Carb Choices

[plovett]

EH has a different secondary metering block, and a .002 larger IAB.  It also has Chevy specific throttle shaft and the driver side has 1/4'' NPT threaded into the main body for some accessory that the -1 does not have.

Otherwise they function pretty much the same.  I bring them both up so if someone is looking for one at a swap meet, they would know that they are both desirable.

Thanks!

[My427stang]

You got some very good answers here, I have one way to simplify the jet discussion though (maybe too much even) but just the same....

Everyone understands that you need an "air / fuel mixture"  it's a ratio of one to the other, goal is between about 12:1 - 14:1 depending on what the engine is doing.

So, if you increase the size of the carb in CFM (air flow) then you need increase the fuel too (jet size)   So in very basic terms, although a jet for a 770 seems large compared to a 600 it has to be., the air is increased so the fuel needs to be


Now Drew is likely ready to jump at me  because it isn't that simple, other sources that contribute to the jet size required are secondary sources of fuel (power valve channel restriction...another jet that feeds in at low vacuum), booster design, emulsion circuit design, air bleeds, etc, but overall, a bigger carb has to have more fuel from somewhere and usually, it's more main jet

An example, a garden variety 850 takes an 80/88 jet combo, with the secondaries not having a powervalve, so bigger carb, bigger jet, and then when you take away a power valve out back, even bigger jet.  So you can see how much those other sources come into play.

Last thing, I do not expect you will love that Avenger series without work unless you get lucky.  They can act goofy at times, although I haven't specifically used a TRUCK avenger. The Street Avenger series in general has used an odd emulsion circuit that delays the transition from idle to main fuel.  Some combos (and some people) don't care, some have a slight hesitation or bucking when lightly accelerating.  It's worth trying if you have the carb, especially if it's an engine with decent vacuum.  Also, it's easily fixed by someone like Drew if it bothers you, but other than that, it's really just a decent carb with funny vents and I think a little more float control.

[Drew Pojedinec]

Nah, I won't string you up, lol.....

Ross, the truck avenger, you'd love it.  Has mini annular boosters in the primary with no HSAB.  Typically they are fat at idle, stupid lean off idle, and really fat as the idle feed and boosters run together for about 1200rpms.
Have downlegs in the secondary but it doesn't matter, they'll never open anyway.
As far as fixing one, my advice has always been to just sell it on ebay and start with something that needs less work.

[My427stang]

Nah, I won't string you up, lol.....

Ross, the truck avenger, you'd love it.  Has mini annular boosters in the primary with no HSAB.  Typically they are fat at idle, stupid lean off idle, and really fat as the idle feed and boosters run together for about 1200rpms.
Have downlegs in the secondary but it doesn't matter, they'll never open anyway.
As far as fixing one, my advice has always been to just sell it on ebay and start with something that needs less work.

LOL definitely different than a Street Avenger, not that I like those that much either.

It's amazing what Holley does to "improve things"

[Barry_R]

It's amazing what Holley does to "improve things"

LOL
Some of the newer stuff can be pretty good - but some of it is so wrong that it hurts.
Like an annular booster with no HSAB...who thought that was a good idea?

I really like those old 3310 780s and the CJ 735s.....still about the best OE calibrations for drivability and smooth street performance.  They simply drive really well.

[Drew Pojedinec]

Bored and want to do some reading Ross?

https://www.tapatalk.com/groups/racingfuelsystems/viewtopic.php?f=25&t=1683&p=16284&hilit=truck+avenger#p16284

I like the 735 CJ stuff as well, I didn't mention it as they are often expensive.  I just scored 4 of them for cheap, hope to do them sometime in the next month or two.

[My427stang]

Wow thanks Drew.  I wonder what they ever wanted to accomplish with that 670?  Can't say I'd want to have to try to make one of those work

There has to be something acting like a HSAB in there, I just can't see the liquid fuel behaving nicely without something in a circuit. A kill bleed in the booster itself maybe?

Does the 770 have the same setup?

[Drew Pojedinec]

I think the 770 has downleg secondaries.

The few that came in were a few years ago and I didn’t write down calibrations at that time.

The angle channel is high, so no kill bleed or siphon break needed.

[WerbyFord]

Wow thanks Drew.  I wonder what they ever wanted to accomplish with that 670?  Can't say I'd want to have to try to make one of those work

There has to be something acting like a HSAB in there, I just can't see the liquid fuel behaving nicely without something in a circuit. A kill bleed in the booster itself maybe?

Does the 770 have the same setup?

I have a 390cfm Holley R6390 from a 392cid International Harvester truck.
Same deal, PMAB=0 on the main body, all PMAB=0 on the block.
PIAB=.070", big, like this 670sa carb.

The R6390 runs really strong (on a little engine), it has won more GTECH shootouts on my 6cyl inline than any other carb.
So they must have done something right in there.

All 4 boosters are regular straight-leg, and the secondary bleeds all look pretty normal as do the jets.
Why go to this configuration of PMAB==0 everywhere? Strange!

[Tobbemek]

For what ever reason Holley made there choice to calibrate the truck avenger carbs that way those carbs don't function properly on a regular car 200 ore 500 Hp dosent matter. It will take a skillful person like Drew to rework it to function on a car ore even a truck what that matters.
Get another carb or rework it.

The idea with the Main Air Bleed is to lean out the fuel curve in the upper part of the curve because the signal to the booster increases whit air flow in a not linear path so the carb will turn overly rich otherwise.

[440sixpack]

Okay, so everything I hear and read on the truck avenger is it's a POS.


The 3310 EH sounds like a good option,  I see lots of them on ebay.  but I don't want to buy a worn out junker with mismatched parts and cracked housings and try to fix it.   so what would be a viable alternative in something new ?   All I see are street avengers and double pumpers and I don't need that for a 4x4.

[Drew Pojedinec]

I have little experience with new carbs, and can't advise there.

I have about a dozen EH or -1 3310's that I could restore.  It'll cost roughly the same as a new Avenger, but it'll be blueprinted and I test run them.  It'll look like the ones I posted above. 

I didn't mean to participate in this thread and make it seem like a for sale dealio......

What you have:
-Edelbrock that runs great
-Truck avenger that hasn't been tested.

Given what you have on hand I'd either run the Edelbrock, or test out the truck avenger on a known good engine.  I would be scared to test an unknown carb on a new engine.... just too many things to be watching for.

[RustyCrankshaft]

I don't like to introduce too many variables at once because if something goes wrong it's really hard to figure out what exactly the problem is.

The Edelbrock, even if it's too small, would be my choice first. One less thing to worry about. Once everything is dialed in, then switch to something else so there is only one variable to deal with. Especially if you run that Avenger. I'm no carb expert, but I haven't had good luck with "newer" Holleys except for a few "race" carbs and even then some of those didn't work. I got an XP last year that had a bad mainbody out of the box.

Someone who is good at carbs can fix an avenger, but I haven't had one that every really worked right.

[Heo]

I had a 870 street avenger it had a slight delay
untill i put on a fourhole spacer or adjusted the
floatlevel to high

[440sixpack]

Drew,  I'll give that new carb I have a try but if it gives any trouble at all you'll be hearing from me.