I have a 68 road runner 3:55 gears 4 speed with a stock 440 out of a 73 winny the tq carb was junk threw it out switched from the newer spread bore to the earlier square because that's all I had at the time and I'm on a budget low!! Also I'm using an eddy 750 carb carter mech fuel pump
No mods to engine has the motor home heads with the extra cooling passages and the different tappered plugs autolite 23 to be exact. And I have hooker comp headers with flow master exhaust. Timing is set at 10 initial with the vac advance. Vacuum is around 16 hg the problem is when you get on it it falls on its face won't hardly do a good burnout also backfires at times when you get into it
It runs better hot and is perfect at cruise speeds but if I wanted a cruiser I would drive my truck! Tuneup is all new coil orange box wires distributed rebuilt etc. I hope I have given enough info specs. Also it idles perfect!! Just as soon as u give it a good smack it dyes out then picks back up I just want a better response and I'm about to throw the carb in the garbage
Do you guys think carb or the intake switch maybe???
Any help would be awesome

So I had the same problem a few months ago with my 440 from a Motorhome with 3.55 gears and 4 Speed using the same carb. I used an O2 Meter and was able to jet/spring/rod most the stumble out but not 100%. I eventually changed to an Eddy 800 and the problem went away.

If you google "Edelbrock 750 stumble" you will see many, many references to problems with that carb and various big blocks. One problem is the accelerator pump is just not big/fast enough to maintain a good mixture from idle and it leans out for a second or two creating a condition that causes your acceleration to studder.

The short answer is you have a common compatibility problem with that carb and your block. If you want to try to correct it, you can with a little work. If you want to dump it and get another carb there are plenty of people here with varying recommendations. I can tell you that I went with the Eddy 800 and the problem is gone.

When u say o2 meter did u use a o2 sensor or tool?
Also what besides CFM is the major difference in the 750-800 eddys?

"Timing is set at 10 initial with the vac advance."

Should be with vac advance off and plugged. Is that what you meant to say?

R.

As far as the difference between the 750 and 800, I'm not sure anyone knows, but the 800 works a lot better than most of the 750s.

Now get the umbrella out for the shower of predictable "My 750 runs 10s" comments. Some of those carbs work, and I suspect some of them work because they're never under load at the transition point, they're always above it.

R.

I thought my slightly built 440 was a pig that only ran well wide open. Then I tossed my Eddy 800 and bought a Street Demon 750. Night and day difference. Don't waste your time and money trying to make it work, it won't. The Eddys work well on small blocks but they have a real problem with an off-idle dead spot on a big block.

Sorry, yes I meant to say Air/Fuel sensor and gauge. We welded a bung in each exhaust side and when I am doing carb work, I remove the plug, insert a sensor, calibrate and then do my jetting, rod and spring work. The kit cost me under $140 on Amazon and it lets me see how the fuel looks at high-vacuum, low-vacuum, idle, etc.

I was able to get my 750 to work with a barely noticeable stumble by changing the accelerator pump hole, jets, springs and rods. I documented my settings somewhere here on Moparts.

As others have indicated there are far easier ways to get your car running smooth again by simply swapping out the carb.

I switched to the same edelbrock 750 carb on my stock 440 and had the same results. Runs terrible and eats gas. Glad to know it was not just me having the same problem. Might try a modded TQ when I swap the motor out to another carb.

This has been covered here a time or two;

https://board.moparts.org/ubbthreads/show...e=1#Post8266084

In before Mr. yuk says ditch the eddy and get a Holley

I had issues with the eddy 750, but love my 800 AvS..

I would suggest looking into one for the 440

Mikey

I tried the Eddy 750 and the Eddy 800. Both bought new. Overall they both had the same manners. I used the Edelbrock tune up kit, tried different mods, the one thing that worked to make it just drivable was to back the timing down enough to notice a loss of power. I think the problem is aggravated with a low vacuum cam.

Anyone is welcome to PM me if you want to buy a low mileage Eddy 800 at a good price.

http://m.summitracing.com/search?keyword=thermoquad


Fyi
Summit stocks thermoquads