Before I jump back into this thread, let me begin with an apology to Mike. It was not my intent to jump down his throat and discount his experience or opinion as having no merit. Through discussion via PM, I can see from his view why he felt I did.
Back to the subject at hand. Joe, if I sat here typing for an hour, I could probably list 30+ potential contributions or primary causes to the problem you are experiencing. As Mike already mentioned, the 90* V6 has terrible harmonics by design. Add to this the fact that the factory does not balance rotating assemblies, they just slap together parts that fall within a tolerance and you have a recipe for an earthquake at times. It is quite possible that you got one of the engines with parts on the opposite end of the tolerance scale causing an internal imbalance. I have not heard anyone mention a smoother running car from a BHJ, I have often heard reports (in any engine not just an SC) that after having a rotating assembly balanced the engine ran smoother than ever before.
He claimed that actually our SC engines were supposed to have a lenghtly beaking in period that most owners didn't observe. Instead they romped on it and it caused the cam not to take a proper set.
I cannot agree with this at all. I am refering to the cam not taking a proper set. The break in is geared more to the piston rings than the cam and with a hydraulic roller cam, there really isnt anything to break in that would cause your symptoms to my knowledge. My suggestion is to begin a process of elimination. I mentioned your heater hose on the motor mount and the possiblity of the clamps (presuming you used clamps to hold it in place) rubbing the bracket(s) but you didnt reply back on this.
I get a nice puff of gray smoke that sort of smells oily when I first start the car cold
This has me a bit concerned. I don't believe oil passing through from the PCV would be left unburnt to this extent. Here is what I suggest as starting points that require more time than money:
- Inspect your balancer for any visible signs of damage and notate if it appears to have any runout to the naked eye.
- Pull each of the plugs, noting which cylinder it came from and inspect each carefully. If you do not know how to read a plug, get someone that does.
- Find out what your trusted Ford tech charges to do a fuel injector flush. This is done while the car is running and can really help out with gummy injectors. I presume this is still your daily driver and you cannot put the car down to have the injectors thoroughly cleaned off the car?
- While the plugs are out, do a compression test AND a leak down test on each of the cylinders. Make sure your battery is fully charged and I suggest even having a charger/starter attached to your battery during the compression test. Now would obviously be a great time to change plugs if they are due or show signs of need. What wires are you running on the car and how old? I suggest before pulling plugs you ohm the wires and make sure they fall within manufacturer's specs.
Mike makes some good points about sourcing the frequency and origin of the vibrations worth looking into which will certainly aid in diagnosis.
David, I believe you may be confusing what Joe is mentioning of solid mounts to be solid metal which they are not. Unlike the older cars and hotrods which often had solid mounts installed for performance reasons (to avoid delay of getting power transfered from the engine to the pavement) these solid mounts are solid rubber as opposed to the factory mounts which are hollow inside and contain a hydraulic fluid in that cavity to dampen vibration. The solid rubber mounts were used on many 3.8 engines that had a counterbalance shaft in the lifter valley to dampen vibration (ours do not have this). On a related note to the chain, watch out for knock retard. Introduction of new harmonics in the engine by solid coupling such as the chain, can cause the knock sensor to trigger. The grand national has this issue and many people run a nylon strap off the alternator bracket to postively locate the engine without getting KR from introduced harmonics.
Joe, report back to us with your findings
Paul