360 engine vibration

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I agree on the compression testing.... pulling the plug wires one at a time and sensing a drop does not tell you that all cylinders are firing evenly.

The next thought along that line is the compression numbers that you reported earlier, which I think were 150 psi? If that is the case, then perhaps the pistons in there are not stock pistons. A '78 360 motor is a low compression motor, around 8:1 static CR, and that typically would run more like 125-135 psi. If the pistons are different than stock, then there is a good possibility that the balance is all wrong inside. So, please re-run the compression tests for this reason, and to check for consistent compression between all cylinders.

One observation on the TC: I am a bit puzzled that there are NO weights anywhere visible, or any drilled holes in the outer flange or any other other evidence that the TC itself has been balanced. I keep looking at the 1st pix in post #48 and looking at the upper left area of the TC flange and seeing what looks like a place where a rectangular weight might have been. But I cannot really tell. Bottom line: Is the TC balanced?

And, as the OP has suggested himself, the cam may be toast on a lobe or 2....
 
Compression all good 150 PSI across all cylinders. the damper looks relatively new.

Oil and filters changed twice, cant really go on a long run as car not yet UK road legal, so at present only had it ticking over and rev up to about 2000 rprm, maybe a blip to 4k now and again. I might drop the oil again or try the additive and oil flush. A lifter problem would fit the bill for the frequency of the vibration. It feels like its missing on a cylinder and lumpy. The front pulleys ( v belt ) have a slight wobbly but the harmonic balancer is steady, so I will strip this off , check part number and post a picture and eliminate that wobble.
If I take the plugs out, rocker covers off crank over and measure lift on all valves that might show up a stuck lifter?
 
OK, on the compressions.... so less likely in the cylinders or valvetrain. A really bad lifter that would make it feel like a cylinder is dropped would more than likely show a different compression reading.

I would definitely take off the valve covers and check the lift and inspect all the valve train components. Also, after a brief warm-up, push down on each rocker at the pushrod end when its respective valve is closed; any softness will indicate a leaky lifter. To check them when each valve are closed, you will have to rotate the engine a bit at a time.

Strictly speaking you need to check lift at the lifter body to make sure that the cam lobes are all good. If a lifter is collapsed for example, then the lift there will be low but the lobe will be good.

Do you have an ohmeter? I would check the end-to-end resistance in each plug wire to see if they are consistent.
 
nm9stheham said:
I agree on the compression testing.... pulling the plug wires one at a time and sensing a drop does not tell you that all cylinders are firing evenly.

The next thought along that line is the compression numbers that you reported earlier, which I think were 150 psi? If that is the case, then perhaps the pistons in there are not stock pistons. A '78 360 motor is a low compression motor, around 8:1 static CR, and that typically would run more like 125-135 psi. If the pistons are different than stock, then there is a good possibility that the balance is all wrong inside. So, please re-run the compression tests for this reason, and to check for consistent compression between all cylinders.

One observation on the TC: I am a bit puzzled that there are NO weights anywhere visible, or any drilled holes in the outer flange or any other other evidence that the TC itself has been balanced. I keep looking at the 1st pix in post #48 and looking at the upper left area of the TC flange and seeing what looks like a place where a rectangular weight might have been. But I cannot really tell. Bottom line: Is the TC balanced?

And, as the OP has suggested himself, the cam may be toast on a lobe or 2....
Click to expand...
Hi, thanks for input. Ive run the compression test a few times and reads 150PSI across all cylinders, all plugs out for cranking.

I see what you mean about the TC. So if im correct you can get a TC that is balanced for a 360 engine. OR use a neutrally balanced TC and the BM flex plate BUT the TC would still need to have some sort of balancing i.e. weights or drilling.
It was a while ago i removed the transmission but it did not have any welded on weights or evidence they had come adrift, i did look for this. But didnt look for drilling, wonder if they could be on the other side?
 
ok guys good info, its 7:38pm so off to garage now to check

1) PSI all cylinders again
2) investigate front pulley wobble
3) inspect TC from sump side to look for any part numbers, evidence of weights or balancing
4) remove rocker covers and check all valves opening and closing and amount of valve lift on each.
 
uber cool said:
I see what you mean about the TC. So if im correct you can get a TC that is balanced for a 360 engine. OR use a neutrally balanced TC and the BM flex plate BUT the TC would still need to have some sort of balancing i.e. weights or drilling.
It was a while ago i removed the transmission but it did not have any welded on weights or evidence they had come adrift, i did look for this. But didnt look for drilling, wonder if they could be on the other side?
Click to expand...
Yes on the 2 options you outline.

