Hi everyone,,

I have been reading a bit on carbs, and i think I want to try a Holley 390 carb on my stock slant 6.

If I purchase the carb from summitracing, will it be a straight bolt on? or do I have to change parts on it?

What about buying it straight from holley? (on-line)

What would I have to do to the carb in order to make it work well for a dailly driver on a 82 d150?

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Slant power!!!
At least I try...

Do a search on this site about the Holley 390, and you'll find a lot of information about tuning, and what needs to be done to make it work.

It is not a bolt on. First, you will need a four barrel intake. I'm sure you have that figured out.

The primary jets, pump cam, Power Valve, accelerator pump shooter, secondary plate, Secondary vacuum spring and possibly the air bleeds will have to be changed to make this carburetor work.

The closest thing to plug and play will be an Edelbrock 500 AFB. It will need some tweaking as well.

Next, you will have to re-curve the distributor.

Without an increase in compression, and a cam to take advantage, a four barrel will not improve performance.

The stock exhaust will be a real bottle-neck.

Without building more engine, better exhaust flow, and adjusting the ignition to fit, a four barrel will not net you anything at the track, or out on the street. It makes a bit more noise, and adds bling under the hood.

There are two barrel options that can improve performance with much less modification.

Read up in the Engine build matrix located in the FAQ for the Engine section.

CJ

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Part of Tyrde-Browne Racing

I already have a 2.5 inch exhaust on the truck.
And I have hie ignition with a after market high out put coil.

I would like to buy a "new carb" but it seems that everyone carries remaufactured carbs only.

were could I buy a good, new, two barrel carb at?

Could you recommend?

_________________
Slant power!!!
At least I try...

By two barrel, do you mean a BBD?

If so, check with Dan. He periodically pulls a rabbit out of his hat with an appropriate NOS carb.

If your willing to put a little work in the engine, there are other options. A bump in compression will allow you to run the 350 cfm Holley universal that is available new. The 500 is not a good choice for a driver.

Describe your exhaust. Anything larger than 2-1/4" on a stock single manifold doesn't accomplish much.
The exhaust charge is going to slow down and cool too quickly with a 2-1/2". Wrap the head pipe if that's a single. It will help, but it's still pretty big.

Compression, valves, and mild head work will build some power. Depending on what you have for transmission and rear gears, there is some available performance there.

If your willing to get the compression up into the 9+:1, you will see improvements across the board with the two barrel and will be in range of using a four barrel. For street use, the Edelbrock intake is a pretty good choice. Street/strip and drag, look at the Clifford intake.
10:1 and a bit of cam, coupled with some head work will really wake it up. Headers, or Dutra Duals can uncork the genie once you have some compression to work with.


CJ

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Part of Tyrde-Browne Racing

ok, thank you,,

I have a pair of headers that i have not installed. They are the "double" header. I have been planning on installing them. Should I, or should I wait untill I build a better engine?

And If I should, on a stock engine, what size exhaust shouls I use?

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Slant power!!!
At least I try...

For pipe size off the headers, go 2" back to a single muffler, then a single 2" over the axle. If you like duals, keep the tail pipes aft of the muffler small to keep velocity up.

A single tail pipe will dry out better, so will last longer.

For best results, if you decide to go for the four barrel, get yourself some instruments that will help you in your quest. I've been there!

1. Tachometer. You need to know what the engine speed is.
2. Vacuum Guage. This will tell you what circuits of the carburetor your are using at any moment in time.
3. A/F gauge. Imperative for tuning. Reading plugs doesn't tell you, in conjunction with teh Vacuum gauge, what is going on with the circuit of the carburator you are working with.

I ran a Holley 390 on an Edelbrock on an otherwise stock engine for quite a while. I had the luxery of DusterIdiot building my distributor, testing, then returning to his garage to work things out on the white board for further modficication. He also helped me out with my first street port on the head.
That's been a couple years, huh DI?

I ended up with a 20 second car. Pretty close to what it was with the 1 bbl.

Things got much better with heavy modification. On a good day on sticky rubber, it can dip into the 14's. Not bad for a '74 four door tuna boat.

The good thing about the 390 was the fuel economy. It jumped from 16 to 24 mpg running down the freeway. Small primary four barrels can deliver excellent mileage. The drawback being, they must be carefully tuned to do it.

Give Dan a shout and see if he can come up with a carburetor that fixes your issues. What's wrong with the one you have? For a stock build in a truck, I can't think of a better match than a BBD.

CJ

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Part of Tyrde-Browne Racing