Originally Posted by navy02ws6

Am having some idling issues with my father's 1980, which has a brand new 330hp 350 HO Vortec crate engine. Basically, the car runs great, but wants to stall every time it's idling at a stop. Car currently has the correct original Quadrajet, which has been rebuilt once by myself, and then again by a GM Technician who seems to know his stuff and has been in the business for a while. New float, new choke, new choke pull-off, metering rods, etc. He seems to think that it has a hairline crack somewhere in the casting that is causing it to want to stall when stopped and idling. They're recommending we get a new carburetor.

Now here's some back story on the car. When we bought it last June, the car had been sitting for two years without even being started up. Ended up putting the crate engine in it, rebuilding the trans, and basically going through all the mechanicals on the entire car. At this time, the gas tank was drained. The car is just now running and driving for the first time since then, and I put enough Techron concentrate to treat 24 gallons of gas when I filled up the tank earlier this week. Have driven it maybe 50 miles since then, but it seems to run about the same as it did before.

I'm worried about several things -- first and foremost, I have always been a Quadrajet guy and have had one in every carbureted GM car I have owned. I know absolutely nothing about other carburetors, although I have heard that pretty much everything other than Holley is junk. Second, hood clearance with the Quadrajet that's on there now is at an absolute minimum. We really wanted to keep the stock air cleaner, but that was not possible due to clearance, so currently the car has a cheap 2 inch chrome open element air cleaner. I'm not sure which is taller, a Q-Jet or a Holley, but I do know that if a Holley is any taller, we would have serious clearance issues if we had to use one. Does anyone know which is taller and by how much?

As you all probably know, no one makes a brand new Quadrajet at this point, and I've heard nothing but horror stories with out-of-the-box rebuilt carburetors. However, Jet Performance Products does make several different performance grades of Quadrajets, which are significantly more expensive than everyone else's rebuilt Quadrajets. Are the Jet products really any better or more reliable, or are they just more expensive? I'd really like to stay with a Q-Jet, but I really don't like the idea of something rebuilt vs new.

The other option I've found is the Holley 0-80555C, which claims to be a spreadbore direct replacement for the Quadrajet, but only flows 600 cfm. This carb also has vacuum secondaries and electric choke, which I must have. 600 cfm just doesn't seem adequate to me for a 330hp engine -- I've had cars with 305s that only put out 150hp that still had 750 cfm Q-Jets from the factory. Has anyone had any experience with this carburetor? Will it work with the factory fuel lines, cruise control brackets, etc.? I'd really prefer not to have to get a bunch of adapters to make this thing work. More info on this carb here http://www.summitracing.com/parts/HLY-0-80555C/ .

What do you guys think?

