Got my 340 started! Have a question about the idle.

[340727Dart]

Well, I finally got my 340 started this past Saturday. It lit right up and has absolutely great throttle response, plus it runs great. I only have about 30 miles on it so I haven't gone full throttle yet.
I set the timing by ear as I don't like my old timing light. There is no pinging, plus it starts easily, so I think I'm fairly close but it doesn't want to idle in gear.
The converter is a Jeg's unit that was supposed to have 3000 rpm stall but it feels a bit tighter than that.
With the car in neutral and warm it idles fine at 1000 rpm but I thought it would be lower than that.
The cam is a Comp Cams "purple plus" with .474" lift on intake and exhaust and 233* duration at 0.050" on intake and 240* on exhaust.
I'm currently using an Edelbrock 600 cfm carb that I richened up with bigger jets. The plugs are uniform in color and have a nice, light brown tint. That makes me think I'm close on jetting.
So, why doesn't it want to idle in gear?

Thanks.

[6 packin]

That cam is not that radical! And very streetable! I should idle in gear with maybe 14-16 deg intial timing with no problem and Idle at 700-900 RPM's all day! You need to get a timing light for sure! Also spend the extra 30$ and go with the 1 that has the timing dail on the back side to check total advance. Around 70$ at Autozone. Best money I have spent! If still wont idle there with these setting is somthing wrong there for sure. Maybe youR JEGS converter is locking it up, with 3000 stahl ther should be no Idle problems in gear or not!

BTW I have almost the same cam and stock converter and mine idles just fine. although a looser converter would help big time

JUST FYI

[Doug Wilson]

6 packin is right on the money.

[biggerhammer]

check the vacuum pull, see if you have a leak! won't idle with an intake leak , maybe base of carb. too

[sixpackcuda]

I'm leaning towards biggerhammer. Can you play with the throttle while in gear and get it to stay running. You should also check the timing like 6 packin suggested. Can you get it to idle lower in neutral? While it's at idle, cup your hand over the carb top, if it gets better than it's lean and probably does have a vacuum leak. If it gets worse it is too rich.
The converter will vary stall speeds according to horsepower.

[MY340]

TK, What's your idle vacuum? If you have a vacuum leak it may be lower than it should and cause poor idle quality plus this could cause the metering rods to go up if your springs aren't rated 2-3" lower than the vacuum at idle. If they are you should hear them buzzing/rattling of course. Just an idea from someone who knows very little.

[340727Dart]

sixpackcuda, I have to constantly work the throttle pedal while sitting with the car in gear. If not, the engine will die.
I bought a good dial back timing light tonight and set the initial advance to 15*. It was up around 32* before I changed it. So much for setting it by ear.
After setting it at 15*, I tried revving the engine up to about 2500 rpm and the timing did not move.
It's a stock distributor, with both springs still attached.
Can I just remove one of the springs so I can get the mechanical advance to move sooner?
MY340, the engine has 7" of steady vacuum at idle. I had the orange 5" springs on the metering rods. After reading your reply, I changed them to the yellow 4" springs.
I haven't yet checked for a vacuum leak.
Unfortunately, that will have to wait until tomorrow. I don't think my neighbors will appreciate me running the engine at this time of night. Did I mention the city attorney lives four houses from me? He's one guy I want to stay friendly with.

[sixpackcuda]

Woah! 7" is way too low!! Take a can of carb cleaner and spray around the base of the carb and intake to look for leaks. It will change your idle dramatically. Just be careful as it's flammable!
Did you have the heads shaved? If so did they do the intake too??
Can you move the cam in the dist. by hand? (turn the rotor with engine off) It may be frozen. You can change springs but I wouldn't recommend just using 1.

If you can keep it running in gear while stopped, the torque convertor isn't to blame for the stalling. It would be like having the brakes on full and letting the clutch out on a stick.

Good Luck and keep us posted!

[biggerhammer]

wow, only 7"'s? needs to be 12+, with a really big cam it should be 11 or better, stock is 18-22, sometimes higher, depending on the application and engine, you definitely have a leak somewhere, check your brake booster if equipped, base of carb. check the butterfly rod too, see if the bushings are worn out.

[cuda66273]

Can't wait to hear more on this one....

