scottmoyer

Ok. I need some assistance here with the '82. I recently took it in to get some work done and have adjustments made. I haven't driven the car for weeks and last weekend, okfoz drove the car and it drove really bad at constant throttle. It was bucking at steady throttle.

The other issue is with acceleration. The car is dead at 2800 RPM. It feels like the IROC-Z at 4400 RPM. Off the line, the 3.23 gears will launch the car to 2800 and the car just flat lines there. Shift into second, get more acceleration up to 2500-2800 and it does it again.

The shop that did the work recommended replacing the carb and getting rid of the computer. He said the two aren't working well together anymore and should be eliminated. Does anyone know what I might be experiencing here? I'm thinking the bucking is related to the ethanol gas that I had to put in over 6 weeks ago and is probably bad. I'm trying to burn it out this weekend. But, what about the rest? Timing? Carb adjustments? Bad carb? Bad computer? Thanks for any advice.

dagwood

iTrader: (5)

My 82 did the same thing before I had the carb rebuilt. The problem is finding someone who knows how to work on them. The parts manager at our dealership is a wizard at them, and he is who rebuilt mine. I also had the timing advanced probably 17 degrees or so. The car ran like a completely different animal after that. Pulled hard right to redline. If you want, I can ask my guy what he'd charge you to rebuild yours. You could ship it to me and I'd ship it back to ya. When he did my carb, he only had it for 2 days.

Here's how it ran afterwards........

sofakingdom

iTrader: (1)

I think it can be summed up in one word:

You are trying to drive an ANTIQUE. It is beyond unrealistic, unless you're made out of pure money, to expect to pay someone else to participate in your hobby for you.

It's probably not the gasoline. Probably also not that drivel about the carb and ECM.

More likely, it's the fuel filter. At least that's where I'd start with it. Change that out YOURSELF - not "take" - and see what happens.



You can see where it goes in this photo (although your fuel line probably won't look quite the same as mine)... behind the big nut on the front of the carb, where the arrow points. To change it, you have to take the fuel line off at the nut, WITHOUT letting the big nut spin while loosening the small one (the small one being equivalent to the rightmost blue one in the photo). Support the big nut with a wrench whole loosening the small one out of it. Once the fuel line is free, unscrew the big nut, and the filter is up in there. Soak the small one's threads with penetrating oil such as PB Blaster or Kroil for acoupla days before attempting. Be VERY careful when putting the big one back in, specifically, install it fully all the way up to the gasket BY HAND , BEFORE putting a tool on it, to avoid cross-threading it; and tighten it only GENTLY, maybe 10 - 12 ft-lbs. Support it while tightening like you did while loosening. You'll need a 5/8" line or crow's foot wrench, a 5/8" open end wrench, a 1" open end wrench, and (surprise!) a fuel filter.

dagwood

iTrader: (5)

Yep, and be ready for a little spring to come flying out at ya. I started there with my car, too, and was shocked to find my 36 year old OEM AC Delco fuel filter with 22k miles on it looking like brand new.

I agree too with the shop being a problem. They dont know how to work on a Quadrajet.....and they told you they dont want to. That's the same exact reason why so many Quadrajet carbs got thrown away over the years. They're actually a great carb if you know what you're doing with it.

CPC Norwood

My LG-4 runs like a champ. OP's problem is the Quadrajet. I rebuilt mine 15 years ago did a fuel filter also. The key is to keep ethanol fuel out of the motor to the largest extent you can or if you have to use it be sure to run a fuel stabilizer all the time.

I can buy non-ethanol fuel locally. The funny thing is that non ethanol fuel also has an odor that smells like real gasoline should.

chazman

iTrader: (4)

I don't think I'd listen to that shop. It's amazing how it's so hard to find anyone who doesn't consider carbs voodoo black magic needing immediate replacement. I like sofa's advice about the fuel filter. Quick, easy, if it works great, if not move from there. It sure sounds like fuel it being restricted. Are you sure your cat isn't clogged?

Also sounds like Darin's guy did a great job on his Q-jet.

