I'm running a 70 cuda with a 340 4 speed I have a holley Carb 750 on it now.
I have a LD340 1inch spacer.

Running X Heads Have a purple cam 280/ 484 108 centerline 50%

Have TRW Pistons H-Beam Rods Stock Cam I built the engine for the

street. with low end torque DONT HAVE THAT NOW. My Int settings are

18 and final set 35 total When i purchased the carb from a freind rebuilt it for me. Just never has the low end i would like. In fact it was very hard to spin tires at stop. Also running a 3/8 fuel line

Any Idea's Thanks Kevin this has been a 2 year problem.

I'm trying to remem the other thread, 3:55's right? your timing is in the ballpark. What's the actual CR or cranking compression if actual CR was not measured? Might borrow an eddy or holly 600 from a buddy for a day & see what transpires. Might adv the cam 4 deg & recheck intake (I remembered ) PV clearance after you adv it. I somewhat suspect not enough cyl psi rather than overcarbing

Lots of places to look.Verify cam timing and compression.What gears are you running?
That cam is'nt my first choice for torque(especially in a short stroke 340).Short of swapping cams I might suggest advancing this one and see what happens.
A smaller carb will likely help with the low end throttle response as well.

Thought about changing the cam any recommendation on that.I've advance the timing to 20 Deg ran and started good but hard starting Backed the dist back to where it would start ok back to same problem. I'm running 3.55 gears. Alittle lost right now Thanks Kevin

Hi

Bear with me but some techical stuff I'm not sure of. How do you measure the CR not sure.?

Not enough cyl PSI.? Not sure what you mean Used to be pretty sharp years ok Just looking for help Thanks Kevin

one thing that helped me a lot when using the 484 years ago was to use lighter springs in the distributor and disconnecting the vaccuum advance. they are mopar performance p2932675 and cost less than 20 bucks. use one of the springs in the kit and retain the smallest of the 2 already in the distributor. also, tailoring the shooter sizes in the carburator helped a LOT too. btw the 750 holley is very well suited for the 340, be it double pumper or not. you just need a little bit of fine-tuning, thats all .good luck.

i forgot to mention one thing: remove that spacer underneat your carb cause it costs you a bunch of torque under 4500 rpm or so.

When you bumped the initial up to 20 how did it perform (other than hard cranking)? when is your total in (what RPM where it wont advance anymore)?

Hi

Thanks for responding When it was hard to start it actually ran good power was good. Wouldn't start hard starting backed off and started easly. Idont have a RPM gauge so its not sure I run it up to where i think its about 2500-3000. my vacuum goes up to about 17-18 bounces a bit.I know this car has good power just need to find it. Total i figuerd about 2500 35total

650 holly is fine

IGN. use the "vac gauge method" to set initial then w that figure in hand shorten the slots to get 35 total then play w the springs & w them picked out set the vac adv (if used). More on the above later, I need to get to work, boss likes it when I show up on time. W the initial set if it still cranks labored, wire in a toggle sw for the ECU & w it off start cranking it w the key then close the sw. EDIT I'd dial in each subsystem of the dist in order then the carb and later (or right now) adv the cam 4 deg (recheck intake VP clearance if you think it's anyway near ~.125) then you'll need to go thru the dist again as the increased cyl psi will change your timing requirements then the carb again so yes might be for the better to adv it now which'll make the long block as good as it can get (as is)

It's not your carbs fault. It's your cam choice. Unless you are running 3.91's that cam is not going to be a "stump puller" Also You should bump your timing up some.

Here's what he said on his other thread.........

"Mixture screws seem sluggish

can turn them all the way in runs but not very good. It should stall

out but does run. I had the carb rebuilt a year ago Cant drive it now

live in north East."

The most significant thing with the MP 284/484 cam ,if you really have that one, is the narrow LSA and the tuning required to get it to behave well. As mentioned, it needs gear, converter, more init. mech. advance, 36 degree total, proper cam phasing, proper intake/carb match and on and on.

You haven't even started with the carb tuning. Get the distributor recurved FIRST! Many people blame the carb for a lazy off-idle stumble when they have never touched the distributor. The tune the carb. You may have to open the secondaries to drop the primaries closed more and get those idle mixture screws to be more sensitive. A HUGELY overlooked necessity that's easy to do but most just suggest a cam swap. Then play with pump squirter size and pump cams. A 650 is all you really need for that combo too. It would need the above tuning too. Become a carb guy, there's no voodoo once you take the mystery out.

YES, there's better cams. BUT, they need tuning to your unique application too. Why not learn for free on your old cam.

When I bumped to 20 sounded really good seem to have the power no hesitation. But the dreaded hard start. I purchased Dist springs from summitt today. See how that goes. Sounds like i went with the wrong cam I wasn't sure at the time. Did have some good positive things. I have a hard time remembering things lucky it ran i guess. I know my oil pressure was low like 40 hot highway 30lbs idle 10-15 According to what people are saying the shop i had put the cam and bearings in probably had a bearing not right over the hole in the block. OK will wait for the springs see how it goes will let you know Kevin

It's all about tuning.

A combo like that should have plenty of low end torque.

I had a 318 with 360 heads, .480 cam, headers, M1 single plane and 750 3310 Holley. I would boil the tires from a stop and bark 2nd hard even with really low compression and 3.23 gears.

Did you degree in the cam or slap it in there? Could be part of the problem..

Sounds like you're about ready to tear into the distributor. Make sure the weights are clean and function properly. A cheaper set of springs is the Mr. Gasket #925B springs. Usually go for $11.00.

Carbs can be picky. We had a brand new 750 3310 that some of the plating came off of and got lodged. Truck ran fine until we put about 500 miles on it then started acting up. Dipped it, blew out all the passages and it worked perfect.

I Did not degree the cam people I new said since i wasn't racing it wouldn't need to do it. I will get the dist springs couple days cant drive it just got 15 inches of snow. If i changed cam;s what would work for me. If the springs didn't help. If i would of had the money would of gone crate motor.

FInd a old dual point accel dist they have a virtual perfect timing curve for 340 esp if you are unfamiliar with recurving one also cheap. Set the total to 40 - 42 degrees to start. Forget initial as long as car starts Carb use 28-31 squirters depending on temp jet frt 71 the rears 76-78 again temp altitude to be considered USE A 4 HOLE SPACER not a open one get a good dual plane do not use a performer unless its a RPM. Get a set of 3.91s or even 4.30s that car will plain haul tail and if it doesn't you need to look for something wrong internal

Hey

Wanted to let you know that today messed alittle bit with the car and noticed that secondarys are not put any gas the rear of the carb. Waiting on the springs thought I'd let you know about the secondarys thanks kevin

I really appreciate the help as i;m alittle lost. There's things i should of done different alittle late now. So now no fuel to secondayars not sure about that will check it out. If i change cam will have to pull the engine right.? ok thanks Kevin