1st Time Poster - 1st Mopar - Engine dies when put in gear

[defend21]

Hey guys, this is my first post and I'm working on my very first Mopar.  Have been a Pontiac guy and now have two different types of Trans Am's.  I have a 70 Challenger T/A with the 340-6.  Engine has been rebuilt, carbs cleaned, 8mm wires, fresh plugs, timing is 10 deg BTDC at idle.  Idles great at about 900 when warmed up.  Every time I shift into gear, the car will die.  I've gone over the vacuum diagrams that I can find, most are 440 diagrams.  I added a vacuum gauge between the booster and manifold and it's reading 10-11 at idle.  I have no experience with a six pack, have been reading plenty (like where the idle adjustment screw is, and what an idle solenoid does), but that does not translate to experience.  I'm not sure what to check or do next.  Been driving it and shifting into N when I come to a light or have to stop. 

[Moparal]

How is it when driving?  Big cam? If so stall speed?  Was the cam degreed in?  might could use more initial timing.  The outboard carbs have a/f mixture screws to that may need to be adjusted to. 900 rpms and 10btdc seems like a bigger cam.  Is it doggy on the bottom end? 

[high perf mopar]

Hey guys, this is my first post and I'm working on my very first Mopar.  Have been a Pontiac guy and now have two different types of Trans Am's.  I have a 70 Challenger T/A with the 340-6.  Engine has been rebuilt, carbs cleaned, 8mm wires, fresh plugs, timing is 10 deg BTDC at idle.  Idles great at about 900 when warmed up.  Every time I shift into gear, the car will die.  I've gone over the vacuum diagrams that I can find, most are 440 diagrams.  I added a vacuum gauge between the booster and manifold and it's reading 10-11 at idle.  I have no experience with a six pack, have been reading plenty (like where the idle adjustment screw is, and what an idle solenoid does), but that does not translate to experience.  I'm not sure what to check or do next.  Been driving it and shifting into N when I come to a light or have to stop.

i had the same problem with my last setup..old school solid lifter cam,nothing too big but would die when putting it in drive..2 things i did made all problems go away.

1.installed a B28 vacuum can on the distributor so all vacuum advance was in at 8"..and hooked it to MANIFOLD vacuum..not carb ported and limited it to 8 degrees max vacuum advance xtra..20 degrees intial + 14 degrees for a total of 34..plus the 8 vacuum..when u open the throttle blades the xtra vacuum degrees goes away..still ava thru autozone..
if u try to run too much advance without vacuum u run into other problems like starting it.

2.made a idle set screw so i could open the outer carb blades to help idle,,just like the competition series 6 pak setups.u can set all 3 carbs for idle quality.really woke the motor up..all above settings r what i use today..but thats after tuning the out boards with there idle air screws..

never died again when dropping it in gear..the idle set screw on the outboards was abig deal as far as tuning the 6-pak setup..

[cudabob496]

wires crossed on your tranny, on circuit that prevents car from starting unless in park? If starts in park, and
dies in gear, may be it.

I mean, sounds hopeless, I'll be over to haul it away for you!

[Strawdawg]

I am guessing the same as Al.  Sounds like a tight converter and a bigger cam that needs a little more slip in the converter to keep from being jerked down when going into gear.  Kick the initial timing up as suggested and see if that helps.  Maybe a half turn more open on the idle air screws as well.

Once you have it idling in drive, try putting your foot firmly on the brake and ease down on the gas.  Note what rpm you are seeing when the rear wheels begin to try to turn to give us an idea of the converter stall speed

[defend21]

One other note, happened after I posted last night.  Was having a hard time starting and noticed carb caught fire.  Was only a few seconds and put it out, then after letting it sit for a minute, started right up.  Sounds like it may be a combination of timing and set screws.  I'm going out to try those ideas.  I have to run pickup some timing tape so I can check total timing as well because I can only see +10 either way from 0 on the standard timing marks from factory. 

[Strawdawg]

for this purpose, just look at the distance from zero to ten and turn it about 50% more to approximate 15 degs.

I would make sure the carb is not flooding or leaking fuel into the engine because it should not be catching fire in normal circumstances if the timing was at ten degs advanced.

[high perf mopar]

One other note, happened after I posted last night.  Was having a hard time starting and noticed carb caught fire.  Was only a few seconds and put it out, then after letting it sit for a minute, started right up.  Sounds like it may be a combination of timing and set screws.  I'm going out to try those ideas.  I have to run pickup some timing tape so I can check total timing as well because I can only see +10 either way from 0 on the standard timing marks from factory.

thats usaully a sign of too much advance..i tried mine at 38 degree's no vacuum and it was coughing back thru the carb upon startup also..back it down and look into the vacuum method mentioned.if u just start cranking more timing into it without letting the vacuum do it 4 u it will get worse. i think u would be good to go     .alot easier than swapping converters 

[defend21]

Ok, here are my results.