Anyway, looks like John broke it, he should buy it!

scottmoyer

The shop I took it to is "supposedly" knowledgeable in this area as he builds/restores old cars for people all the time. Now, this was my first time using this guy and I may go to another shop that I do have experience with that also is old school mechanic. It's hard to find someone that knows how to work on these cars, and I'm not carb savvy, so I have to rely on others that are more experienced. The carb was rebuilt a few years ago when my father had the car and the filter was also replaced. Probably less than 500 miles since rebuild and filter. However, I'm finding the shop that did the work for my father years ago charged him for stuff and did a crap job. I have a receipt that shows the valve cover gaskets were replaced 1000 miles ago, but I just replaced them again to find the holes blown out and leaking everywhere.

The good news is the car shifts good, the new clutch works well, the shifter itself works like it should now and it's almost fun to drive. Once I get this taken care of, I think it will be fun to drive. The upgraded sway bars have tightened the turns considerably. I still have 9 year old rock hard H rated tires that need to be replaced with new. John suggested that I put the 16" IROC-Z wheels on the car with 245/50 Z or W rated tires and the car will handle superbly. Still not sure I want to buy tires if I'm looking to sell.

Charlie, do you think a 29k mile car will have a clogged cat? I know it's possible if the car was running rich. I did question that also, though. I have a rattle at the cat that I need to remove. Not sure yet if it's the cat or the shield.

sofakingdom

iTrader: (1)

All of those stories are why it's utter and total nonsense to take an antique car to "shop".

You're just going to continue to suffer incompetence, laziness, lack of effort, time-minimization, lack of knowledge, and all the rest of what comes with "shop" and old cars, as long as you try to go that route.

Learn to do simple stuff like this yourself. Enjoy the feeling of satisfaction that comes from enjoying something you BUILT instead of BOUGHT. Since skill with carbs is something rapidly disappearing from the face of the Earth, develop your own. It will MORE THAN AMPLY repay you throughout the remainder of your future ownership of that car.

I agree with the 16" wheel advice. Although, nowadays it's getting harder all the time to find true "performance" tires for a car this heavy and wheels that small. But it's nowhere near as hard as finding rubber for 15" wheels, which apart from drag racing and such, is nigh onto impossible.

As far as the cat: get up under it and tap on the shield and see if that's the noise. Also, a clogged one will make the exhaust produce a hissing kind of noise when accelerating; if it sounds normal, it's probably more or less OK. Which is to say, lack of that sound doesn't prove that it's "good", only that it's probably not The Problem At Hand.

CPC Norwood

FWIW.. Unless OP has been running a bad additive continuously over the years or running leaded gas - the cat will not be the source of the issue.

dagwood

iTrader: (5)

I agree. I think his car only has 20k some miles on it, too.

chazman

iTrader: (4)

. I don’t know. But I’ve had cats fail without explanation. And the symptoms were very much like yours, rev up to 2500-ish and hit a wall. Sounds like something is restricting flow. Either air/fuel going in or exhaust going out.

ray jr

iTrader: (2)

here is a fact about clogged converters and low mile cars .. right before i sold my 85 iroc with 5,000 miles on it a few years ago the car all of the sudden starting running like crap .. i decided it was the converter and took it off and gutted it and the car ran perfect after that .. so low mile cats can clog with no warning ..

dagwood

iTrader: (5)

Huh......so they must evidently deteriorate and fall apart on the inside, then? I stead of being plugged with carbon and junk?

I had a new Z28 back in 2000, and after about 4k miles it started running like absolute garbage. Same deal.....get it up to like 4,800 rpm and it would fall flat on its face. After about 35 days in the GM dealership......they finally figured out the problem. A baffle broke in the muffler and was restricting exhaust flow. They put a new muffler on it and she'd sing at 6,300 rpms all day long lol. After all that time in the shop without fixing the problem, I was looking into Lemon Law....I was super pissed and that was all the problem was lol

chazman

iTrader: (4)

Food for thought, when GM deleted the cat on the Euro bound Z28E, the LG4 jumped from 145hp to 165.

dmccain

iTrader: (2)

Sure sounds like the cat to me or the fuel filter Sofa mentioned. I would also NEVER put ethanol blend gas in a car that sits any amount of time, or mower, boats, etc for that matter. Wish I had the extra $ id love to have your 82 it's probably my favorite car on this board. Good luck im sure it's a minor problem.

chazman

iTrader: (4)

For about 90% of us, not going with E10 is not an option.

sofakingdom

iTrader: (1)

Yeah the cat on the LG4 was the old "pellet bed" type... total POS. When the L69 cam out it was one of the first that had a "honeycomb" style. Blew me away the first time I looked through mine and could see right through it.

