Which Harmonic Balancer?

[vmrod]

I don't remember how many RPM's I lost, but I remember (this was 7 years ago) a squeal whenever the A/C compressor kicked on, and also my engine felt like 'something' was trying to stop it from turning. This problem persisted until I could actually see the A/C pulley turning slower than the belt and I could hear the squeal coming from that place.

I don't think you need to go to a corvette specialist for the problem. I bet an A/C shop would be your best bet. Ask if they can test to see if the compressor is binding up. (Alot of A/C shops are charging $25 for a A/C diagnostic. Not too bad.)

Just reassemble your car, but remove the A/C belt. You can at least drive your car then. Bring the belt with you to the auto shop.

There's one more test that you may be able to do yourself. What if you removed the A/C belt. Now, with the car running and the A/C turned on, see if you can spin the pulley yourself and how easy it is to turn. If it is excessively tight, then you can take the car in to the A/C shop for professional testing (I know, again).

 

[77-4speed]

Removing the belt and spinning the pully is an interesting idea! I will tell you this though, the A/C belt has no markings on the side or bottom and does not heat or squeal at all.

The car doesn't drive any different except for the noticeable parasitic loss in power. The engine doesn't really fight the A/C and it doesn't over heat. The only real problem is the shudder.

How many rpm's does your car lose now when the A/C is turned on? I figure that 300-500 is probably acceptable for A/C loss.

Russ

 

[vmrod]

Unfortunately I don't know. When I had that problem. I took the entire compressor out of the car. I never put another in. I even took out the evaporator core (or whatever it is by the radiator. My car has been dormant for 5 years now, and I am finally starting to work on her again.

Perhaps the reason that your belt is not warm or does not squeal is because the compressor did not yet reach that bad stage of binding up, but only just starting to get tough to turn.

Perhaps someone else can help out with suggestions too?

 

[77-4speed]

Thanks for the input vmrod,

I guess I'll have to take it to another place when i get the diff. put back on. I guess $25 isn't that bad to have the thing checked out. If it comes back ok then I'll have to work on making sure everything is perfectly balanced.

Best of luck with your car. I'm sure it'll be back on the road in no time

Russ

 

[vmrod]

....hmmm let's see. I'm rebuilding my power steering control valve this weekend. (removing it this evening). Rear shocks will be coming in next week. I need rear tires, exhaust system, and new temperature and oil pressure sending units, new rag-top...etc. The interior needs a big facelift too. (whew!)

good luck with your car. I wish I only had your trouble!

 

[Bullitt]

Reading this thread and the fact of rpm drop, begs the question: Russ, do you have an idle compensator solenoid? This raises the idle speed when the A/C is turned on. I don't remember seeing one on your carburetor, but I know Edelbrock sells them.

--Bullitt

 

[vmrod]

-Bullit,
don't you find it odd that his belts buckle and shake when the A/C is turned on? I realize that the RPM's drop down, but does revving the engine to normal idle eliminate the problem. Even so, I don't believe an engine is suppose to be misbehaving so terribly at lower RPMs like that.

I can't wait to find out what the problem is.

 

[77-4speed]

Bullit,

No, I don't have an idle compensation solenoid. I looked them up at Summit and they want close to $100 shipped! I only paid $3XX for my carbureator!

To answer your question vmrod, the belts don't shake until 900-1400 rpm. Anything above and below that and the car behaves normally.

I can't wait to find out what this problem is either. I'll definitely post when I find the answer, although it might be a while

Russ

 

[c4ever]

Russ,
I,ve been following this post and agree, I don't believe the A/C belt should slap around at low RPM but my 82 has the same problem with the A/C running. Runs smooth without the A/C. Annoying as h**l. My mechanic said it is not abnormal for the C3 and he's done a great job on both the vettes. Keep us posted cause I'd like to get rid of this annoying noise at idle. Not to mention I can't believe the belt even holds up.

Carlo

 

[Bullitt]

I've never understood why Edelbrock's soleniod was significantly more than Holley's. Edelbrock's kit does come with the bracket and wiring, I assume, but I've seen them around $80. The Holley soleniod is around $40-50. :confused $300+ was too much for the carburetor. Maybe that was for a new unit, but I remember only paying $240 for a 600 cfm remanufactured one with fuel filter. That was from Competition Sales in Stinkerdena, but there's one off of Longpoint, 713-686-7890. You can also try calling Direct Performance Warehouse at 713-864-9888. They're off of Hempstead Rd., right beneath the 610 West Loop. I think they're still in buisness. Maybe they can get you a better deal.

Yeah, it's odd that the vibration only happens at a certain rpm. It's evident that the flex fan is causing the noise, but the shaking has me stumped. I don't think the shake should be happening at all. Perhaps more bracing of the compressor brackets would help. Russ, is there any slack at the mounting points for the compressor? Do the bracket bolt holes seem to be elongated too much?

It is possible that the NAPA unit is just bad. Would two be bad? Yes. I've experienced two bad replacement alternators on one car before, so I'm sure it's happened to others.

--Bullitt

 

[77-4speed]

Hey Bullit,

Summit's price for the solenoid was in fact ~$80. I don't know why they are so expensive. The carb was in fact new since I was uninitiated in the automotive world at that time, I just called Summit and said, "I need a new carb for my 77 L-82 vette". They sold me the most expensive Edlebrock for the job. The 600 cfm EGR set up with electric choke. If it were to happen today, I'd order a reman. 650 cfm non-egr with electric choke. One of these days I'll pick up the solenoid, just not today.

Russ

 

[vmrod]

hey '77,
did you ever figure out the problem yet?

 

[77-4speed]

I'm pretty sure that the movement of the belt is normal. I've looked at others with A/C and most of the belts also vibrate quite a bit. I do think that it is just a natural vibration for the flex fan at that rpm.

Russ