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My Corvair reminded me that rebuilt parts can still suck

I have long been an advocate of the humble carburetor. When you take the time to understand its jets and venturis, the result is an easy to tune and rewarding existence. I had to eat my words recently though, as my 1965 Corvair Corsa gave me nothing but headaches for weeks on end. What hurt more was that the headaches were self-inflicted.


This is a companion discussion topic for the original entry at https://www.hagerty.com/articles-videos/articles/2019/05/24/corvair-rebuilt-parts-can-still-suck
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As Dick O’Kane said in his wonderful book “How To Repair Your Foreign Car,” “Carburetor is a French word meaning ‘leave it alone.’”

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Old, used carbs are a dice game. I will not invest more than some time, a good carb cleaner soak/scrub, and the cost of a rebuild kit in ANY old carb. I learned my lesson with remanufactured carbs (rebuilt just like you would at home, just “painted up” to make them appear new) and even professional carb restorations (complete with rebushing and “the works”) are, in my experience, a big crap shoot! I once spent over $300.00 having a carb restored … twice … only for it to end up in a parts box and replaced with a good used carb that cost $25.00. I would honesty take my chances with a new, “China” carb with a guarantee than to spend money restoring an old, poor running or condition unknown carb. If your determined to have a carb restored, do yourself a favor first. Soak the carb out and rebuild it with a kit first, install it, and see how it works. If it runs great, either live with it or then send it out to a known quality carb restoration guy. If its a dud, look for a better core, soak it and transfer the carb kit over and try it until you find a winner BEFORE sending it out for a resto. A 30 plus year old carb has endured a huge amount of heat cycling though its life. These things are aluminum, old aluminum at that (the technology of metal manufacturing has improved vastly over the decades; provided that a new carb has been cast from quality metal stock). These old carbs will warp over time and after extreme heat (if a carb has ever been on fire, even for a minute, it’s toast and only fit for the trash can). Yes, some will argue and defend their carb resto guy and I will not argue that some are better than others, but unless the resto comes will a trustworthy complete one year satisfaction guaranteed, money back, we will pay all the shipping to try to make it right warrantee, I wouldn’t touch a resto on a known bad or untested carb with a 50-foot-pole!

As a Corvair owner and helper with the local club projects, I’m keenly aware of “rebuilt carburetor” problems. Adding the secondary idle mixture does work to promote a smoother idle IF done correctly as documented by Steve Goodman @ Rear Engine Specialists in Colorado. I’ve done the mod myself and was pleased with the result. I do my own carbs and I’ve found after about 5 decades that some of these old carburetors are beyond rebuilding. Corrosion, cracks, deformation from over tightening the hold down nuts. The other issue is few, IF ANY, rebuilders actually test the “rebuilt” on an engine. That said reputable folks will exchange a carburetor if it is bad. Did Kyle contact the rebuilder???
The other issue is aftermarket parts quality, not just a Corvair issue. I often have to fix or modify aftermarket equipment to make it work. After market ignition systems are a real headache as some have vague generic instructions and folks do not install them correctly. I just got two cars running that the new owners bought cheap because the previous owner (or their mechanic) could not get to run properly. The issue was simply mis-matched/incorrectly installed electronic ignitions. Once sorted the cars ran great.

Sadly I see more and more folks giving up on “old cars” simply because they can’t get them to run, and are not able find a qualified mechanic who can do a proper job.

BTW - I don’t charge for the time I contribute help the members of my club.

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I bought a 1965 Corvair Corsa brand new in the spring of 1965. I never messed with the carbs except for replacing the octopus style air cleaner with 4 hogs hair air cleaners. After a while I was experiencing issues when acceleration. It seemed as though the carbs weren’t balanced. I noticed that the linkage was worn and I couldn’t make compensation for the ware. I took it to the dealer and their shop Corvair specialist solved the problem by thinking outside of the box. Instead of replacing the linkage, he built up the worn areas of the linkage with weld and polished it. He said that the linkage would not ware out like the replacement linkage and it cost me a fraction of the cost of new linkage. The carbs were in perfect balance after that. I autocross this car on a regular basis until I made the worst car mistake of my life: I traded it.

