Added 470 CFM carb.

[sir loin]

Just like the title says, I originally had a Holley 4160, 390 CFM. After much tuning on this new engine, I realized (and gambled) that I was under carbed. Originally, the TB on this engine was 400 CFM (someone correct me if I'm wong). But I figured with more flow add-ons like an Edelbrock intake, headers, and cam it would work.

Here's a pic:


I'm getting close to going to the dyno shop. I have a buddy in Tampa that owns a Mustang shop.
Here's the engine and mods, any guesses on HP?

Engine: 1994 3.1L Iron Heads
• Heads shaved/rebuilt all new components (valves, seats, springs, etc.)
• Block professionally cleaned, acid bathed, freeze plugged, etc.
• Crank balanced, new harmonic balancer
• Totally rebuilt 3.1L bored .030 over
• New oil pan, high volume oil pump
• New pistons, rings
• Remote oil filter
Ignition/Timing:
• Mallory coil, ignition box, Unilite billet distributor
• Double roller timing chain
• Magnecor 8.8 mm wires
• “Phase 2” High Torque cam, new lifters
Induction/Fuel:
• Edelbrock Torquer 2 intake
• Holley Truck Avenger 470 CFM carb.
• Mallory high volume fuel pump
• All AN fittings and braided lines
• One Fram and one Jegs fuel filter
Exhaust:
• Edelbrock ceramic coated headers
• Flowmaster Y-Pipe
• Flowmaster off-road, diamond plate series 60 muffler
Cooling:
• New water pump
• Northern brand over-sized, all aluminum radiator
• Jeg’s billet overflow can
• Electric fan

[ezrollin]

No,it wasn't under carbed with the 390,but it is over carbed with a 470 !

[Wiz85]

It's hard to tell, but if you dyno with the 390 and then the 470 and it made quite a bit more power then yes it's under carbed. But it's possible to tune a 470 bad enough to get the same amount of power as the 390 carb. So optimal tuning from both carbs would only be able to tell. Plus, I've seen articles that have 450 hp SBC's than dyno with 750+ cfm carbs and then use a 600 cfm carb and the power drops very little amazingly. Food for thought.

[Canyonero]

Isuzu Trucks FTW!

[turboD]

I think the advantage is that the carb is a vacuum secondary type unit. As is the case with these carbs, the secondary will only open when the engine can handle the air flow. Holley offers a great deal of tune-up thru the secondaries with spring kits, variable orifices, sec. metering/jets, etc. The trick will be in getting a good base tuneup (on the engine and carb), then keeping a record of the changes as you go. It's great that you have some way to get dyno time, but remember to have everything set the best that you can as the initial startring point (timming, plug heat range, valve adjustment, cooling system, Float level adj., etc). It helps with the down time during the pulls. D

[sir loin]

No,it wasn't under carbed with the 390,but it is over carbed with a 470 !

Can anyone else add to that statement?
Why would the 470 be over carbed? Only thing I could think of would be WOT when everything is flowing; the full potential of 470 CFM. I did use Holley's chart to find the right CFM for cid, RPM, etc. and (as a rule of thumb) it says I'm a little over carbed.

I've got everything up and running, took it for a test drive. Couldn't wait, forgot to bolt down my hood scoop and it blew off and slid down the street.
Holy S**t! What a difference in low-end torque and off idle start. Night and day.

Still tuning though, I had my timing down with the 390 CFM. I may have to advance slightly more. Also messing with the secondaries, it seems to bog a little when they open. Installing a heavier spring so they open a little later when more air is flowing higher in the RPM range.

[Canyonero]

Isuzu Pickup, Shiny Engine, Hood Scoop... Let's see the rest.

[ezrollin]

From the top of my head carb cfm=cubic inches x rpm / 3456 x ve 180x6000/3456x.85=265 cfm or cfm@100% ve=312. So,a 390 would be more than enough.There are jets,springs,etc available for the 390 to dail it in....go online or get a book on tuning a Holley to make adjustments.

