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Change The Timing Chain?


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I have had several people "who should know" tell me the only thing a GM 3.8L engine needs as the miles add up (140K to 150K) is a new timing chain and sprockets. Who can confirm or deny this? What happens if the chain breaks? I have 142+K miles and hope to be changing jobs in Sept. (40 mi. one way commute). Tring to get my options figured out.

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There isn't any traditional way to check for timing chain stretch on the 3800 engine. Older engines with distributors could be checked by moving the crankshaft back and forth and watching the distributor rotor. Usually about 5 degrees or so of crank movement was acceptable. It may be possible to approximate this by checking for movement though the cam sensor hole but the timing chain tensioner may not allow this to be an accurate check. 150k seems to be a reasonable time to change the chain and sprockets, especially since it sounds like you will be putting a lot of miles on. Good time for the water pump also and be sure to check the oil pump cavity in the front cover for scoring and clearance. While the harmonic balancer is off examine it closely for failure of the rubber and bonding between the inner and outer ring. The engine is pretty robust and the timing chain and damper are about the only mechanical items to look for.<P>------------------<BR>Hal, btk@vbe.com

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Guest kennyw

2-SEATER. and if we just keep on driving the car past the 150,000 what can we expect? Is the motor an interferance motor? Will the valves get bent? I hear Reattas with over 200,k. They never mentioned changing the chains and sprokets................

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All,<P>I had a timing chain and sprocket set put on another Reatta I owned, thinking it was the nylon-covered type used in the 60's and 70's. It wasn't..it was the all steel type. <P>Based upon that, changing the timing set is more dependent upon your maintenance and driving conditions. If you change oil often and do a lot of highway driving, you could go to 200K. If not, doing it now is a good idea. <P>While they are doing that, have them change the harmonic balancer, water pump and the little plastic button under the timing cover. I don't remember what it's for (don't have the service manual in front of me) but it didn't come with the timing chain set and the shop that did it on my last Reatta said it was important. I think it keeps the camshaft from creeping out of the block. They took longer to do the job but wanted to replace it while they had it apart. <P>Good luck.<BR>Joe

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Guest kennyw

REATTA MAN, THANKS FOR THE ALL METAL PARTS. I have used synthic oil along with [Mila-tech]. There is almost no metal wear using this combination. The car is running so well I will not even think of touching it for a cam chain. All I need is to get the dam dimming of the dash lights. Then I can just drive it for a while.............

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A lot has been said in the past about these timing chains. To find more input do a search.<P>My opinion is to replace the timing chain set around 150,000 miles give or take. For a skilled mechanic it is not that big of a job. If the chain slips or comes off the following can happen:<P>Car will stall on the road or no start causing a need for a tow.<P>The car is taken to a shop and put off because of other work scheduled.<P>A charge of $50-$100 for dignositc time to tell you what happened.<P>You are at the mercey of the shop and there prices so unless you want to pay for another tow to the next shop.<P>You may have to wait a more time because some parts were not ordered ahead of time.<P>You run the risk of bending all the intake valves (happens less than half the time)<P>You run the risk of cloging op the oil pump pick up and contaiminating the engine with fragments of broken parts. If the oil pan and pick-up is not removed and cleaned after a failure you are risking engine damage.<P>To sum it up I have done a great number of failed 3.8L chains. Done some head jobs because of this. And maybe replaced 1 or 2 engines because of what I said about clogging the pick-up or pump by-pass.<P>Order the chain kit ahead of time with a front cover gasket set. Also get the tensioner and cam button. The cam button was redesigned. The button helps control cam walking. Cam walking causes chain and sprocket wear because the cain is not running strait at times.<P>A good number of times you need to replace the front cover. At one dealer we would recomend it before teardown. It's a GM part and sometimes has to be ordered. The spot on the front cover where the cam button rides wears bad. Like I said this keeps the cam from walking. The oil pump gears are also in the front cover. The gears being steal and the cover allumimn you know the cover is the most worn part of the oil pump. Replacing the front cover and oil pump gears can give you a little more life out of your older engine. The pump gears come with a new pressure relief spring assembly too. I recomend everything menchened.<P>The harmonic balancer does go bad at time but is easy to do on it's own. I did one in a parking lot in some other state in 15 minuits. I wouldn't worry about unless you see a defect in it.<P>I almost forgot the water pump and bypass hoses. If older replace those too while the parts are on the bench. The water pumps are cheep and don't seem to have the longest life.<P>Make sure if the front is remove to change the oil afterwords. Do to coolant and dirt contamination in the oil.<P>I need to do mine soon. It has 141,000 miles and I can hear some extra noise from the front cover. Sometimes you can feel/hear the chain slop by moving the crank back and forth slightly. <P>If you want to do preventive maintence do it all. Otherwise keep on driving.<P>Tom

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You shouldn't have a problem after 88 starting with the 3800 Buick used all steel as previously mentioned. The older 3.8s used a nylon camshaft sprocket that usually only last 75k or so, which is probably what your source was refering to. A timing chain going isn't good though because you can end up with bent vavles. But this not a big problem since Buick used a chain tensioner. Your good until this goes. On my 87 there is an updated tensioner and button. I think these were standard on 88s and newer, but I'm not sure.<P>-T

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I did mine at about 80K because it was clicking. The tensioner wears and the chain slaps around. I would definitely replace it at 150K. Be careful when you are re-installing the crank pulley that you don't damage the sensor for the ignition.<P>------------------<BR>

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I did mine at about 80K because it was clicking. The tensioner wears and the chain slaps around. I would definitely replace it at 150K. Be careful when you are re-installing the crank pulley that you don't damage the sensor for the ignition.<P>------------------<BR>

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