Carb Choices

[440sixpack]

In the process of getting my 428 back together.   it came with a perfectly tuned Edelbrock  that runs great but I run a Holley on everything. 


I have a brand new 770 Truck Avenger I got somewhere.  would this be too much for a street 428 with 10-1 compression ,  a mild roller cam and pretty much stock otherwise.  this is in a '76 high boy with a 4spd.   I think I'd be better off with a 650 but if this would work I have it.

[cjshaker]

The 770 is not too big. I don't know what makes it a "truck" carb though?
Just for comparison, I ran my 68 F250 Highboy with a stock S intake, which is very similar to yours, and it did a great job. My engine would have been similar to yours also, except it was a 390. Mild solid cam that resembled the Ford 390 "GT" cam, headers, C4 heads...and a 750 VS Holley. That carb/intake duo worked perfectly for that combo, idled great, had tons of low end grunt and pulled really nice to about 5000 rpms, where the cam started to give out. A better intake might make a little more power, but I doubt you'd feel it, and it also might kill a bit of the lower end. My truck got used, hard, for almost 25 years, so I was ok with the minor trade-off. I think you'll be pleasantly pleased with your combo, provided it's tuned right.

Edit to add that, personally, I think the 650 would kill more power than anything but the factory log exhaust. A 428 is a fairly good sized engine; bigger than a 650 can feed.

[Tobbemek]

The Truck Avenger carb has some strange futures in them you have to take care of, better have Drew to advise you on that part, the 770cfm is not a trouble.

[440sixpack]

The Truck avenger series has a stupid vent tube in the air horn for extreme off road angles or something.   just something to make Bubba feel like he has a special carb I guess.


As far as the rest goes it looks pretty much like a run of the mill street avenger.  but maybe I need to check it out.

Holley calls for a 570 to a 650 in there carb selector,  but they always lean to the small side it seems. 


Do you think I should break in the rings with the Edelbrock and then switch it afterwards ?   I don't know how the jetting will be so it might be a bit rich.

[cjshaker]

Carb calculators always seem to be on the conservative side compared to what actually works best, or what an engine can use.

It's always best to do a break-in with a known good carb. The last thing you want is a lean or rich condition during that crucial stage. It would even be wise to do some initial driving with the known good carb, then switch it out after everything gets broken in.

[My427stang]

A 750 vacuum secondary is my go to carb on anything but the mildest truck FEs.  360s and real mild 390s can be happy with a 600, but your build should be happy with a 750-770

FWIW, my temporary truck motor, tight quench std bore 390 4V, mild Crane hyd flat tappet, Streetmaster, and headers runs perfect with a 750, so it's certainly not too much carb for a 428 with more cam and likely more compression.  In fact, it runs so nice I am questioning why I am building the EFI 461 for it right now

The 770 is not too big. I don't know what makes it a "truck" carb though?
Just for comparison, I ran my 68 F250 Highboy with a stock S intake, which is very similar to yours, and it did a great job. My engine would have been similar to yours also, except it was a 390. Mild solid cam that resembled the Ford 390 "GT" cam, headers, C4 heads...and a 750 VS Holley. That carb/intake duo worked perfectly for that combo, idled great, had tons of low end grunt and pulled really nice to about 5000 rpms, where the cam started to give out. A better intake might make a little more power, but I doubt you'd feel it, and it also might kill a bit of the lower end. My truck got used, hard, for almost 25 years, so I was ok with the minor trade-off. I think you'll be pleasantly pleased with your combo, provided it's tuned right.

Edit to add that, personally, I think the 650 would kill more power than anything but the factory log exhaust. A 428 is a fairly good sized engine; bigger than a 650 can feed.

Doug, they certainly can run well with the S intake, and I would never say an uintake is required, but I can tell you, when mine worked for a living I went from an S to a 428 PI and it was night and day with no other changes. Same carb, same distributor, just an on the truck intake change.  The truck at the time was a 390 + .030 low compression with the 204/214 cheapo cam sold through NAPA, bone stock D2TE-AA heads, 600 1850 with a set of headers.

I've told the second half of the story before, but about a year later was when the Performer 390 came out, I swapped the PI because the exhaust crossover rotted out and the Performer was such a turd on the whole curve, I fixed the PI intake and swapped it right back.

