Anyone here prefer the ol' Q-Jet? Are they as hard to tune as rumored? Thought I'd as the C3 community as they were OE until the CFI year. I'm contemplating carb choices for a C4 conversion. Last Q-Jet car I had was a 1978 Olds Delta 88 350, in stock form it did quite well and made a terrific noise when you mashed the pedal.

 

Many of us prefer them although they are no longer available new.
They are one of the best mechanical mixers ever produced.
STAY AWAY from box "reman" units.......
Our member here Lars is an expert on these Q-Jets and can answer anything you may need to know and then some....
I keep three or four on my shelf for myself and customers.....I look for super nice cores and buy them periodically.....
I have an Edelbrock Q-Jet 1902 on my wife's 82' Z-28 and it is flawless......

Jebby

 

Why go from a TPI or CFI Corvette back to a carburetor powered Corvette? I have a 1988 C4 and I absolutely love the TPI system it came with. Once they are operating properly they do everything pretty darn well. If you have either a CFI or TPI the best thing would be to get the original system working properly. There are plenty of people with lots of experience at getting the TPI systems working really well on the C4 section of this Forum. My 1988 C4 will even get up and over 30 mpg on flat highways while the AC and Stereo are cranking.

Crossfire equipped Corvettes are not looked on favorably by some because of their unique systems. There are a whole lot of guys on this Forum with very fast CFI equipped Corvettes and they are more than happy to help to guide you through the hurtles. I personally had some issues with my TPI system at first but I quickly learned how they work and then it was fairly easy to get a good reliable Corvette using the factory TPI system. The only negative thing about the TPI Corvettes is that they fall flat after hitting about 4500rpm but on my 1988 that is happens way past the Hand Cuff zone in my home state of Virginia. I have a fast C3 for getting kicks with but when I get behind the wheel of the C4 it is a totally different experience and is a lot of fun to drive. Unfortunately there are many asian cars that can beat a TPI Corvette but they are not driving a C4 with all its comforts. I have a buddy who offered me a pair of LS3 engines that I could have dropped between the wheels, I did not take him up on it because I like the simplicity of a Corvette with a plain old small block with a distributor I can adjust. There are plenty of reasons to put an LS engine in one But if you want a LS powered Corvette there are lots of C5 and C6 Corvettes out there that are cheap.

By the amount of work and expense of switching a C4 back to a carburetor you could probably get a really nicely running Corvette and still have the more efficient operation of a Fuel Injected Corvette. Removing the EFI systems will hurt the value of the Corvette and make it very hard to use on the roads in some states. The same thing goes for when people remove the Atari dashboard the C4's came with, what is a C4 if it isn't all the 1980's flavoring and design? I put a high flow catalytic converter and a Chambered Exhaust on the C4 and it sounds really ferocious despite only having 255 hp. It may not be fast but the "fun factor" is sure there.

Please don't take my inquiry as negative as it is your Corvette and you can do anything you want to it. I am just curious why you want to step backwards into a carburetor?

 

I'm getting close to 60 and, like many in this age bracket, I felt a compulsion to find a car like the ones I drove and tinkered with in my earliest years of driving. I looked for a 60s-70s F-body and Mopar B-body and was shocked at the entry price tag. I came across this 1984 C4 by accident, it's a beater with hacked wiring all over, terrible rubber door seals, and awful primer, it starts and runs at 2k RPM with idiot light blaring. However the engine doesn't smoke or knock and transmission shifts right into gear. I got it for less than the 700R4 sells for on ebay so I look at it as a blank canvas to make an early C4 without the constraints of EPA focused Crossfire 350 restrictions.
I also just completed a 1985 Kawasaki restoration with an overbore and tuning carbs is something I have an affinity for.

