Macadoo

Hey folks,
I'm still in search of the perfect carb for my 455, 030 over with ported and polished J heads.
I went through a couple Quadrajets using Ruggles book but I made a rookie mistake; I was hunting for a good idle by modifying the idle circuits when, in fact, I had the preload on the lifters too tight. I had one to the point that it would break the tires loose at the 2-3 shift but it wouldn't idle well and stalled a lot. I'm a Q-jet guy and know quite a bit about them now, but the constant tearing them apart to make small changes is getting a little old.
I'm looking at the Edelbrock AVS 800 CFM 1813. Folks say bolt 'em on and forget 'em. I know that's not very true but I like the external access for swapping parts.
I'd Love to go EFI but I just don't have the cash.
Opinions?

Engine specs:
455 bored 030 over
Ported and polished J heads
Cam is .512" in and out with a 110 LSA (a bit much, yeah?) with Comp Cams roller tip rockers. I dialed it in and the heads have matching springs
9.6 -ish compression with forged Wiseco pistons with hand-filed rings, stock rods with ARP bolts
Performer intake, dual plane (I have an adapter for a square bore)
Hedman long tube headers
Carter Muscle Car HV fuel pump with a QF regulator
HEI limited to 13*, making up the rest at the crank, MSD weights and springs activating as soon as I hit the gas but not at curb idle (850 rpm)
200-4R trans with a 2500 stall converter
3.73 rear gears
It pulls a steady 14 inches of vacuum.

cutlassefi

Macadoo

227 intake, 233 exhaust. 110 LSA (as stated above). Sorry Mark, I should have known that. I'll have a look at the QF.

Macadoo

Yeah, that's a bit pricey. Pretty though. Mark, what do you not like about the Edels? Because it's the old Carter design?

oldcutlass

I like the Holley 3310 vac secondary 750cfm Its simple and inexpensive and will bolt right on.

coppercutlass

I gave mac a 3310 It was barely enough for my needs on my last 355.

Mac what are you looking for in a carb ? idle still ? or off the line performance ?

I have a friend who has an 850 demon that may work for you.

Firewalker

The holley Street Demon. 625 CFM model is good for 500hp, and the 750 for past there.

The only Holley style carb I like is the Quick Fuel Carburetor BR-67214 Brawler. About $385 when on sale

cutlassefi

olds 307 and 403

As said the Street Demon 750 are good carbs but a bit on the small side but should provide decent performance and economy if tuned properly. They are basically new 3 barrel, improved version of the Thermoquad. People including Cutlassefi like the Quickfuel carbs for a Holley style carbs. Or find a 800 cfm Qjet core to build.

Macadoo

Thanks for the input Eric. But Copper is correct; the 3310 didn't keep up. But to be fair, I didn't do any part swaps to get it tuned.

I think I have the idle pretty good, finally. It was the same thing you posted to Youtube; getting the mechanical advance out of the picture at idle, but kicking in just when touching the throttle. I't s a little high in park but works well at curb idle. I read about a lot of guys talking about a "nice, crisp throttle response." I'd like to have that. Maybe it's the 200-4R. I still need to modify the governor to lengthen the 1-2 shift. And honestly, I'm tired of pulling the carb and air horn to make the slightest change in a Q-jet.

That BR-67214 gets good reviews for sure. Some posts say it's just a rebranded Proform. But that Proform gets good reviews too and is a little more expensive.

Which is why I'd like something easier to tune than a Q-jet. The Edelbrock has easy access to the rods but I think that's not true for the jets. But the airhorn comes off pretty easily.

cutlassefi

coppercutlass

Mac a tight converter will pose issues you cant tune out. Keep that in mind. Your converter could not be enough for that set up or possibly was made too tight. Fwiw

olds 307 and 403

Some have luck with Edelbrock carb, many do not. One member compared the Carter to Edelbrock castings, the Carter were much better. Remember even the AFB/AVS had hot start issues back when they were factory carbs. I really think that was a big part of the Thermoquad getting the Bakelite body. Go with Mark's recommendation, especially if looking for maximum power. Personally I can adjust my part throttle on my Qjet in minutes through the air horn. I slotted the APT adjustment and added a slotted threaded plug. A flat screwdriver is used for both. A couple of turns out adds noticeable performance gains, in a couple of turns adds 2 to 3 mpg. Along with the secondary rod change, it makes a big difference. Of course an AF gauge is the only right way to tune your car. Curious, what kind of mpg is achieved with these new Holley style carbs? Can they match the Street Demon or Qjet, both with an ideal tune?

Firewalker

The tuning on the Street Demons is pretty straight forward, with little to change and virtually all of that on the outside of the carbs. Very much like the AFBs or AVS or Thermoquad carbs are. You can go from thrifty gas mileage to strip tunes in a few minutes, with a few turns of screws or a swift change of rods and or springs.

Kenne-Bell racing tested the Thermoquad versus the Quadrajet versus the 850 Holley, and found the Thermoquads matched the 850 in the quarter, but with the gas mileage and driveability of the Quadrajet. This was all in the early 70s on a W30.

