Holley Truck Avenger Carburetor yes/no ? (1 Viewer)

[nordwind]

Holley Truck Avenger Carburetor yes/no ?

Last week I had a friend in my workshop.
He is the type of person what buys the carburetor at the first
and then build everything else from his rig around it,
Well, he saw my new carburettor and the only thing he had to say was.
"You should sell the pump, preferably to someone you do not like."!?
I said nothing, would I say something, he would not stop talking for the next two hours,
But no doubt he is good in Carburetors,
I have never used a Truck Avenger Carburetor,
what do you think,?

 

[splib]

SBC?

I've heard pretty good things about them as far as performance and milage.

 

[fieldsken1]

i have a 670 on a sbc 350 works fine and not bad on the milage. i did however change a spring and the main jet to make better

 

[bikersmurf]

Holley's had a reputation for being hard to make work off road. They do work well on the street once they are set up right.

 

[brooklyn]

I put the 470cfm avenger on the FJ40 (V8/283) and I like the way it works so far. The old carb was terrible on cold starts and had a dead spot on acceleration that I was never able to cure.

With 470cfm no cold start issues and no dead spots. Ran a little rich out of the box, but after an adjustment it was fine. Did have to set the fuel level. Holley gives you good instructions, so this was easy and only took about 30 minutes.

Haven't had it off road yet, but looking forward to trying it at angle. Fuel economy seems to be about the same. Truck does seem a bit more responsive on acceleration; which is nice.

 

[kennyfj40]

I also run the 670 cfm on my 350 and it works great. I have had it off road twice and no problems on off camber situations. I may need to re-jet or look at the settings as mine seems to drink gas. Just my experiance.

 

[matros]

works great in off camber situations but my 670 is way to rich for sbc 350 and i have rejetted it down four sizes. Friend has a 470 on sbc and is great.

 

[Splash]

I run the Truck Avenger on a 302 and it does great off road. I ran the Rubicon several times last year and never had any carb isues when off camber. I have had a bit of a challenge tuning it due to running from sea level to 7,000' on a regular basis.

 

[Brian in Oregon]

I had a 670 Truck Avenger on my mild 350 in my '71 FJ40.

I did not care for it, and replaced it with a QuadraJet.

The worst part of it was the fuel mileage (can't use the phrase fuel economy, there is none). I could not get this over 8 to 9 mpg regardless of jetting. And if you do get it lean, it starts backfiring badly when cruising at highway speeds. The secondaries, out of the box, are almost ten (!) jet sizes too large.

Also ran into issues with the secondaries. I usually did not open the secondaries, except on heavy grades or needing a lot of acceleration. It could go quite a while before the secondaries were opened. This led to issues with the secondary needle sticking to the seat, and the fuel in the secondary bowl being evaporated away. Step on the gas hard enough to open the secondaries, and it would kill the engine. As my carb came from the factory, the secondaries were fully closed when at rest. This leads to the condition I described. Had to readjust them to be slightly cracked at rest, allowing a slight fuel flow. This helped prevent this issue, but resulted in more fuel being used at idle, and the idle was more difficult to adjust. Still, it wasn't all that bad. Most Holley carbs are designed for the secondaries to be slightly open, so perhaps mine was not adjusted correctly at the factory.

The 670 was far too large from a cfm standpoint for my mild 350. I had no bottom end. 1st gear starts had to be made. I could not do a 2nd gear start without a lot of clutch slippage and a lot of gas. The lack of low end torque killed any idea of crawling. This showed one of the reasons why a six is better suited for low rpm work.

On the plus side, the 670 Truck Avenger made a lot of power. From a power standpoint for mountain grades, carrying a heavy load, pulling a trailer, it's an outstanding carb. It also does quite well at steep angles, just as Holley says it will.

I got tired of the above issues and especially the fuel mileage, and decided to try a QuadraJet or a Ford Autolite 2100 2 bbl. Didn't matter which, as I intended to try both.

The 2100 has a good reputation as an off road carb, and from experience on street vehicles, it is reliable and dirt simple. I was rebuilding these when I was 16. Didn't try one on the 350 because I came across a QuadraJet first.

My particular Quadrajet is off an early 80's Corvette. While that sounds exotic, it's actually jetted and set up for a tradeoff of power verses minimal pollution, via a lean mixture. Just what I was looking for. It had an electric choke, but I converted it with a Micky Mouse conversion kit to a choke cable.

Fuel economy went up. A lot. Best ever was 12 mpg, though 10 to 11 mpg is typical. That's 2 to 4 mpg more than the 670 Truck Avenger.

It idles a helluva lot better than the Truck Avenger, and uses less fuel doing so.

Because the secondaries share a common fuel bowl with the primaries, there is no need for the secondaries to be cracked open slightly to prevent stagnant or evaporated fuel in the secondary fuel bowl. (The 2100 of course has no secondary fuel bowl, nor do the Edelbrock carbs.)