Still, eeeeeeezy enough to make an intelligent guess as to whether it's the culprit or not.

Ethanol blend gas is almost totally unavoidable these days. Some places less than others but still. IMO its effects are greatly exaggerated by people with the usual Neandertal aversion to change. The same kind of people that put "breathers" on valve covers on street cars, and "rip out all the computer junk" from everything they get their p****-pullers into. The same ones that perpetuate all the Friday night McDonalds parking lot monkey-spank.

scottmoyer

I can put the car on the lift and see how easy it will be to put on an exhaust kit. To keep the car legal, I'll look into a high flow cat and new muffler, but keep the exhaust tips as they are for that factory look. I'll also call the other shop and see when I can get the carb adjusted or rebuilt.

As to the comments earlier about learning how to rebuild the carb myself, I really don't have the time or the energy to figure that out. If mechanics have been working on them for years and can't figure it out, why would I think that I have a clue. Plus, I wouldn't be doing it again any time soon, so I know I'd forget what I just learned. I'd rather pay the "experts" to do these complicated fixes like trans and carb, I'll enjoy the other stuff I have been able to figure out and do myself. Like painting a car, there are people that specialize in it and I don't want to think I can do a better job than they can. Lastly, it was 95* and felt like 108* here today so I really have no interest in killing myself doing some of this.

burnout88

The cat is a likely culprit! But if you need the carb redone send it to Cliffs.
https://cliffshighperformance.com/

JA85z28 used them and was happy with what they did on his rebuild.
https://www.thirdgen.org/forums/auto...onversion.html

daveb123

Just now seeing this, as an old school Q-jet guy and 82 LG4 owner of 27 years, I've got some thoughts. First the shockingly low boiling point of 10% ethanol gas cannot be over estimated in a carb'd car. My 82 that otherwise runs fine runs like garbage after 10-15 minutes of running in warm weather. I can shut off the engine and hear the fuel boiling in the float bowl when it's 85F or warmer. No symptom when it's cooler, that ought to be easy enough check in your car. Also as others have said, the pellet type converters are unbeliveably restrictive at best. Back in the 80s I saw plenty of them clog up with low miles, 20 or 30K. When I removed it from my car, the results were astounding, it felt like two plug wires had come loose and were re=connected!

scottmoyer

Ok. Carb and cat will be looked at. Thanks.

SolarGoldRaptor

I had a similar issue on a '79 Mustang, ran fine under 50kph, but struggled going faster and couldn't get past 100kph, misfires, high fuel consumption. After rebuilding the carb, replacing all the fuel hoses, the filters, the ignition, there was one last thing left to check : the timing on acceleration. Put the strobe light, turned it on, the advance didn't move. I tested the advance vacuum and it was fine so I pulled the distributor and took it apart. And indeed, the advance mechanism was rusted out and barely moved. After cleaning and greasing, the car ran perfectly. So check that, it was a free repair.

scottmoyer

I will definitely check the distributor. The mechanic did state that replacing the carb, intake and ignition system would solve my issues, so maybe the distributor is culprit. Like you, I can find that out when I adjust my timing.

Drew

iTrader: (58)

Yikes, I'm late to the party... Problem with the Compu-Qjet is that even when they were current, the 'fix' was to throw them away and get a Qjet from a non-compu-controlled Chevy and drop in a vacuum HEI. Before long they went the way of the Dodo and EFI took over, so if you've got a mechanic that knows carbs, they probably don't like the compu-Qjet, and if they know EFI they don't like any carbs. Just the way it is. If someone you trust knows someone they trust that is reputable for fixing those carbs, it's probably not a bad idea to give it a shot. Otherwise, classic wisdom still works as well as it ever did. My junkyard 78 Camaro carb in my 83 Camaro ran great, when something or other broke, a remanned 78 spec carb took over and it ran great until the car moved on. If your car wasn't as nice as it is, I'd be very tempted to dump the computer controlled carb, but given it's condition I'd be willing to risk an expert rebuild.