Parts interchangeabibility. lots of parts like rods, and springs, and floats and needle and seats are interchangeable between the AFB, AVS and thermoquads and the Street Demons. So for example, you could use brass floats and .120 or larger needle and seats in the Street Demons, if desired.

Macadoo

As you know, this converter came from Midwest Converters so quality is not guaranteed. But I can feel it kick in around 2400 or 2500. That shouldn't be too tight for my power band if my numbers are correct. If it's in the trans, I have to get to the shift points first. I have a good article on modifying the governor (which is inside the pan) and I'm making that a winter project. And while i'm in there I'm going to get the right speedo gears in there as well.

That all sounds pretty good to me. No drilling out idle tubes and air bleeds?
Well sir, like I said, I was making some major mods on my APT Q-jet hunting for a good idle when it turned out to be the preload on the lifters was too tight. I went through Cliff's instructions for setting the APT a few times but my results were always the opposite of what was supposed to happen. When tip-in was supposed to decrease the idle, mine raised and vice-versa, lol. I never did get that nailed down. Don't get me wrong, I was determined to be the local "Quadrajet guy" but I went through three Q-jets and all of them were warped beyond repair. I thought about buying the straightening jig but lost interest at that point.
I would also be interested in know about the gas mileage of the newer Holleys. One of the reasons I like the Q-jets is because of the small primaries. Currently I'm getting 18+ mpg (highway) with the 200-4R overdrive locked.

I know nothing about this design. What are the springs of which you speak? Is it like the vacuum activated power piston of the Quadrajet?

Firewalker

The springs that push the fuel rods up, on the primaries, when vacuum drops enough and you need more fuel.

Macadoo

Informative video, thanks man. Those are very much like the power piston in a Quadrajet. And exactly like the Edelbrock, down to the shape of the metering rod cover.

matt69olds

olds 307 and 403

What is your trans shifting at? The small weight I grind down a lot, tap and locktight a small screw and grind the head down even with the weight. This brings the factory 4000 rpm shift points to 5000 rpm with stock springs. You might be able to increase it some with a lighter spring and it will stay in place. The Street Demon/Thermoquad was basically Carter's answer to the Qjet. Holley eliminated the Bakelite body, Aerospace polymer now, leaky O rings, divorced choke and secondaries that needed a special tool. Too bad the they don't have a 800 or 850 cfm model.

Macadoo

Yeah man, I've been through a couple of modded Q-jets using Ruggles recipes. My main problem was finding a core that wasn't warped, especially the air horn but also the main body and base plate. I have four of them and all horribly warped. i'm just ready to try something different.

Yup, that exactly what I'm talking about doing with the governor. Except my shifts don't reach 4k, more like 3500. At least that's where it's at with the proper amount of preload on the TV cable.

Macadoo

With an automatic transmission and street use, shouldn't I be looking for a vacuum secondary carb? They seem hard to find above 750 cfm without BIG money.

Firewalker

I don't think Holley wants these to be known for ultimate power and going fast, so limited their CFM sizes, but that can be changed for those who dare and actually need more than 750 CFMs.

The question might be how does a 500 CFM rated at 3" 2bl carb can make over 500 horsepower, when it's only 353.5 CFM rated at 1.5 inch 4bl levels. Its because the advertised flow is somewhat meaningless on a running motor, where increased vacuum increases its CFMs. So if a 353.5 cfm carb can make 500+ horsepower, then a 750 cfm might not be that shabby.

ragz442

I know nobody likes Ebrock's, but I've used the 1407 manual choke for over 15 years and feel it's a decent trouble free carb for street use. My question is everyone says it's a relabled Carter, but it has Weber stamped on the side. Are Carter and Weber the same?

olds 307 and 403

I agree on a Street Motor, the 750 Street Demon would work fine.

coppercutlass

Mac if you wanna try an edelbrock. I can borrow a 750 cfm from my boss and we can try it on one weekend and see how it works. He also has the tuning kit. He wants to sell one and he owes me a favor or two.

Firewalker

https://www.chevyhardcore.com/tech-s...on-carburetor/

A link on tuning a Street Demon, though this will apply to other cars somewhat.

olds 307 and 403

Check out the reviews for any carb you buy. The Street Demon has good reviews, nearly all the negative reviews are when they first came out with the 750. I am sure the Quickfuel carbs will also have very good reviews. I think my next carb will be the Street Demon 750.

Firewalker

Some suggestions on the Demon Street carbs, for those that buy them. Buy some of these clips of the right size, to replace a couple of C clips found on them. The R Hair pin clips are much easier to pull off or install back on, with needle nose or regular pliers, then the tiny C clips that come on them.

Before installing take them apart, to make sure the floats are set correctly and lightly oil the teflon gaskets. Teflon only resists sticking in the presents of oil, like non stick pans.

Leave the bottom bolts out when putting it back together, and only use the 2 top bolts to hold the 3 parts back together. This will allow the easy removal of the top for tuning if a jet change is required, without taking the carb off the car. Put the bottom bolts back in when tuning is finished on the jets.

