Motor mounts are new, trans mount is the old one but it's good, I reused the clutch and pressure plate that I had because the clutch only has about 15,000 miles on it. However, when I bought the dowels from Ford for the pressure plate they didn't press into the flywheel. They were a little small and I pushed them in by hand. So when I installed the pressure plate I was able to mave it slightly. I thought it was centered when I tightened it down but I guess it could have been off just a hair. However if that was the case wouldn't the vibration get worse the higher the rpms went? You can feel the vibration from about 1400-2000. Above that you don't feel it.

The weight on the harmonic balancer is small than the old 50oz one from the old engine so I assume it's the correct 28oz one. I started the car up and watched the pulleys and they are perfect. I also felt the engine while I rev'd it a little and to me it feels like the vibration is towards the rear. So maybe the flywheel is incorrect or I don't have the pressure plate centered. So I'm going to pull the trans to take a look.

By the way, this sucks!

If it were out of balance it WOULD get worse with higher rpm as the rotational inertia would be increasing. If it comes and goes through an RPM range, that's a harmonic thing.

Not always, driveshaft, u joints and even pressure plate problems can all happen in a certain RPM range. Sometimes the rotation only effects them at a certain speed. I've dealt with it in one for or another on one of my vehicles at one point. I snapped 3 of the 4 joints in a u-joint on my driveshaft in my first f150. It would only vibrate in second at around 35mph then the rest of the time it was gone.

I pulled the trans and the part number on the flywheel is for a 28oz imbalance. I going to take the flywheel and pressure plate over to Rancho Engine and machine and see if they have dowels that fit the flywheel so that I can locate it properly. Then I'll put it back together and see if the vibration is still there. If it is I'm taking the car to Coast High Performance to get their opinion. Guy, can you ask Dick a question though? I weighed my pistons before and after I smoothed out the sharp edges. Each piston ended up 1 gram lighter. All the pistons before were either 547g or 546g. After they were 545g and 546g. I also matched up the heavier pistons with the lighter rods when I assembled them because they varied by a gram as well. Can you ask him if taking a gram off each piston would be enough to cause the vibration?

I took the flywheel and pressure plate down to Rancho Engine and they said that there isn't enough movement in the dowels to cause a vibration. So I called CHP and they want me to pull the harmonic balancer and bring it and the flywheel to them so they can check them for me.

I just pulled the balancer and compared it with the old one. Of course one is a 50oz and the other is 28oz but that doesn't mean anything when comparing the timing marks to make sure the new one didin't spin a little. I stacked the old one on top of the new one and lined the key way slots up. As you can see in the photos the timing marks are dead on so it doesn't look like it spun. So hopefully it is just not balanced correctly or the flywheel isn't. If they are both good then the engine has to come back out and I have to take the rotating assembly back down to CHP to be rebalanced. If that happens I'm going to be pissed!

Was it balanced for that actual flywheel and balancer?

No, but that shouldn't matter as long as the manufacturer balanced them correctly. If they weren't balanced correctly and rotating assembly was balanced to them of I ever needed to replace either then the new ones would cause a vibration.

It does matter, they go by records when they balance something as opposed to actually weighing the pieces. Most of the time it doesn't really matter. But its always better to have the actual parts balanced to one another. When I built the dart motor we had it balanced at a different company to my exact parts, instead of probe doing it. It sucks because replacement parts wont be matched correctly but such is horsepower.