86Horn_EB_77]

I think you're going to find the quickest route to a balancer that fits is the universal 3 and 4 bolt damper at summit racing. It has both bolt patterns and three sets of timing marks. (And the 28oz imbalance you need for any year 351 or Pre-82 302 with a 2 piece rear main)

Looks from your pics like you still have the (correct) 3 bolt Bronco damper and a 3 bolt serpentine pulley from some kind of 351 truck serp set-up, with a driver's side water pump inlet.

I tried to find cheap Dorman balancers on Amazon - but the parts references try to tell you that any Bronco newer than 68 uses a 4 bolt damper that have a stick out for a sheet metal pulley - that does not fit a ANY Bronco. Look up the damper for a 66-68 Bronco - that will give you a 3 bolt with a flat face, which is what you want. (or just buy the summit universal balancer)

 

[Timmy390]

Post some pics of the complete serpentine belt setup you have and some can identify it and then you know what balancer to order.


Another option is DamperDudes They rebuild them and I've heard good things.

Tim

 

[fatboy4211]

Here’s some pics.
Original serp setup was purchased on this site. Then the motor fell off engine stand and broke drivers side bracket. Found a replacement but not real happy with it. Seems to extend out further than what I see on others in our site.

 

[fatboy4211]

What application did you use for your new damper? And what is the engine out of originally?
Later model obviously, due to the serpentine belt setup. Or it could have been swapped on to the engine as well as the engine swapping into the Bronco.

Bought engine off of For Sale item here on site. Came out of a bronco in Houston and he stated it was a running 302 when he pulled it out of his bronco. I took it straight to a motor builder to rebuild and he informed me it was a 351w. Afterwards water entered one of the cylinders and busted the block. He replaced the block and it was running nicely. Suddenly the light vibration went ballistic. And I have no clue as to engine year model.

 

[fatboy4211]

I think you're going to find the quickest route to a balancer that fits is the universal 3 and 4 bolt damper at summit racing. It has both bolt patterns and three sets of timing marks. (And the 28oz imbalance you need for any year 351 or Pre-82 302 with a 2 piece rear main)

Looks from your pics like you still have the (correct) 3 bolt Bronco damper and a 3 bolt serpentine pulley from some kind of 351 truck serp set-up, with a driver's side water pump inlet.

thanks ill look that up

 

[Jdgephar]

I finally figured out the pic application problem

Chased down the degree angle of rear axle due to 2" lift. NOPE
Removed front drive shaft NOPE
Moved exhaust away from contact on oil pan NOPE
Adjusted carb...which helped a wee bit NAAA

Vibration is minimal at low speeds and is crazy annoying at 50-60mph. a heavy drone like sound with vibration. We think the balancer went out of wack.
This engine has approx. 200 miles on it. ran just fine but the bronco has always had a very light drone that was mostly unnoticible

Anything at issue with the engine should be an issue that follows engine RPM, not overall speed. I wonder if there is still something drive train related. One more test could be removing the rear drive shaft and drive it with the front drive shaft.

How does the 9" third member feel if you try to rotate it by hand?

 

[Timmy390]

I'm stumped as to what front dress that is but the A/C bracket is home made not stock.

If I had to "guess" Truck or Van based off the Alternator

Tim

 

[rguest3]

Looks like an Explorer Front Serpentine. (Less Power Steering Reservoir) This serpentine would have had a 50oz. Balancer if that is what was reinstalled. Wrong balancer if this is the case.

Need a 28oz. for the 351W. You will also need a 28oz. Flex-plate or Flywheel as well.

 

[Timmy390]

Looks like an Explorer Front Serpentine. (Less Power Steering Reservoir) This serpentine would have had a 50oz. Balancer if that is what was reinstalled. Wrong balancer if this is the case.

Need a 28oz. for the 351W. You will also need a 28oz. Flex-plate or Flywheel as well.

I just know someone with more brains would know.....

On a side note....I thought the Explorer front dress used a plastic fan? I've never seen a metal fan in the junk yards....I guess it has been changed?

Tim

 

[fatboy4211]

Anything at issue with the engine should be an issue that follows engine RPM, not overall speed. I wonder if there is still something drive train related. One more test could be removing the rear drive shaft and drive it with the front drive shaft.

How does the 9" third member feel if you try to rotate it by hand?

yep we tried that too.
the third member appears to be good

while in park we have increased the rpm and vibration comes to life

 

[fatboy4211]

I'm stumped as to what front dress that is but the A/C bracket is home made not stock.


Tim

yes ac bracket is a Vintage Air universal bracket


If I had to "guess" Truck or Van based off the Alternator
probably is a truck model. is the actual explorer model smaller? if so i need to get one

now that i think about it....it did come with a plastic fan but the metal one was use...Hmmmmm

 

[Timmy390]

I think rguest3 nailed it......If it's Explorer the balance is 50oz and the W needs 28oz

Tim

 

[Broncobowsher]

First picture sure looked like the Explorer accessory drive.

contact Damper Dudes. Tell them you need a 28 oz-in Explorer damper. you might be able to get yours rebalanced.

 

[fatboy4211]

Ill try the Dampner Dudes. Once i get that i will update yall on progress but hopefully the fix

 

[sanndmann3]

Explorers came with both metal and plastic fans. From what I have seen, the early ones were metal. guessing 96 & 97...? seems like i see 2 plastic fans for every metal one.

Hopefully DD fixes you up...

 

[Jfryjfry]

Maybe I missed it but have you isolated it to the engine? If it vibrates at 50 bad, put it in neutral And let idle and confirm that it changes. It should also vibrate just revving it up to the same rpm while parked.

Try different things to figure out if it is transmission, drive shaft, wheels, brakes, or engine.

Unless you already have and I just overlooked it!