I know this subject has been beat to death but... I am building a lq4 for my 69 Camaro. I have a nice motion hotrod cam for it and ported 243 heads. I am looking at intakes and at this point I could go with a ls6 intake or a single 4 barrel I kinda like going with the carb as that is what I am used to and would be a lot cheaper for me. I already have a nice fuel system for a carb and would have to replace all of it. Would the benefits of a ls6 intake outweigh the easy carb install?

 

First much respect for you and your Jedi carb knowledge. So please understand my opinion that following comes from dealing with a lot of carbs back in the day, a cylinder washed engine and very few carb Jedi.

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Per 20-ls1-intake-manifolds-tested seemed to me all of the carbureted intake pretty much under performed in the less than 3,500 to 4,500 rpm range one actually drives around in. So if the car is a driver one of the fuel injected intake manifolds like the LS6 or Fast 92/102 usually offer more overall under the curve.

In my 40+ years of driving, carb vs fuel injected- carbs are Always More Problem prone and finicky require more adjustment etc. I like the nature of set it and forget it electronic fuel injection. Folks that like to tinker may feel differently.

My personal opinion the only carburetor that I've ever had that actually was great on a driver was a professionally tuned (Lars of the Corvette Forum) Rochester Q-jet. It drove nearly as well as fuel injection.

Carburetor's are horrible for long term engine durability because on cold start they wash the cylinder walls down far more than fuel injection. Carb'd small block chevy pretty much needed rebuild if it lived 100,000 miles if carb'd. Have ran a small block chevy nearly 400,000 miles with fuel injection and it still didn't need a rering.

A lot of folks, that think they know how to correctly tune carb's - actually don't. Even back in the 1980's it was pretty hard to find a real carb Jedi. I wish I had $2 for every pig rich at idle Holley, I saw back in the day...

My 72 vette still has a carb, a well tuned Demon but I really hate it. On the dyno the Demon can't keep the A/F nearly perfect through the rpms like fuel injection can. It's also pissy after sitting inside during the winter months even with Stabil etc. My three fuel injected LS's NEVER have that issue after sitting ~3 months in winter.

Of course if your a carb Jedi, then stick with what you enjoy and like. We all have different preferences etc. However other than the Qjet, I've really disliked the carb on every car I've ever owned, despite its elegant mechanical simplicity ✨️

 

Most of my carb experience is from drag racing.Hard to beat a 750 dbl pumper. But then again its all wide open unless your cruising though the pits.
So if I go with a fast intake and figuring the engine will make about 500 hp should I look for the 90 or the 102. I know to big of a carb will cause all kinds of problems at part throttle. Or a carb intake with a holley sniper.

 

RH has a bunch of videos talking about the differences between plastic intakes and carb intakes.

 

The "burns-your-eyes" idle can also be the product of an idle mixture that is too lean. An overly lean mixture will not burn as completely, leading to misfires/unburned fuel entering the exhaust. Many common street Holleys have relatively lean idle circuits, especially the two-corner idle carbs - it's hard to ever make those pig rich at idle unless you have the throttle blades open too far, thus pulling fuel from the transfer slots (which is a common problem when folks try to get a big cam to idle by using only the primary idle screw - in this case, like you said, they either don't know any better or they think they know what they're doing but clearly don't...lol).

I hear folks talk about this, but it's not something I've ever personally experienced in my many years of storing various vehicles. The current Holley on my '71 is from 2008, and the last time I had the fuel bowl off (for various tuning changes) was 2012. It sits every year from late October to April or sometimes early May, so literally 5-6 months, ever since I installed that carb 14 years ago. I have never rebuilt this carb, it has never needed it. Runs perfect every spring, just as it has ever since I dialed in the tuning. I store the car in an unheated garage, with E10 fuel because it's all we have in my area (full tank, always full for storage to minimize air/humidity in the tank), and my own personal blend of Stabil and Red Line SI-1 fuel treatment.

I follow the same storage process and duration for my '98 Z28 with its factory original fuel system, only thing that's ever been changed is the filter. Zero problems there either.

My personal opinion is that it's not really fair to categorize carbs as being inherently more prone to post-storage issues. Once the fuel in their bowl(s) evaporates, which can happen just as easily during the summer if they sit for a few weeks, there is really no difference if they sit for another 2, 3 or 6 months as far as the carb is concerned. Older gaskets and pump diaphragms might be more susceptible to deterioration from modern fuels, and then might be more prone to issues once they have been allowed to dry out prior to going back into service, but I've had zero issues with the modern Holley blue gaskets.

