The exhaust is a pace setter.
Got any other pics of the pressure plate that you didn't post?
there is a serial number pressed into the housing, also you can zoom in on the pressure plate forks and get an idea of which pressure plate you have.
These are current listed pressure plates part number and pictures, older pressure plates have different part numbers and flat forks on the diaphragm.
My ACT clutch dissertation:
Heavy duty pressure plate, MZ010
Torque capacity 420 ft/lbs
Light to moderate pedal effort, aggressive engagement, increased gear rattle
Moderate friction life, extended by ACT's exclusive diaphragm design, rigid design may increase spline wear
Xtreme pressure plate, MZ010X
Torque capacity 560 ft/lbs
Moderate to heavy pedal effort, aggressive engagement, increased gear rattle
Moderate friction life, extended by ACT's exclusive diaphragm design, rigid design may increase spline wear
MaXX Xtreme pressure plate, MZ010XX
Torque capacity 625 ft/lbs
Heavy to very heavy pedal effort, aggressive engagement, quicker shifts, increased gear rattle
Moderate friction life, extended by ACT's exclusive diaphragm design, rigid design may increase spline wear
(Torque capacity's are with 4 or 6 puck sprung and rigid disc's)
Heavy duty:
Xtreme
MaXX Xtreme :
Release bearing fork crack:
Release bearing wear on pressure plate forks:
You can see these are really thick forks, so the most aggressive ACT pressure plate.
An mx6 GT I bought came with a brand new ACT clutch, unsprung 6 puck and nightmare pressure plate, I installed it in my 89mx6GT.
First the ACT walked the crank on a freshly rebuilt block(new factory bearings and rings and honing), everything was mint but I changed it anyway.
Installed another factory cleaned and honed block (broken in the F2T crank can handle the pressure plate) , after 6 months the release fork cracked, I adjusted the clutch pedal but after a week I couldn't disengage the clutch so I pulled the transmission and changed the fork.
5 or 6 months later I was having trouble disengaging the clutch, checked the release fork, it wasn't cracked so I though the crank was walking again until I puled the rubber vent boot off the transmission and looked at the clutch forks. The release bearing was not worn or seized or damaged in any way.
I pulled the clutch out of the car and installed a centerforce stage 2 clutch I had kicking around and dropped the act and a flywheel off at bully clutch.
After the proper breaking in, millage and time the centrforce slipped at 15psi (junk).
Installed a bully stage 4 clutch 6puck unsprung disc and needle bearing pressure plate with 700 ft/lbs torque capacity.
Light pedal engagement, aggressive/instant but controllable engagement (due to light pedal effort), fastest shifting (due to light pedal effort), no increased gear rattle (due to light pedal effort), reduced wear and tear on components (due to light pedal effort).
The pressure plate is very heavy and extremely thick but the needle bearing diaphragm makes it very easy to disengage and once the forks are flipped (pedal to the floor) the pressure plate offers no resistance (Pedal doesn't push against your foot).
My ACT clutch's MaXX Xtreme Effort pressure plate review:
When not destroying the engine or itself the ACT stage 4 6puck unsprung clutch disc and Mr. Universe pressure plate lock the crank to the transmission and don't slip at all while offering your left leg the workout of a life time.
If you think the clutch pedal is hard to get to the floor (you will be giving the drivers seat and steering wheel a strength test) wait until you try and hold it to the floor, the Aneurysm Detecting pressure plate is designed to increase resistance with pedal travel and offers the most resistance at full pedal travel giving you the best possible work out, you will feel the burn.
If you got impatient waiting at long red lights the Maxx Xtreme Leg Cramp pressure plate will make holding the pedal down for 30 seconds feel like a lifetime. This ACT Torture Device doubles as a security system, you can leave the key in the ignition and the doors unlocked, no one else can drive the car, most can't get the pedal to the floor, those who can will stall the car, your friends will only ask to drive your car once and never bother you again.
As well as giving your left leg the most challenging physical work out of it's life, the ACT clutch's Will Fight You Every Step Of The Way pressure plate also works out your whole body while offering you the opportunity to practice and improve or hone your engine swapping and transmission removal skills.
Eat your Wheaties and enjoy your Advanced Clutch Technology Medieval pressure plate.