This was a long bed 4x4 NP435 4 speed at the time, with 3.70 gears and 36 inch rubber, plowed snow, pulled anything I needed back to the shop and it really gained everywhere and no loss whatsoever.  I certainly think the S and T code intake have their place, but IMHO a mild 390 out breathes them pretty quick

[Drew Pojedinec]

Since my name was brought up......
Truck avengers are weird.

If I had one carb to pick, it would be this:

IMG_1132 by Drew Pojedinec, on Flickr

IMG_1137 by Drew Pojedinec, on Flickr

These EH 780's work well on 390's, 428's, heck most everything to be honest.

[440sixpack]

Anything in particular on a truck avenger to be aware of ?

[plovett]

Since my name was brought up......
Truck avengers are weird.

If I had one carb to pick, it would be this:

IMG_1132 by Drew Pojedinec, on Flickr

IMG_1137 by Drew Pojedinec, on Flickr

These EH 780's work well on 390's, 428's, heck most everything to be honest.

The downleg Holley 780 3310-1 is the overall best musclecar carb ever, in my opinion.  Factory installed on 302's, 396's, and 454's.   Works well on 14 second cars, and all the way to 9 second cars.  Amazing carb.

paulie

[Drew Pojedinec]

Anything in particular on a truck avenger to be aware of ?

Well..... they were built for one reason.  Offroading and the truck being at weird angles.
So yeah, it's cool for rock climbing.  I don't do any of that, so the carb is kinda just "meh" in daily driver status.
I know, I know, I'm a carb guy, but I think if I was doing serious rock climbing I'd be using fuel injection.
I'd have to look at my notes, but the emulsion is drastically different, and if I recall the two that came in, both where fighting lean spike issues.
Try it out, you've already got it....

The downleg Holley 780 3310-1 is the overall best musclecar carb ever, in my opinion.  Factory installed on 302's, 396's, and 454's.   Works well on 14 second cars, and all the way to 9 second cars.  Amazing carb.
paulie

There are a handful of others that work really really well all around, but the 3310EH and -1 are so common, it's hard for me not to use them as a go-to carb when someone asks for a mild performance suggestion.

[440sixpack]

I'll give it a try but if it doesn't run great I'll ditch it.



I know there are a million variables but don't you think 74 main jets on a mild built 428 at 3000 foot  elevation  might be a little rich?   they say that's what they come with so I was thinking more like a 68  the 670 comes with to start with.

[Drew Pojedinec]

I know there are a million variables but don't you think 74 main jets on a mild built 428 at 3000 foot  elevation  might be a little rich?   they say that's what they come with so I was thinking more like a 68  the 670 comes with to start with.

Jetting isn't like an on/off switch.... jetting isn't engine specific.  Jetting is venturi and throttle plate specific with a dash of signal thrown in the mix.
For example, If I put a 600cfm carb on a 445 stroker, my main jet would be 66-67, really not gonna be a ton more or less.  If I had to go over 68 I'd start looking to see what is out of whack.
Now, toss on a 750 carb and all of a sudden I'm running 72-74 jets.
Toss on a 780 downleg carb like I pictured above and we are running 68 jets... why less?  air bleed differences, booster differences, PVCR's that are massive, plus from the factory that early 3310 had a 10.5 power valve, so you can cruise lean and clean, push the throttle a little the the power valves starts to pull open.

Same reason I can run 1, 750 carbs on a 445ci engine and run 72 jets.  Add two carbs?  Probably gonna run 70 or 72 jets again   Each restriction is being pulled on half as hard.  Knock out those downlegs and install Annular boosters and all of a sudden 72 jet is stupid rich and you are jetting down to 66 just to get in the neighborhood

blah blah blah, just bolt on the truck avenger and see what happens. (be better still to go test it on a known good engine)

[440sixpack]

Makes sense.

[plovett]

The downleg Holley 780 3310-1 is the overall best musclecar carb ever, in my opinion.  Factory installed on 302's, 396's, and 454's.   Works well on 14 second cars, and all the way to 9 second cars.  Amazing carb.
paulie

There are a handful of others that work really really well all around, but the 3310EH and -1 are so common, it's hard for me not to use them as a go-to carb when someone asks for a mild performance suggestion.

Are there any significant differences between an EH 3310 and a 3310-1?

[Drew Pojedinec]

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.