Moparchat - Home of MOPAR enthusiasts worldwide!



Go Back   Moparchat - Home of MOPAR enthusiasts worldwide! > Technical Forums > Performance Talk

Click here to search for Mopar cars and parts for sale.


Reply
 
Thread Tools Display Modes
  #1  
Old 11-17-2002, 10:45 PM
340727Dart 340727Dart is offline
Inactive User
 
Join Date: Mar 2002
Location: Northwest Arkansas
Posts: 42
Question 340 starts cutting out/surging above 85 mph

Last week was the first time I took my Dart onto the Interstate with my newly rebuilt 340.
I nailed the throttle at about 30 mph and it pulled very hard up to about 85 when it suddenly nosed over. The engine was still running but, as long as I was on the throttle it was stumbling and/or surging. Once I let off the throttle and coasted down to about 70 and got back into it, the engine ran smooth back up to 85 when it started acting up again.
Today, I took the car back out and got it up to a little over 90 when the engine did the same thing again.
I've got a high volume Carter mechanical fuel pump feeding the 600 Edelbrock.
I'm thinking the fuel tank pickup filter may be clogged. I'd be willing to bet the filter is the original.
A friend of mine is thinking the engine may be going lean and recommends jetting up to .100 on the rear. It's got the original .095 jets in there now.
With the 3.91 gears and 26" diameter tires, the engine was turning well over 4,000 at 90. I wasn't really watching the tach as I started getting into traffic.
The engine pulls hard to 6,000 in 1st and 2nd on the 727. The problem starts once the car's speed really builds up.
Anybody have suggestions as to where I need to start?
Thanks.
Reply With Quote
  #2  
Old 11-17-2002, 11:07 PM
dave571's Avatar
dave571 dave571 is offline
Inactive User
 
Join Date: Feb 2001
Location: carstairs,alberta,canada
Posts: 2,809
Default

T in a fuel pressure gauge and set it up so you can see it while running, then duplicate the fault and observe pressure.

Before I pulled the tank out, I'd look for a kink in the metal fuel line. I have seen it before.
Reply With Quote
  #3  
Old 11-18-2002, 02:19 AM
coolcarz coolcarz is offline
Inactive User
 
Join Date: Jun 2002
Location: Rosamond, ca
Posts: 268
Default

I would replace the fuel filter, sounds cloged, even if it a few starts old.... car sits fuel tank gets crap in it plugs fuel filter really quick, I know just went through a few, after my car sat 10 years surged like crazy , new fuel filter one run down srteet, surged, came home replaced fuel filter again.... no surge until it got cloged up, lots better now after 5 or so filters....its lean alright...... hehehe

coolcarz
Reply With Quote
  #4  
Old 11-18-2002, 08:26 AM
mtrv8n mtrv8n is offline
Inactive User
 
Join Date: Jul 1999
Location: new york city
Posts: 904
Default

My first impression is that the 600cfm is small for a 340,and the power you feel in 2nd gear is lost to the tall gear in 3rd.

Don't forget, at 90mph your fighting wind as well as gearing...
Reply With Quote
  #5  
Old 11-18-2002, 08:31 AM
mtrv8n mtrv8n is offline
Inactive User
 
Join Date: Jul 1999
Location: new york city
Posts: 904
Default

geez, too early in the day for me, your should read you're.
I forgot to add, I'm running an 800cfm on my 360, and wouldn't put less than a 650 holley or 700 eddie on the 340.

surging may also be an indication of an air leak, try running at 5000rpm, but steady, not accelerating, in 2nd gear, and see if it doesn't surge there also.
Reply With Quote
  #6  
Old 11-18-2002, 07:12 PM
delbert delbert is offline
Inactive User
 
Join Date: Oct 1999
Location: Avon, IN, US
Posts: 17
Default

I would bet your problem is fuel delivery to the carb, as you suspect. It's running OK at lower vehicle speeds because your carb still has enough go-juice in it to keep up, but after a several second of acceleration, the fuel system can't keep the bowls full.
Reply With Quote
  #7  
Old 11-19-2002, 05:18 AM
cuda66273's Avatar
cuda66273 cuda66273 is offline
Banned
 
Join Date: Dec 2001
Location: Beaverton Oregon
Age: 71
Posts: 3,685
Default

How hot is this 340?

You do have at least 3/8 fuel lines all the way ..right?

600 Eddy stock replacement carb for stock 305 chevys....no comment.......but, lemme guess...recommended by Summit...

What's the part number on that pump?
What's your cam duration at 50?
What's your static compression ratio?
What's your vacuum reading at idle in gear?
What's your shift point?
What's your local altitude?
What's your initial and max timing and where's it coming in at?

Lot's of "what's" ...all leading to a 7 digit part number that'll make that 340 run like a raped ape up to whatever RPM or MPH you've got the balls to push it to.

Mediocracy is not an option for a real Mopar Guy...leave that crap to the 86 camaro's 350/350 with a 350 gear bowtie boys and the 5.slow rustangers...let's get you dialed.