Initial settings again:  900rpm idle in park, 10 vacuum, 10 BTDC timing, vacuum advance connected at distributor to card.  When shifting into R or D, car would drop rpm and die.

First, I blocked off the vacuum advance at the distributor, and advanced the timing to about 15-16.  Used a sharpie as suggested and measured the distance for another 5 degrees.  Not precise.

Pic 1 showing timing light and vacuum after adjusting timing.  RPM is now 1300 and vacuum is 15.

Pic 2 is just a shot of the motor

Now I noticed that the idle is lower in N than it is in P so I adjusted the idle set screw on the center carb to around 950 while in P which lowered to 900 in N. 

When shifting into R or D, the car does not die and the rpm drops to 600-650.  It looks like I lose 300 rpm when shifting into either R or D, is that normal?

I setup my timing light so I could see the rpm's through the windshield while cycling the tranny.

Pic 3 is just a picture of what I was watching. 

Should it be that low when in R/D, or should I raise the idle a bit?  You could almost say it was border line stalling but maybe now I'm just paranoid. 

Should I leave the vacuum advance on the distrib plugged?

[72cudamaan]

You still haven't said anything about what cam or convertor you have. That makes a big difference
in trying to determine what is right or wrong. A 300 rpm drop is very excessive with a stock to mild cam, but
if it's a larger cam profile then it may be okay.

[Strawdawg]

try checking the stall speed as I suggested above.  It sounds like it has a pretty good cam in it and the converter is on the tight side.  I am going to guess you get about 1700 when you try the brake stall test.

[Bullitt-]

Now I noticed that the idle is lower in N than it is in P so I adjusted the idle set screw on the center carb to around 950 while in P which lowered to 900 in N. 

When shifting into R or D, the car does not die and the rpm drops to 600-650.  It looks like I lose 300 rpm when shifting into either R or D, is that normal?

IF this adjustment helped then I think I know what the problem was, your idle transition slots were exposed. Do a Google search on Idle Transition Slots & you will find many articles on the subject.     My car with stock converter drops about 150-200 rpm when put in gear.   You may still have some timing and/or carb tuning to do.

[BS CUDA]

IF this adjustment helped then I think I know what the problem was, your idle transition slots were exposed. Do a Google search on Idle Transition Slots & you will find many articles on the subject.     My car with stock converter drops about 150-200 rpm when put in gear.   You may still have some timing and/or carb tuning to do.

Holley refers to it as curb idle - perhaps a Holley carb install manual will help as a guide in reference to curb idle etc. I realize you run a six pack but .....

[defend21]

Still looking for cam specs, I can't remember if it was a stock or a mild upgrade.

Wheels try to turn around 1500 and then override the brakes and makes the car go forward at about 1700 rpm.

It was still acting funky so I raised the idle rpm to 1150 from 950 and when I put it in gear it drops to 675-700.  If I go and then start to stop, it drops all the way down and then cuts out and I have to shift to N or P to start up again.  This sure is a strange problem, seems to be multiple things at one time.

I found the part number for the B28 in a corvette forum because it had changed many times I guess.  The current part number is Duralast DV1810 at Autozone.  Here is a link to the other forum tracing back the part number:

http://forums.corvetteforum.com/c1-and-c2-corvettes/2453730-where-to-find-b28-vacuum-advance-can.html

[high perf mopar]

Still looking for cam specs, I can't remember if it was a stock or a mild upgrade.

Wheels try to turn around 1500 and then override the brakes and makes the car go forward at about 1700 rpm.

It was still acting funky so I raised the idle rpm to 1150 from 950 and when I put it in gear it drops to 675-700.  If I go and then start to stop, it drops all the way down and then cuts out and I have to shift to N or P to start up again.  This sure is a strange problem, seems to be multiple things at one time.

I found the part number for the B28 in a corvette forum because it had changed many times I guess.  The current part number is Duralast DV1810 at Autozone.  Here is a link to the other forum tracing back the part number:

http://forums.corvetteforum.com/c1-and-c2-corvettes/2453730-where-to-find-b28-vacuum-advance-can.html

the reason i run that one is all vacuum advance is in at 8"..my idle in gear is a hair under 10"..b sure to limit the total travel of the arm by slipping a piece of rubber tubing or such that fits down into the slot on the can,otherwise you'll get 15+ degrees more timing,,by installing the stop it's around 8..plenty to help at idle,,remember,,manifold vacuum,,not carb vacuum.i have mine hooked to power brake port nipple on the back of the intake..