My 1974 corvette has the stock engine and transmission in it with the 4 barrel Rochester carb. I would like to improve the drivability of the car and add some more modern conveniences that fuel injection systems offer ect. and my question is would it be worth it just to fix my carburetor or just switch it to something more like a Holley Sniper EFi? The carb on my car works ok, still needs more adjustments etc, but would EFI be a better system to run? I've seen plenty of positive and negative reviews for EFI systems, especially Holley.

The Holley system I'm looking at can be found here
https://www.holley.com/products/fuel...parts/550-511K

Thanks!

 

Are you going to install it yourself ? If the answer is no , then maybe look at just sending your carb to Lars and following his tune up papers for the ignition ,timing. Lots of guys on here have done just that and say there way happy with the result

 

Send an e-mail to Lars Grimsrud (V8FastCars@msn.com) and ask if he would be willing to refurbish your carb. If he will, the result will be 'better than new' operation and performance of the Quadrajet carb. That will save you a TON of money over replacing it with a turnkey EFI system....AND eliminate the headaches of tuning the system to get it to work well.

He is very affordable and will do a great job on it.

 

If you plan to keep it mostly stock, send your carb to Lars, swap the intake, air cleaner, drop in an HEI distributor and install a set of headers.
Your driving experience will improve as will your fuel economy.

 

I am going to install the EFI system my self. I’d like the turnkey option and other things too etc. I can install it for much cheaper than if I took it to a shop.

 

A couple of things to note to install a Holley Sniper EFI:

Benefits/no warm up issues/Good at any elevation
Cost
Installing new 3/8" supply and return lines
Installing exterior electric fuel pump or in tank pump.
If existing fuel tank is reused you'll have to drop it to install the 3/8" return line
Installing a new EFI fuel tank from Holley or Tanks Inc.
Installing new HEI distributor
or
No warm up issues/Good at any elevation
Install this Atomic EFI
Less cost
Easier installation
Watch the tech video of both the Sniper and Atomic.
Also installation of fuel lines with out the body raised or removed is not a pleasant endeavor ( be careful what you wish for).
Or as others have commented have Lars do a number on your carb, gain performance and drivability, save yourself money and potential grief.
Just my thoughts.
Best of luck

 

Cool , no one does better work on your car than yourself. I have a Holley system but it's still in its boxes so I like seeing others do installs of these modern marvels !

 

Eventually I want to go to the sniper system. I would buy the tank that has the pump and sender in it and I already use an MSD distributor. I priced it out and its just over a $2000 investment for all the small stuff. The benifits have all been listed but what you may not know is how good the tuning will be optimized by the computer for performance and fuel economy. If you plan on upgrading the performance in your motor you will need to add an Air fuel ratio gauge to tune yours optimally yourself unless you llke to try and read plugs. If done correctly reading plugs is very time consuming and frustrating. Hotrod garage did a show on tuning and the computer EFI system was within 6 HP of what a dyno tech could get out of the car afterwards. Te guy doing everything manually was over 20 HP off. I have a A/FR gauge and I tuned the carb at idle, cuise and WOT with it, no plug reading necessary. Very convienient and great results. Over 15mpg running on the highway at 3500 RPM which is about 78 mph (3.70:1 rear)

IF you keep the quadrajet, which I run, then get it setup properly with Lars, get a good tune and save that $2500 bucks and put it towards a 5 speed conversion. That is where the drivability will be greatly enjoyed.

Good luck, keep us updated on which way you go. If I could afford it, I would get both so I could cruise to the west coast and not have issues at altitude.

 

If you do this swap, DO NOT put 30 or 40 psi down the length of the car's 45 year old fuel supply line.

 

If you do go EFI you will need to change out the miserable low rise Q-Jet manifold or deal with mixture issues.........these bolt on EFI units do not like dual plane manifold all that well......since there is no carb signal, there is zero need for a 180 degree design manifold (dual plane)......the 180 degree design was created for the sole purpose of increasing carb signal down low on the street.

