I have a holly installed. Its been rebuilt a number of times and has given me a lot of problems. My GM aluminum intake is square. The number is 14044... (rest of digits under the rear fuel bowl).

Bob

 

Hello Benito,

I would call the folks at A.E.D. and ask them for their advice in your situation. These guys are experts at carburetors. They buy the bare Holley Castings and do all the machining, in-house to the parts. They can make you the very best carburetor right out of the box. Their prices are not that bad considering the attention to detail and support that they give you at AED. Call them and ask them what they could do for your engine combination.

Here is the website for the AED Company in Richmond,Virginia: https://aedperformance.com/

I see that you have considered the EFI option at one time. I am one of the "Semi- geezer" C3 owners who has installed his own EFI system. It is not that hard to do and the difference in performance is not a big deal. I installed a Holley Stealth Sniper on my 427 and it was very straightforward as long as you followed the instructions. I bought my entire EFI system from a Company located near Melbourne, FL called efisystempro.com and they are one of the best EFI sales groups that I have found. Efisystempro will sell you a Holley system at a great price and then support you getting it operational by providing 24 months of Customer Service by a Holley EFI systems Expert. No waiting for Holley tech support to answer.... The tech called me before I even got the parts and gave me his contact information and got to know me a bit.
EFI is still within your reach if you want a "bit" of a challenge. It is nice to have the immediate starting and smooth idling of the EFI system controlling the fueling and ignition simultaneously. I had budgeted $2500 for the swap. I ended up spending "around" $1700. This included the OEM Fuel Tank Module for the EFI system as well as the master installation kit. I was going to replace my fuel tank but did not have to, the final price was close to $700 LESS than I had budgeted!

If the carburetor is the direction you want to stay with then know that AED can make you a Holley that will eliminate your troubles.

If your Quadrajet experience was so good, maybe you should find a good core and have Lar's perform his magic on it, and he could make it the best carburetor you ever had for your Corvette!

 

A Q-Jet will be superior to a generic Holley, especially in terms of throttle response and gas mileage. They are however carefully calibrated by GM to each specific engine combo, and therefore like stock engine combos.

I believe the L46 350 HP is one of the single best all-around engine combos to ever come out of GM. Power and efficiency.

Since you have a stock L46 350-350. Let me share this with you.
A recent poster, with his same engine as you, got 26.5 MPG with his Lars breathed on Q-jet, on the highway, with a 5 spd O.D. trans, cruising at 1900 rpm at 70 mph.
A Q-Jet can be pretty efficient indeed!

Good luck trying to get a Holley to do that. And I had a 70 LT-1 for 30 years, and spent a lot of time racing and tuning it.

Your manifold appears to be a Bowtie version of the LT-1 intake, a GM 14044836, for square bore Holley carbs.

If you have a square bore manifold, the easiest solution is to stick with an AED version of a Holley. You can go with a 750 cfm on a 350, but it will run better overall with a vac sec one. Just like GM did on the LT-1s. 350s really do not need 750 cfm, below 7500 rpm.
You mpg will take a hit vs a Q-Jet. I got 15 mpg out of my LT-1, factory vac sec 750, at 70 mph at 300 rpm with 3:55 gears. And 18 mpg out of my similar tuned all stock 336 geared L48 with a stock Q-jet.

In my opinion double pumpers are a race car setup, and are not needed or intended on the street. Period. If you know how to tune a vac sec Holley. Worst myth out there. It is just like taking off the vacuum can on the street, just because the race cars do it. A street engine is not a race engine. It has different requirements. They do make a Brawler vac sec version. Street engines value part throttle, race engines could care less.

If you put a double pumper on there, with the rather mild L46 cam, it will run very rich, below 3000 rpm, and you will have to do a lot of deep Holley tuning, to try to get the under 3000 rpm zone as good as a vac sec would have been to start with. You will be lucky if you get it past 12 mpg. And you will be doing IFR and air bleed jet adjustments, not just jets. If those are not adjustable, you will be drilling on the carb. In the long run it will not run any better than a vac sec. The only thing it does better is hit the slicks/tires harder on the initial launch, it is very tuneable there. That is what they are made for.

I only spent 45 years, hanging around my best friend and speed shop owner, tuning both street and race cars. From mild to wild. Listen or not, or listen to the internet if you like.

 

He doesn't have a stock L46 already has a Holley with a square bore aluminum intake.

