Forced Induction/Nitrous and Forged Pistons
Thread Starter
Le Mans Master
Joined: Feb 1999
Posts: 5,877
Likes: 1
From: Park Ridge IL
Re: Forced Induction/Nitrous and Forged Pistons (542C2)
Well a little update. I had a little time to work under the car. I tightened up the exhaust bracket that I suspected of causing what I initially thought was piston slap. Unfortunately that didn't eliminate the noise, but since I had the car up on stands, I cranked up the engine and used a dowel against my ear and against various parts of the engine in an attempt to determine where the noise was coming from.
The valvetrain on both sides of the engine were pretty quite, with the exception of the tale-tell ticking of the solid lifters. The bottom end was pretty quite as well, although the "slap" was more noticeable. I could definitely tell it was coming from the rear of the engine, actually it sounded like it was coming from the torque converter. I stopped then engine and took a closer look at the converter, and realized that the converter bolts that attach it to the flexplate were slightly loose.
When I initially assembeled everything, I used red Loctite, as well as star lock-washers on the bolts, but they managed to loosen slightly. They were still tight, at least 40-50 ft lbs. The problem is that the converter is tapped for 10mm bolts, but the holes in the flexplate are 7/16", so there's a little slop. What was happening is that during warm up when the idle is still a little rough, the bolts were hitting the insides of the bores in the flexplate. When the engine warmed up and the idle smoothed out, it was no longer a problem. I pulled the bolts out, cleaned them, and reapplied Loctite and retorqued them and the noise was gone.
Since I was under there, I went ahead and drained the oil and pulled the pan anyway, just to give everything a good look since. Everything looked as good as new.
The valvetrain on both sides of the engine were pretty quite, with the exception of the tale-tell ticking of the solid lifters. The bottom end was pretty quite as well, although the "slap" was more noticeable. I could definitely tell it was coming from the rear of the engine, actually it sounded like it was coming from the torque converter. I stopped then engine and took a closer look at the converter, and realized that the converter bolts that attach it to the flexplate were slightly loose.
When I initially assembeled everything, I used red Loctite, as well as star lock-washers on the bolts, but they managed to loosen slightly. They were still tight, at least 40-50 ft lbs. The problem is that the converter is tapped for 10mm bolts, but the holes in the flexplate are 7/16", so there's a little slop. What was happening is that during warm up when the idle is still a little rough, the bolts were hitting the insides of the bores in the flexplate. When the engine warmed up and the idle smoothed out, it was no longer a problem. I pulled the bolts out, cleaned them, and reapplied Loctite and retorqued them and the noise was gone.
Since I was under there, I went ahead and drained the oil and pulled the pan anyway, just to give everything a good look since. Everything looked as good as new.