 

Hello again Garage Hermit,

I under stand your plight as I too am already 64 and have had 5 crushed discs in my lower back for the past twenty five years. I bought my First Corvette in 1991 and it was a a pretty rough 1968 Corvette that started life as a L71 Corvette. Being a early 1968 means it is a Convertible and over the decades I have restored it to a good driver with the 427 set up like a L88 Engine. It has been a labor of Love and lots of $$ but the final results are a blast to drive. A while back I was tired of dealing with ethanol and carburetors so I bought a Holley EFI system and installed it in place of the carburetor. I have five carburetors that have been on that engine over the years and the best was still more work than I wanted to have to deal with. Now my 1968 is fuel injected and still a blast to drive. getting a Fuel Injection system dialed in was not too bad even for a person who had never installed one on a car from scratch.

My wife and daughter wanted a Corvette so we bought the 1988 C4 and it took a bit of a learning curve to learn about. The EFI system on that car is the TPI system like I mentioned earlier. My C4 is more of a highway cruiser and I use it to go to church in and the likes. The C4's are really neat cars in their own right.

Your having a "First Year" C4 makes that Corvette kind of special, especially in the eyes of collectors. Have you looked or asked anyone about the running issues the engine is having? The crossfire is a pretty straightforward Corvette engine and if I had one I would be eager to get it back to a good drive-able condition. It is not as complicated as the TPI systems and the cost of the parts is not that bad either. Have you purchased the Factory Shop Manual for the Corvette? They are available in print for about $85 and on DVD for about $35 and the factory shop manuals are the absolute best for the C4's. They are full of trouble shooting charts and very helpful.
Very few C4's have any kind of good rubber on them as the factory used a lot of junk back in the day. I have replaced all the seals on my C4 and re-painted it myself. As far as wiring goes they still make all the harness' in reproductions and are very affordable. If the basic engine has good compression and the transmission works it would not be that hard to make your C4 run like it did when new. I am on the C4 section of this Forum a lot and I know from personal experience that the cross-fire engines are pretty straight forward.

It really boils down to what your plans and time allow. I have a sand blasting cabinet and a couple scanners which have made working on the fuel injected cars pretty easy. I remove the parts and then clean them, repaint them and re-install them. The biggest problems I have had with my engine was the EGR went south causing the emissions to go wacky and the car failed the emissions inspection in Virginia due to Higher Nox levels because the bad EGR was stuck. I ended up replacing the fuel injectors and the Fuel pressure regulator along with several other parts. The reason the job was no fun and a lot of labor was due to the silly TPI intake manifolds. You don't have the parts like the TPI cars do. Yours is essentially two throttle bodies working together and the fuel pressure is lower than what the later cars need. Just be glad you did not buy a LT1 Corvette (92-96) as those are potential nightmares. Whomever thought of putting the timing controls under the water pump should have lost his or her job. My son-in-laws best friend got a really amazing deal on an LT1 and all I could say was he should have walked away... Your Crossfire is a much easier system to fix as it is much simpler than the later systems. Being a carburetor person you should have no problem with two throttle bodies. The toughest thing is to have a scanner that works with the OBD1 cars and those are few and far apart. I bought a system from 1320 Electronics that works on my laptop and lets you see what is happening inside the system. A very handy tool that was not too expensive.

I used to road race motorcycles on the east coast back in the mid 1970's. I know what you are talking about when playing with the four cylinder engines and their individual carburetors. I still have a 1984 Yamaha RZ-350 water cooled twin cylinder and love playing with it. They did use a computer back then to control the power valves that essentially change the size of the exhaust port as the engine rpm's climb. Today's gasoline has ethanol in it and it forms little white ***** of paraffin inside the float bowls which eventually stall the cylinder out. The engine never gets hot enough to keep the paraffin in liquid form and having rubber intakes makes the problem worse. Where I live I have to go about an hour drive to buy pure gasoline and it is a royal PIA. I have worked on everything from my BSA 441 Victor single cylinder to the Honda CBX's. My all time favorite was the 1971 Kawasaki H2 which was pure speed, that bike would go from 0-60 in 2.3 seconds if you could hang on. I loved Motorcycles and when I got married my wife liked the idea of a Corvette over another motorcycle.