 

A quadrajet has better throttle response? I call B.S. on that. A double pumper Holley has quicker response.
Even a vacuum secondary Holley is better . They call them quadra bogs for a reason until you have a knowledgeable tuner work on it.
Better gas mileage? Tuning and throttle opening effect that. The op has a square bore intake any Holley type carb will suit him well.

 

The 4150 & 4160's are ok - typically they seam to fall out of tune. The Brawler which is a 4150 Vacuum secondary in bothe 600 / 750 models are easier to tune due to the float level sight glasses.
I had one on a 72 nova i worked on. I liked it and the only 4150 series I'd buy.

Saying that I have now have used both the Street Demon's 625 / 750 - I can't say enough about them.
750 on the 454 Stock
625 on the 390 bird Stock
Both Scream to redline and throttle response is well like fuel injection.
Choke operation is easy and allows me to literally drive off in less than a few minutes. Original carbs needed like 10 minutes to warm up with out any stumbles - this saves a ton of gas.
Gas mileage is way up.
Read about them and read about the Goggle Secondary Valves

Anyway good luck

 

Street Demon seems to be based on the old AFB or AVS car. It uses tapered metering rods on the primaries, like the Q-Jet.
Those metering rod carbs offer far superior throttle response and fuel control at part throttle vs any Holley that uses main jets only, and it's hard to tune Air Bleed and IFR orifices.
At least you can still get parts and support for Holleys and Street Demons, even AVS.

The Q-Jets are very difficult to get parts and support for, I only know of 2 or 3 places I would trust with one.
There may be a slight advantage to the Q-Jet over the Street Demon/AVS, with GMs engineering, but parts are much harder to come by.

 

Thank you. All things considered, the Q jet is not going to happen. Great info.

 

I believe I've settled on the Brawler 750 vac secondaries. During my research I did not find the numbers 4150 you quotes Do those numbers just designate vac secondaies? Thank you again.

 

Brawler BR-67320 750 CFM Brawler Street Carburetor Mechanical Secondary
From the Holley Website

 

Brawler BR-67319 750 CFM Brawler Street Carburetor Vacuum Secondary-Black

Grabbed the wrong one.......this is the vacuum secondaries.

 

Hey, I should have asked - What is your intention for the car? Drivability, cruising, burnouts, qtr miler?
I think answers to those questions are important in your build.

Me I want drivability, and cruising - however don't let me down when I want to do a couple burnouts.

 

4150 means 2 metering blocks - fr & rr, 4160 means front only

If you want a Brawler I would prefer this one.
https://www.holley.com/products/fuel...parts/BR-67258
4150, vac sec, 2 metering blocks, 4 corner idle, elec choke, and adjustable air bleeds.

It's all you need. And uses your existing intake.

 

I put a. 650 brawler on my chevelle 454 to break the engine in I was surprised how well the motor ran , After break in I went stealth sniper the motor ran better with the brawler , it's a low cost good carb you will be pleased.

 

I think the Street Demon is based off of the Carter Thermoquad , like what would be on a 1971 Duster 340

 

As mentioned...a Holley 750 DP is about the most universal carb on the planet. Pretty much will work well on anything. That said...while there are lots of "boutique" carb builders of the Holley design (heck Edelbrock even makes one now)...Holley still knows how to make a carb. I've had great luck with Holley Street HP 750 DP's out of the box. They work great on hot street motors.

Don't get too enamored with all the extra tuning ability some offer. It's easy to get things way out of whack and not needed usually.

I tend to use "larger" carbs also. I ran a 1050 Dominator on my street 427 and it was great. True dual plane intakes "like" larger carbs also since at WOT each cylinder only sees two throats vs 4. .

I've got a 50+ year old Holley 750 DP on my mild 302 Mustang and it's great.

JIM

 

Everything stated above is true and accurate, including the recommendation for the HP 750.
Lars

 

Thank you all very much for the great ans varied input. Im going to purchase the holly 4159 650 Brawler. Again, THANK YOU ALL.

 

You were recommended to go with the 750 why aren't you doing that?

 

After all the info provided and listening to a number of videos,in particular one from a prior prior fuel system engineer using the equation (available on line in two different forms)"
CFM = (CID x max RPM x Volumetric Efficient)/ 3456 ( a conversion factor). VE is estimated to be .85 for a street engine with a few performance up grades.
(350 x 6000 x 0.85)/ 3456 = 516 CFM. Then consider octane of gas as the lower it is the more gas is needed. Therefore more than 516 CFM flow is needed. There is a chance that a 600 CFM would be fine, but because of your input, I stepped up to 650 CFM.
https://video.search.yahoo.com/searc...7d&action=view