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Steve40th Air Conditioner vibration 1993 with headers
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Its been a while since I have been on here. Need some help guys.
93 LT1. I have headers without the brackets that go to the exhaust manifolds since 2001.. Within the past couple months, the Air Conditioner vibrates when I do some hard accelerating.
If I turn it off and do the same acceleration, vibration goes away.
I out a stethoscope on the compressor while running and it sounds like a spinning machine, under load and off. No real change.
Belt is new, belt tensioner is new.
What would cause a vibration under load..
Posted on: 9/10 21:50
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CorvetteBob Re: Air Conditioner vibration 1993 with headers
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I’m in the midst of a project, and there’s been a couple times I’ve addressed this exact issue.
If you haven’t got the little spacers on your headers for longer bolts, I suggest you try to come up with some. Often, guys cut the old ones off the OEM manifold.
For a bolt, you can usually get away with using a factory double ended bolt that came off your original system also. You may at this point be able use the oem rod.
I went to a home improvement store and got some steel tube. The wall was thin, so as I recall I got ~1/2” and the next size down to use for additional strength.
Then I cut them to length, Insert the tubes together and use a vise to smash one end of the combined tubes. This may or may not be easy, depending on your vise.
Tip: don’t use aluminum tube as it’ll split when you crimp it.
At this point it’s just drilling the flattened part for the bolt on the exhaust, bend it, then complete the compressor end.

One thing, if you used the oem support rod, and a spacer long enough to accommodate the angle to clear your headers, just make sure you have a bolt that give proper thread-in length so as not to strip out the hole. Another way is to use threaded rod cut to length, a nut to fasten the header, and a second nut for the rod.
I hope this helps.
Posted on: 9/11 15:40
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Steve40th Re: Air Conditioner vibration 1993 with headers
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Hey, I used OEM exhaust manifold bolts with spacers. I read an old thread where a person said the length needed etc.
It worked, but I only put on that goes from outside of ac compressor to center headers bolts at cylinder #3.
Thing is, I never had this vibration for many many years, drag racing, street running it hard.
The only issue I have had with the Compressor is the clutch burnt up about a year or so ago. I put a new one in. Wonder if I screwed that up. I took the bolt out, and put everything back in, including the washer/spacer.. Maybe that is wrong?
Posted on: 9/11 20:13
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CorvetteBob Re: Air Conditioner vibration 1993 with headers
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From here I’d try looking at the entire accessory drive system. My reason is that on an 86 it sounded all the world like the steering pump was shot. Turned out to be a diode in the alternator.
My point is
A) yes, something may have happened when you changed the a/c clutch. But after re-reading your description, I think the compressor is reaching the end.
B) if you still have the old tensioner, try putting it back on in case you got a bad one.
C) check your water pump and other belt driven components. You never know what might turn up.
I know it’s not much to go on, but it might be worth a try, and it’s free to listen to.
Best of luck, again, I hope this helps.
Posted on: 9/11 20:41
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CorvetteBob Re: Air Conditioner vibration 1993 with headers
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One final thought, is your a/c mounting bracket possibly cracked?
That’s been known to happen on rare occasions.
Posted on: 9/11 20:43
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Steve40th Re: Air Conditioner vibration 1993 with headers
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Quote:

CorvetteBob wrote:
From here I’d try looking at the entire accessory drive system. My reason is that on an 86 it sounded all the world like the steering pump was shot. Turned out to be a diode in the alternator.
My point is
A) yes, something may have happened when you changed the a/c clutch. But after re-reading your description, I think the compressor is reaching the end.
B) if you still have the old tensioner, try putting it back on in case you got a bad one.
C) check your water pump and other belt driven components. You never know what might turn up.
I know it’s not much to go on, but it might be worth a try, and it’s free to listen to.
Best of luck, again, I hope this helps.

I ended up putting a new tensioner on as the replacement was bad. Its quiet and barely moves when revving the engine.
93 has the LT1 water pump driven by camshaft.
I have one belt and everything is okay.
Remember, it only does it with AC and 2/3rds type pulls. Haven't tried it WOT, but AC would shut off during that pull.
I am wondering if , when I did the clutch, I need to check the gap, as the spacer is the only one that came out.
Maybe there is a mesaurement to check, and I might need to adjust.
If compressor is going out, I will need someone to vacuum it out and put back in.. R12 is an issue, unless they can pull it all out.
Or convert to 134A
Posted on: 9/11 21:00
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Steve40th Re: Air Conditioner vibration 1993 with headers
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Quote:

CorvetteBob wrote:
One final thought, is your a/c mounting bracket possibly cracked?
That’s been known to happen on rare occasions.

Hmm, not sure where to look, but its something to look into.
Posted on: 9/11 21:00
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Steve40th Re: Air Conditioner vibration 1993 with headers
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Where have LT1 style AC brackets broke/cracked? I have heard of the L98s , older ones mid late 80s..
Posted on: 9/12 10:50
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CorvetteBob Re: Air Conditioner vibration 1993 with headers
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I’ve only read on here and that other forum about the cracking. But it seems it was on the early and late L98’s, and the LTx cars. More so on the ‘88 and later cars.
I don’t really know where they’re prone to crack.
Posted on: 9/12 16:16
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CorvetteBob Re: Air Conditioner vibration 1993 with headers
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Did you ever find the issue causing the vibration?
Posted on: 9/17 23:44
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Steve40th Re: Air Conditioner vibration 1993 with headers
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Not yet. When I get home in a week.
I will check the gap on AC clutch.
Other than that, winters coming, I will have allot of no ac needed time, lol.
I will find it..It might take a miracle, but I will.
I am going to redo the plugs too. Just for giggles..
Posted on: 9/17 23:55
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rklessdriver Re: Air Conditioner vibration 1993 with headers
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My 92 did the same thing..... I never worried about it.
I have noticed it on a couple of other LTX cars I built for other people.... it bothered one guy so I fabricated a brace bracket down to the second header bolt,similar to the factory one, and it stopped enough to make him happy.

I don't know why your car didn't do it from the start but every one I have put headers on or taller valve covers where you remove the brace to the alternator and or the support rods that go to the manifold vibrated noticeably afterwards.
Will
Posted on: 9/18 2:54
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Steve40th Re: Air Conditioner vibration 1993 with headers
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Quote:

rklessdriver wrote:
My 92 did the same thing..... I never worried about it.
I have noticed it on a couple of other LTX cars I built for other people.... it bothered one guy so I fabricated a brace bracket down to the second header bolt,similar to the factory one, and it stopped enough to make him happy.

I don't know why your car didn't do it from the start but every one I have put headers on or taller valve covers where you remove the brace to the alternator and or the support rods that go to the manifold vibrated noticeably afterwards.
Will

The only thing that has been done is the tires. Reason I say this as before, the tires were old and didnt grip at all.
Now that I have stickier, fresher tires, I think the vibration is noticeable as I wasnt able to do 2 to 3rd gear pulls often without breaking traction all the time.
The vibration may have been there since I put headers on.
Just a theory, over thinking maybe..
Posted on: 9/18 9:12
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