Carburetor recommendations wanted

[C500]

Hey guys,

My '69 440 has been rebuilt and recently 'run in', specs below. I have a Proform 750 on it now, mechanical secondary. It stumbles a little off the mark. I took it for a 30 minute drive yesterday, and went well. After parking up for lunch, couldn't start it so easy a couple hours later. Almost everything on it is new. Any other suggestions on issues why it won't start? Seems worse after going for a drive.

I've had it Dyno tuned and the Compression is 10.2.

440, +30 thou block (4.35 bore, 3.75 stroke) deck surfaced
CAM: Crower Hydraulic (271HDP) Flat tappet, Advertised Duration 271/284, Lift .486/.496 Part 32242
HEADS: 440 source stealth heads, with some porting
PISTONS: JE / SRP Flat top, Forged aluminium, 2.062" compression distance (piston head volume 6cc)
Cast iron HP exhaust manifolds
OIL PUMP: Melling, Part number M63
FUEL PUMP: New Carter
WATER PUMP: Stock
HARMONIC BALANCER: 440 Source, Elastomer Dampner, Part number 200-1128
New coil
Edelbrock CH4B dual plane intake.
Crank grind -10 thou
Engine balanced
Firecore leads
Orange box ignition (have tried the Hi-Rev 7500 blue box, no difference)

[70 sublime]

Do you have a spacer between the carb and the intake ?

Sometimes they help with keeping the heat out of the carb and boiling the fuel out when you shut it off

[C500]

Do you have a spacer between the carb and the intake ?

Sometimes they help with keeping the heat out of the carb and boiling the fuel out when you shut it off

No, I could try one. You thinking vapor lock?

[mopar346]

I am currently having a heck of time with vapor lock (Florida) so that was my first thought as well when reading the hard start. First off, the quality of fuel is so poor I have to run non-ethanol in everything old. Eldebrock carbs on cast iron intakes seem to be the worst about it, admittedly not a fan of Edlebrock carbs period but this absolutely clinches it for me. I changed my 68 RT over to a Holley and then returned it to a functioning return line system and that seems to have cured it but time will tell. I have a T-quad on the 69 RT but no return line and it can be victim to vapor lock, a little Comet I have same deal and it I'm not running non-ethanol it's been known to vapor lock running down the road! CJ with a 360 and Edlebrock but on an Aluminum doesn't seem to be as susceptible to it but I also don't put major miles on it.  Bout the only one I have virtually no vapor lock issue with is the AAR, I attribute this to the fact of the aluminum high rise that is actually high and the fact that Holley fuel bowls sit out in mid-air. MY square body Chevy dually gives me no issue either, factory 70 aluminum intake (decent high rise) and a Holley. I share all this just to say I have a number of set ups and have worked on this same issue for a while.

As for your set up, forgive me but not knowing exactly what a Proform 750 is puts me at a little disadvantage, as well as not knowing if you have easy access to non-ethanol 93 fuel. Anyway, if the carb is an Eblebrock throw it away (let the hate begin!) , if you aren't running non-ethanol, you should if you cant, ? I've been told Shell V-power is non-ethanol and I haven't found any info to contradict that, when I travel I run it since it's easy to find and I do not experience ethanol type concerns with the cars performacnce. Do you have a return line? If not I'd looked at putting one back on it with the anti-vapor filter (I believe they came that way from the factory, probably for a reason. All else fails, 6 pack it, my 500 will have one but I'm trying to avoid it on the RTs just to have some variety. Obviously, the basics of fuel line to close to the engine block or exhaust. THere a company called Cool carb that I'm dying to try one of their plates but I haven't so you can buy that and give us a report or maybe someoen with one will chime in, not a stock look though.

Just my 2 cents but I have a reasonable amount of experience with the scenario with multiple Mopars as well as other makes. Good luck

[mopar346]

The carb boiling sticky thread also has a lot of interesting info.

[b5blue]

Similar build but vacuum sec. Proform 750. I had to go up about 2 sizes on primary jets and got much better idle, off idle swapping to an MSD dizzy. 

[C500]

I am currently having a heck of time with vapor lock (Florida) so that was my first thought as well when reading the hard start. First off, the quality of fuel is so poor I have to run non-ethanol in everything old. Eldebrock carbs on cast iron intakes seem to be the worst about it, admittedly not a fan of Edlebrock carbs period but this absolutely clinches it for me. I changed my 68 RT over to a Holley and then returned it to a functioning return line system and that seems to have cured it but time will tell. I have a T-quad on the 69 RT but no return line and it can be victim to vapor lock, a little Comet I have same deal and it I'm not running non-ethanol it's been known to vapor lock running down the road! CJ with a 360 and Edlebrock but on an Aluminum doesn't seem to be as susceptible to it but I also don't put major miles on it.  Bout the only one I have virtually no vapor lock issue with is the AAR, I attribute this to the fact of the aluminum high rise that is actually high and the fact that Holley fuel bowls sit out in mid-air. MY square body Chevy dually gives me no issue either, factory 70 aluminum intake (decent high rise) and a Holley. I share all this just to say I have a number of set ups and have worked on this same issue for a while.

As for your set up, forgive me but not knowing exactly what a Proform 750 is puts me at a little disadvantage, as well as not knowing if you have easy access to non-ethanol 93 fuel. Anyway, if the carb is an Eblebrock throw it away (let the hate begin!) , if you aren't running non-ethanol, you should if you cant, ? I've been told Shell V-power is non-ethanol and I haven't found any info to contradict that, when I travel I run it since it's easy to find and I do not experience ethanol type concerns with the cars performacnce. Do you have a return line? If not I'd looked at putting one back on it with the anti-vapor filter (I believe they came that way from the factory, probably for a reason. All else fails, 6 pack it, my 500 will have one but I'm trying to avoid it on the RTs just to have some variety. Obviously, the basics of fuel line to close to the engine block or exhaust. THere a company called Cool carb that I'm dying to try one of their plates but I haven't so you can buy that and give us a report or maybe someoen with one will chime in, not a stock look though.

Just my 2 cents but I have a reasonable amount of experience with the scenario with multiple Mopars as well as other makes. Good luck

Our fuel in New Zealand is not great quality. Only one fuel company has ethanol in their fuel, and it's a 10% mix, but all advice by them is that it should NOT be used for carburetor engines, only for fuel injection.

The Proform 750 I have is a mechanical secondary, and similar to a Holley. I have an alluminium intake in the CH4B. It looks very similar to the factory cast iron one, and not a high-rise. I'll get a phenolic spacer, doing some research in type/thickness etc. Any suggestions welcomed... open, 4 hole, tapered 4 hole, 1 inch, 1/2 inch etc

[b5blue]

I'm using Jomar 1/2" 4 hole matched to the 750. You need to check clearance from hood to air cleaner. (I also use CH4B.)

[C500]

I'm using Jomar 1/2" 4 hole matched to the 750. You need to check clearance from hood to air cleaner. (I also use CH4B.)

Thanks, I'm thinking 1/2" too, the CH4B is low, will check clearance, but should be plenty. Not sure if 4 hole or open is better suited.

[b5blue]

CH4B- Jomar 1/2- Proform 750- factory dual snorkel air cleaner clears 70 Charger hood. 

[C500]

I'm going to ditch the Proform and try something like an Edelbrock AVS 2, 800 CFM. Phenolic spacer first though.