This problem was noticed after the 1st rebuild but there was NO WAY I was going to take the car back to those jackasses who tried to blatantly rip me off. These guys didn't do the rebuild, just in removing/reinstallation of the motor + carb rebuild. The rebuilder himself is supposedly reputable. This second rebuild done by same rebuilder, new guys doing removal/reinstallation. Get the car back...same vibration as before. Plugs, wires, distributor cap/rotor, ignition coil are all new. New flexplate and torque converter. Trans mount is less than 2 yrs old. Things that I'm sure are the same as the last rebuild and some even before the 1st: Original harmonic balancer Stock exhaust system w/ small aftermarket muffler. Original intake Original Autolite 2100. Has had some junk pass thru but seems clean other than what I discuss in my "Carb hitting" post. Stock distributor but converted to Pertronix Ignitor III. Motor mounts looked cracked but do not look collapsed and no excessive motor movement. Not sure when (if ever) these were replaced. Any more ideas?
The crank is new from the engine rebuild. The Flexplate and TC are new from my transmission refresh. I had the transmission guy reconfirm the correct weight (28oz) for the Flexplate.
The crank is new from WHICH engine rebuild? If the crank was replaced in the first engine rebuild, and kept in the second engine rebuild, maybe its not a 28 oz crank. Sure hope its not the wrong crank. Were the new flexplate and TC used on both engine rebuilds? If yes, I would include them in the list of suspect parts. Whatever was changed between the first and second engine rebuild is probably OK since changing those parts didn't change the problem. The transmission guy can confirm the part number, but can't (didn't) confirm that the parts was balanced correctly during manufacture. I had a flexplate that was the correct part number but the imbalance was not correct. Engine had a bad shake. The problem got fixed by replacing the flexplate. Check the harmonic balancer first. If you were to run the engine without the TC, you could remove the transmission, remove the bell housing from the transmission, bolt the bell housing, block plate and starter back on the engine. The engine would be supported only by the engine mounts, not the transmission mount. Wouldn't be real stable but you might get by with it. Not sure I'd try that. If you removed the transmission, removed the TC, put it all back together and ran the engine I think you'd have a big problem. The transmission circulates the fluid thru the TC.
The crank is new to this rebuild, along with the flexplate and TC. I did notice some oddness today over lunch when playing with the timing light to strobe the harmonic balancer. I attached the pickup to the coil plug wire to the distributor. It seemed like I noticed an odd flicker where the strobe lighting didn't seem really consistent at around 2000 RPM where I'm seeing the problem...very faint and no real noticeable pattern. Again, I'm using a Pertronix Ignitor III. Not sure what this could be...maybe nothing, especially compared to what might be seen using points. Also, I noticed some slight wobble around the HB and belt pulley. I watched the center lug for the HB and it looked very steady. The balancer too looked pretty steady...maybe a touch of wobble. The pulley looked like it had some slight wobble to it. I could watch from under the car and watch the pulley mounting bolts and it looked like they were kind moving around slightly, along with the outer edges. Any more ideas? Anyone else try this before?
Not a issue, done same several times over the years... Without a trans the engine sets close to even on the mounts... Again no issue but not necessary, the pump can't operate without the converter...
The crank is new to this rebuild, along with the flexplate and TC. I did notice some oddness today over lunch when playing with the timing light to strobe the harmonic balancer. I attached the pickup to the coil plug wire to the distributor. It seemed like I noticed an odd flicker where the strobe lighting didn't seem really consistent at around 2000 RPM where I'm seeing the problem...very faint and no real noticeable pattern. Again, I'm using a Pertronix Ignitor III. Not sure what this could be...maybe nothing, especially compared to what might be seen using points. Also, I noticed some slight wobble around the HB and belt pulley. I watched the center lug for the HB and it looked very steady. The balancer too looked pretty steady...maybe a touch of wobble. The pulley looked like it had some slight wobble to it. I could watch from under the car and watch the pulley mounting bolts and it looked like they were kind moving around slightly, along with the outer edges. Any more ideas? Anyone else try this before?
I normally wouldn't hesitate to run the engine without the transmission, especially with an exhaust system hooked up. Just don't know how bad the shake is or how much clearance the fan has. My car shook pretty bad with the incorrectly (im)balanced flexplate. If that's the problem here, the engine might get to rockin' pretty good even at low RPMs. I guess nothing in the transmission would be turning with the TC out. Good point.
Here's the pict of a stock 50oz and the SFI 28oz flex... The 50oz weight is 4 & 3/16" at it's widest(bottom) and approx 7/8" in height... This plate also has a similar size opening cut at 180* opposite the weight that isn't on the 28, but again that one is a SFI ... The 28oz is 3.5" and approx 75" in height...
its easy for pulleys to get bent and wobble. its really easy to remove the belts and crank pulley and run the motor. try this first. i doubt its the problem but its a possibility and very easy compared to the next steps. i just had 2 cars that had new flywheels that had vibrations. one was an engine that was rebuilt and balanced with an auto flex plate. then the owner swapped in a t5 and had a vibration. we had to have his new motorsport flywheel which is always spot on for a 50oz balance, match balanced to his old flex plate. their was a 30 gram difference between the flexplate and flywheel and that made all the difference. the other one was a brand new ford crate 302 with an aftermarket stock replacement 50oz flywheel we got from a local clutch company. it vibrated at all rpms and bad at 2000. we got the motorsport flywheel and had it checked against the balance of the flywheel that we got from the clutch company. it was 90 grams different. we installed the motorsport flywheel and it was smooth as silk. this problem most likely is that the new crank was not balanced with the new flex plate thats in the car. theirs a chance that the engine shop will need to take the motor apart and balance the rotating assembly with the new flex plate to make it smooth.
