I have just picked up this 73 dart swinger, it has a pretty nicely built engine. the guy said it was either a 318 or 340. but it has a carter afb, edelbrock intake, headers, and a pretty lopy cam. now this is my first mopar as i was a bowtie guy. so be gentle lol. it idles fine and starts up very well even when it's cold as hell out. but when i am at a stoplight in drive it shakes, i also notice it does it in park only when i turn the wheel.( it has power steering). so basicly it does it under load. But it doesn't do it while driving. i checked the dual exhaust, but it's hung pretty well my next thought are the motor mounts? what would you guys suggest?? any past experiences?? thanks

 

j -

Welcome aboard

Basic stuff, check timing, a/f mixture and even idle settings. A vacuum leak might cause that as well. Last I checked, use the same procedures as you did on that other "brand"...

Even a miss might not be noticed at higher rps, but might be more evident at idle.

To check the motor mounts, just have someone watch the motor (from the side ) while you hold the breaks and apply the gas. Don't think that's it though.

Archer

 

Archer,

i've had timing and a/f mixture problems before on my ex's and they never vibrated like this at a stop. i just got the car i traded it for my montero sport straight across ( think i got the better end of the deal) so i am still digging through the records to see what all was done to the car. but as far as the engine besides a small leak at the header flange it runs like a raped ape, starts and idles smooth. havn't hooked up a timing light but i've been around engines of all sorts for 15 years and i think i can rule out the things you mentioned. but i am not affraid of being wrong either lol

 

j -

OK, cool - you've got the stuff covered. So what you're really asking is the motor stumbling or is it just not mounted correctly? You probably know more that I do, so the best I can do is try to act as a sounding board.

1. The part that's telling me something with the idle circuit (carb) or timing or miss-fire, is that you're feeling it at a stop light in gear, but not at higher rpm. (We're also assuming that the cam isn't on the hot side with a lot of overlap.)

2. All motors with stock mounts rotate do to torque. but you know that, so we can take the question a little further, it is torgueing too much? If that were the case, you should feel it on a straight acceleration as well (do you?)

You didn't mention if the car has a tach or vacuum gauge, or if you can hook one up - that might shed some light on it.

Archer

 

Only my input take it as you want: Hard to fix cars on the phone or internet so like I always say only 3 things needed to make a motor run, you have compression we know because it does run, you have spark again its running but is it good strong spark underload with all the Ingnition fully heated up, electronics that test good cold can be faulty when heated sometimes or thats when they like to crap out, 3rd is fuel which to me except for the "Turn the wheel' part sound like it might be whats making it shake, and at that without feeling or hearing it hard to say what part but look for a nice hot spark when it does it and make sure mixture is good, it does not matter what cam with what profile you set every engine to highest vaccum reading that is possable before it stumbles - street cam getting 15 - 16 in. awesome, nasty cam getting 7 - 10 see ya at the gas station ..... hope this helps and sorry the steering thing is throwing me off - Jake

 

Well i dug through the records and no dice on any info on the supposed engine build. yes it's a bit on the nasty side for the cam, cuz i've gone through some gas let me tell you. BUT i think i found the problem....
the dumbass who installed the exhaust hard mounted it to the frame, no rubber hangers, just straight flat stock welded to the tubing then bolted to the frame. now i might be crazy but with harmonics and the long *** amount of exhaust tubing i thing it might be the culprate, what do you think?

 

here she is, i think it was worth the trade

 

That would be a real good place to start if thats the case, I see what your saying now and that will do it for sure thats why they rubber mount them - cranking the wheel loads the motor and it twists and makes it shake make sence to me - good idea none the less to now and then check all the settings like fuel & timing being a motor is an ever wearing ever changing peice of machinery and needs attention, Jake

 

The rims alone or even rotted to the ground is my vote, very nice triple black A Body for sure good find

 

exaust is a good place to start. curious what are your rpm's reading at a warm idle?

