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Timing Belt Slipping
https://slantsix.org/forum/viewtopic.php?t=48876		 Page 1 of 1
Author:  aspen76 [ Tue May 22, 2012 6:33 pm ]
Post subject:  Timing Belt Slipping
Hey guys,
So I was driving my car earlier today and the idle was at 700 and it sounded smooth. I just got done driving around a little and the idle was changing causing it to idle rough. I'd be driving and everything would be perfect, but then I'd stop and my idle would sit at 600 and slowly fall to approximately 300 where it would bog real bad, like it was missing. Does this sound like a slipping belt? If not what could be causing it?

Thank you guys for your help,
Aspen76
Author:  sandy in BC [ Tue May 22, 2012 6:49 pm ]
Post subject: 
Its not your timing belt slipping.....I dont know what is causing your problem....but its not the belt.
Author:  SlantSixDan [ Tue May 22, 2012 7:03 pm ]
Post subject: 
Your car hasn't got a timing belt, it's got a timing chain. With age and miles, the chain can slacken and cause the cam and ignition timing to retard, which takes a bite out of performance and fuel economy. But it doesn't generally cause this what you describe. I think your problem is more likely to be found in the carburetor and/or distributor.

One question: What's the weather like in your area right now (or more specifically, when the problem occurred)?
Author:  63gtcv [ Tue May 22, 2012 7:04 pm ]
Post subject: 
/6 doesn't have a belt. Sounds to me like maybe your carb is loading up. Floats are just a tad low causing the carb to slowly begin to flood and thus poor and falling idle. If, when the idle drops, you rev it up some, does the idle return to normal and then start to drop again? If so, check your float. Another thing could be just to clean the seat on the needle valve, where the fuel enters the carb.
Author:  SlantSixDan [ Tue May 22, 2012 7:11 pm ]
Post subject: 
Quote:
Floats are just a tad low causing the carb to slowly begin to flood
No. A too-low float doesn't cause flooding. A too-high float (or one that has absorbed gasoline and is too heavy) does.
Author:  63gtcv [ Tue May 22, 2012 7:17 pm ]
Post subject: 
I always thought that when the carb gets full the float is at it's highest point and closes the needle valve. I know that when I had crud from my gas tank entering the carb it would cause the valve to not close and flood the carb. Wouldn't a heavy float sink and open the valve?
Author:  aspen76 [ Tue May 22, 2012 7:24 pm ]
Post subject: 
Well I just had a mechanic help me set up my super six set-up, so if it's one of the two I'll put my bets on the carb. Though this did happen when I had my 1 BBL on but at a much slower pace (and by slower, I mean it took about 3-4 months for my idle to fall to the 300 causing rough idling).
Well I picked up my car from the mechanic around noon and drove it home, it was around the low 90s. When I took my car out later (around 8pm) it was probably high 70s low 80s.

Would soaking the float in carb cleaner for about a week ruin it? I had rebuilt the BBD before installing it and it seemed like a good idea to soak just about everything I could get a hold of. If the float is bad, how do I tell?

Timing belt... Shows how much I know :(
Author:  SlantSixDan [ Tue May 22, 2012 10:38 pm ]
Post subject: 
Quote:
I always thought that when the carb gets full the float is at it's highest point and closes the needle valve.
Correct. And if the float is set too high, the carb will be too full. If the float is set too low, the carb will not be full enough (which doesn't show up at idle).
Quote:
Wouldn't a heavy float sink and open the valve?
Yes.
Author:  SlantSixDan [ Tue May 22, 2012 10:40 pm ]
Post subject: 
Quote:
Well I just had a mechanic help me set up my super six set-up, so if it's one of the two I'll put my bets on the carb. Though this did happen when I had my 1 BBL on but at a much slower pace (and by slower, I mean it took about 3-4 months for my idle to fall to the 300 causing rough idling).
Interesting...how many miles on this engine?
Quote:
Well I picked up my car from the mechanic around noon and drove it home, it was around the low 90s. When I took my car out later (around 8pm) it was probably high 70s low 80s.
That rules out throttle ice-up.
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Would soaking the float in carb cleaner for about a week ruin it?
No, because this is a brass float. If it has a leak, then it'll slosh when shaken.