If there is anything I can do to help be sure to PM me. I think that you might have something worth fixing up and it would be worth something down the road. Especially if you paid less than a 700R4 costs on Fleabay. Take a look online and ask about the crossfire and see the kinds of help you will get on the C4 segment. There are some really crazy guys on their who LOVE their CFI Corvettes and they are very good at solving the strange quirks that appear in them.

Just remember that old guys need to have fun as well, and you are never too old to have a nice Corvette. Prices today are ridiculous on anything from the early C3's with Chrome Bumpers. The later C3's post 1974 are not that bad price-wise and occasionally there are some really nice cars at reasonable prices. There are some good deals every now and then, I have seen some high mileage C5's and C6's that are very reasonably priced but they are more modern than the vehicles that we saw growing up. I always admired my Uncles 1969 BB Convertible as that was the coolest car I had seen while growing up. In High school there were plenty of Boss Mustangs and BB Chevelle's with Cowl Induction. Today the guys that had them all drive Kias and I finally have a Muscle car....

Best regards,
Chris

P.S. There are also several people who have done what you are thinking about and put carburetors on the CFI engines. You might find more specialized help on the C4 part of the Corvette Forum.

 

I really can't do justice to your post Chris as I'm tied up at work but the information and experience is appreciated. I looked for Crossfire intakes but they're just not being made anymore.

 

The best source for ANY kind of information on that Crossfire system is going to be from the Factory service manual. Me I tend to do better with the old fashioned hard copy of the set. For the 198 there are two books in the set. One is al the mechanical stuff and the second book is just the electronics. They are priceless when you are working on a C4.
They haven't made any new Crossfire manifolds in many years I suspect but there followers who have them know all the tricks on how to extract all the HP you can with the system. They are making them into 12 second cars and that is probably faster than many of the toys we played with in our youth.

Like I mentioned I would start by posting your issues on the C4 Forum but put Crossfire in your title. You will find more information and help than you would be expecting but there are many Corvette Forum members who absolutely love the CFI system used on the 1984 Corvettes.

Helm Publishing produces the FSM's in hard copy and RockAuto sells the DVD with the manual on it.

 

The thing about the Crossfire system is the just terrible intake that they were bolted to.......this intake was designed solely for torque production but failed miserably at that too.....the intake ports are just blocked off too much.
On a bone stock 82' CFI Camaro......a 2101 Performer intake, Edelbrock headers, and a nice Q-Jet is worth 1.5 seconds in the 1/4 mile......the 84' Vette is not as bad due to it having a much better exhaust system...but still will pick up .5 to .7 seconds in the 1/4 mile with a 2101 and a Q-Jet......
The CFI isn't a bad system.....it just chokes the engine off too bad......the Renegade intake is the bomb for them,30-40 horsepower out of the box, but sadly...is no longer available......our member Buccaneer here made them and can't get anyone to cast them to his standards now.
I have an 82' Z/28 that I converted 14 years ago to the parts I mentioned......it is hard to describe how much better it runs compared to the Cross-Fire setup......simply no comparison.

Jebby

 

GM's engine department in the late '70s - early '80s made some horrible stuff. Take the 301 Turbo T/A intake and heads as another example.

 

1981 was an absolute low point in automotive history.....Chrysler's Lean Burn, Ford's VVT carb, the Turbo T/A, the CCC feedback system on ALL carburetor equipped GM cars......
The CFI was nothing like them at all....it was a brilliantly simple system that pre-cursored the millions of TBI equipped GM cars well into the 90's.......but how they got that intake past engineering is a mystery.

I am not encouraging you to remove the system......but if you ever want to make power, the intake has to go.

