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Bad Vibration at 2000-3000RPM

  • Thread starter Thread starter Rona
  • Start date Start date Apr 16, 2022
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    347 stroker sbf vibration
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7991LXnSHO

wanna catch the space herp
10 Year Member
Sep 1, 2010
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Kearney, NE
Apr 21, 2022
#21
  • Apr 21, 2022
  • #21
Balance is most likely for shaking like an expletive (like it will fly apart) at that RPM. The RPM is a specific clue, like a tire that vibrates at highway speed.
Shop mess ups happen, and when they do, it is much worse than a misfire, and is very memorable.

But before tearing it apart,
check the plugs to see if one is different. And check to see if you have spark at each plug. To do that, you can check the wires with an ohm meter and inspect the ignition components. But there are variations on this gadget to see if the spark system is working at each plug. I’d be more comfortable with electronics to try this rather than pulling one wire at a time. If the high output system is not phased by it, a leaky boot will light up your life and the headers are often darn hot.
Lisle Spark Tester Amazon product ASIN B0002STSC6View: https://www.amazon.com/dp/B0002STSC6/ref=cm_sw_r_cp_api_i_VMCHJZPRQJT5N1SBY1PP
 
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CAMTWO1070

Active Member
Dec 17, 2021
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Apr 23, 2022
#22
  • Apr 23, 2022
  • #22
If your engine shakes whether its in neutral or drive it could be a multitude of things but my first thing Id say to check is the coil and how its wires for + & -....MSD is made in China....

Without doing a leakdown test its hard to say without whittling down the questions....

When your engine runs what does a vacuum gauge say??????

Have you tried disconnecting the mallory and tried running it without it?

What type of alloy pistons do you have and whats the bore to piston clearance?

Whoever did the machine work did they use a torque plate and did they align bore the main caps for the stroker crank?

Are you sure all the chamfer sides on the rods are facing the crank fillets?





The other thing I saw others suggest is it being possibly the bellhousing alignment.....It is very important but if it does it in Neutral and driving its not likely.....

I got mine down to almost dead nuts perfect but anything more than .010" out is too much and must be adjusted using offset dowel pins......




Good Luck figuring it out..
 
J

Jarhead67

5 Year Member
Nov 24, 2018
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Windsor Locks, Connecticut
Apr 23, 2022
#23
  • Apr 23, 2022
  • #23
Rona said:
Yeah sorry I did I replied twice though. Yes at 2500 setting timing it vibrates the whole time. My timing at idle is 32 degrees. There is no change from idle to 2500 for some reason. I’ve tested it multiple times. I don’t understand the setup. I bought the car with that ignition setup. Firing order for f303 cam is 13726548
Click to expand...
I can’t imagine a reason to run 32 deg timing. Try backing it off to 14 - 16 deg btdc to see if it makes a difference. Are you using vacuum advance in the distributor? If so, set the timing with the vacuum advance disconnected and the vacuum line plugged.
 

7991LXnSHO

wanna catch the space herp
10 Year Member
Sep 1, 2010
7,387
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194
Kearney, NE
Apr 23, 2022
#24
  • Apr 23, 2022
  • #24
Jarhead67 said:
I can’t imagine a reason to run 32 deg timing. Try backing it off to 14 - 16 deg btdc to see if it makes a difference. Are you using vacuum advance in the distributor? If so, set the timing with the vacuum advance disconnected and the vacuum line plugged.
Click to expand...
I think @Jarhead67 said the distributor is locked out. So whatever he sets it at will be the total timing. 14 deg will idle fine, but will be a dog under full throttle acceleration runs.
@Jarhead67 let me know if I have the right thread.
 
S

Sunshine Guy

New Member
Jul 19, 2023
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Jul 19, 2023
#25
  • Jul 19, 2023
  • #25
Rona said:
The crank, flywheel, balancer all went to machine shop for balance yes. And if it’s clutch then wouldn’t it not shake if you push the clutch in? Cuz it does
Click to expand...
I know this is an older thread but in case someone is searching to solve a similar problem:

Disengaging the clutch removes the clutch DISC from the rotating mass (and everything else from the transmission rearward), but NOT the pressure plate. The pressure plate is a heavy component with the potential to cause a large imbalance.

If one forgets to install any required dowel pins between the crank and flywheel, or between the flywheel and pressure plate, enough misalignment between components might occur to cause some imbalance.

If none of this is the case, I'd suspect the possibility an error was made when balancing the rotating assembly.
 

FastDriver

I was uncomfortably high & wearing a helmet
SN Certified Technician
Sep 5, 2001
6,100
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Vass, NC
Jul 19, 2023
#26
  • Jul 19, 2023
  • #26
Specifically what plugs are you running. What's the part number? Are the motor mounts in good shape?
 

AeroCoupe

lube between the nut and the face. I know my lubes
Founding Member
Oct 28, 2001
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Jul 20, 2023
#27
  • Jul 20, 2023
  • #27
I am pretty sure that there are no dowel pins between the crank and the flywheel on a small block Ford. Only ones I know of are flywheel to pressure plate, block to bell housing, and cam shaft to cam gear. There are also the rolled alignment rings for the head to block and timing chain cover to block but that is it.

I would have like to have known if the pressure plate and clutch was also balanced with the combo. My 331 was balanced and then the machinist put my RAM clutch steup on it just to make sure the clutch package did not have a problem. But I digress and being that this thread is over a year old and OP hasn't been seen since May of last year I doubt he will see any of this.
 

General karthief

wonder how much it would cost to ship you a pair
20+ Year Stangneter
Aug 25, 2016
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polk county florida
Jul 20, 2023
#28
  • Jul 20, 2023
  • #28
AeroCoupe said:
OP hasn't been seen since May of last year I doubt he will see any of this.
Click to expand...
Damn kids these days, wadda ys gonna du?
 

AeroCoupe

lube between the nut and the face. I know my lubes
Founding Member
Oct 28, 2001
5,892
4,015
183
Claremore, OK
Jul 20, 2023
#29
  • Jul 20, 2023
  • #29
Damn sure not going to turn the wrenches for them.
 

85GTStangGuy

5 Year Member
May 19, 2021
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Jax, Florida
Jul 20, 2023
#30
  • Jul 20, 2023
  • #30
General karthief said:
Damn kids these days, wadda ys gonna du?
Click to expand...
They never have engine vibration issues when they build their cars in Need for Speed or Forza, so they can't relate.
 
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