This is relating to a non f-body which is an '84 Grand Prix with a 305 4-barrel carb. It has a mileage of about 70k but Im not sure if it has repeated after hitting 99,999.9 giving it an estimate of about 170k.

What are signs of the timing chain beginning to fail or does it just go in a snap? I hear a sound from inside the car(when running) as if the vent is running on med to high, but it is not. At first the sound seemed to have come from around the center of the firewall within the car, but when i checked the engine bay it sounds as if it is coming from the area of the fan run by a pulley. The fan seems somewhat wobbly even after tightening but could the low-frequency hum sound come from the worn fan. I dont think it's the water pump since it seems tight where the fan mounts to the pump.

My main question is does a worn timing chain make noise before it fails? And can anyone give a hint what the noise is if it does occur? Hopefully this isnt the case since it is my brothers daily driver. Thanks.

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Shouldn't bother putting this but hey what the heck:
1988 Maui Blue Firebird 305 TBI stock (w/ 190,000+ miles and still running strong )

 

Wobbly fan, sounds like it might be the fan clutch.

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Rob
'86 TA 305 TPI

 

I agree with ROB, it's probably something to do with the fan. Alot of the time the fan clutch will fail such that the fan runs all the time, which makes quite a bit of noise. Just replcae the fan clutch with a thermostatic one, don't fool around with the cheap centrifugal kind.

Timing chains don't really make any noise when they die. Usually they die when driving down the highway, totally out of the blue. About the only warning you might get is that they often get so much slack as they reach the end of their life that they actually wear a hole through the timing cover at the bottom right, where the chain comes off the crank gear as it travles around. That's where the slack is, and it gets to be such a big loop that it hits the cover. So if you suddenly get a massive oil leak out the front of the motor down low, buy a timing set (and a timing cover!!) immediately.

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"So many Mustangs, so little time..."

 

I'm no expert and don't know about your sound, but I can tell you what my timing chain sounded like and I just got done replacing it, about 1/4 of the teeth were gone off the cam sprocket. It was giving a non rhymthic metallic tapping sound which got progressively louder until the car wouldn't start. Initially I thought it was the water pump but when I pulled her all apart, the water pump impeller was fine but my timing gear teeth were gone. Needles to say, I replaced everthing. Also, the car ran like crap and when I checked the timing,the only way I could get the car to run was with the timing way advanced, guess it skipped some teeth. She is running now, have a new tapping sound from the valve covers, aren't cars fun?

 

Thanks R.O.B. and RB83L69. If the fan is the original, is it the centrifugal type that you say? What's the difference between the centrifugal and the thermostatic? Thanks again.

 

HW,

Could be the fan clutch hub, or the water pump, or both. Remove the belt and check for play at the shaft (not foreplay with the shaft).

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Later,
Vader
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"No matter how hard you try you can't stop us now"
Adobe Acrobat Reader 4.0

 

Not that I'm answering a question here, but I'd say as soon as you can find a warm place to work, replace the timing chain anyway asap! I did mine at about your mileage- and my car's much worse to do. (The whole water pump back is the gasket area on the 2.8 V6- and that gasket area is the aluminum timing chain cover! What a pain those pieces are to scrape clean of old gaskets!)


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-Tom P (Hot rodded 1986 Firebird 2.8l) from http://www.f-body.net/mailbag/3rd/3rd_mailbag.html message boards
---Think your car could be pic of the week? Visit http://www.f-body.net for details!

 

in regards to the timing chain,whether it's worn or not,I would replace the timing chain with a double roller. the stock cam gear is a cheap fibercoated aluminum gear.mine just broke at est. 110k,half of the teeth were shaved off!!this never would have happened with a stronger steel double roller set.

 

The original is theremostatic.

Centrifugal ones disconnect at high engine speeds regardless of the temperature of anything; thermostatic ones apply or decouple according to the temperature.

I'd bet Billy's metallic sound was the chain hitting the timing cover...

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"So many Mustangs, so little time..."

 

What are the consequences of the timing chain breaking while the engine is running? Is the engine toast?

I had the worry that mine was making a noise and inneed of replacement, but after getting two different opinions about it being the timing chain or the water pump, the water pump began to leak and replacing it solved my problem.
Later


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West Coast Performance
1989 Formula 305 TBI

 

Actually, EVERY timing chain that has ever gone on me; the car just didn't start one day. The car was running fine when I last turned it off, and then just wouldn't start the next time. I never had a timing chain on any V8 break on me.

But if one did, you'd probably suffer the same fate as many OHC engines where the timing belt breaks (seen a few of those)...damaged valve train. Many of those OHC cars just use a belt of some oriental plastic. Metal chains like most V8s generally just stretch.

To test your timing chain, remove the distributor cap and turn the engine back and forth. If it takes more the 5* of the crank to cause any movement in the distributor's rotor, I'd consider replacing it.

Of course, if you replace the timing chain, also change the gears. Good time to think about the waterpump if it hasn't been replaced in a long time. I hate going back a second time to fix something I could have done the first time I was there.


[This message has been edited by Glenn91L98GTA (edited January 09, 2001).]

 

Adam89F: I've heard and learned that if it(timing chain) goes out while the motor is turning you may end up having some bent/broken valve's (the ones that remain open), damaged cam and possibly some holy pistons since the cam stops turning in sequence with the crank.


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Shouldn't bother putting this but hey what the heck:
1988 Maui Blue Firebird 305 TBI stock (w/ 190,000+ miles and still running strong )

 

Small block Chevy motors with the stock cam will not usually destroy anything when the chain breaks, unlike some motors which fail spectacularly. There happens to be enough clearance in a SBC with a low-lift cam to prevent stuff from hitting. I just had one break on me the other day, so I got a good memory refresher. All the ones I have had experience with failed whle running, usually at high speeds; what happens is not the chain breaking, but rather the phenolic teeth stripping off the chinesium gear the factory uses. I have heard of quite a few failing at startup but I have never had one of mine go out that way.

I did have a big block chain to fail on me one day while driving down the freeway; it bent all 8 intake pushrods, it was a 454 so it has the weenie 11/32" ones but didn't hurt the valves. I guess the pushrods servced as the "fuse" or weak link and protected everything else. I put a chain, a set of pushrods, and a set of Comp roller-tip rockers on it and it runs great to this day.

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"So many Mustangs, so little time..."

 

Here's something the Crane Cams website pointed me to, under their tech articles/cam & valvetrain questions page, called "an article on cams"- here's the link:
http://www.howstuffworks.com/camshaft.htm

Here's a fun picture from the article:




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-Tom P (Hot rodded 1986 Firebird 2.8l) from http://www.f-body.net/mailbag/3rd/3rd_mailbag.html message boards
---Think your car could be pic of the week? Visit http://www.f-body.net for details!

 

wow!!!!#$%@ I just had my t-chain go at 35mph,even after the chain & gears were replaced, it still didn't run right! it's hard to figure out quite what happened 'cause it's a "non-intrusive" valve train as mentioned earlier,last time I tried to crank it, it just coughed and spit gas right up through the carb as plumes of black smoke came from the exaust,I'm in New England right now so doing the chain was enough for me,once it started snowing,I just said Fk it and sent it in for a brand new longblock...that engine is bad luck anyways!! after seeing those pics I'm glad I didn't waste any more time with it.

 

tom,thats the coolest website I've ever seen!!!! that stuff always makes me dizzy to think about,that working diagram would be a big help in choosing the right cam shaft.