High speed air bleeds

[Geoff 2]

Stabbing the throttle on a 950 cfm carb on an engine that doesn't need 950 cfm is always going to run lean after the pump shot is used up. The single plane intake makes it worse [ which is why I asked about the type of intake ]. Gearing & weight come into it also. Probably doesn't do it [ or is less bad] in 1st gear.
Consider the known FACTS. The 440 Magnum came with a 750 cfm carb & made 375 hp. It was used with a DP intake which meant each cyl only got 375 cfm. Each cyl on your engine is getting 950cfm! Nearly 3 times more than the magnum!
You have a 'too big a carb problem', not a jet or air bleed problem. Not enough air speed through the big venturiis. Air speed creates the depression [ vacuum ] to pull fuel from the boosters. Low air speed, less fuel.
I would fit a 600 AFB or 650 AVS carb & you will be amazed at how well the engine performs!!

 

[Aron Gleason]

Stabbing the throttle on a 950 cfm carb on an engine that doesn't need 950 cfm is always going to run lean after the pump shot is used up. The single plane intake makes it worse [ which is why I asked about the type of intake ]. Gearing & weight come into it also. Probably doesn't do it [ or is less bad] in 1st gear.
Consider the known FACTS. The 440 Magnum came with a 750 cfm carb & made 375 hp. It was used with a DP intake which meant each cyl only got 375 cfm. Each cyl on your engine is getting 950cfm! Nearly 3 times more than the magnum!
You have a 'too big a carb problem', not a jet or air bleed problem. Not enough air speed through the big venturiis. Air speed creates the depression [ vacuum ] to pull fuel from the boosters. Low air speed, less fuel.
I would fit a 600 AFB or 650 AVS carb & you will be amazed at how well the engine performs!!

Yeah, thats why my carb guy said the 950 would work good on my motor cause he knows his stuff. But then again I have a so called friend who knows more about what my motor needs but has problems getting his car to run good.

 

[lewtot184]

Its a 440, and the carburetor is a 950 double pump carb. Not too big. I got it from a very reputable source who knows a thing or 2 about carb sizing. I already know i have to deal with the secondary side.

please find the carbs List number.

 

[Aron Gleason]

please find the carbs List number.

70210 quick fuel carburetor

 

[Budnicks]

I wonder if it is just dumping way too much fuel in the carb
#10 lines & a 950 cfm carb & it goes lean 'doesn't sound right'

does it have a bypass regulator ?
dumping whatever above the 5-7psi the carb needs back to the tank
I always have ran a 1 size smaller line for the return line,
so it doesn't spike it has ample fuel constantly

is you fuel system/electronics all on relay/s ? (like 30 amp Bosche relays)
& an arming switch, all quality stuff not cheap like Harbor Freight crap
so it doesn't spike bad (If so, check all the connections)
with any other electronics being used at the same moment/time

do you have a fuel pressure gauge inside ?
is it electronic or mechanical gauge ?
so you can actually see what the fuel pressure is when this happens
(cheap electronic gauge could be 'out of wack' too)

so you know exactly what the fuel is doing, not just an AFR
(they can & are known to be wrong, especially cheaper versions)

Just spitballing here
Sort of either sounds like an ignition problem
or something going on with the ignition inside the distributor,
ground or grounding out at the wrong times, possibly

do you have a known good vac. advance distr. to try ?
may save you a bunch of headaches, quick easy swap

your current 'ignition curve' could be 'way out of wack' too
not coming in fast enough, with mechanical springs or weights "wrong"
&
or adding in "a pourly tuned carburetor", that may be too big too

does it have HP manifolds still, not a good set of headers ?

my car is choked down (even with the 'ported HP manifolds')
& it has a lil' problem there, but it's tuned out of it

in theory;
Cubic Inches x RPM -/- by 3456 = total CFM
at *100% at wide open throttle
you need a bout 80%-85% of that CFM
unless it's extremely efficient
example;
440cid x 6,500rpm -/- by 3456 = 827cfm
at *WOT, at 100%, almost nothing is at 100%
unless it's extremely tuned well, full out race stuff, that's even rare

can you read plugs ?
this chart below may help with timing & AFR,
pay attention to the ground strap & where it is
what color & discoloration wise

your AFR reading/gauge, could be "way out of wack too"
it's not that uncommon, junk out there
is the O2 sensor in the right place ?
"not down by the bottom of the head pipe"
it needs to be up like 90* from the bottom, or it won't work right & won't last
it will get wet, not read correctly

also sound like a Powervalve problem, like it dumping at the wrong time
like a 2.5 where you need a 6.5, from the AFR (16-17:1) reading your getting
or the jets under the powervalve could be off/wrong

David Vizard SA216 (Car Tech Books) has a decent book
on Super tuning & modifying Holley Carbs

put a know good distributor in it
here's a schematic for a std later (Like 73) version of a CEI 4 pin ignition

good luck I don't know what else to tell you,
getting some bad advice or bad part/s from the people
or you have a problem you haven't narrowed it down to yet

 

[Aron Gleason]

Its all good advice Budnick. But ive had this problem for many years with no solution. I used to run a dead head fuel system with #8 fuel line, and ive always had a autometer fuel pressure gauge. For the last 6 years I upgraded the fuel system with #10 fuel line and a return style regulator, before that it had a holley regulator. The fuel pump is wired with bigger gauge wire with a quality relay which turns on and off by a toggle switch.