[Ortie666]

Personaly I use the 390 mech. secondary tunnel ram one with a shaved choke horn on a all stock motor.. but my buddy tryed a 450 and a 500, the 500 worked but was bad out of the hole, the 450 worked great.. his was a 2.8L iron head 260 cam with port job, headers, ect.

[sir loin]

Personaly I use the 390 mech. secondary tunnel ram one with a shaved choke horn on a all stock motor.. but my buddy tryed a 450 and a 500, the 500 worked but was bad out of the hole, the 450 worked great.. his was a 2.8L iron head 260 cam with port job, headers, ect.

Thank you!!!

I'm glad to hear someone's personal experience with carbbing these motors.
Honestly, I think I'm over-jetted, especially with the secondaries.

Out of the hole the 470 rockets past my 390 (which is for sale BTW). But when the secondaries open it bogs. First I'll look for vacuum leaks, then advance the timing. Worse case I'll try to jet 4 lower on the secondaries. I'm also buying a advace timing kit for my Mallory distributor, I want to make it two stage.

The primaries may be a little heavy on the jets too, but I'm changing to 1.6:1 rockers, so I'm going to wait. Also, my current headers are shorties and I'm going to a long tube which may help breathing

Holleys are notoriously rich anyway, so we'll see.

[geoffinbc]

I'm just glad I stuck with EFI

[Ortie666]

Thank you!!!

I'm glad to hear someone's personal experience with carbbing these motors.
Honestly, I think I'm over-jetted, especially with the secondaries.

Out of the hole the 470 rockets past my 390 (which is for sale BTW). But when the secondaries open it bogs. First I'll look for vacuum leaks, then advance the timing. Worse case I'll try to jet 4 lower on the secondaries. I'm also buying a advace timing kit for my Mallory distributor, I want to make it two stage.

The primaries may be a little heavy on the jets too, but I'm changing to 1.6:1 rockers, so I'm going to wait. Also, my current headers are shorties and I'm going to a long tube which may help breathing

Holleys are notoriously rich anyway, so we'll see.

That could be the case, id try the jets first, and if that doesnt work it might be from the vacume drop, so the way Ive fixed that is hogging out the small ports on the edlebrock manifold to match the otherside, then there should be more volosity at higher rpm, or by time the secondarys open.. Ohh, and if it just bogs its the jets, but if it bogs and babbles(sputters farts) its the lack of volosity threw the carb

[sir loin]

That could be the case, id try the jets first, and if that doesnt work it might be from the vacume drop, so the way Ive fixed that is hogging out the small ports on the edlebrock manifold to match the otherside, then there should be more volosity at higher rpm, or by time the secondarys open.. Ohh, and if it just bogs its the jets, but if it bogs and babbles(sputters farts) its the lack of volosity threw the carb

Great advice....I have a question you may know the answer to. Do I use a 4-hole or open gasket on a dual plane intake? I have an Edelbrock Torquer II that's a dual plane, it came with the open or one hole gasket. The 390 I used a 4 hole Morosso gasket, or does it matter?

[Ortie666]

Great advice....I have a question you may know the answer to. Do I use a 4-hole or open gasket on a dual plane intake? I have an Edelbrock Torquer II that's a dual plane, it came with the open or one hole gasket. The 390 I used a 4 hole Morosso gasket, or does it matter?

Well it does to a point, if you use the 4 hole one it will up the vacume and response( by therory) because the its sealing the carb across that deviders (so 2 barrels to 1 port), If you use an open one there is a little bit of space there that will ballence the 2 banks, so it would be like (4 barrels to 1 port), its not enough to really make a diffrence in top end, but it will create slight turbulance right under the carb, in my case i hogged that down a bit and knife edged it because i have a nitrous plate, and when the rails sprayed it would interfear.. So I would just go with the 4 hole one, kuss you have plenty of carb for top end

[ezrollin]

I wouldn't be so eager to get rid of the 390. The 470 is bogging when the sec. open because it's to big.You should find out why the 390 wasn't performing on the primaries,holleys aren't that complicated.I had a 390 on an Offy manifold with a 260 cam and it ran strong.Check the jets,air bleeds etc;etc on the 390. There's a reason why both offy and holley both recommend the 390, because it's the right carb.