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Author Topic: 80's GM 60degree V-6 help  (Read 1313 times)

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Offline Cvillechopper

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80's GM 60degree V-6 help
« on: September 20, 2010, 07:30:35 AM »
I've got my Fiero back together and took her out for a test run this weekend.  She is pulling pretty nicely and feels very decent but I've got a high-pitch sound when I accelerate under load.  It's not there at idle or when revved in neutral.  Has just about the same pitch as the jet cars on The Jetsons had if you remember that.  I can accelerate slowly and not get the noise unless I'm on a hill and have to give her a little more.  It is consistent and the sound changes frequency with the rpms.  Any ideas? 

Thanks
James
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Offline syth82

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Re: 80's GM 60degree V-6 help
« Reply #1 on: September 20, 2010, 07:36:58 AM »
You're sure it changes with revs and not speed? Maybe a torn intake boot, then? Is it an auto trans?
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Offline Cvillechopper

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Re: 80's GM 60degree V-6 help
« Reply #2 on: September 20, 2010, 07:54:20 AM »
5-speed Trans.  It seems to be changing more with the rpms than speed as it's consistently with the engine sound in each gear but I could be wrong.  Will have to take her back out this evening and check that more closely. 

Just started thinking about an intake leak maybe making that noise but it seems pretty loud for that.  Will double check the intake just the same.

Thanks
James
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Offline TwoTired

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Re: 80's GM 60degree V-6 help
« Reply #3 on: September 20, 2010, 12:55:02 PM »
Whistles can be pretty loud just by blowing into them.

It sounds like a vacuum leak somewhere.  How old are the hoses/tubing?
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Offline Skunk Stripe

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Re: 80's GM 60degree V-6 help
« Reply #4 on: September 20, 2010, 01:01:25 PM »
How long have you had this car? I only ask as maybe if you have not heard it run before, it could be intake noise. I know some vehicles will have intake noise that sounds high pitched.
A vacuum hose is a possible culprit too.
Also, the gear lube may be different than before and maybe it is a bit of gear noise at higher rpm that you are hearing.
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Offline Gaucho

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Re: 80's GM 60degree V-6 help
« Reply #5 on: September 20, 2010, 01:09:19 PM »
When you say "I've got it together", does it means you had the engine out of the engine bay?
If it's a Five speed is not uncommon to have a bad pilot bushing during re installation. They can get pretty noisy.
Gaucho
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Offline Cvillechopper

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Re: 80's GM 60degree V-6 help
« Reply #6 on: September 20, 2010, 04:01:40 PM »
I've had the car for a few months and did get to drive it a few months ago.  It had a pretty severe exhaust leak so I had to drop the engine and transmission to get to it.  The transmission was never separated from the engine so I'm hoping it's not the pilot bearing.  I took her out this evening and found out a little more.  The noise gets louder the harder I accelerate.  I'm starting to think one of the exhaust manifolds I put on has a pin-hole leak in it.  The guy I bought it from supposedly had a professional welder reinforce a few points.  They look kinda crape but solid.  I'll be getting a mechanics stethoscope tomorrow hopefully so I can see if it's that or something else. 

I did check the vacuum lines with some throttle body cleaner and don't appear to have any leaks.  I have replaced almost all of the soft rubber vac lines but some of them are a hard plastic and are original (about 22 years old).
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Offline tsp37

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Re: 80's GM 60degree V-6 help
« Reply #7 on: September 20, 2010, 06:18:00 PM »
If the noise increases with an open throttle it's probably not a vacuum leak.  Does this car have a serpentine belt?  You may hear an idler pulley.
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Offline Cvillechopper

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Re: 80's GM 60degree V-6 help
« Reply #8 on: September 20, 2010, 06:47:24 PM »
Quote from: tsp37 on September 20, 2010, 06:18:00 PM
If the noise increases with an open throttle it's probably not a vacuum leak.  Does this car have a serpentine belt?  You may hear an idler pulley.

It does have a serpentine belt and I had to remove and reinstall the harmonic balancer when I did the timing chain and gears.  Not thinking that it's that since when I just took her out a bit ago I noticed that the noise gets louder the more I push the gas regardless of rpm or mph.
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Offline mattcb350f

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Re: 80's GM 60degree V-6 help
« Reply #9 on: September 20, 2010, 07:27:34 PM »
So it appears to be a 'load sensitive' noise. Could be a severely clogged catylitic converter causing exhaust to leak out up stream of it. A blocked muffler could do the same.