During my time as an automotive technician, I became well known for my carburetor work. You can’t achieve success without a good core. If the carburetor on your vehicle worked well for a reasonable length of time, do not exchange it for a factory rebuilt unit. Find a well known custom rebuilder & have your OEM carburetor overhauled. Too many times, an automobile came into my shop with an exchange carburetor that was not suited to the application. Many factory rebuilt carburetors were found to have worn out throttle shafts or were missing parts.

Over the years there have been a few linkage mods. Now a replacement linkage is made by Roger Parent (posts on Corvair Center forum) that is precise and handsome. The only issue it it is has numerous adjustments to make during installation. The linkage does come with good instructions. Definitely for for someone with mechanical skills.

I’ve done a couple installations and once sorted the linkage works very well.

That is a good point about having a functional core.

The modification Kyle did was to replace the secondary carburetors with ones that SHOULD use a simple Corvair 62-63 carb BASE. If he just installed primary carbs from a 64 or later Corvair on the secondary positions, then that usually causes idle problems.
BTW - new throttle shaft kits are available for the Corvair carburetors and almost always need to be replaced.

On my 1966 Corsa convertible that I first bought in 1/68 and found again in 2014, I sent all four to the Carbmeister guy down in Florida. The fellow who redid my entire drivetrain put them on the engine and it didn’t run right at all.
Tested several times – still bad.
On the phone with the rebuilder talking it all through, and still didn’t work properly.
He said to send the secondaries back, which were replaced at no further charge and it ran and tested just fine.
Something about a reputable rebuilder seems important.

Why I haven’t worked on my own car in years: installed an exchange master cylinder, but the brakes still didn’t work correctly. After replacing most of the brake system I gave up and drove the car as-is for years. Eventually I had to replace the master cylinder a second time - and guess what, the brakes worked fine after that. The actual problem was simply that the aftermarket master cylinder was defective from the very beginning. A few years later, replaced the master cylinder on an MR-2 clutch and no matter how many times I bled the brakes the pedal wouldn’t get firm. Spoke to a Toyota mechanic and he said that the problem was obvious - the exchange cylinder was defective. Replaced it and had the system working in 5 minutes. Got a rebuilt water pump for an 80’s era Dodge that was in worse shape than the one I was trying to replace. Had a Pontiac Fiero that kept going through clutches; I replaced the master cylinder, slave cylinder, etc. but it kept happening. Finally found out from a transmission expert that Pontiac had produced a series of fixes for the clutch issue that were incompatible; if you used a Change 1 master cylinder with a Change 3 slave cylinder for example, the clutch would wear out prematurely. But only a factory trained mechanic would have been aware of this. Yes I got my money back for all of the defective parts but nobody gave me my time back.

Corvair carbs aren’t rocket science, but they are science. Always rebuild your original carbs if at all possible. Soak the disassembled units overnight in really good toxic cleaner intended for that purpose. Wash clean then use carb cleaning spray and fine wires to ensure that EVERY passageway is clear. Use a known level surface and fine emery paper to sand flat every mating face. Use the old steel check balls and a hammer and punch to restore the check ball seats. Rebush and install new throttle shafts as necessary. Use a high quality rebuild kit with Viton rubber parts. Repair or replace worn linkage parts. Finally, make every adjustment in the exact order and manner described in the kit instructions. If you think a few thousandths of an inch one way or the other won’t matter you are wrong. A carburetor is an analog computer carefully programmed to mix gasoline and air in precise proportions under a wide variety of driving conditions. Messing up any step in a rebuild is like putting a bug in the carb’s control code. It’s ultimately not that difficult, but you have to be detail oriented and respect the technology, which is not as simple as it might first appear. When you are ready for a master’s level experience, try a Quadrajet, a task made easier with a vintage GM Line 9 Catalog and the dedicated set of factory tools. Fuel injection is simple in comparison!

