Brought Dart to shop to fix idling issue and car runs like s**t!

I’ll explain a little background on this situation so that it is easier to diagnosis my possible issue. First let me again thank all of you that have helped me within the last year while I was tackling a lot of suspension and engine work on my 67 dart. I have learned quite a bit from all of you. Thank you.

Well I had upgraded the 383 in the dart with edelbrock performer rpm heads switching from the iron 915’s that were on it. I worked on the car for the last 6 months as much as possible and through some trial and error and a lot of help from everyone I was able to do the head change replace the timing gears and chain, put on an aluminum waterpump, install a geometry kit for the Harland sharps on my edelbrocks. I just couldn’t get it to run right. The valve train was very noisy even after rechecking the adjustments on the rockers. It also ran real rough and I wasn’t able to get the 650 speed demon to idle down @ 800-900rpm like it used to. So I was at a loss, winter was here, the dart was outside and so I brought it to a local restoration shop. They said they would get the car worked out and tune it up sweet.

Come to find out first thing they said was that I had 2 plug wires going from the cap to the wrong cylinders. Well running on six instead of eight would do that. That I’m sure was a factor in a rough idle. Simple idiotic beginners mistake by me. Always check the easiest things first I have now learned. They also said that about 3 of the lifters were slow to pump up but still had a little life in them. For reference the lifters were standard mopar performance hydraulic flat tappets about 20 years old. Since the engine was built back then I put about 15,000 miles on the engine. I though ok I’ll replace the lifters when I have my garage finished and a comfortable place to work. I go to test drive the car today they tell me it’s all set and running great.

Either they are idiots or never got on the car to the point of even 4000rpm. The carburetor idle was set at 1200-1400. Even with the old mopar performance cam in it that is too high. The cam is 484 lift 284 duration not crazy radical. The old engine with the 915 heads had a ton more power and throttle response then it does now. After driving the car and getting the rpm’s up it started backfiring terrible through the exhaust. I noticed it was backfiring much more on the passengers side.

I think the issue is that the lifters were worse then they thought and they still reassembled the engine. Im thinking there is at least 2 partially collapsed lifters on the passenger side and one on the drivers side. Wouldn’t that account for the excessive fuel not being burned and being dumped in the exhaust igniting in the mufflers? Also that would account for the real noisy valve train under the valve covers and the rough idle that can’t be turned down like it used to? It would also kill the engines power/performance. Shouldn’t the Ede head upgrade be noticeable in a power gain?

I brought the car back to them and went through all the issues. I told them make it right! I just recently bought Rhoades lifters with the eventual intention of replacing them and told the shop to put the new lifters in and set up everything based on those. Am I thinking correctly on this one?

If this is the same shop that did your clutch work, find another shop.

You should search for AJs tuning tips and do them in sequence. He does a great job of explaining the steps and reasoning behind them .
Your build is pretty straight forward and fairly mild . It should idle around 750 and be smooth thru the powerband .
Did they by chance adjust your valves ?
They might be tight if its backfiring .

Did the car ever heat up enough to open the choke and get off the fast idle cam?

you can get that 284/484 down to about 700. Had one in a 340, strip dominator intake and a 650 Demon...and it idled just fine that low. idled even better with a Holley spread bore for some reason. crazy looking carb, great idle. Dont trust anything, double check everything, 18436572 CCW..not hard to confirm. Whats idle vacuum reading?

Yup Rusty same shop that did my clutch work. I know this place hasn’t started on a high note. I believe they rechecked my rocker adjustments which could be hard to do if several of the lifters are shot. The ede heads were gone through by a mopar machine shop I have used and trusted they checked all the tolerances out of the box and recut some of the valve seats before I bolted them on. Idle vacuum right now is at 10inhg. I checked it today when I drove the car. I think with better tuning I could get it up to 12-14inhg. Yes I had the car out driving around for about 30 minutes it had fully warmed up. Thanks for the suggestion mbaird I’ll check out AJ’s tuning tips. Could the lifter issues be the cause of many of the problems?

mbaird said:

You should search for AJs tuning tips and do them in sequence. He does a great job of explaining the steps and reasoning behind them .
Your build is pretty straight forward and fairly mild . It should idle around 750 and be smooth thru the powerband .
Did they by chance adjust your valves ?
They might be tight if its backfiring .

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Keep in mind it has an aluminum flywheel. It is NOT going to idle down compared to one with an iron or steel flywheel.

LovetheA's said:

Yup Rusty same shop that did my clutch work. I know this place hasn’t started on a high note. I believe they rechecked my rocker adjustments which could be hard to do if several of the lifters are shot. The ede heads were gone through by a mopar machine shop I have used and trusted they checked all the tolerances out of the box and recut some of the valve seats before I bolted them on. Idle vacuum right now is at 10inhg. I checked it today when I drove the car. I think with better tuning I could get it up to 12-14inhg. Yes I had the car out driving around for about 30 minutes it had fully warmed up. Thanks for the suggestion mbaird I’ll check out AJ’s tuning tips. Could the lifter issues be the cause of many of the problems?