Originally Posted by Matt Gruber

7t9l82- here is my article-
.
Here is my best old school low cost replacement carb pick
If you start off with a great carb, you will be happy with little tuning. Holley put a lot of effort into their Q-jet upgrade, take advantage of their hard work and use it! It is flowing on the boosters by 1500 rpm, perfect for overdrive. (most popular Holleys don't flow anything from the boosters below about 2500 rpm cruise, too high for good manners, and the transition gives about 3 mpg less on the street, even after being properly tuned by an expert ) Square bore carbs used on the street are primative compared to a spread bore 4165-6210. Those square bore carbs may be great for racing, but too often, they suck gas on the street
The primarys on a 4165-6210 are properly jetted for Chevy V8's, but your engine needs at least 12" of vacuum at idle, and should be able to idle at 800 rpm or less to use this carb with no mods.
The 4165-6210 gives me 18-20 mpg stock with a 355 and a mild(224/224 110 LSA) cam. Improve the WOT richness, and you are done!
The 4165 has 2 inch secondary throttle plates; like on a Dominator 4500.
Note: Carbs with bigger primarys often will cruise on the idle transition circuit and get as bad as ~9 mpg. That can be improved with oxygen sensor tuning, but guys not into super tuning should just start out with a great carb in the first place: Buy the Holley 1970 street legal 650 cfm double pumper 4165 model, #6210 cat# 510-0-6210 at Jegs (8-09) for $449(or shop around) I buy mine used at swap meets for $15-50, and they ALWAYS need to be rebuilt, even the 1st one I bought in 1975. Now they can have leaky passages as they are so old. So a new one is not a bad deal.
Also get a power valve plug 510-26-36 $5.
Plug the secondary only!(not the primary)
Get jet kit 555-15020 $15(extra jets for fine tuning at the track for fastest mph)
Install #78's(.089" dia) in secondary.
Or use the maxjets .088" for $5
If you don't have the spreadbore pattern, get the Weiand manifold or the RPM QJET Then you can use this great carb and save yourself a lot of time and money,
I assume you have one or 2 of the Holley carb books, and are familiar with all the adjustments and basic set up.
The little known 4165 is fun to drive, gives excellent mpg and instant throttle response. This is because it has 1:1 linkage; the front & rear open together(after 0.24" front) With a stick it will tend to spin the tires on a quick shift even when you let up on the gas between shifts(when racing). Road racers prefer the quick response of 2 accelerator pumps and 1:1 linkage. They want to win! Automatic or stick, it doesn't matter, 2 accelerator pumps and 1:1 linkage will let you exit a corner faster.
You see, while more common, a vacuum secondary Holley carb adds a slight delay. They are progressive, first the front opens all the way, only then does the rear begin to open. You have to push the pedal more to get the car to respond. Not the case with a 4165! And the 4165 gets great mpg when you take it easy. If you don't have the stock 4 hole manifold, be sure to get the #1905 base gasket; very important! See previous page for details.
Are the primarys too small? At 0.24" throttle(it goes 1:1 by 1/4")
(rear closed) cruise is anything up to ~120 mph. If your heads have ports thought to be "too big" the 4165 may allow their use due to the increased velocity and better atomization.
Out of the box, the 4165-6210 will be very close. Holley did all the hard tuning work for you! But they don't have your combo, and don't know your driving style, so no carb will be perfect. After changing the rear jets on the 4165-6210, the remaining difference may only be about 1%, so is it really worth the time and money to pick up maybe 5 more HP? And nothing in the mpg at cruise area? Only if you are championship racing, or enjoy tuning as a hobby.
I've been using them since 1975. Had a 283 back then and it worked great with no mods. Now I use it on my 355. Friends use it on a stock 427 and a stock 454!
How did I find it? My 1st Holley, in 1972 was a universal performance, that CUT my mpg to 14 from 20! Then in 1975 I bought my C1, missing the carb. I asked my friend Al, if he thought the 600 cfm double pump 4776 would be a good pick. He said NO! IT WILL SUCK GAS LIKE YOUR OTHER ONE. THE ONLY HOLLEY THAT WILL GIVE GOOD MPG AND MAX POWER IS THE 4165-6210. It did not bolt on, so I had to go to a swap meet to find a Q-jet manifold.
So 19 years later, at the Circle Track Trade Show, I ask the Holley reps IS THERE A NEW, BETTER
CARB? They ask every detail about my C1 and surprised me by saying NO THE 4165-6210 IS BEST FOR STREET USE. And they gave me a catalog. On the cover it says SPECIAL STREET LEGAL CARB SECTION INSIDE! It is in there saying it is for 1965-1970 327, 350 and 402 Chevy. So if your 1st pick was WRONG, join the club.
As for "new school" the Summit 600 VS SUM-MO8600VS $260 gets good reviews on CF.. This is a redesign of the Holley 4010. It has removable annular boosters, and jets and pv in the bottom of the bowl. No need to drain gas to change jets! This design can't leak like a 4150/4160/4165. Can fine tune the air bleeds w/$34 kit. I tested a 4011 in my 72. The square bore model is a budget idea if a spread bore 4165-6210 can't be used. Another nice carb VS 680 cfm, check out the Quick Fuel Slayer SL600VS. Changable IFR,bleeds, jets, PVCR, all of them unscrew for fine tuning. $299. See test in Oct-2012 Car Craft.