 

[lewtot184]

the 70120 number doesn't come up as any carb. i did look at a couple of 950 quick fuel carbs and their base line is 78 primary jets with a 4.5 power valve and 86 secondary jets with no power valve. i think this would be a good starting point.

i don't like the cellulose canister filter on the suction side of the pump. electric pumps, all of them, are poor pullers and good pushers. that's why they need to be located as close to the tank or cell. if you need some filtration before the pump use a 100 micron screen.

 

[Aron Gleason]

the 70120 number doesn't come up as any carb. i did look at a couple of 950 quick fuel carbs and their base line is 78 primary jets with a 4.5 power valve and 86 secondary jets with no power valve. i think this would be a good starting point.

i don't like the cellulose canister filter on the suction side of the pump. electric pumps, all of them, are poor pullers and good pushers. that's why they need to be located as close to the tank or cell. if you need some filtration before the pump use a 100 micron screen.

Well ive always had a 6.5 power valve in the primary side. Don't know if a 4.5 pv would make a huge difference, but id be surprised if it did.

 

[Aron Gleason]

Id hate to say this, but if I dont get the carburetor issue figured out and the oil leak fixed. It might be up for sale by summer time.

 

[Budnicks]

Its all good advice Budnick. But ive had this problem for many years with no solution. I used to run a dead head fuel system with #8 fuel line, and ive always had a autometer fuel pressure gauge. For the last 6 years I upgraded the fuel system with #10 fuel line and a return style regulator, before that it had a holley regulator. The fuel pump is wired with bigger gauge wire with a quality relay which turns on and off by a toggle switch.

Yeah
I know sometimes it's a chore to find the culprit
I had a similar situation like your description is
it was a Pertronix Flamethrower Coil (near new, just put it in like 6 months prior)
going out, for like 4 months
I did everything under the sun, except that damn coil
trying to figure it out

the plugs readings were my best clue,
it was showing a different pattern on the ground strap,
I knew was off from setting should have been (like it was too retarded, I knew it wasn't)
led me to it was ignition & not fuel problem
so I started to replace the obvious 1st, a coil

junk right out of the box (even brand new)
sometimes even reputable brands
that used to be dependable

again good luck

 

[RemCharger]

^^^^ before throwing the car in the garbage, check / or swap
Coil
Coil wire
Cap
Rotor
Check good power to the coil.
Plugs gapped .035
A lean spot will show a weakness in the ignition as Budnicks is saying

 

[old guys rule]

Ive always messed with the idle air bleeds to get the cruise afrs correct. But I read where the high speed air bleeds will help with a cruise to wot stumble by richening the emulsion circuit which should help with the stumble if im understanding it right. And I've messed with the accelerator pump cams, some cams help but doesn't completely eliminate the stumble. Am I on the right track?

A guy in California sells a thin plate for between the main body and throttle plate with an extra intermediate feed to solve just that problem. I haven't tried it yet myself. I'll get his name and address when I get home from Dr. Appt. Dave

 

[Aron Gleason]

A guy in California sells a thin plate for between the main body and throttle plate with an extra intermediate feed to solve just that problem. I haven't tried it yet myself. I'll get his name and address when I get home from Dr. Appt. Dave

Are you talking about the Thompson powerblast plate?

 

[old guys rule]

Are you talking about the Thompson powerblast plate?

The one I'm referring to is made by TMP Carbs. contact @ TMP carbs.net. I don't have a current phone number. His name is Troy

 

[Aron Gleason]

The one I'm referring to is made by TMP Carbs. contact @ TMP carbs.net. I don't have a current phone number. His name is Troy

I'll check them out

 

[old guys rule]

I'll check them out

My latest info on him: Troy Patterson 565 Hartnell st. Unit 1135 Mtry CA 93942

 

[Aron Gleason]

My latest info on him: Troy Patterson 565 Hartnell st. Unit 1135 Mtry CA 93942

I looked but didnt see what you're talking about. And he doesn't have a actual website, just Facebook so I couldn't look it up.

 

[old guys rule]

I looked but didnt see what you're talking about. And he doesn't have a actual website, just Facebook so I couldn't look it up.

That was my last contact with him. I'll check again. Hope he hasn't gone out of business.

 

[old guys rule]

That was my last contact with him. I'll check again. Hope he hasn't gone out of business.

For a while he was moving around. Try TMP Carbs 10030 & #1 Canoga ave Chatsworth,CA 91311. 818-885-0410. Hope he's still there, he has always had a lot of good products. That's all I have,sorry. Dave

 

[old guys rule]

For a while he was moving around. Try TMP Carbs 10030 & #1 Canoga ave Chatsworth,CA 91311. 818-885-0410. Hope he's still there, he has always had a lot of good products. That's all I have,sorry. Dave

The & must be a miss print. Should be a - Also try - TMP- gov.com