Jebby

 

My vote would be to keep the CFI setup, but that's just my personal opinion. As suggested above, get on the C4 tech/performance section for detailed help! The stock CFI intake needs to be ported....a lot, the casting in stock form is an absolute joke, that's for sure!
But another option, if you don't want jump through all of the CFI hurdles, is instead of a carb swap, you could change the intake and throttle bodies to a single, larger throttle body intake, like the ones used throughout the '80s and early '90s. Or a modern EFI aftermarket system like mentioned above.
Not that the '84 will ever be in the same league as the C1s, but there was a time when everyone was taking off that "junk" mechanical fuel injection and swapping to a carb or carbs....in hindsight, maybe not such a good choice. The '84s need to be appreciated for what they are, what they did for the evolution and future of the Corvette family!!! The CFI was the only engine option for '84, rated at 205 H.P.(net), this was more H.P. than the standard Corvette engine for a decade (give or take) and it's always ripped on for it's "low" H.P. But in reality, made more H.P. and it was faster than nearly all stock L-48 C3s, furthermore in 1984, put up against what Porsche and Ferrari were making, it performed the best! The 1984 L83 CFI Corvette is the perfect example of, it's not about how much horsepower you make, but how efficiently you can get it to the ground and in my opinion, the most fun you can have with 200 H.P. (obviously I'm a little biased)
Good luck with whatever you decide to do, anyway you choose, you will have fun with your vette and that's all that really matters👍

 

Jebby,
Are the bodies of Q-Jets of a particular year the same no matter what Chevrolet model they were used on? For example, will a 1970 Camaro, Chevelle, El Camino, etc., Q-jet have the same internal passages as a Corvette Q-Jet where only the jets and rods are different?

 

No. Air bleeds (both mains and idle) and internal calibrations differ significantly from one body part number to another. Some Q-Jets, used on the same engine in different model cars (some years, the same carb was used on Vette, Nova, and Camaro) will be identical. But if the carb number is different, the air bleed calibrations will be different. Air bleed sizes have a much greater effect on a carb's operation that the jetting component sizes.

Lars

 

I went with a Street Demon, I like the design and low height to match with the intake. Wasn't aware they made a spread bore.
Thanks for all the input


To the stay with the CFI suggestions I'm not going to try to tune and, more importantly, rely on 38 year old speed density electronic engine management.

 

Thanks Lars. I thought I recalled reading that here but couldn't locate the info.
Re: your comment about some years using the same carb on Corvettes, Nova, and Camaro: They'd carry different stamped numbers though, right? How can one determine a cross-over carb that's identical?

 

If the stamped number is not the same, the carbs are not identical. There is some difference in configuration or fuel metering that is different. There are several years that the same carb was used on the Vette as on other vehicles, and in these cases, the carb number is the same. Some examples include:

In 1972, carb numbers 7042202, 7042203, 7042902 and 7042903 were used interchangeably on all 350-equipped (standard engine) Monte Carlos, Chevelles, Novas, Camaros, Corvettes, and El Caminos (only difference in application on these carbs is auto or manual tranny and Federal or California emissions). You cannot tell if a 7042202 carb was originally installed on a Monte Carlo or a Corvette, but if you're looking for a rebuildable "core" on eBay, you'll find that all 7042202 carbs are "Corvette carbs." They made about a million "Corvette carbs" in 1972...

In 1973, carb numbers 7043203 and 7043202 were used on standard 350 engines in full-sized Chevrolet, Chevelles, Camaros, Monte Carlos, El Caminos, Corvettes, and Novas. Again, you'll find all of these carbs being sold as "Corvette carbs," even though about a million of them were built... The 7043212 and 7043213 carbs were used in the high performance 350 engines in both Vettes and Camaros.

In 1974, the Vette and the Nova shared the same carb numbers on 350 engines. Both the Vette and the Nova used the same 7044206 in automatic cars and the 7044207 for manual transmission. They likewise shared the same carbs for the California cars (7044506 and 7044507),

In 1976, the M4M style Q-Jet was common and shared with the Vette and the Nova on the standard engines: Carb numbers 17056206, 17056207, 17056506 and 17056507 were shared with Nova and Corvette. The L82 engines received a unique carb number.

The common, shared carb numbers continued through the end of the '70s with the Corvette sharing the same carb numbers as the full-sized cars, Chevelle, Monte Carlo, Camaro, Nova and El Camino. The only Vette-unique carbs were the L82 carbs, and these carried a different number to designate the different calibration on the high performance engine.

 

That, right there, is worth the price of admission! Thank you Lars.