Sofa is right on the money (gee, imagine that ) 82 still had the pellet style cat. The cats that gave all cats a bad reputation. Take it off and hide it somewhere with the rest of the OE take off parts, and get a modern honey-comb style cat. While you're at it, I'd bolt on a set of HO/TPI manifolds, and probably a sweet mandrel bent Magnaflow Y-pipe, and so on. While I understand that probably doesn't really fit with your goal, it'll be a relatively easy bolt on that you'll feel in the seat of the pants.

Not that I believe any of the above is necessarily the cause of the sluggishness. But if I was leaning in those directions as possible points of interest, that's what I'd be looking at. Good luck mang.

scottmoyer

Thanks Drew. The mechanic is exactly what you said he is. He is an old school carb guy that told me to junk the computer and go with a non computer controlled carb and ignition system. His recommendation was to replace the carb with a Holley carb, Edelbrock intake, HEI ignition system and call it a day! He then said to do a full exhaust including headers all the way to the muffler. With the car being for sale, I don't think I want to spend that much right now, but I am willing to get it running right with current configuration, but replace whatever might actually be bad.

So, I'm going to start with the timing and see how that goes. From there, I may attack both the carb rebuild and replace the cat, as it's possible the car needs both. Finally, I'll address the distributor and ignition system.

Drew

iTrader: (58)

There's a certain wisdom in the suggestion... Most entry level Edelbrock intakes are low enough profile to fit under the hood, and have provisions for a lot of stuff the stock intake would have, while still being (technically) an upgrade. I'm not sure about 82, but at least by the mid 80's the LG4s had an aluminum intake from the factory. With the stock LG4 cam, a Qjet, etc and the goal to stay under the stock hood, I wouldn't consider most aftermarket intakes to be worth the trouble. I wouldn't change it unless switching to a square bore carb.

Holley carbs are EASY, and effective. They usually run better than the Carter style carbs, too. But on a 305, the small primaries of a Qjet make for great response from idle without bogging, and great gas mileage if a person stays out of the gas. Obviously if a person has a lead foot, the absolutely MONSTROUS vacuum secondaries on the Qjet flow plenty to support power. They're just a hair more finicky and specialized over the Holley square bores. The fact that they fit and everything bolts right up, makes the Qjet the ideal substitute for a Qjet, regardless if the Qjet is completely mechanical or the compu-feedback version.

I have a hunch that if you fixed the sluggish throttle response, given your history with the car, and the effort that has gone into it, you might just reconsider selling it and decide to hold onto it awhile longer. In which case, a little spent on the exhaust, might not be a bad thing.

dagwood

iTrader: (5)

I think your car is way too nice and original to change the carb, exhaust, etc. I still say have the factory carb rebuilt, and if anything, gut the cat and put it back on. I'll say it again, my carb guy rebuilt the carb on my 82 and I reinstalled it and it ran perfect. I didnt even need to adjust anything. And he's cheap. He just loves to do it.

jmd

iTrader: (4)

Post here instead of the carb subforum, eh Scott?

If your boy didn't learn the E-Q-jet(s) any time since 1979, he's not going to start now.

At a minimum starting point, learn how to adjust the secondary air door for the upper rpm range respones. Fun, noisy, and helps keep the faith that "ditch the Q-jet" isn't the way to go.

The rest of the Q-jet is easy to service if you have the desire. The tools are a little tricky to chase down, but they're out there (eBay) with effort.

The only frustration point for me was dropped airhorn tube(s). My stolen '87 had the original Q-jet from my '86. That Rochest had over 250k on 2 rebuilds. Ethanol is not scary.

1MeanZ

iTrader: (9)

Here is my $.02. start with the fuel filter, then check timing (base and total advance), then check the cat. My experience is similar to Charlie's, and I'm near certain your cat is bad, but the other stuff is free so do that first. I've had FANTASTIC luck with magnaflow cats. I've purchased probably 10 of them and not one of them has ever gone bad on me, but all my cars are EFI and run pretty clean.