Throttle response at low rpm is excellent. I can easily make second gear starts, which I could not do with the Truck Avenger. It will idle up hills, which the TA would not. It will lug down to the point where you'd think the FJ40 had a straight six in it, not a 350 V-8. I'd have to rate it's off road low end throttle response as outstanding.

When the secondaries do kick in, it gets up and runs, but the power level is not on a par with the Truck Avenger. On the other hand, it still isn't burning through the fuel like the TA either.

The QuadraJet also does quite well at steep angles.

Drawbacks of the QuadraJet are lack of power at mid-range when compared to the Holley. It's like there is a flat spot between economy and power. I'm not talking about a bog, but rather that you have to give it more throttle than you'd need to on a Holley for power. Likely this is due to the transition between coming up on WOT on the small primaries and when the secondaries start kicking in.

Another drawback of the QuadraJet is that they are not easy carbs to tune. Fortunately, mine runs fine as it is.

BTW, QuadraJets have a reputation for bogging, to the point where they're nicknamed the QuadraBog. I've never had that issue on mine except when the engine is cold.

Another thing... when the Holley got really hot, it got cranky. When teh QuadraJet gets hot, it just gets better and better. Even on the hottest day it is a delight to drive, and the hotter it is, the better the throttle response. Because of the leaner mixture, it may be promoting better fuel atomization, perhaps even vaporization, resulting in better mixture distribution to the cylinders. The spark plugs are textbook perfect, as opposed to the TA, which were always showing rich mixture.

The QuadraJet runs so well that I never did get around to trying a 2100.

I also never tried an Edelbrock on the FJ40, though I have one currently on my Chevy Pickup with a 454. This is a 750 cfm, which is way too large for the 350 in the FJ40. If I wanted to try an Edelbrock on my setup, I'd opt for a 500 (first choice) or 600 cfm AVS and add spring loaded needle and seat assemblies. Edelbrock does make an offroad AVS in a 650, but for a mild 350 I think it may be too large for best low end throttle response. These carbs are also not the easiest to adjust for mixture, because of a complex needle and jet relationship. You need to know how to read plugs. Edelbrock makes a tuner kit, which ain't cheap, and that's going to be needed if you want to go beyond factory settings other than curb idle and secondary air door ajustment (only on the AVS, not on the Performer).

If you're going to try a Truck Avenger with a mild 350, I'd recommend going with the 470 cfm. I have no experience with it, but in theory it should provide better low end throttle response and economy than the 670 will. Keep in mind that you're probably not going to be turning the engine much over 4000 rpm, negating the need for the extra CFMs on the carb.

 

[eknuik]

This is a 670 truck avenger goin up without missing a beat, it was the driver that chickened out and stalled.
YouTube - calico part 4

 

[bsmith123]

Holley

I guess if I had a brand new one in a box I'd prolly try to make it work but I had pretty good luck with old Q-Jets

I know the bogging issue can occur but a lot of times (at least back when I had them) it was just a simple matter of replacing a spring and re-adjusting. Sometimes people would adjust them to open all at once thinking it would make for more power but it is better to have a gradual open

I think I did a mod out of Car Craft or Super stock or one of those that had you oversize the fuel passage for the secondary well a little

But on my rig I have a 2F so I just sent that and my distrib to FJ40JIM

 

[SargentSnotz]

Had nothing but bad luck!!!

I had one on a mild built amc 304 and had nothing but bad luck. Brand new out of the box it had flat spots on acceleration. Tried different accelerator pumps and even jets. Ended up going to jet performance in huntington beach california and had them build me a quadrajet carb. They built it to my motor specs and usual offroad environments. Tunned it to run in sand dunes but it also worked great crawling. Made it through johnson valley hammers without it stalling or loading up. Then i bought anotherone for my dads jeep. (highly reccommend quadrajets.)

 

[splib]

Good info, Brian. This should help quite a few.

 

[Downey]

Holley's had a reputation for being hard to make work off road. They do work well on the street once they are set up right.

And they work just as well off road once you have them set-up properly!!!!!

 

[Brian in Oregon]

Good info, Brian. This should help quite a few.

Thanks.

BTW, I had another 670 Truck Avenger on my '71 Chevy 454 pickup with 4.10 gears. 6 mpg at best. With the factory 89 jets (!) in the secondaries, if you stood on the gas pedal, it would literally run the secondary fuel bowl dry before it shifted into 3rd gear, killing the engine for about three seconds. Despite a big electric fuel pump, the transfer tube could not refill the secondary fuel bowl fast enough.

I have an Edelbrock 750 on it right now. It's up to a whopping 8 mpg. And no problems running the fuel bowl empty. This carb is much more streetable, yet still makes good power.

At one time this truck did 10 mpg, with a plain Jane Holley 600. But that carb was a loaner.

Still going to try a QuadraJet on it when I come across a decent one.

