The car: '86 sport with a full Tii swap.

Whats been done so far:

-s5 engine block w/ fd rotor housings (has mild port)
-installed using s4 parts (ecu, manifolds etc)
-fcd
-3" downpipe, to a high flow N/A cat, then borla catback
-fmic
-walbro fuel pump


Questions:

1)
The car's engine is a bit rough. Idle is perfect, but when above idle, specifically around 2.5k rpm, and 5k+ rpm's. It almost seems unbalanced. Oddly enough this stopped after it flooded, so it was butter smooth throughout the rpm range. Next few times it was started, again it was rough in the specified rpm ranges. I have not yet checked the spark plugs, but intend to do so tomorrow. I was thinking it may be a faulty leading/trailing coil, or a stuck injector. I have been getting decent milage so far, last tank was about 18mpg (mixed driving). Any ideas of what to do, or ways to eliminate some of the causes?

2)
I had a racingbeat rear camber arm installed in the car, and after an alignment I got a nice rattle from the rear, and an occational thud of the diff againts the chassis. The rattle was found to be the top locking nut, that backed off, and was just spinning on the threads. I'm fairly confident the front diff mount is broken. It happens when I let off the gas, then push the gas, or when abit rough with the clutch.
-a)
I'd like to know if the front diff mount was to be welded together, how much diff/road noise would travel to the cabin, and would a welded front diff mount be detrimental to the driveability of the car?
-b)
Would it be detrimental to the car if the front diff mount was to stay as it is for a few months till the next tune up?
-c)
If I were to weld the front diff mount, would that damage the diff after time, or would it cause any damage down the road?

3) The car's boost levels are starting to drop abit (maxes out around 5-6ish psi), and like to confirm its the cat thats fouled/melted. Any thoughts?

I've been searching alot recently, and havent been finding much info about some of the long term effects of the welded diff mount, and am absolutly clueless on the rough engine stuff. Any help would be much appreciated.

 

Ok- I believe i found the cause of the vibration: a loose alternator belt, and the alternator rubbing against the strut bar. I'll know for sure later today.


Any help with the other questions?

 

2b. when you leave play in the drivetrain it creates stress on other driveline parts U-joints trans and trans mounts, etc.

mounts are made of rubber for comfort only. The fact that they are rubber causes loss in power and torque so welding them would have little effect to the car other than comfort and possibly rattling nuts and bolts loose.

Sounds like the cat could be your boost issue I would have a "test pipe" made and I would never put the cat back in but I live in IL so its not that big of a deal here.

 

1) After driving around with the alternator belt tightened, it seemed to fix alot of the issues of the rattle up front. I also removed the strut bar for the time being till I can find a way to prevent any possible collisions with the alternator.

2) Ok- Heres what I found about the subframe: the racingbeat camber adjuster forced the arms that control the camber of the rear hub against the chassis, and caused all of the issues, such as light decelaration followed by a thud. It was the suspension just reacting to the load of the drivetrain. Had it adjusted so there was clearance, and now it looks like I have about -3 degrees of rear camber. I have another camber kit in mind: "CAMBER ADJUSTERS, REAR CONTROL ARM" from >>>link<<<

Perhaps something slimilar can be used to adjust the rear camber. Anyone have any knowledge of adjustable rear camber adjustment parts?

 

Has anyone had any experiance with JIC-Magic's rear camber adjuster? Heres a link: >>>link<<<

Does anyone know of any other camber kits for the rear?

 

Interesting web links. If I had it to do over again, I'd install the two seperate rear camber links instead of the single adjustable link.