I urge you to do the carb LAST, as its likely not the problem. If you have to get into the carb, do a rebuild only, don't start changing stuff inside. Only thing I'd adjust is the rate the secondary air doors open, and that's only if you have the dreaded quadrabog. Since the engine is stock, leave the jets and metering rods alone or you'll create other issues.

scottmoyer

Quick update...Orlando has been very hot this week with a daily heat index of over 110* so I couldn't do anything after work. I did start early today before the heat and made some timing adjustments. I couldn't set the timing correctly as the adjustment plate was missing. So, I made small adjustments.

The initial check showed the timing mark bouncing all over, so I adjusted up until the idle smoothed out and the mark stopped bouncing. Then I retarded it some. The idle was smooth and the it accelerated smoothly and without stutter. Took it for a test drive and found that I had excessive pinging, but I had pull up thru 4000 rpm. I kept adjusting the timing down until I had minimal pinging, but still had acceleration thru 4000rpm. I'll take the car out this weekend and see what it does with premium unleaded instead of the 87 octane in it now.

Maybe later today, I'll swap the cars around on the lift and see what I can do with that cat.

Thanks

scottmoyer

Another update...I filled the car with premium unleaded yesterday and drove it about 10 miles. The car still isn't driving as it should and still might need more timing adjustments. I also pulled the cat off. Is there any way to tell that it's bad? The pellets still sound loose inside and when put on end, some fell out. A combination of light grey and black.

Any brand suggestions on a new cat? All other exhaust plumbing will remain stock, so it will just be a cat swap.

jmd

iTrader: (4)

85 Vette / L69 style 4 bolt inlet/outlet, as long as you can find one that is not necked down in between the in/out flanges. No reason to stay with the ill-flow LG4 parts.

1MeanZ

iTrader: (9)

For a replacement cat I'd go with a Magnaflow or Catco unit.

scottmoyer

Ok guys, I'm back with more issues regarding the cat. I ordered the Magnaflow and it won't bolt up, even though it says direct fit. The part number on Magnaflow's website is 93418 for the 1982 4 speed 5.0L. The pipes are a direct fit, but the air tube on the car ends a good 6" before the air tube inlet on the cat. Also, the rear mounting plate on the cat doesn't have any nuts welded to it, so the factory bolts can't be reused to mount this. I also found that I can't mount it to the body mount as there are two holes to mount it, but only one, unthreaded hole on the cat.

In keeping this system as original as possible, does anybody know a better part number cat that is a direct fit for all mounting, even the air tube? Thanks.

burnout88

I know Walker makes replacement cats but I have no personal experience with them. They also make an air tube extension but it is a universal.

scottmoyer

Update!! I installed the Magnaflow cat and removed the body mount entirely. The new cat is only about 5 pounds, so the bracket isn't necessary. I finally got the car on the ground and took it for a test drive and would you believe the thing pulled all the way up to 4k. YAY. You guys were right that the cat was my problem.

I need to find a cap for the AIR tube, or I need to find the extension to connect it up. The car also sounded so much meaner. I guess the factory cat was so restricting that nothing was getting out.

I plan on setting the timing again now that it can breathe since I set it by adjusting it and test driving it. The timing guide appears to be missing. Maybe my carb guy did know what he was doing after all.

burnout88

Awesome! Are you sure the timing tab is missing? I remember on my LG4 it was mounted at the 12:00 o’clock position and very difficult to see. You basically had to get up on the nose of the car and look straight down through the water pump to see it. It’s odd that on a low mileage car it would be missing.

Here is a link to the walker universal extension. Looks kind of cheesy.

scottmoyer

I can't say that the timing tab is missing, but it's not where I expected it to be. I'll go back out and check it again. I did order an AIR tube extension from my local parts supplier. I'm hoping it's not the cheesy looking one that I've seen elsewhere. My supplier is a die hard 3rd gen guy, has an '86 IROC-Z and knows the story of this car's originality, so I'm hopeful he's getting me a good setup.