 

[nordwind]

Thanks for all the reply,
I have a 670 cfm,
I'm not sure what to do...

there are three possibilities
- I use the 670 cfm
- I trade in against a 470 cfm
- I sell the carburetor and go for something else

I forgot to say, I use a GM Prformens 383 with 340 hp
and I'm looking for low RPM performance
The fuel consumption is important for my family but not so important for me,

 

[eknuik]

Fuel consumption was not a consideration for me especially when you dont get it at the snails pace wheelin and also its a box goin' down the road with heavy tires and low gears......I had the edelbrock 750 on this warmed over 400cid and it would studder on a speed bump, the Holley for this engine has been a huge improvement and runs very good on the trial, i guess I'm one of the lucky ones. Chose wisely but I think the 470cfm will be too small for a healthy 383cid.

 

[Brian in Oregon]

Realistically, how many rpm's are you going to wring out of the 383?

If you take cubic inches, multiply by rpm, then divide by 3456, that will give you your theoretical cfm air flow.

But, unless it is a pure race engine, the volumetric efficiency is going to be less than 100%. A well built street and strip engine might run 80% to 90%. A plain stocker might be 70%. The point here is you then multiply the above result to get a true airflow. (Volumetric efficiency basically is factoring in the resistance to air flowing through the intake manifold, past the valves, and into the cylinder. Big cams, big ports, and big valves give better efficiency. Small ports, valves and cams give lower efficiency, but also can give better mileage and better low end torque.)

Example...

I have a 350 Chevy. I never go over 4000 rpm with it in my FJ40.

350 x 4000 divided by 3456 = 405 cfm.

Since I have a stock engine, multiplying by the volumetric efficiency ratio of 70% = 283 cfm.

Thus, a Holley 670 Truck Avenger is overcarbed on my engine by a factor of 2.3x.

So, let's look at your 383. And let's say you're more of a leadfoot than I am. And let's say you have a good RV cam or maybe a mild street rod cam.

383 x 5000 rpm divided by 3456 = 554 cfm theoretical.

Now let's say that you have 80% volumetric efficiency. That gives 443 cfm.

So.... I don't think a 470 is going to be undercarbed unless you have a pretty healthy cam, large valves, and big intake ports and exhaust, and/or you're exceeding 5000 rpm. And if your 383 is more of a stocker other than stroke, the efficiency could be closer to 70% to 75%.

 

[nordwind]

Hir is my motor data:
It is hard to understand, GM recommends a 750 CFM


HT 383 Technical Information
Horsepower ..................... 340 @ 4500 RPM
Torque .......................... 435 @ 4000 RPM
Max. Recommended RPM ..... 5000 RPM
Compression Ratio ............. 9.1:1
Partial Engine ................... 12498332
Block ............................ Four bolt main, cast iron
Crankshaft ...................... 12489436 Steel “4340”
Connecting Rods ............... 12497624 rods
Pistons .......................... 12489437 High silicon aluminum
Piston Rings .................... 12522848
Camshaft ........................ 14097395
Cylinder Heads ................. 12558060 Vortec
Intake Valves ................... 10241743 1.940"
Exhaust Valves .................. 12550909 1.50"
Valve Springs ................... 10212881
Rocker Arms .................... 1.5 stam steel
Intake Manifold ................. 12496820 Aluminum dual plane w/dual carburetor pad and EGR
Tortional Damper ............... 12498008
Flex Plate ....................... 14088765
Spark Plugs ..................... R 44LTS or Rapidfire #3
Fuel ............................. 87 Octane
Ignition Timing .................. 32° total @ 4000 RPM with vacuum advance disconnected
Technical Note:
GM recommends a Rochester Quadrajet or Holley 750 CFM carburetor for the 383 applications.

 

[Brian in Oregon]

Hir is my motor data:
It is hard to understand, GM recommends a 750 CFM


HT 383 Technical Information
Horsepower ..................... 340 @ 4500 RPM
Torque .......................... 435 @ 4000 RPM
Max. Recommended RPM ..... 5000 RPM
Compression Ratio ............. 9.1:1
Partial Engine ................... 12498332
Block ............................ Four bolt main, cast iron
Crankshaft ...................... 12489436 Steel “4340”
Connecting Rods ............... 12497624 rods
Pistons .......................... 12489437 High silicon aluminum
Piston Rings .................... 12522848
Camshaft ........................ 14097395
Cylinder Heads ................. 12558060 Vortec
Intake Valves ................... 10241743 1.940"
Exhaust Valves .................. 12550909 1.50"
Valve Springs ................... 10212881
Rocker Arms .................... 1.5 stam steel
Intake Manifold ................. 12496820 Aluminum dual plane w/dual carburetor pad and EGR
Tortional Damper ............... 12498008
Flex Plate ....................... 14088765
Spark Plugs ..................... R 44LTS or Rapidfire #3
Fuel ............................. 87 Octane
Ignition Timing .................. 32° total @ 4000 RPM with vacuum advance disconnected
Technical Note:
GM recommends a Rochester Quadrajet or Holley 750 CFM carburetor for the 383 applications.

Recommended max rpm 5000 and they recommend a 750? Sounds overcarbed to me. Especially when you do the math.