3800 V6 Snapped Timing Chain = > Damage?
Question:
Hello, I just replaced a broken (snapped completely) timing chain in my 1990 Lumina 3.1L V6. Now, it hardly runs and I have no pressure in 3 of the cylinders (2 cyl in front, 1 in back). Can someone tell me, is this a ‘destructive’ engine? I mean, is it possible for the moving pistions (after the break) to reach and clobber the valves? If so, what is the chance that its ONLY two rebuilt heads that it needs (could more be damaged? Like the pistons). If not so, what the heck could have happened? Engine ran fine until timing chain broke. Thanks for any help, Bob
Response:
>Hello, >I just replaced a broken (snapped completely) timing chain in my 1990 >Lumina 3.1L V6. >Now, it hardly runs and I have no pressure in 3 of the cylinders (2 cyl >in front, 1 in back).
To the best of my knowledge the 3.1 is not an interference engine, so I would start by double and triple checking your installation of the new chain.. — Mark – Oshawa, Ontario, Canada Chevy Astro / GMC Safari Message Board! Click Below! http://pub37.ezboard.com/bchevyastroandgmcsafari
Response:
Could have damaged pistons, valves, push rods… Your Subject says 3.8 but this says 3.1-which is it-they are NOT the same motor. – Hide quoted text — Show quoted text – > Hello, > I just replaced a broken (snapped completely) timing chain in my 1990 > Lumina 3.1L V6. > Now, it hardly runs and I have no pressure in 3 of the cylinders (2 cyl > in front, 1 in back). > Can someone tell me, is this a ‘destructive’ engine? I mean, is it > possible for the moving pistions (after the break) to reach and clobber > the valves? > If so, what is the chance that its ONLY two rebuilt heads that it needs > (could more be damaged? Like the pistons). > If not so, what the heck could have happened? Engine ran fine until > timing chain broke. > Thanks for any help, > Bob
Response:
Sorry about that (have both engines in my driveway). Its the 3.1 that I have… in a chevy lumina. Interference or not? Bob – Hide quoted text — Show quoted text – > Could have damaged pistons, valves, push rods… > Your Subject says 3.8 but this says 3.1-which is it-they are NOT the > same motor. > Hello, > I just replaced a broken (snapped completely) timing chain in my 1990 > Lumina 3.1L V6. > Now, it hardly runs and I have no pressure in 3 of the cylinders (2 > cyl > in front, 1 in back). > Can someone tell me, is this a ‘destructive’ engine? I mean, is it > possible for the moving pistions (after the break) to reach and > clobber > the valves? > If so, what is the chance that its ONLY two rebuilt heads that it > needs > (could more be damaged? Like the pistons). > If not so, what the heck could have happened? Engine ran fine until > timing chain broke. > Thanks for any help, > Bob
Response:
Mark, Well, I had the timing mark on both sprokets at the TOP 12:00 o’clock position when I pushed them on. They then appeared to stay lined up OK. (The lower sprocket was keyed, the upper was on the ‘pin’ at 9 o’clock.) Is there something MORE to this that I could have overlooked? This was my first attempt at a timing chain job (did a timing belt once). Any advice appreciated, thanks. Bob – Hide quoted text — Show quoted text ->Hello, >I just replaced a broken (snapped completely) timing chain in my 1990 >Lumina 3.1L V6. >Now, it hardly runs and I have no pressure in 3 of the cylinders (2 cyl >in front, 1 in back). > To the best of my knowledge the 3.1 is not an interference engine, so > I would start by double and triple checking your installation of the > new chain.. > — > Mark – Oshawa, Ontario, Canada > Chevy Astro / GMC Safari Message Board! Click Below! > http://pub37.ezboard.com/bchevyastroandgmcsafari
Response:
My understanding is that the crank sprocket timing mark is to be at 12:00 and the cam sprocket mark is to be at 6:00 at installation. An "expert" at www.partsamerica.com told me that the 3.8 L is a non-interference engine. – Hide quoted text — Show quoted text – >Hello, >I just replaced a broken (snapped completely) timing chain in my 1990 >Lumina 3.1L V6. >Now, it hardly runs and I have no pressure in 3 of the cylinders (2 cyl >in front, 1 in back). >Can someone tell me, is this a ‘destructive’ engine? I mean, is it >possible for the moving pistions (after the break) to reach and clobber >the valves? >If so, what is the chance that its ONLY two rebuilt heads that it needs >(could more be damaged? Like the pistons). >If not so, what the heck could have happened? Engine ran fine until >timing chain broke. >Thanks for any help, >Bob
Response:
Bull! The 3.8 is a self eater.
– Hide quoted text — Show quoted text -> My understanding is that the crank sprocket timing mark is to be at > 12:00 and the cam sprocket mark is to be at 6:00 at installation. > An "expert" at www.partsamerica.com told me that the 3.8 L is a > non-interference engine. >Hello, >I just replaced a broken (snapped completely) timing chain in my 1990 >Lumina 3.1L V6. >Now, it hardly runs and I have no pressure in 3 of the cylinders (2 cyl >in front, 1 in back). >Can someone tell me, is this a ‘destructive’ engine? I mean, is it >possible for the moving pistions (after the break) to reach and clobber >the valves? >If so, what is the chance that its ONLY two rebuilt heads that it needs >(could more be damaged? Like the pistons). >If not so, what the heck could have happened? Engine ran fine until >timing chain broke. >Thanks for any help, >Bob
Response:
Most likely you have bent a couple of push rods and/or valves when the chain snapped. Both the 3.1 and 3.8’s WILL do damage if the chains jumps enough teeth or breaks. I will say that in all my years (25+)in the business, I have never seen a chain break unless something else has also failed, but I can also say that I have certainly not seen it all! Anyway, the amount of damage will be directly related to engine RPM at time of failure. Low RPM wil take out push rods and valves, high RPM will also kill pistons. First remove the rocker covers and check the rocker arms for excessive play. This will be the first indication of something bent in the valve train. If no push rods are bent there is a good chance nothing else is bent, then go back and recheck your timing. However, if you do find bent push rods, I would recommend removing the heads and inspect the extent of the damage. Hope this helps! Harry > Hello, > I just replaced a broken (snapped completely) timing chain in my 1990 > Lumina 3.1L V6. > Now, it hardly runs and I have no pressure in 3 of the cylinders (2 cyl > in front, 1 in back). > Can someone tell me, is this a ‘destructive’ engine? I mean, is it > possible for the moving pistions (after the break) to reach and clobber > the valves? > If so, what is the chance that its ONLY two rebuilt heads that it needs > (could more be damaged? Like the pistons). > If not so, what the heck could have happened? Engine ran fine until > timing chain broke. > Thanks for any help, > Bob
Opinions expressed herein are my own and may not represent those of my employer.