Don
Reply With Quote
  #8  
Old 11-19-2002, 09:13 AM
340727Dart 340727Dart is offline
Inactive User
 
Join Date: Mar 2002
Location: Northwest Arkansas
Posts: 42
Default

Cuda66273;
I can see I still have some work to do. In order of your questions, here are the answers.
The car has 5/16" fuel line.
The Carter fuel pump part number is M6902. It's supposed to pump 120 gph at a 6 p.s.i.
The cam's advertised duration at 0.050" is 233*/240*.
Compression is 9.5.
The engine has 6" to 7" of vacuum at idle, in gear. I do have the appropriate metering rod springs in the carb.
I shift the engine at 6,000 rpm. It has a cast crank, so I don't really lean on it.
Local altitude is about 1,300 ft.
Timing, well, who knows. I have always timed by ear. I get just a bit of ping when I first lean on it but, it's momentary and goes away quickly, so I figure I'm right on the edge with the 93 octane.
As far as the carburetor, I'm trying to locate a 3310 Holley. But, I first need to change the fuel pickup's filter. However, according to my local Dodge dealer, they are on backorder and nobody in the area has one. I'm probably just going to take it off and use two filters. One just outside the tank and the other between the fuel pump and carburetor.

Thanks,
Ted
Reply With Quote
  #9  
Old 11-19-2002, 02:05 PM
cuda66273's Avatar
cuda66273 cuda66273 is offline
Banned
 
Join Date: Dec 2001
Location: Beaverton Oregon
Age: 71
Posts: 3,685
Default

1. Your fuel line is too small for that motor you need to upgrade to at least 3/8's

2. the pump should be OK for street use. We have the adaptors to switch over to AN -06 lines to the carb, this will give you all SS braided line to the carb...rubber hoses are just fuse....ssssssssss

3. That Eddy carb cannot and never will be able to read the manifold signal with that duration and will never no matter how much I was to tune on it run correctly.

4. I wouldn't be afraid to to wind it to 6500 with a cast crank, as long as it's put together right....you do have the 340 rods and good ARP bolts in them ...right?

5. Your distributor is way off and out of phase I'll guarrantee it.

6. Another fuel filter will even further restrict your fuel flow, if your using the inline $5.00 filters they flow at about 40 GPH...eventually they will ruin your good pump and lean your motor out and poof....another customer for our machine shop....spend the money and get a Fram HPG 1, they will flow 110 GPH or better yet buy the BG 5000 filter and your set for life no matter what engine you should ever install in that car. The difference in price really isn't worth the difference ion performance.

7. Open up that tank and yank that sock off the pick-up and throw it away...a good filter will replace it and their worthless anyhow.
8. Forget that 3310 Holley and slap on a Mighty Demon 650, they will flow in the 730-780 range and give you instant throttle response. If your convertor is less than 3000 stall then a 650 Speed Demon would be best for you, if you interested we have one in stock. After we talk one on one I'll make the decision on whether you should have a Vac secondary or mechanical set up. We will also swap the power valve to a 5.0 and rejet it for your elevation...this is all included in the price of the carb from us.

Lemme know...
The toll free number in my signature should be up by tomorrow
Don
Reply With Quote
  #10  
Old 11-19-2002, 03:16 PM
ajmopar's Avatar
ajmopar ajmopar is offline
Inactive User
 
Join Date: Jul 2002
Location: Stoney Creek, Ontario, Canada
Age: 54
Posts: 806
Default

Don't forget to change the pickup tube on the sending unit to 3/8" as well. Not hard to do. Once you unsolder the 5/16 pickup out of the sender, take a center punch (one that tapers up to over 1/2") and use it to enlarge the hole to just fit the 3/8" line you bent to fit in place of the old one (put a deep socket on the other side and tap the punch into the hole on the work bench). This gives you a nice rolled edge that is easy to solder to the tube. Just be careful not to f up the sender for the fuel guage and you will have no problems. I have done this a few times with no ill results.
Reply With Quote
  #11  
Old 11-19-2002, 07:04 PM
340727Dart 340727Dart is offline
Inactive User
 
Join Date: Mar 2002
Location: Northwest Arkansas
Posts: 42
Default

Cuda66273, you have mail.

Thanks.
Reply With Quote
  #12  
Old 11-21-2002, 10:26 AM
cuda66273's Avatar
cuda66273 cuda66273 is offline
Banned
 
Join Date: Dec 2001
Location: Beaverton Oregon
Age: 71
Posts: 3,685
Default

340727Dart

Call me..the toll free number rings to my cell phone, wait until after 10 PST, I'll have time to talk then.

1-866-866-7845

Don
Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Surging RamSport Ram Truck Chat 1 06-09-2006 10:40 PM
Engine surging chucklynn Performance Talk 25 07-12-2003 10:40 AM
Surging Daytona 2.5 rico_stalone Front Wheel Drive Chat 1 08-19-2001 12:01 PM
Surging . . . Mopar_nutz Front Wheel Drive Chat 6 03-20-2001 01:00 AM
Starts, won't start, starts, won't .... Squad Performance Talk 4 03-13-2001 02:38 PM




All times are GMT -4. The time now is 04:34 PM.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.
. . . . .