I would expect to see some evidence of balancing on a neutral balanced TC. But if it was one of the few that came out of assembly and just happened to be perfect, then it could not have any marks. I'm just making the observation.... and yes it could be elsewhere. The TC is not hard to pull and re-install... just messy..... You have a lot of unknowns to deal with so I'd not rule out anything.

As for the compression numbers, it sounds like you have tested it well. I just would not expect 150 psi from stock '78 360 pistons, especially if this has any moderately sized cam in it.

Speaking of which, do you have any idea of the cam in this thing?
 
nm9stheham said:
OK, on the compressions.... so less likely in the cylinders or valvetrain. A really bad lifter that would make it feel like a cylinder is dropped would more than likely show a different compression reading.

I would definitely take off the valve covers and check the lift and inspect all the valve train components. Also, after a brief warm-up, push down on each rocker at the pushrod end when its respective valve is closed; any softness will indicate a leaky lifter. To check them when each valve are closed, you will have to rotate the engine a bit at a time.

Strictly speaking you need to check lift at the lifter body to make sure that the cam lobes are all good. If a lifter is collapsed for example, then the lift there will be low but the lobe will be good.

Do you have an ohmeter? I would check the end-to-end resistance in each plug wire to see if they are consistent.
Click to expand...

If it had a bad lifter and not opening valve fully but was closing could this still give a good PSI reading?

Ive had the rocker covers off this weekend and thought I had found the fault as the rockers on cylinders 2 to 8 had same of the rockers LH and RH swapped , see post 40 on page 2, swapped this over and no difference.
Yes have ohmmeter will check , but I'm on a new set of leads, again no change.
 
nm9stheham said:
Yes on the 2 options you outline.

I would expect to see some evidence of balancing on a neutral balanced TC. But if it was one of the few that came out of assembly and just happened to be perfect, then it could not have any marks. I'm just making the observation.... and yes it could be elsewhere. The TC is not hard to pull and re-install... just messy..... You have a lot of unknowns to deal with so I'd not rule out anything.

As for the compression numbers, it sounds like you have tested it well. I just would not expect 150 psi from stock '78 360 pistons, especially if this has any moderately sized cam in it.

Speaking of which, do you have any idea of the cam in this thing?
Click to expand...

I agree rule nothing out. Although I can say its not ignition as everything has been changed or substituted at some point.
As for engine spec or vehicle history I have no idea. If you scan my other thread on the car itself, you will see its had lots spent but the previous owner clearly had no idea about assembling it correctly.
71 Dodge Dart Swinger in England
From my notes I was getting 155 to 160 PSI across cylinders.

The only history I have is that the previous owner traded it into a ford dealership and the the dealership sent it to auction the chap i bought it from traded in import cars and he bought it from the auction for himself. He had it sat in his garage for 12 months and then sold it to me as he had lost interest in it. I suspect one or both of these sold it for the vibration reason, as they couldn't bottom out the problem. I mean who traders a classic Dodge Dart into a modern dealership unless you want to get rid of it! However I'm a bit of a fault finder by nature , I never overlook the smallest or simplest issue or poo poo any advice (hence the questions here). Once I saved the opening of a $40 m rail depot for about 10 cents of parts , when the experts said we need to spend $$$$ on new door control equipment , I found a 2 pin dip plug missing on a PCB. Anyhow I digress! off to the garage and will report back soon. Thanks for tips and comments so far, Im sure a few like minded heads and engineering know how will get this sorted soon.
 
Its on fresh fuel, bought 2 weeks ago. tank has been replaced ( replaced in USA at some point). has new glass fuel filter ( never seen any dirt in it) and I think pump changed as I have old spare in boot (trunk).
As an observation I didnt think the rockers lifted much when turning over by hand. In fact the when the rocker rail was removed the pushrods are pretty much at an even height plus or minus 3/8" I was expecting a bigger difference as per other engines im used to?

