Has anyone ever noticed a big difference when replacing a really high milage chain with a new one? Just ordered a ED timing chain set, so i'm hoping to possibly fix some lingering issues with the car... (bad throttle response while cruising, failing emissions etc.) Around 140,000 miles on my old one i think.

 

up up up im curious

 

Unless the chain's broken or severely stretched (highly unlikely), I doubt a new one would change anything. Since you have a 95, you should upgrade to an ewp and get a double roller chain while you're in there as well. Those issues sound more like a possible throttle body, injector, or O2 sensor issue. If it doesn't happen at WOT, then more likely the O2's.

 

I have experienced a slight off idle stumble before with an old chain. The new one cured the problem - at least for a while until I lost the oil pump.

 

Well here's the catch. I've replaced nearly every sensor on the car. O2's, ICM, MAF, IAT, CTS, TPS, Fuel pump, FPR, Injectors, CAT, EGR... etc etc. You name it, at some point i've probably replaced it. Even had a new engine rebuilt, but I'm worried the chain was reused from that build.

Anyhow, I have an oil leak @ the timing cover and have already purchased a ED timing set. I want to retain my mechanical WP since this is my daily, no plans on going to an EWP . My old stock injectors are getting professionally cleaned as I'm typing this as well.

Thanks for the feedback Chris, do you have any more details on how many miles were on your old chain, what kind of power it put down and what type of abuse you put on it? I do drive my car quite hard when the weather is nice.. I wouldn't be surprised if I've stretched it a good bit.

 

I will admit, I beat the ever-livin crap out of my car, so back when it was running and had 80,000 on the clock, I stuck in a new cam, new springs and hardware, and a new replacement timing chain. Life was good for a while.......then I started to notice that every so often the car made all kinds of noise, but it never really seemed to be going anywhere, and other times, holy hell hang on. When I tore the engine down, I took the chain off the sprockets WITHOUT removing either sprocket! I could not believe that I never smacked a piston and valve together, and neither could anyone else I showed by putting the chain on and off in front of them to prove it stretched that far. I tore that engine down with 110,000 on the clock.

 

So on a new stock chain.. you beat the living crap out of your car for 30,000 miles and it was so stretched you could pull it off the gears? Holy hell that kinda scares me.. I'm not cammed but I do think I fall under the "beat the ever-livin crap out of my car" category...

Did you get any pictures? I want to show them to my mechanic, he looked at me like I was crazy for wanting to replace the chain

 

I think the pics are here somewhere, I am looking and will ask the wife when she gets home. It all started at the track, on back to back runs with ET streets on and 13 lbs of tire pressure. Each run the bog after the clutch came out got bigger, and bigger. I was only getting a 1.7 on my 60', and that stayed pretty constant, but I kept rasing my dump rpm, the last one at 5000. My times were all over the place, 13.039, 13.6, 13.32, 13.99, 13.89, and my idle started getting off as the night went on. After that, out on the street, like I said, sometimes it would run real hard, other times it was just alot of noise and no go. I am not bashing the stock chain, well, ok, maybe the stock one, but not the HD one, which I should have ordered at the time, but I didn't. The new engine has a double roller going on it, and I had thougth about a belt drive, but my machinist said I should be just fine with the double roller.

 

i've seen stretched chains. i've also seen broken sprockets. i've seen bent sprockets and i've seen bearings fly out of a car.

your oil leak is likely a bolt near the cover. i dont remember exactly where but it's not under the cover. there's a bolt close by that is notorious for leaking if tape isnt used when replacing. you dont even have to take off the water pump to access it i know that...and it's not under the cover. it's on the upper right side of the cover (i think). i can't remember what it does but my friend fixed my "cover leak" for me and he tried to explain it to me and i dont remember the details. sorry...i'll ask him tomorrow.

 

Thanks for the feedback Chris, do you have any more details on how many miles were on your old chain, what kind of power it put down and what type of abuse you put on it?


Toby,
The car had 100,000. It was a '79 Cutlass Calais 305 that I tried to hop up that probably put about 200 at the wheels. The gears were the "low noise" nylon gears and had worn/stretched pretty badly. The off idle stumble that alot of guys experience with these LT1's is improper closing/setting of the throttle blades. That's it pure and simple. I say this after experiencing it myself and trying to trace why it was stumbling. I checked everything and eventually wound up grounding the temp sensor in the water pump. It apparently told the computer that it wasn't warmed up and richened it enough to make the stumble go away. I drove around like that for a while until I finally cleaned the area in the throttle body where the blades close. It eliminated the problem the right way. I don't know why it took me so long to figure this out. Especially after having some years of experience with the Rochester Q-jet "bog."