Too much carb for my 440?

[66four40]

Here is as much about the combo as I know. I bought the car last November and only have one summer under my belt. This is also my first old car. The motor was rebuilt before I bought the car and this is the info I was given.

440 - late seventies
10 - 1 compression
Mild Mopar Purple Shaft Cam of unknown grind
Heads ?, need to pop off a valve cover to see which heads it has
Stock intake
800 cfm Edelbrock
Points - Have Pertronix with the Flame Thrower coil, just need to get to dad's house to re-time the car and install.
8.5 mm MSD Super Conductor wires
stock exhaust manifolds
2400 stall converter
3.91 sure grip

When I bought the car, the previous owner said it was a 600 Edelbrock. I looked at the part number on the carb and determined that its an 800, bonus! Wondering if the carb is too big. We need to spend some time tuning the car a bit but what to know if I should be looking for a 750, or should we be ok. Dad is my go to guy/crew chief and would love it if I just went out and bought a 750 Double Pumper. Well, I don't have $400 Canadian pesos burning a hole in my snow suit pockets.

Bring on the questions!

Cheers, Derek

 

[super-bee_ski]

I'm no expert BUT, I was "schooled" on this Forum once or twice about this very same issue.

Here is what I have been taught...

The 440 CAN HANDLE a 750CFM easily, as most likely a 800CFM.

Now, many here on the Forum will tell you that a Holley is easiest to set up.

 

[GTX MATT]

The 800 will be fine, and the 800 AVS Thunder Series (rather than the AFB) even better. If its a manual choke, even better.

Don't buy a 750 Edelbrock whatever you do, they're noted for have a plethora of issues. 750 Holley DP would be fine as well, really depends more on what cam you've got. I prefer Holleys myself but you're good with the 800 though. Tune it and when you do have 400 dollars burning a hole in your pocket then you might want to give the DP a try.

 

[Badvert65]

I have TWO 700 cfm Holly carbs (modified, actually closer to 750) on a 440 that has seen regular street duty. Don't let anyone fool you, a 440 can really take a LOT of carb and still run great.

 

[terzmo]

750 came stock....800 is fine...enjoy

 

[lewtot184]

the 800 is a good choice. the 800avs that i have played with on a friends 427 'vette was too rich on factory calibration. jetted it down and played with the accellerater pump circut and ended with a beautiful driver with great power.

 

[Meep-Meep]

The fundamental rule of carbs is they live on vacuum, or better put, the proper low pressure signal. The pressure differential is what makes them work. End of story. That said what you need to do is try as many different types and sizes as possible. Start small and see how it does. If the car is primarily for the street then you want the smaller CFM. If you spend most of your time with your foot to the floor then go bigger for top end power. Another note: Contrary to popular belief a larger carb may actually run leaner. This is due to the fact of a weaker signal across the boosters thereby not allowing for proper fuel flow. At this point you don't know what you have engine wise. Unless your engine was measured you are only guessing at compression. Cam? Same thing. Do a cranking compression test first to get an idea of what you have. Then set timing to 36-38 deg total with as much initial as the engine can stand to cover for the big cam. Likely 15 deg BTDC. You may have to limit the internal advance, meaning take some out of the distributor so you can run more initial while keeping the total at 36-38. Ignition system is in good shape and some sort of high energy setup? Basics first then diddle with the carb.

 

[super-bee_ski]

I have TWO 700 cfm Holly carbs (modified, actually closer to 750) on a 440 that has seen regular street duty. Don't let anyone fool you, a 440 can really take a LOT of carb and still run great.
View attachment 214419

Ah, YUP...That IS a BAD VERT!

 

[1969CoronetR/T]

I ran a 800 cfm Edelbrock for five years with stock heads without any problems. Dyno tuned every year and ran great.

 

[Bigal75]

I got 2 800 Edelbrocks on my set up...but it's a few cubes larger ;)

 

[66four40]

The fundamental rule of carbs is they live on vacuum, or better put, the proper low pressure signal. The pressure differential is what makes them work. End of story. That said what you need to do is try as many different types and sizes as possible. Start small and see how it does. If the car is primarily for the street then you want the smaller CFM. If you spend most of your time with your foot to the floor then go bigger for top end power. Another note: Contrary to popular belief a larger carb may actually run leaner. This is due to the fact of a weaker signal across the boosters thereby not allowing for proper fuel flow. At this point you don't know what you have engine wise. Unless your engine was measured you are only guessing at compression. Cam? Same thing. Do a cranking compression test first to get an idea of what you have. Then set timing to 36-38 deg total with as much initial as the engine can stand to cover for the big cam. Likely 15 deg BTDC. You may have to limit the internal advance, meaning take some out of the distributor so you can run more initial while keeping the total at 36-38. Ignition system is in good shape and some sort of high energy setup? Basics first then diddle with the carb.

