A couple of years ago we built a specially prepared Turbocharged 3.4L pushrod engine. The engine had all of the usual good stuff; Comp cam, Sprint headers, MSD Ignition/wires/coil, port matching, #24 injectors, specially programmed ECM etc. We also added a set of Ross Forged racing pistons as the engine would be turbocharged with 8-9 psi of boost. From the day the engine was first fired up it ran great but had some ticking noises. After a re-adjustment of the valvetrain and the ticking was still evident so we assumed that we must have missed something. So we did another high precision valve lash readjustment before Carlisle using a dial indicator. Result-the ticking noise was still there. Some further checking with a stethoscope revealed some interesting things. First off a noticeable tick comes from the injectors opening and closing. The engine runs 24 lb Ford injectors and at idle they click due to the small pulsewidth that they need. Second, the engine has headers with a turbo with a muffler. The headers emit a ticking noise as well. Third and most surprising was the obvious. How did we overlook this. We used Ross forged racing pistons which need to be installed with a much wider piston-wall clearance than the stock cast pistons. Those pistons really tick, especially so when cold. This is commonly called "piston slap." If you use forged pistons as we did, be prepared to live with some piston slap as well.. You will add strength to the engine using forged racing pistons and this gives increased reliabilty especially for racing with a turbo but you might experience slightly more piston wear . Bottom line is that I've just learned to live with my "ticking engine". The Fiero engine runs great and it's fast enough to keep a smile on my face. Just goes to prove that some ticking noises should be considered normal.
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05:50 PM
PFF
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Dirty Harry Member
Posts: 347 From: Orlando, FL, USA Registered: Jun 2003
Wow you got that figured out quickly. At Carlisle you were talking of removing the cam. Glad you found the source or should I say sources.
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07:43 PM
fierosound Member
Posts: 15253 From: Calgary, Canada Registered: Nov 1999
Bottom line is that I've just learned to live with my "ticking engine". The Fiero engine runs great and it's fast enough to keep a smile on my face. Just goes to prove that some ticking noises should be considered normal.
Do you have any problems with your knock sensor picking these noises up as "false knock"? If so, how did you tune your ECM to minimize the timing errors?
Do you have any problems with your knock sensor picking these noises up as "false knock"? If so, how did you tune your ECM to minimize the timing errors?
-Tony
Tony : the ticking is most prevalent when the engine is cold. At elevated RPMs the sound diminishes. On the highway it doesn't seem noticable. I don't think that my knock sensor is being falsely triggered but I'll do a scan of the knock counts just to make sure. Dave: I got working on finding the source of the ticking noise after church on Sunday after I arrived home from Carlisle. I jsut used a mechanics stethoscope and the "light came on". I guess that you just got to love the slap of forged racing pistons which I believe is attributable to the extra piston to wall clearance that they necessitate. However, those Sprints and the 24 lb injectors also make a bit more music to my ears. I only put 1500 miles on the engine per year so I guess that we will live with it. Raydar: I believe that Hypereutectic pistons have a more stable coefficent of expansion with heat than do forged pistons. As such they should be quiet but not a good choice for my engine as they tend to flake when under boost..
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10:42 PM
Matt Hawkins Member
Posts: 586 From: Waterford, MI Registered: Oct 2000
I have been using hypereutectic pistons in my 3.4l DOHC turbo car for three years with no trouble. Good fuel and spark control make forged pistons an option, not requirement. Many factory turbo cars run hypereutectic.