My tips for Operation:
The position of the steering wheel and drivers seat are key to the operation of ACT clutch's Atlas workout* Pressure plate, the seat should be close to the steering wheel to offer the best leverage point, braise your entire body to the seat and position your foot over the pedal, as you start pushing on the clutch pedal pull on the steering wheel to avoid braking the seat back or ripping it from the floor, avoid pulling too hard on the steering wheel to avoid bending the wheel or ripping it from the column, a careful balance of pressure to the seat and pull on the steering wheel is required to get the pedal to the floor from a seated position. Roughly 150 lbs force on the pedal is required to get the ACT Why Is My Leg Shacking pressure plate to disengage the clutch disc.
It is recommended to position the steering column so once the clutch pedal is pressed to the floor your left knee can be braced under the steering column bezel while waiting at the tree, start line or red light. ACT's Luke Crank Walker brings you an hour workout in seconds.
My only real criticism of the ACT Big Left Leg pressure plate would be that there is so much pressure trying to raise the clutch pedal that attempting to shift under acceleration on bumpy roads can/will kick your foot up and off the pedal causing miss shifts.
*as seen in comic books.
ACT states the Maxx Pain pressure plate and 4 puck rigid disc clutch kit offer the quickest shifts.
I don't know about you but I can get a pedal requiring 28 - 30 lbs pressure through a gear change with a tap of the toes, I had to kick the clutch pedal like it owed me money and try to rip the motherf&*ker from the firewall when running the ACT. I mean the ACT Maxx Xtreme pressure plate might have the fastest engagement because the pedal comes up faster than a human can lift his foot but getting the pedal to the shift point is definitely slower for all mere mortals that can fit in a Probe, mx6 or 626.
For anyone interested in experiencing an identical simulation to pushing the clutch pedal with a MaXX Xtreme pressure plate, get in your car (manual or automatic) don't start the car, pump the brake pedal once with your left foot, now try to push the brake pedal to the floor.
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On a serious note after writing the above I zoomed in on the picture of the pressure plate on the engine, it does not appear to be a MaXX Xtreme pressure plate, so you have 420ft/lbs or 560ft/lbs torque at the crank rating, it should take less effort to operate the clutch pedal and be less of a pain in the ass, it should never crack your release bearing fork.
There are two "types" of pressure plates, those that after the diaphragm forks/splines/fingers move a certain distance needle bearings, pivot bearings or rod or other flip and hold the actual pressure plate away from the clutch disc with minimal effort (pedal has resistance going down but takes no effort to hold to the floor) and pressure plates that you could call "unsprung" the pressure on the diaphragm required to get them all the way to the floor is required to hold them to the floor.
Although this may sound like it's a simple question of more effort, (personally it was cool, stiff clutch pedal, manual rack steering, short throw shifter, stiff brake pedal and soft gas pedal, the car was so much fun to drive the effort was worth it and it all got easy including using the clutch) but the power exerted on the pressure plate from the release bearing and hydraulic clutch assembly which is 6:1 pedal travel to master plunger travel X whatever:1 slave to release bearing travel (usually 2:1), so pressure on the pedal X 6 X 1.5-2 or say 30ft/lbs X 6 X 1.5 = 270 ft/lbs pressure against the pressure plate, that would be a conservative pressure for a factory F2T clutch, if the pressure plate "pivots" when the pedal is to the floor (hold it with a couple fingers) you can calculate how much pressure is at the pressure plate/flywheel when holding the clutch = very little. If the pressure plate dose not pivot and there is 30, 45, 75 or 150 pounds resistance holding the pedal to the floor how much pressure is pushing on the pressure plate/flywheel/crank/ low pressure oil film between the central crank bearing (thrust bearing) and crank to keep the crank centered during idle (low oil pressure) and that is all that is resisting against the clutches pressure.
So load on the crank and release bearing and clutch system are much higher with an unsprung pressure plates when holding the pedal down. Could still walk the crank or wear the pressure plate forks (only slower).
Writing this and thinking about it don't pump the clutch pedal no mater what kind until after the engine has been started and runs a while, especially with rebuilt engines, jump the safety neutral switch at the clutch pedal and start the car in neutral (bleed the clutch after getting the engine running and up to oil pressure). Use the clutch on cars that have been sitting a while as little as possible to start it and let the car and oil warm up with the car in neutral, only gravity bleed hydraulic clutch systems and avoid pumping the clutch pedal with the engine off or running with cold oil. Any time a crank moves without oil pressure it's bearing against crank friction.
I hope you checked the piston ring gap like Juan mentioned on page 1, forged pistons heat and expand faster than cast pistons and cylinders walls, they require being warmed to op temp before every use (idle for warm up).
Also you should find out what bearings your friend had installed in this engine, it will decide your power potential tri- metal bearings deflect and take high boost crank deflection but bi metal bearings don't.