Keep us posted

[71383bee]

I agree with the consensus here. 7" of Hg and no idle is definately an intake leak. Check your gaskets and your vacum fittings...I accidently disconnected my PCV once and it drove me insane for half an hour! Finally my girlfriend pointed it out while I was getting out the tools to yank the carb.

[Doug Wilson]

Please forward you girlfriend's name address and phone number (and email address) to : www.ThunderboltRanch@msn.com

Does she like poor, old, ugly married men with a MOPAR johnson??

[72Challenger]

You've gone and blown it now, Doug. Haven't you learned yet that as soon as one of us old ugly married guys mentions that he's poor, the ladies just disappear?

[Doug Wilson]

You never can tell when one might need a project.... and MAN, am I a project!!

[Firelord]

LOL Doug. You know there are other forums for that. They are called Dating forums!

[Doug Wilson]

Dating forums in this house go right along with divorce court forums!... can't have one without the other!

[340727Dart]

Let's get back to the subject at hand.
I have checked for vacuum leaks and found none. I absolutely cannot get the car to idle in gear if I don't have the neutral idle set to 1200. With that, it will idle at about 850 in gear.
I sprayed brake cleaner everywhere, and there was no change in the engine at anytime.
After playing with the mixture screws some, I got the idle vacuum up to about 9.5", which I take it is still too low for the cam.
The heads were not shaved, nor was the intake manifold.
The only common denominators between this new engine and the one I pulled out of the car are the Torker intake manifold and the Edelbrock 600 carburetor. I did have trouble with the old engine having low vacuum and wanting to die while idling in gear.
I have manual brakes.
With the engine idling at 1200, it will choke off when I put my hand over the mouth of the carburetor. Does that indicate the carb is too rich?
I know one thing, that supposed 3000 rpm stall converter is much tighter than that. The car will start spinning the tires against the brakes at about 1800 rpm.
So, what next? I'd rather not start swapping carburetors. That can get kind of expensive.

[Doug Wilson]

Have you replaced the cam or timing chain & gears?

How many miles are on the engine?

[biggerhammer]

do you have a pcv valve?, see if you can plug that and check vaccuum again, maybe a crack in the intake, is the carb. new? check the butterfly rod, if the bushings are worn or oversized it will leak there, but I don't think carb. is problem, but take it off and check the compression outline on the gasket, maybe slightly wrong fit, check both sides. I have seen this on cars(mostly chevies) where they used the wrong gasket and it didn't conform correctly, causing a leak.

[George G. Leverette]

I have a similar problem with a new 360 install, the car runs rough and idle drops drastically in gear. Sprayed carb cleaner in the Edelbrock 600 and noticed slight improvement, both of the vacuum fittings on the front of the carb shows about 4" at idle and will rise with more throttle and both will go to 0 at WOT this is confusing and probably my problem. Disconnected all vacuum lines except the dist and PCV, have a slight ping just before shift points. Will keep watching these posts.

[biggerhammer]

don't check the vaccuum at the carb. check it at a manifold source for a better reading, some carb. ports are vaccuum limiters

[340727Dart]

The carburetor is just like new. I've had it since new, and it's only got about 150 miles on it.
The engine is brand new and has about 45 miles on it.
I ended up timing it by ear again and I can get it to idle in gear at about 850 rpm. However, I had to turn up the neutral idle to about 1300 rpm just so it will idle in gear.
It looks like I wasted $83 on that fancy advance timing light.
The engine fires right up, hot or cold, and there is no pinging under heavy load.
After playing with the idle mixture screws, idle and timing, I now have about 9.5" of vacuum at idle in neutral.
I guess I'm going to leave it alone for now and put some more miles on it, then tinker with the timing and idle some more.

[ajmopar]

Do you think maybe the balancer has slipped? Sometimes the rubber gets rotten on the balancer and the outer ring slips on the inner, rendering timing marks useless, not to mention the danger of the balancer coming apart at high RPM. Just a thought, but I would verify TDC on the balancer with a positive stop in #1 spark plug hole. Give it a shot.

[MY340]

TK, The carb sounds fine as it should stumble or die when you put your hand over it. If your plugs are light brown like you say your pretty close and it doesn't sound like a you have a vacuum leak. I still have to wonder about distributor and balancer too since you are having trouble timing it. Heck if it don't ping and starts easy give it some more intial as this will help idle quality. You may be able to bring the idle down some then. Putting some more miles on it can't hurt either as things do change after break in. Good luck.