 Matt.
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Offline syth82

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Re: 80's GM 60degree V-6 help
« Reply #10 on: September 20, 2010, 07:35:06 PM »
It's not the pilot bearing. That only makes noise when the clutch is disengaged, as that's the only time it's moving. The throwout bearing could do it, but the noise would obviously change as soon as you put pressure on the clutch. My money is still on the intake boot or something similar. Anything outside the throttle in the intake tract could make noise off idle under load. It could be a vacuum leak, but I'd expect you to hear it at idle, too. A belt or pulley noise would probably happen just as easy sitting in neutral as it would while driving.
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Offline Don R

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Re: 80's GM 60degree V-6 help
« Reply #11 on: September 20, 2010, 10:16:22 PM »
do you have the stock air filter on?
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Offline Cvillechopper

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Re: 80's GM 60degree V-6 help
« Reply #12 on: September 21, 2010, 05:50:36 AM »
Stock (new) air filter and new Cat but it's clamped on so I'll have to look at that.  It's got the original muffler so maybe I'll have to look at replacing that...
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Offline Spanner 1

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Re: 80's GM 60degree V-6 help
« Reply #13 on: September 21, 2010, 07:21:54 PM »
Interesting replies, most of which you have ruled out, I think.
I think it is your radiator cap releasing pressure as you acc. the water pump increases pressure in the cooling system and the rad. cap 'breaks' it's seal and 'screeches' ( variable with load/rpms ). A new cap is always a good idea after a few years, cheap and just might be the solution  ;)... IMO.
P.S. Coolant won't be released when this happens, the noise I mean, not sure why, trapped air ?
« Last Edit: September 21, 2010, 07:28:26 PM by Spanner 1 »
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Offline Cvillechopper

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Re: 80's GM 60degree V-6 help
« Reply #14 on: September 22, 2010, 03:41:33 AM »
Quote from: Spanner 1 on September 21, 2010, 07:21:54 PM
Interesting replies, most of which you have ruled out, I think.
I think it is your radiator cap releasing pressure as you acc. the water pump increases pressure in the cooling system and the rad. cap 'breaks' it's seal and 'screeches' ( variable with load/rpms ). A new cap is always a good idea after a few years, cheap and just might be the solution  ;)... IMO.
P.S. Coolant won't be released when this happens, the noise I mean, not sure why, trapped air ?

That's an idea!  Fieros are notorious for having trapped air in the coolant system.  I tried to get it all out but will have to check into that.  The system is a little different than most in that there are 2 caps, one at a neck just above the water pump and another on the radiator in the front of the car.  I hope it's something that simple...
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Offline zanorak

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Re: 80's GM 60degree V-6 help
« Reply #15 on: September 22, 2010, 04:51:51 AM »
Or your alternator. Or the water pump. Or (classic GM) the belt tensioner. I swear they make those things out of the packaging you throw away from mcdonalds.
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Offline Cvillechopper

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Re: 80's GM 60degree V-6 help
« Reply #16 on: September 24, 2010, 05:12:38 AM »
So I've figured out that the sound changes based on engine load, not rpms or vehicle speed.  Last night I started testing the vacuum lines with a hand pump and found one that needed to be replaced.  The rest will get tested tonight (or tomorrow depending on what the wife allows) and replaced as necessary.  There was definitely an improvement in how the engine revs up but it's still not quite there.  Hopefully I'll find another and all will be well but I'm still not convinced that this is the cause of the sound.  It just seems like it was too loud for a vacuum leak...
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Offline Raef

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Re: 80's GM 60degree V-6 help
« Reply #17 on: September 24, 2010, 06:01:05 AM »
these motors have a differant sound to them. the reason they trap air is due to intake gasket leaks. I have had three 2.8 and 3.1 engines and I have have to change the intake gasket in all of them at least once. check for a milky condensation on the bottom of the oil filler cap on top of the valve cover. I know it's not the source of the noise but keep an eye on it.
I have 2 feiro parts cars, 1 is a gt if you need any parts


Mark
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Offline Cvillechopper

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Re: 80's GM 60degree V-6 help
« Reply #18 on: September 24, 2010, 06:22:08 AM »
Quote from: raef on September 24, 2010, 06:01:05 AM
these motors have a differant sound to them. the reason they trap air is due to intake gasket leaks. I have had three 2.8 and 3.1 engines and I have have to change the intake gasket in all of them at least once. check for a milky condensation on the bottom of the oil filler cap on top of the valve cover. I know it's not the source of the noise but keep an eye on it.
I have 2 feiro parts cars, 1 is a gt if you need any parts


Mark

What year is the GT?  I have several parts I'm going to be looking for as $$ (and the wife) allow as I progress on the restoration.  List so far:

mud guards inside rear wheel wells
Dash (black top speaker surround piece)
Seat recline handle surrounds (both sides - gray)
Seat recline handle (passenger)
Possibly other interior parts in like-new condition (no vinyl peel - gray)


Let me know if you have any of these that would be suitable for a restoration.  Hoping to make this a show car since it's an '88 GT with factory t-tops.  Only 614 made and the overwhelming majority of those have been trashed or heavily modified.  I just love them as they came off the assembly line...

Thanks
James
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