Shooting the breeze. What’s the 1/4 mile time of a 340 challenger?

[kawahonda]

Had a good highway outing today. Her first, actually!

~3000 RPM @ 65 MPH with the 3.73's and 26.1" tires. Surprisingly very quiet...no engine noise, and smooth. Plus a great power band to be in for passing! 340s seem to love cruising at 3,000.

The interstate would be a different story of course.

[Skid Row]

  Congratulations "kawahonda" on your initial real road test! Your results show the effort and attention to each part of Your Build
that lots of us have followed.

[RUNCHARGER]

I bet it feels much more lively with that gear in there. A 340 will have no problem with 3000 at 65MPH.

[Mark_B]

340's are supposed to pull a punch. 

Here's one up against at 426 Hemi and it doesn't do too bad.

[kawahonda]

That's a really fast 340!

Thanks for the responses. I'm really trying to walk that fine line of making it fast but keeping it stock. So far, I've been pretty successful. Just needs to get a couple runs on it to see where she stands now!

I probably won't do too much more in the name of performance this year. This year to recap was distributor tuning, carb rebuild (still needs some fine tuning), and gears.

My next area of attack is to rebuild the alternator and to have some PDR done.

For performance, at this point I'd have to start tearing into things, so I need to make sure I have everything planned and thought out...probably a next winter thing. I'm thinking the camshaft is the next item on the list. A higher stall converter would be nice, but that's a lot of work.

Engine is very healthy and doesn't need to be pulled for quite some time. That's when I was planning to really look into the stall of the converter.

[Mark_B]

That's a really fast 340!

Yes and an A66.  But can't believe that's stock, there must be some magic under the hood.

[kawahonda]

Question for you guys:

What's the easiest/safest way to jack up the car in order to replace the speedometer gear? It seems to be located about right smack in the middle.

Two options:

1) Lift up the front end (both sides) and hit it that way.

2) Lift up only the driver side of the car (front left and rear left) and hit it that way.

What option gives the most access?

[JS29]

2)   

[kawahonda]

Done!

Quick question for you guys. I'm pretty sure I'll be fine and dandy, but wanted to check.

Speedo-gear successfully installed. 40 MPH is 40 MPH again!

I lost 1.5 quarts in the process. My tranny mechanic filled it up with Dex III following shift kit.

I replaced with 1 quart of Dex III.

I had to improvise, so I put in .5 quart of Mopar ATF+4.

I think that's OK, but I wanted to double check.

[kawahonda]

I think I've asked this before, but I wanted to check. One of my future performance plans is to place on a big block Carter AVS carburater. Is this a simple bolt-up, no mods necessary? What carb part # should I be looking for?

According to hotrod.com, they simply threw on an 800CFM AFB carb on a stock 340 motor and netted 35.6hp and 22.8lbs of torque on factory-spec'd stuff. That's a stupid amount of increase from a carb swap and makes me think it's a great idea to try it. Now of coarse, this doesn't include any drivability tests....just dyno pulls.

"Those old enough will remember that it was popular to swap out the original small AVS (about 600 cfm) for the larger bore version (about 750 cfm) from the 440 Magnum."

Is this true? @RUNCHARGER, @Chryco, @1 Wild R/T?

[1 Wild R/T]

True, I doubt 35 Hp but it definitely made a noticeable difference... 

FWIW as anecdotal evidence, my first R/T SE was originally sold new by Holton Dodge in Patterson California... Some may recognize Holton  AKA Harry Holton who raced a SS/DA Hemi Dart & later a SS/DA Hemi Cuda.. My car was originally sold to an older man who didn't particularly care about performance.. It was only serviced by the dealership & was traded back in to the dealer in late 74 on a new Cordoba..  When I bought it the 440 seemed pretty lazy, I tweaked & tuned & it wasn't till I bolted a Holley on it that the car woke up....  At the time I didn't really question the why, just stuck the original carb on a shelf....  15 years later I'm restoring the car & I want the stock carb back on it... And I check the numbers only to find I have a 70 340 AVS....  Later I'm talking to one of the guys who turned wrenches in Holton's shop.... Well it seems they had a 340 Dart that they were doing some performance work on when my Challenger was traded in....  A quick swap & suddenly that 340 Dart was much livelier...

[kawahonda]

Haha....your carb may be on that Dart 340!

Now the question is, which Carter AVS models should I be on the lookout for? My current one is an 340 Auto ECS carb. I would assume that whatever model #s I need to look for would need to be for the automatic.

Heat riser choke would be nice, but I'll probably convert it over to electric. My heat-riser works sometimes. Other-times I have to pop-open the hood and "flick" the rod to close the chokes, then it starts up just fine and dandy. I wonder if the big block AVS could still utilize the same heat riser choke alignment/position of the 340?

The heat riser system....is that something that I just need to clean? I have no idea how it works, other than there appears to be plate for it on the intake...

Anyhow, getting off topic. But it sounds like big block AVS swaps is a real thing, and 340s, even stock, seem to welcome 740 CFM. Just not very well documented at all.

[1 Wild R/T]

I would be looking for a 69-71 440HP carb, they all have the divorced choke & your bimetallic choke unit should work fine with the 440 carb, it's a bolt on deal, every connection & linkage point is the same.. Just bigger venturi's....   

If your gonna do an electric choke why both to track down an original carb? just throw a aftermarket carb on it....  I have no love for the Edelbrock AFB's but haven't heard anything bad about the 800 AVS's..... 

[kawahonda]

Interesting...so that "plate" on the intake is actually a thermostat housing. It may just need to be replaced if it is not working consistently. Doubtful that it's not working correctly though. Just trying to learn...

Rod pushes upward to choke the engine. Assuming when the temperature reaches a certain low level, the action of fully pushing in the gas pedal to the floor (semi-slowly) should operate this. In my case, it doesn't do this consistently when the engine is cold. Sometimes yes, sometimes no.

Rod pulls downward to un-choke the engine. Assuming when the temperature reaches a certain hot level, the action of the gas pedal/air should operate this. In my case, the rod correctly pulls down during driving after it warms up enough.

It's the initial action of closing the choke plates where mine has trouble. Maybe there's an adjustment on the carb that I don't know about. Maybe the divorced choke unit needs to be cleaned or replaced since it works correctly one way, but doesn't work consistently the other way?

You're right, if I'm just going to convert with an automatic choke, I could just get a new Edelbrock carb. The problem I have is from a looks standpoint...it doesn't look stock. Not a fan of the Edelbrock "script" nor the finish of it. Knowing me, I like to do things the hard way. A 440 AVS carb looks pretty much the same as a 340 carb.

Thanks for the info. If I find a 440 AVS I'll continue to inquire. For now, I think I have a more solid understand of how the thermo-choke thing works.

[1 Wild R/T]

Rarely would the divorced choke itself cause what you describe.. Much more likely it's the fast idle cam or the kickoff linkage...