Jebby

 

If your heart is set on efi, go for it. Don't expect a dramatic increase in performance. A well tuned carb can come close to the performance of an efi. This is why I still use a carb.

 

If you are going to have to change the intake manifold anyway, get rid of those stock heads.

 

Unless you have some compelling reason to go with EFI - new motor, some other major upgrade - why not just dial in what's been on there for all those years?

 

I went from a carb to FAST EZ-EFI. It ran horribly and I went back to a carb. I carburetor never did work that great with my 6 speed. It's very difficult to control fuel at low RPM over a broad range of power levels. Last year I tried the Edelbrock Pro-Flo 4. It's amazing in every-way compared to what I have used previously. Startup, cruise, WOT are all fantastic. The system was about $1700 and included a distributor which is all controlled with an android phone or tablet. I spent about $400 on the fuel system. I used a 1982 fuel sender and a Walbro pump with Earls fuel line for the feed and return. I would use this system again in a heartbeat. The manifold isn't really high and the throttle body is shorter than a carb, so I can fit it under the stock hood. Sequential port EFI is much better than TBI too.

 

The Holley Sniper is probably about the best TBI system available right now. It'd work well for you.

A Pro-Flo 4 XT EFI system would look really cool under the hood, if it fits. Sequential multiport certainly is better than TBI.

 

I am running the Pro Flo 4 too for all of these reasons. Haven't driven it yet but it was installed and tuned when my motor was dyno tested. Fired right up and kept running better each time it was started. Very happy with the results on my 350.

 

No way the ProFlo XT manifold system would fit without a huge hood! It's really tall all the way to the water neck.

 

I switched to the Sniper with the entire Hyperspark ignition system. Super easy.
Better throttle response, no starting issues, no vapor locking, easy warm up. Depending on how built your engine is, you will want to eventually get it tuned by a pro.
I will say that I was disappointed that my fuel economy didn't get better. I think it actually got a little worse. Then again it is a 600hp 496, so its hard to tell.

You will want to get the throttle arm extension because without it the throttle is way too stiff and touchy.
https://www.efisystempro.com/sniper/...ter-lever-1952

I also put in the Holley gas tank with the internal fuel pump. All install was super easy.

 

That was my concern too and why I didn’t go with the XT system. I liked the looks of it but decided I wanted to keep my stock hood which I could with the other single plane manifold and throttle body. So just the regular Pro Flo 4 for me.

 

A lot of opinions/thoughts/points of view and none are wrong. Whatever you do, make it your own & drive it every chance you get. That being said, will provide another point of view from the owner of a mostly stock, second owner 69 350/350, 4 speed car. OP has a stock 1974, a properly set up Q-jet is awesome when it comes to starting, driveablity & performance. Your question, " would it be worth it just to fix my carburetor or just switch it to something more like a Holley Sniper EFi?" I'll align with many of the others and say stick with the Qjet but it is your $$ and your car - do what makes you happy and then enjoy.

Lar's is this forums Q-jet guru and always seems more than willing to help...thanks. However, if your Q-jet is stock, unbutchered and you are mechanically minded....try rebuilding it yourself. Below is a link to a Cliff Ruggles Q-jet book. Read the book a couple of times and give it a try. If you go this route, my one piece of advice is to lay a big piece of cardboard on your workbench and document the pieces as you disassemble. Lay them down on the cardboard, write the name of the part next to it with a sharpie and take a pic with your phone. This step will assist in the reassembly and make you more comfortable with the various components. Cliff Ruggles also sells Q-jet rebuild kits.

Last comment on driveablity - make sure the timing curve and ignition are correct. Many point at the carb when they should be thinking about the ignition.

Best of luck and let us know your decision.

https://www.barnesandnoble.com/p/how...xoCpMAQAvD_BwE