Rather than buying a tuning kit from Holey or Edelbrock I would suggest buying a spring kit with the 5 spring sets in it for the AFBs. They are color coded, but will lose there color when in gasoline in the carb, so you need to tag/labeled for which ones are which. Metering rod sets for AFBs can also be found on ebay and in a larger assortment of sizes then the tuning kits. Brass floats are also on Ebay and are the.120 needle and seats. These are strictly low pressure carbs and 4 pounds max is probably the best, for initially sorting them out.

An old hot rod carb trick, to solve carb problems on a lack of fuel is a secondary electric fuel pump back by the gas tank and wired to a switch. It solves the problem of gas not being in the bowls when sitting for weeks. Just turn it on and listen for the sound of the pump to change telling you the pressure is up and the bowls are filled and then turn it off. It can also solve most any problem on a racing take off, with a lack of fuel flow, for whatever reason with it's being turned on in first and second.

Yes, you can suck fuel right through a turned off electric pump. I have run this on all my hot rods for many decades. Carbs can be as easy or easier for power and gas mileage, or starting with the first hit of the switch, as injection. They are a lot easier for trouble shooting and a whole lot cheaper. I have seen a carb get 40+ miles per gallon on the highway at 70+, and I have seen them go 10s and faster with factory style carbs.





https://www.ebay.com/sch/i.html?_fro...clips&_sacat=0

Firewalker

Setting up the 200r4 transmission TV Dent cable for a Street Demon 1904 carburetor

Be aware it says the hole in the Street demon is marked wrong, for the 200r4 TV travel.

https://www.1952chevytruck.com/stree...dent_cable.htm

olds 307 and 403

Holy crap, is that guys first language English? Either way, good to know. It looks like just moving the TV cable to the front TH350 hole fixes it. Demon has an adjustable TV bracket as well.

Firewalker

Yes, the TV bracket is available from Holley for these Street Demons and they are fairly stout pieces btw. The information from him I thought was vital, for anyone using a TV cable with this and something they might need to check at install for the proper hole at the proper travel. The first or front hole does seem to be what he is using, instead of the middle one Holley said was correct.

Macadoo

I dunno' guys; I'm liking this Street Demon carb, The 750 you think? Conflicting information though. Some posts say it will bolt to a dual plane edel intake, some say not. And my wife bought me cool as heck Oldsmobile air cleaner so that fitment is a must. My one hold up right now is that the steering went out on my '14 Ram truck. $2k to replace the whole rack because the pcb went out?! Ugh.
No worries about the TV cable. I have [too much?] experience setting that up.

Firewalker

It will work with your intake as its for either. The air cleaner might need modification, or a spacer ring, or neither. The pump shot arm is possibly why.

olds 307 and 403

Yes, definitely the 750 cfm. It comes with the thin plate to seal up where the carb may leak due to being closer to square bore dimensions on a spreadbore intake. The only issue may be the back single barrel hitting the middle divider, another reason for the plate. I notched my divider which isn't a bad idea anyways. I need to get my motor done to warrant buying one. Good luck.

RocketRonnie

Qjet. They made a 800cfm too

Firewalker

The secondary blade will not hit the divider, because of its goggle shape. Remember the carb sits on the plate also, between it and the intake.

Macadoo

Yeah, the plate and one gasket. But I'll notch if I have to. Not a big deal. I like the post above about changing out the tiny E-rings for larger ones. The secondary air door looks easy enough to adjust; far easier than the Q-jet. And of course the ease of swapping the main metering rods is a plus but I'm hoping I don't have to re-jet. How about the idle circuit? Is it capable of supplying a BB with a wild cam? And I'm still wondering if it will have comparable fuel mileage to the Q-jet.
Lastly, I saw somewhere that folks said the Edelbrock air cleaner fit okay. I have one that I could swap the bottom for and still use my Olds top.
DOes anyone happen to know if the fuel inlet is the same size as the Holley. If so, I'll adapt this AN-6 assembly to fit the Demon.

Macadoo

Firewalker

Maybe on the same fitting,,and a single inlet towards the rear of the passenger side. The fitment of the air cleaner shouldn't be a problem either way. My best guess is I have never seen to big a cam be a problem on their idle fuel mix. Low vacuum may need a change of springs on the rods to keep them down. They are like the power valve on a Holley.
On fuel mileage, they should do was well or even better than the Quadrajets, if finely tuned. I have seen people claim 21-24 mpg after tuning them.

On the jets. The secondary jets are standard Holley which you may already have around there, if needed. The primary jets are not, but tuning with smaller rod sizes might make it all work, if more fuel is needed. A few things to remember is the afb rods come in many diameters, and rods can be made smaller or larger by altering their sizes by adding or subtracting material to them, if you wish. But there are many many new afb rod sizes available if you wish, and not just whatever Holley or Edelbrock offer.

Macadoo

Good info. Thanks Firewalker.

The inlet sizes are not the same but this should do the trick:

https://www.summitracing.com/parts/d...6dem/overview/