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You are 100 % correct!! When I was a mechanic my specialty was Q-jets. I customers come from miles away by word of mouth. You can not believe the messed up Q-jets that used to come in. I actually opened one up that had a bunch of parts just laying in the bottom of the float bowel. I also used to modify Q-jets for really good customers. They will rival any Holley when properly set up. when I taught auto shop I taught some of my more advanced students how to do Q-jets. And, your right, modern injection is simple compared to Q-jets.

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For a few months I worked as a phone tech rep for a large company that did rebuilt carbs. I finally came to the conclusion that the workers must be sitting at a table with a selection of parts and a completely assembled carburetor to use as a guide. Times when I went to the file cabinets looking for info on a particular carb often ended up with no file folder in the drawer.

Often misunderstood, the Q-jet was the pinnacle of 4-barrel evolution. Sure, you could make as much ultimate power more easily with a Holly, AFB or (perhaps) even a Thermoquad, But nothing could touch the fuel economy, part-throttle response and overall driveability of a properly set up Q-jet. And when the air valves began to roll open and feed those massive secondaries, it was as though heaven’s own horsepower chorus had come on song. Not many had access to the parts, knowledge and patience necessary to fine tune Q-jets for modified engines, but done right it was an amazingly accurate and versatile fuel metering device.

:+1:
A variation on the same theme, I learned that they called them “carburetors” because “rotten bastards” was already taken.

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I like keeping things original but sometimes technology has made things far too good to pass on. Take the originals off. Put them on display in your garage and install a set of these.

Technology is great, but costly sometimes.

The cost is up there when you figure you’d need four of these. But how much is your sanity worth?

Adding idle circuits where they weren’t intended didn’t help either. Too much gas (and air) at idle surely wouldn’t help. That it ran good at 2000 rpm indicates it was getting too much fuel and air, not just air. You might have been alright with the new carbs had you plugged the idle circuits. While some cylinders may run a little lean at idle due to carb placement, GM made the secondaries without idle circuits for a reason. Not being able to adjust four idles on standard carbs down enough may have been it…

@robertperdoc - I did not contact the rebuilder. I purchased the secondaries second hand, and the person who purchased them first let them sit on a shelf for a handful of years before deciding to sell them.

I’m not holding it against this particular rebuilder. I’m chalking it up to learning a lesson about doing it myself rather than trying to shortcut the process.

Also, I’m not giving up on this car anytime soon…

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@pedersen.karl - I would also likely need to set up the programming to make all four play nice with each other, since those are meant to be a stand along system each. There is the option of a single carb or throttle body on a spider intake, but I’ve never been a fan of the looks. Call me vain, but I’m not in love with this car because it’s fast.

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Kyle - If you don’t have Bob Helt’s Rochester
book, then get it. The book describes the different secondary
revisions - GM did add a fixed idle mixture circuit in 68, but
those are scarce. In Colorado high altitude counties ALL cars
must pass an emissions test. This is why Steve Goodman came up
with using the 62-63 base under the secondary top so his
customers 140HP cars would pass the test. I do recommend using a
solid throttle plate that the secondaries use (62-63 plates
were notched for the idle transition circuit). Not sure what you
bought - years ago some folks tried using primary carbs on the
secondaries and it didn’t go well.

Speaking of Steve Goodman - eventually your
rear wheel bearing will go bad. You need a fixture to set them
up. Without a fixture it won’t go well. Steve Goodman advised me
on building a fixture and I’ve done my own (I’m retired so I can
“play”) and those for a few friends and found some poor
rebuilds. I’d recommend sending them to Steve for a rebuild.
Done properly rebuilt axle goes well over 50K miles. - Enjoy
your car.