2 x cans of sea foam ordered
 
3/8" is .375", and that times the 1.5 rocker ratio would be valve lift well over .500". So that range of lift difference on the pushrod side makes sense.

OK, on the plug wires..... sounds like you have worked that issue. I am catching up to a lot of what has been done.
 
Feedback from tonight.

I didn't do compression test again. I wanted to try something I haven't revisited 5 times LOL. Although I might just do it again before I put plugs back in.

Removed the rocker covers and noted all the rockers in about the same position see photo below. Now thinking about this maybe I'm used to a 4 cylinders where the pistons are 90deg out and a big difference in pushrod position from 1 cylinder to another. As a cranked it on the battery all moved up and down about the same amount, I took a video and will post later. So nothing too much a miss here however I do appreciate this is cranking speed and not 1000rpm. So still have planned the seafoam and oil change when it arrives.

On to the front damper wobble. The damper part moves in and out from timing mark approx 1 to 2 mm ( wobble) seems the inner part is doing the same, video this too. Bent crank !!!!!! So took out the rad and stripped front pulleys and damper off crank. Turned engine over on battery with DTI on crank only a minor variation 1 or 2 thou if that, could have been the DTI moving too. So happy crank not bent, phew!

Im going to take the balancer to work and run up in a lathe, maybe it got bent when someone pulled it off? But would this wobble account for vibration lumpiness? photos of damper below, is this the correct 360LA one? Has the number 85985 0259 stamped on it.


DSCF6235.JPG
 
Plugs leads , now this has me confused old leads 375 ohm and coil to dizzy lead 152ohm. New leads 5.92k ohm and dizzy lead 3k ohm.

However once again no difference to how it runs. Which ones are correct?
first photo is the old leads

DSCF6232.JPG


DSCF6234.JPG
 
I say the dampener is the culprit. Replace it with a new 1. Not a 40 some year old 1. When a neutral converter is balanced there will be little flat weights on the sides of it behind the ring gear. I hope this helps u. Kim
 
oldkimmer said:
I say the dampener is the culprit. Replace it with a new 1. Not a 40 some year old 1. When a neutral converter is balanced there will be little flat weights on the sides of it behind the ring gear. I hope this helps u. Kim
Click to expand...
ok thanks. so TC weight would be on the transmission side?
 
George Jets said:
I would not worry about the spark plug wires right now, mopar ignitions are pretty fool proof.

I usually just put on a new set of wires for 35 bucks then you know they are good and look nice and all the end terminals are new and proper. New spark plug cap at the same time, this is where some trouble can happen as the used caps can jump the spark between the terminals . . carbon trails inside, seen that happen a lot when it is real humid out. Then you know the wires are good.

On to the next diagnostic on the list. buy an new damper for starters. Nice car you have there so it is worth some new parts.
Click to expand...
Yep its all new leads, cap and rotor arm. Yes on the whole I'm very pleased with the car absolute zero rust or welding.

video here showing valve gear and damper when turned over on battery. I think this confirms the problem.



Now just to work our which of the 47 listed at Summit fit! Or any other suggestions where to buy appreciated.

Im off to bed now , past midnight here and work tomorrow. But thanks for all you support and comments, if you get really bored have a look at my video channel below shows work ive done to date on the Dart and some of my 58 Apache and 63 C10 I built for a friend.
 
uber cool said:
Yep I think so too. Whats your thought on the plug lead resistances?
Click to expand...
The 2 different ranges of spark plug wire resistances are due to 2 different wire constructions/types. The latter, higher values are standard resistance wire, and the 5.7k ohms, etc. is in the normal range. The higher resistance ones would be used with standard plugs, but either can be made to work.
uber cool said:
Damper as removed, is this the correct 360 LA damper?
Click to expand...
The damper looks correct for a 360. The slots are, in effect, 'anti-weight'; i.e., the desired imbalanced weight is on the side opposite to the slots.

That old rubber, with the crack in it, has rendered the damper unable to 'damp' out the internal high frequency crank vibrations. (Those internal vibrations are in the 6-7 kHz range typically, and are not what you are feeling, but can damage/break a crankshaft if not damped out.) Whether that damper has anything to do with the overall vibration is another matter, but it needs replacing due to the age. And Oldkimmer is right... don't use an old damper....same problem: it won't damp properly once the rubber is hard/cracked.
 
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