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I have been lately chasing down a problem with vibration in my engine starting around 3k rpm.
The half shafts are quite solid as long as u-joint at the rear end, so I discarded that area.
Since it was more notorious at the shifter, my car is 4 speed manual, I focused myself in the engine and gearbox area. Gearbox shift pretty well but it has couple leaking places, other than that seems to be OK though.
When reving the engine with engaged clutch is more notorious, but with no clutch engaged whatsoever I feel some vibs as well...however not that many.
So, I paid attention on the harmonic balancer area and I have seen what I think is a missing bolt on the crankshaft pulley, otherwise I don’t think the pulley can be balanced with just 2 of them.
The pulley’s hole seems to be slightly misaligned with the thread so I don’t think I can bolt nothing this way.
My questions are, can I loose the existing 2 bolts, along with the main one in the center in order to rotate a bit the pulley and get all 3 holes fully aligned? What kind of bolts should be installed in that place? I’m considering to even replace all 3 with new ones in order to secure they are the same ones in all three locations.
Last edited by corvetero; Dec 2, 2017 at 12:45 AM.
It looks like the pulley has shifted slightly on the crankshaft balancer. First loosen up the belts on the pulley. Back of the center bolt and the two remaining pulley bolts. Take one of the pulley bolts out and down to the nearest auto parts store to match it up and get either one or all three new with lock washers. Reinstall all the bolts and torque them to the specs in your chassis service manual. Since you have a 4 speed you will be able to torque the bolts (and remove them) without turning over the engine by putting it in reverse or 1st gear with the park brake on. Tighten the belts back up and your done. Some guys use a dab of blue loctite on the 3 pulley bolts. Some don't. You might want to as you lost one already.
Last edited by CanadaGrant; Nov 29, 2017 at 10:58 AM.
It looks like the pulley has shifted slightly on the crankshaft. First loosen up the belts on the pulley. Back of the center bolt and the two remaining pulley bolts. Take one of the pulley bolts out and down to the nearest auto parts store to match it up and get either one or all three new with lock washers. Reinstall all the bolts and torque them to the specs in your chassis service manual. Since you have a 4 speed you will be able to torque the bolts (and remove them) without turning over the engine by putting it in reverse or 1st gear with the park brake on. Tighten the belts back up and your done. Some guys use a dab of blue loctite on the 3 pulley bolts. Some don't. You might want to as you lost one already.
Thank you for the reply.
I guess that there is no problem on using impact gun to loose the bolts, actually would be easier I think.
New bolts just ordered along with washer lock, they are 3/8"-24 0.75 grade 8.
Now is the moment to take advantage and paint the pulley.
I wish this is the reason why I am having those vibes, it will be an easy fix.
I guess that there is no problem on using impact gun to loose the bolts, actually would be easier I think.
New bolts just ordered along with washer lock, they are 3/8"-24 0.75 grade 8.
Now is the moment to take advantage and paint the pulley.
I wish this is the reason why I am having those vibes, it will be an easy fix.
It's a very good chance it is the missing bolt causing some vibration but the pulley itself is off center which is going to compound the vibration. Use whatever you want to remove the bolts but install them using a torque wrench.
Last edited by CanadaGrant; Nov 29, 2017 at 12:24 AM.
How did the balancer rotate without shearing the key off? Been a long time since I pulled a chevy balancer but I thought they were keyed to the crank. Did the key shear?
Stump
How did the balancer rotate without shearing the key off? Been a long time since I pulled a chevy balancer but I thought they were keyed to the crank. Did the key shear?
Stump
What he is showing is the pulley rotated in relation to the balancer, the balancer is keyed to the shaft.
OP, I might look at getting a new pulley. There is a possibility that yours could be bent due to running with uneven torque. If you are not looking to keep it stock the aluminum ones run very well (and look good too).
Hi c,
Here's the original pulley, harmonic balancer, and bolts on my 71.
You can see that even originally only 3 of the holes lined up with the holes in the balancer.
You might want to remove the bolts and take a close look at the balancer too in order to know for sure if a new pulley is needed, or just one more bolt.