[71383bee]

Sorry Doug I don't think that I am going to let this one get away! She is a good girl and she fully supports my addiction. In fact now she is pointing out challengers that she wants at car shows. Too bad that she has expensive taste! I try and point out nice 72-74 challengers, but she goes right back to a 70 R/T convertible! Oh well it could be a lot worse.

Dart,
I know that your motor is brand new, but I too had a similar problem with my initial running of my rebuilt 383. It would not idle below 1000 RPM and it just ran a little goofy. I checked with carb cleaner and it also yielded nothing. So I yanked the carb and manifold and voila...oil was being sucked in between the gasket and the block. Hence the vacum leak! I ordered a new gasket with the crossovers blocked and re installed the manifold and carb and the rest is history. Your cam is pretty close to a stock cam so I would expect vacum to be at least 15" or above. My 383 idles with a steady 14" at 750 RPM and I do have a racier than stock cam in there. If you swear that the carb is good then there just has to be something else.

[BrianU]

TK,

Here is what I pull for vacuum:

340 w/ 10.02 (True) TRW’s
COMP XE268 (.224/.230)
Stock intake, exhaust manifolds with stock pocket ported heads

Fuel: (2.5 gallons of VP-12, the rest 92 pump octane)

Average Cranking compression: 168.125

Plugs: NGK GR5 or Champion RN9YC .037” gap

Timing:
Initial: 18.5 @ 950Rpm neutral w/11 inches of vacuum
Total: 36.0 @ 2100Rpm (Added 1 degree of advance)
Total w/vacuum can 53 degrees @ 2100Rpm w/21 inches of vacuum

Your 7 inches sounds about right to me.

I really don't drop any Rpm from neutral to Drive but I do drop vacuum to 10 inches. It only drops about 50Rpm with the A/C on, to 900Rp

[340727Dart]

OK, you guys who said a vacuum leak was the cause of the poor idle are evidently correct.
I have a "T" fitting on the distributor vacuum line that is capped so I can plug in my vacuum gauge.
Well, today, I was checking the idle vacuum and noticed that whenever I pulled the cap and didn't plug the leak, the idle sped up and smoothed out.
However, for the life of me, I cannot find the leak.
I sprayed brake cleaner everywhere and it did not make a difference.
I installed the manifold while the engine was on the stand and I am sure the gaskets are sealing well.
Is it possible the carburetor has some type of internal leak? It's an Edelbrock 600.
Or, is there possibly a crack in the Torker manifold? I sure didn't notice one before I put it on. I guess it's possible to have a very porous casting.

[biggerhammer]

yes it is possible fot the intake to have a leak, you said you have a torquer? would it be a single plenum manifold? or dual? for street driving you best choice is a dual, as the singles are designed for higher rpm power. also, again, check the butterfly rod for lateral movement, if it moves, then the bushings/plate are worn or oversize, resulting in a vacuum leak around the rod.

[Doug Wilson]

That's exactly the opposite to what should be expected to happen. Your vacuum leak symptoms should have gotten worse.

That response indicates a restriction to airflow, not a vacuum leak. Perhaps a stuck choke blade, bad or maladjusted lifter(s)... something like that. Maybe an improperly installed carb or manifold gasket getting in the way of airflow.

Anyone else??

[ajmopar]

I agree with doug, the extra vacuum leak should have made it worse. I still think this is a timing issue. As I said before, the factory timing mark may be wrong because of a balancer problem, wrong timing cover or whatever. I would buy a timing tape (at a speed shop, Mr. Gasket or Mopar Performance), use a positive stop tool (I made one by hollowing out an old spark plug and tapping it for a 3/8" bolt). With the tool in the #1 plug hole, rotate the engine carefully clockwise (by hand of course-DO NOT USE THE STARTER) until it stops with the piston against the tool. take a piece of chalk or soapstone and make a mark from the zero on the timing mark on the balancer. Rotate the engine counterclockwise until it stops again and mark zero on the balancer again. Now take a tape measure and mark the point exactly in the middle of these two marks. This is actual zero. I would take a scriber and scratch this right into the balancer. Now you can see if your timing mark was accurate, and now you can use your dial back timing light to set the beast up. This may not have been the problem, but it doesn't take long and it surely eliminates a variable. Try it and let me know.