Originally Posted by Matt Gruber

7t9l82- here is my article-
.
Here is my best old school low cost replacement carb pick
If you start off with a great carb, you will be happy with little tuning. Holley put a lot of effort into their Q-jet upgrade, take advantage of their hard work and use it! It is flowing on the boosters by 1500 rpm, perfect for overdrive. (most popular Holleys don't flow anything from the boosters below about 2500 rpm cruise, too high for good manners, and the transition gives about 3 mpg less on the street, even after being properly tuned by an expert ) Square bore carbs used on the street are primative compared to a spread bore 4165-6210. Those square bore carbs may be great for racing, but too often, they suck gas on the street
The primarys on a 4165-6210 are properly jetted for Chevy V8's, but your engine needs at least 12" of vacuum at idle, and should be able to idle at 800 rpm or less to use this carb with no mods.
The 4165-6210 gives me 18-20 mpg stock with a 355 and a mild(224/224 110 LSA) cam. Improve the WOT richness, and you are done!
The 4165 has 2 inch secondary throttle plates; like on a Dominator 4500.
Note: Carbs with bigger primarys often will cruise on the idle transition circuit and get as bad as ~9 mpg. That can be improved with oxygen sensor tuning, but guys not into super tuning should just start out with a great carb in the first place: Buy the Holley 1970 street legal 650 cfm double pumper 4165 model, #6210 cat# 510-0-6210 at Jegs (8-09) for $449(or shop around) I buy mine used at swap meets for $15-50, and they ALWAYS need to be rebuilt, even the 1st one I bought in 1975. Now they can have leaky passages as they are so old. So a new one is not a bad deal.
Also get a power valve plug 510-26-36 $5.
Plug the secondary only!(not the primary)
Get jet kit 555-15020 $15(extra jets for fine tuning at the track for fastest mph)
Install #78's(.089" dia) in secondary.
Or use the maxjets .088" for $5
If you don't have the spreadbore pattern, get the Weiand manifold or the RPM QJET Then you can use this great carb and save yourself a lot of time and money,
I assume you have one or 2 of the Holley carb books, and are familiar with all the adjustments and basic set up.
The little known 4165 is fun to drive, gives excellent mpg and instant throttle response. This is because it has 1:1 linkage; the front & rear open together(after 0.24" front) With a stick it will tend to spin the tires on a quick shift even when you let up on the gas between shifts(when racing). Road racers prefer the quick response of 2 accelerator pumps and 1:1 linkage. They want to win! Automatic or stick, it doesn't matter, 2 accelerator pumps and 1:1 linkage will let you exit a corner faster.
You see, while more common, a vacuum secondary Holley carb adds a slight delay. They are progressive, first the front opens all the way, only then does the rear begin to open. You have to push the pedal more to get the car to respond. Not the case with a 4165! And the 4165 gets great mpg when you take it easy. If you don't have the stock 4 hole manifold, be sure to get the #1905 base gasket; very important! See previous page for details.
Are the primarys too small? At 0.24" throttle(it goes 1:1 by 1/4")
(rear closed) cruise is anything up to ~120 mph. If your heads have ports thought to be "too big" the 4165 may allow their use due to the increased velocity and better atomization.
Out of the box, the 4165-6210 will be very close. Holley did all the hard tuning work for you! But they don't have your combo, and don't know your driving style, so no carb will be perfect. After changing the rear jets on the 4165-6210, the remaining difference may only be about 1%, so is it really worth the time and money to pick up maybe 5 more HP? And nothing in the mpg at cruise area? Only if you are championship racing, or enjoy tuning as a hobby.
I've been using them since 1975. Had a 283 back then and it worked great with no mods. Now I use it on my 355. Friends use it on a stock 427 and a stock 454!
How did I find it? My 1st Holley, in 1972 was a universal performance, that CUT my mpg to 14 from 20! Then in 1975 I bought my C1, missing the carb. I asked my friend Al, if he thought the 600 cfm double pump 4776 would be a good pick. He said NO! IT WILL SUCK GAS LIKE YOUR OTHER ONE. THE ONLY HOLLEY THAT WILL GIVE GOOD MPG AND MAX POWER IS THE 4165-6210. It did not bolt on, so I had to go to a swap meet to find a Q-jet manifold.
So 19 years later, at the Circle Track Trade Show, I ask the Holley reps IS THERE A NEW, BETTER
CARB? They ask every detail about my C1 and surprised me by saying NO THE 4165-6210 IS BEST FOR STREET USE. And they gave me a catalog. On the cover it says SPECIAL STREET LEGAL CARB SECTION INSIDE! It is in there saying it is for 1965-1970 327, 350 and 402 Chevy. So if your 1st pick was WRONG, join the club.
As for "new school" the Summit 600 VS SUM-MO8600VS $260 gets good reviews on CF.. This is a redesign of the Holley 4010. It has removable annular boosters, and jets and pv in the bottom of the bowl. No need to drain gas to change jets! This design can't leak like a 4150/4160/4165. Can fine tune the air bleeds w/$34 kit. I tested a 4011 in my 72. The square bore model is a budget idea if a spread bore 4165-6210 can't be used. Another nice carb VS 680 cfm, check out the Quick Fuel Slayer SL600VS. Changable IFR,bleeds, jets, PVCR, all of them unscrew for fine tuning. $299. See test in Oct-2012 Car Craft.