Awesome post. Tons of great info, and work to do over the winter. The ignition system will be Pertronix Ignitor with the 40,000 V Coil. I haven't done a compression test yet, and need to pull off a valve cover to see what heads are on it. I will need to borrow a crystal ball to determine the cam specs though, unless there is a better way to determine what it is?

 

[Garys1969RR]

You can determine cam specs with a degree wheel and a dial indicator reading off the solid part (outer edge) of the lifter. Check readings just when the lifter starts to move, and @ .050" lift.

- - - Updated - - -

I have a 451 with an 850 double pumper Holley on top and a 1" spacer. Very responsive, doesn't bog when you hit the throttle. But you have to bring the RPM up to about 1800 or 2000 to launch it.

 

[Torkmnstr]

Derek I have almost the same built motor. Except for some bowl porting on the stock heads. I have a holley 750 DP with a proform main body swapped out, which should put it around 800 plus cfm. I have had no problem with her so you are good with the 800.

 

[Meep-Meep]

Awesome post. Tons of great info, and work to do over the winter. The ignition system will be Pertronix Ignitor with the 40,000 V Coil. I haven't done a compression test yet, and need to pull off a valve cover to see what heads are on it. I will need to borrow a crystal ball to determine the cam specs though, unless there is a better way to determine what it is?

Thanks. I did forget to mention the vacuum gauge. After you have the basic timing set with enough advance to have a nice crisp sounding idle put a gauge on it and see what you get. Low vacuum can mean big cam, or high overlap really. The 108 LSA cams tend to pull about 10" at idle while a 112 might go 12". The stock type cams idle really smooth and can be high like 15-18". Some 110-112 LSA cams can still produce a high idle vacuum so really there is no way of knowing what it is unless you degree it or see a P/N on the back. If the car idles really lumpy (hot cam sound) then expect about 10" Hg at idle. This is where someone with experience comes in, so if you have a local guru that has spent a lot of time with American V8's in all sorts of tunings you might want to invite him over for some adult beverages (beverages after he does the tuning!). Some of these mystery motors are best sorted out by being there.

 

[66four40]

Thanks. I did forget to mention the vacuum gauge. After you have the basic timing set with enough advance to have a nice crisp sounding idle put a gauge on it and see what you get. Low vacuum can mean big cam, or high overlap really. The 108 LSA cams tend to pull about 10" at idle while a 112 might go 12". The stock type cams idle really smooth and can be high like 15-18". Some 110-112 LSA cams can still produce a high idle vacuum so really there is no way of knowing what it is unless you degree it or see a P/N on the back. If the car idles really lumpy (hot cam sound) then expect about 10" Hg at idle. This is where someone with experience comes in, so if you have a local guru that has spent a lot of time with American V8's in all sorts of tunings you might want to invite him over for some adult beverages (beverages after he does the tuning!). Some of these mystery motors are best sorted out by being there.

Good idea. I like the adult beverages part. i also really appreciate passing on the knowledge.

 

[jeepers007]

If it idles lumpy, its one of the larger purpleshaft cam grinds.

 

[YY1]

I have a 69 10:1 440 that I ran a 600 (1406) on for a while.

It lean surged pretty bad and you could tell it ran out of fuel about 3800 RPM.

I just put on a swap meet 750 (1407), and the surge is almost completely gone.

Throttle response is better and it carries more vacuum as well.

This engine had a bit of a lope to it, but I have no idea what cam is in it.

 

[Dennis H]

850 Demon here. Lumpy idle. Local Guru to tune.

 

[lewtot184]

a comment on tuning; i have a [email protected] lift, 110 lsa, installed at 106, camshaft in the engine of my 65 coronet. i bet i built a box full of distributors before i found a combo i liked. idles at 15"-16"@950 rpm in neutral, 10"11" in gear at 750rpm. also a ton of carb work but this is what you have to do with performance camshafts.

 

[ZR9B]

every time I had a carb that seemed too big to tune in I would use a four hole carb spacer....helps down low.....the open spacer helps up top.