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You should be able to tell if you have a hydraulic lifter problem by pulling the v/c’s off and see if you have any rocker arms loose ! Also by turning the pushrods ! Yes if the valves are not opening correctly it can cause a back fire thru which ever valve is not opening !!

Idle speed too fast- Did you check the intake seal to the heads? Maybe a slight vacuum leak.

Love the As,
Rusty is right. Find another shop. I know its convenient to have a shop in CT, but not everyone is cutout for these types of diagnosing and repairs, especially Mopar. Of course they will talk a good game as they take your money.
Ask around.
When I was in need of a resto shop, I kept hearing "take it to Gary's". Now Gary was in PA, over 4 hours from me, but it was worth the inconvenience of trailering my Mopar all the way over there.
Nothing better than dealing with a "like minded" Mopar oriented guy who has the knowledge and connections to get through the tricky cases. Dealing with a guy thats not in it just for the money?...priceless.

Not trying to pile on with the shop you took it to, BUT a lot of shops today vs older more experienced shops.......its like comparing McD's vs The Keg. Finding a shop that KNOWS 60 year old cars is hard. Just because they are licensed doesnt mean squat. We as owners either have to invest time to learn(fabo) or be prepared to pay good $$ if we can even find a good shop.
I would think above advice will straighten out the issues. Have you put new Rhoads lifters in? I would think with proper timing, valve lash and new lifters that the problem is minimized/isolated?
Good luck!

A lot of good stuff here, especially for someone like me whose trouble-shooting skills are rusty and out of date. I’m still chanting “ignition, carburetion, compression.” One of my favorite trouble-shooting tools is a cylinder-shorting dwell tach (Snap-On MT460) that I used to sell back in my days as a Snap-On dealer. It was the control unit for their oscilloscope, but you could buy it separately. I sold more scopes (and AVR testers) than any dealer in the Phoenix branch back then because I would train my customers on how to use them. I still miss oscilloscopes too, although modern computerized engine controls have largely made them irrelevant. A quick search revealed several MT460’s for sale on ebay for very reasonable prices. If you have an older car with battery-point ignition, they’re worth a look. I’m pretty sure you could pick the adaptor harnesses for early electronic ignitions like HEI, etc., too.

azaustin said:

A lot of good stuff here, especially for someone like me whose trouble-shooting skills are rusty and out of date. I’m still chanting “ignition, carburetion, compression.” One of my favorite trouble-shooting tools is a cylinder-shorting dwell tach (Snap-On MT460) that I used to sell back in my days as a Snap-On dealer. It was the control unit for their oscilloscope, but you could buy it separately. I sold more scopes (and AVR testers) than any dealer in the Phoenix branch back then because I would train my customers on how to use them. I still miss oscilloscopes too, although modern computerized engine controls have largely made them irrelevant. A quick search revealed several MT460’s for sale on ebay for very reasonable prices. If you have an older car with battery-point ignition, they’re worth a look. I’m pretty sure you could pick the adaptor harnesses for early electronic ignitions like HEI, etc., too.

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That was a good one for for tune ups and engine misses. I was a MAC dealer and we had the ET985 which also cancelled cylinders. I sold a bunch of those as well. Hook it up quick and start cancelling cylinders. Sold! @LovetheA's , you need to go back to basics and check out all components in your tune up. Don't know much about it? Read until your eyes bleed.

You can do the "cylinder kill" manually pretty easily. Pull the dist. boots up gently and loosen the wires in the cap. Couple ways to do this.......

Take something like paper clips or small brads and slip down beside each wire. Now you can ground each cylinder with a grounded probe, watch a tach or vacuum gauge on each "drop."

Or with the wires loose, pull each wire up a little while you slip a grounding probe down into the tower, for each one in turn.

A reputable shop went through the new heads. Do you know if they checked valve stem to valve guide clearance? Seems to me that was a known clearance problem on some Eddy heads. (Too tight)

Also, nothing mentioned yet about correct pushrod length. A lot of things were changed affecting valvetrain geometry since it last was running right

Seems there are a lot of possibilities here and every one will have to be methodically checked and crossed off the list.

KosmicKuda said:

A reputable shop went through the new heads. Do you know if they checked valve stem to valve guide clearance? Seems to me that was a known clearance problem on some Eddy heads. (Too tight)

Also, nothing mentioned yet about correct pushrod length. A lot of things were changed affecting valvetrain geometry since it last was running right

Seems there are a lot of possibilities here and every one will have to be methodically checked and crossed off the list.