Get the three books described in this thread as quickly as you can and…start readin'!
Author:  aspen76 [ Wed May 23, 2012 5:05 pm ]
Post subject: 
I called the mechanic today and he was thinking along the same lines as 63gtcv. He doesn't think it's the float because he set it himself and didn't think it was bad. He figures it's probably a piece of rubber hose or something stuck on the needle. He told me to take it out and floor it for a minute straight to try and flush it out. While I wasn't able to really floor it for that long (Kinda hard in the city, even on the highway cause im tired of getting tickets :roll: ), I did floor it from light to light as much as possible and it seemed to have cleared up for awhile with the idle only dropping to 550ish but at one point it did drop down to 300 so the problem isn't solved yet, I'm going to try again tomorrow. Don't know quite what to do if it doesn't clear up but I'm definitely running through a ton of gas hammering it as often as I am... Think I might open up where the gas enters the carb and carb clean the fitting and use compressed air. Then I'll change the fuel filter just for good measure. Anyone have any other suggestions?
Think it matters if the car is in drive when I floor it? Maybe keeping it around 4000 rpm while in park would work?

The engine has ?87,000ish miles on it. I put the question mark because it doesn't have the hundred thousand digit.

I've almost bought those books before (saw you tell someone else to get them) but I just couldn't pull the trigger to buy them all at once (not used to paying shipping on amazon). I do need to get around to it though and I've seen my factory service manual cd on ebay for like $20 bucks before. In about 4 weeks (once I graduate) I'll pick them up and read, as I'll have a lot more time to read them

As always, thanks for all your help guys, I really appreciate it,
Aspen76
Author:  SlantSixDan [ Wed May 23, 2012 7:01 pm ]
Post subject: 
Quote:
He figures it's probably a piece of rubber hose or something stuck on the needle.
That's not it.
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He told me to take it out and floor it for a minute straight to try and flush it out
Um, no. This guy doesn't sound very knowledgeable.
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Don't know quite what to do if it doesn't clear up
Rebuild the carburetor correctly. I would not bet on your "mechanic" having set the float correctly, just based on his guesses and suggestions.
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Think I might open up where the gas enters the carb and carb clean the fitting and use compressed air
Also no.
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Then I'll change the fuel filter
Not a bad idea if you don't know when it was last changed, but insufficient fuel supply, either because the float is set too low or because there's a blockage, tends to show up at high engine speed/load, not at idle. Which makes sense when you think about it: at idle you've got the minimum fuel demand, so an inadequacy won't show up. At high speed/load, you've got the maximum fuel demand, so that's when inadequate fuel supply shows up.
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Anyone have any other suggestions?
Systematic, informed diagnosis and repair. Not guesses and random parts replacement and "uhhhhh...yeah, Beavis...uhhhhh...you should, like, floor the accelerator and stuff...uhuhuhuhuhuh".
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Think it matters if the car is in drive when I floor it? Maybe keeping it around 4000 rpm while in park would work?
The idea is to fix the problem, not shorten or end the life of the engine. Flooring the accelerator is not going to fix the problem.
Quote:
I've almost bought those books before (saw you tell someone else to get them) but I just couldn't pull the trigger to buy them all at once (not used to paying shipping on amazon). I do need to get around to it though
Yes, in a big hurry. Right now you're flying blind. Knowledge is not an optional kinda-nice thing to have, it is a mandatory first(!) tool.
Author:  aspen76 [ Sat May 26, 2012 6:47 pm ]
Post subject: 
Got it fixed, just needed some adjustment on the idle mixture screws.
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