Timing chain woes...

[carbon]

What would be the effect on performance if a timing chain was stretched out and the damper was toast? This would retard the camshaft correct?

[IsaacHayes]

Dampener, lots of noise, sounds like valve train noise, bad lifters etc (speak from experience)
Chain, it will rob you of some low end torque, and you will gain on the top end.

After I did my chain & dampener the engine was super quiet and had good torque, but I lost some top end I used to have due to the retarded valve timing.

[carbon]

Thanks for that Isaac, that kinda fits with what the car is up to...

What my car does is hesitate on tip in and then it does seem to run good if you get on it if you are already rolling... and then when it comes down to idle it makes a rattling sound for a moment and hangs at around 1100-1200 RPM and then will settle to about 1000 and quiets down... We've already checked almost everything else from valve lash to water pump and alternator and heat shields...

This is an 88 Fiero 2.8

[IsaacHayes]

The bog on tip-in was fixed on mine when I replaced my old ass O2 sensor. The thing gets better MPG and power now too that it's reading right. I used to roll into it when racing from a dig instead of stomping it to avoid the bog... The rich fuel fumes (even with a stock cat) in the drive through finally made me change the O2 sensor. That and high gas prices...

[carbon]

Yeah... the O2 is less than a year old. I have been fighting this issue for quite a while now. I am realizing that I don't have enough money for a motor swap so I need to get this motor straightened out if I can.

[Azrael]

Would timing chain stretch also cause an engine to run hotter than normal? Normally on distributor engines the ignition would be retarded with the valvetrain and retarded ignition timings seem to burn cooler. With our DIS setup the normal ignition timing would remain with a less than expected VE and potentially burn hotter. Or is my thinking off on this?

[60dgrzbelow0]

Diagnosing whether the Harmonic Damper (Dampener?) has gone bad can easily be done by simply painting a thin stripe of white paint (silver indelible marker might work as well ...or oven/refrigerator touch-up paint, too) in a straight, unbroken line the goes across the two inner and outer weighted cast iron-steel segments and covering the elastomer center strip in the process. Run the motor at varied RPMS and then examine the face of the HB to see if the "white line" is either intact...or separated. If the painted white line is broken even just a little... it indicates dangerous slippage proving that the inner segments have either rusted or separated enough from the rubbery elastomer material bonding them together enough to ruin its ability to dampen the enormous vibrational forces that are being transmitted by the con-rods and crank throws...horizontally into the HB. If the outer ring were to come off in an at-speed condition... it could become a deadly missile at worst...and at best...signal the death of your engine soon to happen if left running in this bad condition while its tries to destroy itself internally. You will find many opportunities for the purchase of replacements either at ROCKAUTO or on eBay Motors...

[60dgrzbelow0]

Regardless of whether the actual sensors are sending and receiving their positional signals from the 24X sensor... the 7X (3x) sensor of the DIS Crankshaft will reliably fire the sparks via the PCM. But the problems will get extreme because of the change in the expected, precise physical relationship between the camshaft hardware and the hardware bolted to the crankshaft ...mostly in non-DOHC engines... as these can become catastrophically irreconcilable... Like the Timing Chain getting stretched against badly worn cogs and then becoming loose enough to jump cog timing and leaving valves open at the most inopportune of times... (at TDC).