On the other hand, this will be my first year storing my new-to-me '74 Cutlass, which has a non-original Q-jet that was rebuilt at an unknown time. So we'll see how it does come spring. You mentioned Lars above; he's a great asset to the world of Q-jets and very well respected for his knowledge. I've read through his "papers" while sorting out some issues on my current Q-jet, he's a master for sure. Cliff Ruggles is another Q-jet master who's advice and knowledge is second to none, I've also read a ton of his stuff and plan to sit down with his Q-jet book over the winter. Can't go wrong with info or rebuild/modification work on a Q-jet from either of these guys. In fact, I have an NOS AC Delco rebuilt Q-jet core that I plan to send to one of them for a going-through before putting it on my '74, unless I decide to try it myself using all the advice and info from their publications.

Sorry to get a bit off track, but I would not hesitate to use a carb if the OP is experienced with that and feels comfortable with that option. There are obvious efficiency and consistency advantages to EFI, but for someone familiar with carbs (especially if they already have an entire system ready to go) they are still a relevant option.

As someone who also has one foot in both worlds (carb and EFI), the only real drawback that I see to a carb (at least on a "toy", where maximum MPG is not really a concern) is their lack of ability to self-adjust to changing weather conditions.

 

Please tell us more about your blend of Stabil and Red Linr SI-1 fuel treatment. My 72 vette is normally stored in unheated garage with ethanol free, 100% gas in the tank. I'm lucky and have one source back home in North Carolina. If the car stays in Indiana for the winter, I'm stuck with 93 octane E10.

The then new Demon went on in 2011, required attention immediately with a couple of quality of assembly issues when on my 383. In 2012, it was fully sorted, rebuilt & tuned with the new Dart 400. A full rebuild followed again in 2014 by a carb Jedi aka the Dart 400 engine builder. So currently ~eight years without requiring mechanical repair.

Look forward to seeing details of how that goes. I hope it goes well. I like Q-jets enough I'd have another 60's/70's/80's car in the garage someday with one...wink.

Agreed, folks should definitely build their hobby cars & trucks the way they want, are comfortable with and enjoy. If that's Webber side drafts or injected ITB etc, more power to the Jedi hobbyist.

 

For Stabil, I generally go a little on the "heavy" side of their recommendation (they call for 1 ounce per 2.5 gallons, I'm closer to 1 once per 2 gallons). The Red Line product can be used in a heavy dose for complete fuel system clean-up, but for continual use and/or fuel storage I use it in a ratio of 1 ounce per 5 gallons (this was a recommendation from Red Line many years ago when I first started using it, since then I've seen *some* of their publications state that you can go as little as 1 ounce per 10 gallons, but I've had great results and no problems from the heavier treatment over the long term so I've stuck with it). Red Line SI-1 also contains a fuel stabilizer in addition to its detergent properties and rust/corrosion inhibitors (important for use with ethanol fuels).

My '98 and '71 get driven so little that I actually add the Stabil + Red Line blend to every tank (these cars only see 1-3 tanks per year, normally). So any "older" fuel still in the tank prior to the pre-winter fill-up has already been treated.

But I think an important key here is really to keep the tank full. The less air that's in the tank, the less issues you'll have with ethanol fuels. I know some folks like to store them with minimal fuel so they can immediately fill with fresh in the spring, but that seems to be a common theme in cases where folks run into issues. Using the above blend of products, the fuel in mine has always been fresh enough for maximum performance even after 6 months of winter storage.

Sorry to hear it had such trouble right out of the box, and then another rebuild 2 years later. I can see why you might not feel too excited about carbs after those experiences. But I'm glad to hear that it's been reliable since the '14 rebuild, sounds like you found a good source to work it over that time.

To be fair this Q-jet isn't 100% perfect right now, so the hope is just that it won't get any worse over winter...lol. I've got it tuned pretty well, I've been through a bunch of trouble shooting and its operation has improved drastically, it would seem ideal to all but the most picky folks, but there are still a couple of minor, intermittent issues. Things like this can happen with unknown commercial rebuilds, which this one appears to be (I do not know its history, but date coding indicates that it is not original to the car), as they sometimes assemble these from mix-n-match parts bin pieces that aren't always "perfect". So, eventually, I'll install that good NOS Delco core once it's been freshened up, probably by Lars or Cliff or me using one of his kits.

 

FWIW - I agree 100% a FULL tank of gas to keep as much air out of the tank as possible helps. That's probably as critical as treating the gas before storage.

I'll have to get some Red Line and try it this winter. Thanks for sharing the recipe!