quote Originally posted by KissMySSFiero: Any idea how to fix it? I guess now you know why they have to ridges in it from the factory Swap looks amazing.

Yeah, I guess the stock reinforcing ribs did have a purpose. When gushotrod smoothed the top, he probably didn't think about it possibly vibrating.

Adding spray on truck bead liner to the underside of the plenum would probably eliminate or reduce the vibration as it is pretty tough and normally 3/16 to 1/4" thick. Probably the least expensive option.

Next option purchase another HSR upper plenum with the ribs and install it stock. This will require a slightly larger notch in the decklid support, but other than that it is a bolt on solution that will work with all the other custom parts made for this swap. The stock upper/lower intake is $366.95 from Summit or Jegs:


There is a knockoff version that sells for $285 on ebay that has an upper plenum fabricated from 1/4" thick aluminum:




Or you could look for other custom HSR upper plenums. Here is one in carbon fiber ($1000 and the throttle bracket I made might not work):

[This message has been edited by fieroguru (edited 04-13-2014).]

Back from yet another business trip and back working on the car. Only thing good about traveling is spending the evenings thinking about Fiero stuff.

The drivetrain is back out for clutch issues.




ClutchNet was supposed to ship the exact same clutch/pressure plate as the car had before, but after nearly 2 months of waiting for them, the pressure plate ended up being different. Shame on me for not taking the time to properly compare the two pressure plates. The old one was in the attic and when the new one was red and rivet style I assumed it was the same. They are different, have different clamp loads, and even place the pressure plate fingers in a different spot:




The other error on my part was I didn't bleed the HTOB prior to taking my range of motion measurements, so when the new pressure plate arrived and I checked its finger position, the range of motion looked right with slightly less room for wear vs. release. But it wasn't right and eventually over extended after about 40 miles and 8 hrs of running. FTE is the OEM supplier for the F23 HTOB and I scored a NOS unit on eBay. This one doesn't have any fluid and I will make sure my measurements are correct this time...

Having the engine out it gives me easy access to knock out a few other items.

The bad idler pulley was likely caused by pressing some 3/8" lock washers into the center of the bearing to help center it (the LS4 idler pulley is 12mm ID and I am using a 3/8" bolt for it - done this many times before). These were too much of a press fit and likely enlarged the inner race enough to cause an issue. So before I installed the new idler, I took a stack of 4 lock washers and tuned down the OD so they could easily slide into the new idler pulley. Here is a picture of the old one with the lock washers still pressed in place:


I found another source of light metal rattle (was thinking it was the A/C clutch). Instead it was the heat shield I had added between the alternator and the header primary to keep as much exhaust heat off the alternator as possible. There is about 1/4" between the two pieces and I bent the heat shield to be better centered between the two.


For the intake plenum vibration, I adapted Joshua's suggestion but kept it completely invisible. Once the plenum was off, I removed the brass PCV fitting from the bottom center and bored it to accept a 1/2" aluminum tube:


Pressed in an aluminum tube, drilled 4 air holes in it for the PCV, cut it to precise length and added a plastic cap to the top:


Threaded it back into place and this tube now pushes up the center of the plenum by .008" and should keep it from vibrating.


The other thing I fixed today was upper plenum bolts. The two on the PS had deeper holes in the plenum and were recessed about .14" further than the other side. So I turned up some spacers to fit under the bolt heads to take up the excess space:



If you look closely at the picture of the inside of the plenum, you will see some oil residue from the PCV system. I have ordered a catch can to install down by the transmission to keep as much oil as possible out of the intake.

While I have everything out, I will also mod the cradle slightly to improve room around the rear V-band. I have installed and removed it a couple of times in the car, but more room would make it much easier to do.

[This message has been edited by fieroguru (edited 04-20-2014).]