Regards,
Alan
Use three new 3/8"-16 X 3/4" bolts and heavy duty flat washers. The heavy duty washers are often called "head bolt" washers as they are about 1/8" thick and hardened.
Once you remove the pulley and inspect the balancer, check it for any hammer marks on it's face. I have seen a lot of people use a hammer to install their baiancers which distorts the face and ruins the balancer, causing vibrations. I'm sure that pulley being off center has been causing havoc with your belts and while you are in there this would be a good time to replace them.
Use three new 3/8"-16 X 3/4" bolts and heavy duty flat washers. The heavy duty washers are often called "head bolt" washers as they are about 1/8" thick and hardened.
The have been 3/8"-16 NC threads since 1955. You must be thinking about the water pump flange threads which are 5/16"-18 NF or the crankshaft snout which is 7/16"-24 NF.
The have been 3/8"-16 NC threads since 1955. You must be thinking about the water pump flange threads which are 5/16"-18 NF or the crankshaft snout which is 7/16"-24 NF.
I think you are right.
Based on this picture they seem 16 thread to me. Let see if I have time and take them out to confirm
However, these ones are thread 24, and they advertised for chevy small block.....SS ones though
The have been 3/8"-16 NC threads since 1955. You must be thinking about the water pump flange threads which are 5/16"-18 NF or the crankshaft snout which is 7/16"-24 NF.
You got both balancer bolts wrong. Real big surprise.
3/8"-24 and 7/16"-20
Last edited by lionelhutz; Nov 29, 2017 at 10:20 PM.
You got both balancer bolts wrong. Real big surprise.
3/8"-24 and 7/16"-20
Well, I just pulled out the pulley and I have to say that you and @Derekerek were right...me too
Bolts installed are:
3/8"-24x1"1/4... don't know why that long because they are supposed to be 3/4" long... was Bubba playing around? I think so, see the pictures with the washers, one per bolt
On the other hand the center bolt is 7/16"-20x2"1/4 and as you can see the thread is damaged, I just hope the crankskaft thread is OK, a new bolt was ordered.
And finally we have the pulley or I would have to say pulleys, I didn't know that they can be split. The holes are not elongated, there was only crap and dry mud on the them, they will be cleaned up and painted.
Do you guys have the info about the torque for each bolt?
BTW, the harmonic balancer looks ok with that central rubber belt in good shape, there was no play, dents, cracks or anything to be worry about.
Last edited by corvetero; Dec 16, 2017 at 03:22 PM.
I have been lately chasing down a problem with vibration in my engine starting around 3k rpm.
The half shafts are quite solid as long as u-joint at the rear end, so I discarded that area.
Since it was more notorious at the shifter, my car is 4 speed manual, I focused myself in the engine and gearbox area. Gearbox shift pretty well but it has couple leaking places, but seems to be OK though.
When reving the engine, with engaged clutch, is more notorious, but with no clutch engaged whatsoever I feel some vibs as well, but not that many.
My questions are, can I loose the existing 2 bolts, along with the main one in the center in order to rotate a bit the pulley and get all 3 holes fully aligned? What kind of bolts should be installed in that place? I’m considering to even replace all 3 with new ones in order to secure they are the same ones in all three locations.
Is the vibration recent? That looks like that bolt has been missing a long time.
Is the vibration recent? That looks like that bolt has been missing a long time.
I’m pretty sure it’s been there since I bought the car 2 years ago, but I did not realize until I started driving it a little bit more often after all the work I did on it, hence reving the engine a little bit more to test engine, I don’t use to pass 3k rpm...Sunday driver I know.
The previous owner was an elder man and the car was not driven too much either during the last years, and if so in a quiet way as well, below 3k rpm you barely notice any vibes.
It’s funny, because at the beginning I though the vibes came from the Flex a lite fan, bolted directly to the water pump, so I installed electric fans, and right after I saw this missing bolt.
Other than that the can runs pretty well with no issues whatsoever.
Crankshaft pulley missing bolt
You got both balancer bolts wrong. Real big surprise. 