 

like sportfury said the exhaust is the place to start with the exhaust solid to the frame there is no room for engine torque rehang your exhaust and i bet your problem goes away

 

j, gents -

(Caveat) Like Jake said, really hard to Dx stuff over the net, as we all have different ideas about what "shaking or knocking" sounds like.

I'm not completely buying the exhaust thing, only because unless there is some kind of blockage, the "pipes" don't move much on their own. they respond (move) to engine movement. The hard mounting to the frame does sound a little weird though.

I'd make sure the engine movement is within range first, but yeah the hard mounts should be addressed.

Archer

 

I do agree, yes the exhaust is mounted wrong but I dont think this is the reason for the shake. If the shake keeps up though your exhaust will start breaking "because" of the ridged mount. Jake is also right, it's hard to diagnoise here with what I got but I bet if you go back to basics you will fix it, CHeck your cap for carbon tracking, rotor for pitting, spray a mist of water from a spray bottle on your plug wires and look for little blue or yellow lightning bolts. make sure idle mixture and base idle are correct and pull a plug or two seewhat they look like. If all above are correct to your satisifaction do a compression test. It dont matter what the compression is as long as all cylinders are even across the board. One last thing you can do here is clean your cylinders from any carbon. Get yourself a empty clean pint size bottle and fill it with water. Disconnect the vacuum hose from the pcv valve. Find another vacuum line (scrap piece not from engine compartment) with the outside diameter the same as the inside diameter of the pcv vacuum line, insert the two together. this is nessary to restrict the amount of water entering the engine. start engine and bring up to at least 2000 rpm this is nessecary to prevent hydrostatic lock. Insert vacuum line in bottle of water and let the motor suck up the water. After this happens fill the bottle up again and do it again, do this 3 or 4 time but drop rpm down to about 1000 rpm between bottles (do NOT idle). Make sure engine is warm before you start. I do this all the time when doing tuning ups, later models or classics it works to correct rough idle.

 

well plugs look good, it doesn't miss or stutter. idles (lopey) at about 7-8 hundred. gonna get some new hangers today and fix the exhaust mount back to how it should be. it's not raining today thank god lol i don't know about introducing water into your cylinders, have you opened up the engine and visually inspected it? water and oil don't mix and being that your cylinders and pistons need lube i don't think i'll be giving that a try lol. the only way i know and trust with keeping the carbon biuld up away is to coat eveerything, combustion chambers, valves, the tops of pistons.

 

Water does work, turns to steam inside the hot engine and cleans the carbon off. trick is not to put too much in at a time so it does all turn to vapor not stay in liquid form, and I kid you not we use to slowly pour a cup of water down the carb of old flat head fords to fix their carbon build up problems, always good idea to change the plugs after you do this because the crap will tend to stick to them and foul up

 

if the exhaust is hard to the frame and the idle is low enough the notes coming thru the pipes will low enough to emit rattle. kind of like a sub-woofer at 200 hertz it wont shake the car much at 40-60 hertz it starts rattling the car. exaust noise runs in hertz also (harmonics) low at an idle higher herts as the engine revs

 

Actually yes I have the last time I did a head gasket. The cylinder that the coolant was leaking into was clean as a whistle (just an expression actually whistles can be quit dirty). My appoligizes I have no idea your level of mechanical ability here and if this procedure (as I stated above) isn't done correctly yes it can ruin a engine however; if done as I stated, and depending on the mileage, running temperature of engine and driving habits this procedure works but if your not that mechanically inclined (no offense here) I recommend taking it to your local tune up shop.

 

well just disconnected the back exhaust mount which was the rigid one and it stopped shaking in drive. i would like to poke around more but this damn seattle rain lol. i did take the wife for a ride yesterday to test it out. might have to through some sandbags in the trunk cuz it breaks traction way to easily. thanks guys for all the info and suggestions i'll keep you posted and probably have more ?'s about my new found love lol

 

Broken motor mount? It shakes? But is it missing?