How can i tell if the timing chain is going to break??

Hello, I need a bit of help , Please.

Ive got a HD 82 Suburban Chevy 350 M engine. over 200k miles on it. I dont drive it but maybe 1-2000 miles a year. Idles been dropping down and gas milage getting worse. And when its hot sitting at a light the engine shakes .But not stalls. I honestly think I ws getting about 5-6 mpg. So I checked the timing and it was retarded. And the vacuumn advance hose was split , and another hose too. Ive got it set and the truck runs better then since I got it. But its not a steady timing. It moves a bit down and up about 5 degrees , every 5 seconds. so I bumped it up a bit to a normal 350 setting , and its fine driving around. Real fine. The truck is shifting smoother, and really responsive, and the gas pedal doesnt need to be held down as far. i didnt have to adjust the idle or anything. Its not spark knocking and it accelerates real fast. Im concerned that the chain is sloppy and may break. Is there any way to tell if the chains worn to far without changing it. .

Ive got a 400 mile camping trip coming up and want to drive it as is. If it wont break.

Thanks.

Reply to
None4U
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Reply to
None4U

AFAIK the timing chain lasts from one major overhaul to the next, no matter how many miles. I think the vacuum line was your big problem.

I used to get 15 MPG all the time in my old rusted-out C20 with a 350

4-BBL and Turbo 350 transmission (no lock-up torque converter.) I'm doing good to get 16 MPG in my 2001 Silverado with the little 4.8L V8, and it drops to about 10 MPG in the winter.

Bob

Reply to
zxcvbob

Ive never had a chain fail. But I changed one on a 1980 Oldsmobile 88 and it had the plastic teeth on the large gear and it had 1 plastic tooth left on it. All the rest were in the oil pan. So what you are saying . Is it wont break. Then would it get so sloppy it wont run right or start anymore maybe . Or if i cant set the timing at all as its jumping around all over the place. Then it needs changed??

I was getting about 10 when I first got it running about 4 years ago. And thought that was ok. But I never checked the timing. Its got 411 gears and the turbo 350 no lockup, 4 bbl, motorhome engine. In the book the timing is set 2 degrees less then the other 350s . Im guessing because it is a motorhome engine. I set it like the others because Im not dogging it or towing a trailer. And want the milage now.

Reply to
None4U

Plastic?

I had to change the camshaft in my C20 because I got one of those defective ones in the mid-80's. (BTW, GM refused to arbitrate because I bought the Goodwrench engine from their parts dept rather than it be the original engine) I put an RV camshaft in, and a new timing chain. I don't remember if I put in a silent chain or a roller chain or what; something that was supposed to be better than OEM.

If you think the timing chain is bad, it's not that hard to replace. You gotta take the radiator out, then it's pretty easy to get to. Do not pull the camshaft out or you'll have to take the intake manifolds off and maybe the heads.

4.11 gears? ==(8-0 What size tires does it have? You might want to put 7.50-16LT's or LT235/85R16's or some other 32" or bigger tire to get down to a lower effective axle ratio. (LT255/100R16's might be pushing it, if you can even find them :-) My old truck had a 3.73 rear end, and it was still rated to pull an 11000 trailer just like if it had a big block engine.

Bob

Reply to
zxcvbob

Im gonna let it ride then. Tomorrow I have to drive 26 miles to get my torches . That will be a good ride to seee how it runs. You missed out on plastic timing gears , huh??? Very common in the GM 80s. The teeth were plastic on the large gear , and they would crack and break off one at a time. . If enough of them broke off , the engine would jump time and quit running. I did them on a pontiac 301 once too. Had one missing, but that Olds 88 had them all missing but 1 and it was still running. I think the timing chain is loose. But not sure if it needs changed now. The truck has 245/75 R 16s on it. Tow package is 6000 lbs. It was one of those ones GM grandfathered in in the early 80s with the vehicle weight over 8600 lbs so they didnt have to put converters on it. So theres not a lot to make it get bad milage .

Reply to
None4U

Well it isn't that hard to check it for wear. Pull the plugs (makes it easier to turn engine) Then pull the dizzy cap. Now rotate the engine the wrong way and see how far you have to turn the damper until the rotor turns. Ideally it should move with less than 1/8" movement of the damper. Over 1/2" of movement and I would be looking for a new chain set. Nice thing about the trucks is that you can change the chain easily. Drain the coolant, remove the water pump. Line up the crank damper to the TDC mark. Then pull the damper and then the cover. Now pull the old timing set and install the new one. Install a new seal (redisleeve the damper if it has a wear groove) Install the cover BUT don't tighten it down tight. Now install the damper and allow it to center the cover seal. Then tighten down the cover bolts. I would probably stick a new WP on as well.

Reply to
Steve W.

Reply to
None4U

You might also grab the dist shaft and see how much play you have forward & back or side to side. I think Steve W. will agree that worn dist shaft bearings can make the timing jump around too. Regards JR

Reply to
JR

I don't think there is a good way to predict timing chain failure, you just have to take your chances. But when something rolls over 200k, any long trip will become more of a gamble. Water pump, alternator, power steering pump, belts and hoses, all have to be considered.

If the compression is up on the old beast, you might consider changing out all those items. A new timing set, pumps and alternator, belts and hoses, might really increase your reliability for a few hundred bucks, if the long block seems healthy enough, and you plan on keeping her around. Timing set and water pump especially. But keep in mind that if well maintained, a lot of these truck make 300k plus, with nothing. A good friend of mine has a 95 he bought when it was three years old. He has 370k on it, and has never changed anything but the belt.

Reply to
Tim

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