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If the timing curve and carb are correct it idle at 700 RPM all day long.

What do you have for an ignition and what the timing?? Certain ignitions will die if you pull the wire off the plug and die right quick.

Yes I agree everyone start with the basics and move from there. I think the first thing is to get the new rhoades lifters put in, check pushrod length(I have several lengths). I’ll use the one that is at zero lash at the middle of the adjustment setting in the rockers. Right now the pushrods might be a little short but nothing bad. Then when the valve train is set up right then timing can be adjusted and then setting up the carb. My ignition system is a mopar electronic distributor no vacuum advance with msd 6al box. I think it’s unfortunate that so many places talk a real good bullshit line. This place supposedly works on high dollar European cars as well as American muscle. Let’s just say I’m not impressed. I will say this. The work that I did on various parts of the car where I took my time asked questions and was careful gave me a great sense of satisfaction. It is so much better doing things and learning yourself. I just took a gamble I wanted the dart completed and was going to store it there for the winter. I said yeah just let them get it turn key ready and tuned. I guess another shop that disappoints.

I wanted to answer a couple of questions that were brought up. There is no choke on my speed demon carb. Therefore you have to feather the throttle for a few minutes until the car warms up then idle should be stable. Second I did have a vacuum leak when I re-assembled the engine. That was because when I reassembled the engine the original builder didn’t use valley pan and intake gaskets and dumped on a ton of silicone to seal. Real cheap fix. I had the intake cut down .040 to account for the gaskets and the pan and intake lines up perfect bolted on no more vacuum leaks.

LovetheA's said:

My ignition system is a mopar electronic distributor no vacuum advance with msd 6al box.

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That's a REDFLAG right there.
I know yours is a 383, but I once had a 292/292/108 in my 367 and it liked a TON of idle-timing, But as I took timing away, it would eventually tick over at 700 and less, with a correctly adjusted Transfer-slot exposure.
My current 276/286/110 cam, which is only one size smaller that yours, will tick over at 550rpm, pulling itself along at a tic under 4mph,(Commando 4-speed) at 5* Idle-timing. I'm pretty sure your 383 can nearly match that.

The biggest deal IMO,is for you to prove the valves are closing, and not leaking, and that the cylinder pressure is fairly even. So to that end, I highly recommend both a LeakDown test AND a compression test.
When you do the latter, keep cranking until you get two consecutive about-same-pressure readings.
When you do the former, and if you get poor results; remove the valve gear and redo the test with the pistons at the bottom. Also, at this time, manually rotate the crank thru a couple to a few revolutions noting how hard it is to break and rotate it. Tight rings create a frightful amount of friction, making idling very hard.
The results of these three tests will probably point us to the next move.

The reason that the No-Vcan is a red flag is because at Part throttle, that cam will want a lotta lotta timing, and there is absolutely NO WAY the factory D can supply it. If you try to fudge it, your carb will idle waaaaaaaaaaaaay too far down the transfer slots, resulting in tip in sags, to outright afterfires, or even back-thru-the-carb lean missfires..
The more you retard the idle-timing, the further up the transfers, the throttle-blades will climb, reducing tip-in problems. Most carbs will want the accelerator pump system readjusted after significant changes in idle-speeds.
AJ's guide to Transfer Port Synchronization

One of the problems is today no one wants paper manuals the old Chilton's and Motors Manuals had a lot of basic diagnostic techniques in them. No one knows how to work on points and carburetors any more. Sad.

Tip most of the guys that know how to work on this old stuff are over 60

I wouldn't mind knowing the name of this shop since I'm also in CT and would know enough to stay away. If you don't want to post it here maybe you can PM me? Also I know of a shop that does specialize in Mopars and it's maybe a thirty minute drive for you.

AJ/FormS said:

T I highly recommend both a LeakDown test AND a compression test.

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This should have been done by about post 3 of this thread

Not a bad video with steps. Not a mopar but process is the same.

I have been chasing a slight idle roughness and burble under 2000 rpm for a few years now . Checked for vacuum leak , tried several carbs and 1000 different jet / air bleed / timing combos . I decided to try new intake gaskets and bought a set of Edelbrock embossed intake gasket and some Gasgecinch.

Smooth as a babies butt now !

Thank you everyone for all the input and info. Yes I’ll look into having a leak down and compression test done because that will give me affirmation that I have good cylinder pressure and that the valves are opening and closing properly. I’ll also keep everyone updated on the outcome of this. I just wanted to ask to clarify AJ that I shouldn’t stay with the mopar electronic ignition and no vacuum advance? I should go back to the original distributor and points? I’m determined to get this situation ironed out and made right. I can’t wait until my garage is completed and I can continue to learn and work on my cars in a comfortable garage, take my time and do things correct. Outcome pending.