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vibration
https://slantsix.org/forum/viewtopic.php?t=60501		 Page 2 of 3
Author:  SlantSixDan [ Mon Nov 28, 2016 6:06 pm ]
Post subject:  Re: thanks Dan...
Quote:
I wonder if I could see anything in the fluid, just by draining the converter...maybe there would be bits in there that might indicate damage.
You cannot determine if the converter is imbalanced by looking at (or smelling, tasting, etc) the fluid.
Quote:
It would be difficult to refill the converter without it being out of the tranny,
One does not refill the converter itself. One installs it, then starts the engine, puts the transmission in Neutral, and adds trans fluid in the normal way until it gets to the correct level.
Quote:
so if I'm going to drain it, I might as well pull the tranny - fair statement?
No.

One other thing: have someone gradually rev the engine to and through the vibration range while you station yourself at the tailpipe. Listen for evidence of misfiring in the vibration-speed range.
Author:  '67 Dart 270 [ Mon Nov 28, 2016 8:11 pm ]
Post subject:  Ok
Thanks Dan,

I can try the exhaust sound testing for misfire sounds as well. Pardon my naivete on the tranny stuff...

Brian
Author:  '67 Dart 270 [ Mon Nov 28, 2016 8:20 pm ]
Post subject:  misfire
Supposing it sounds like a misfire...what is the leading or most likely cause of a misfire? Wires, cap, rotor, dizzy, ECU, timing, coil, plugs? I've been through all those before, albeit with a dumb "swap it out" approach; but no change with swapping any of those components and/or varying the timing (I tried advancing, retarding, TDC before). I didn't check the voltage, but the system is charging; I noted that during break in. The only thing I could find before was the lean condition, but I corrected that, and besides it ran very smoothly with that lean condition before the head gasket blew (except for occasional pinging that I was chasing, thinking it was an exhaust manifold leak).

Brian
Author:  '67 Dart 270 [ Mon Nov 28, 2016 8:50 pm ]
Post subject:  timing light
Dan,

Can't I check for a misfire using my timing light? I should see a noticeably different strobe if there is a problem with one of the firings. I did note that the timing mark seemed "jumpy" to me.

Anyway, I'm pretty sure my wires are separated well, I don't think theres an induced misfire. Here's a pic of my setup: http://s785.photobucket.com/user/67dart ... html?o=162

I didn't mention vacuum or intake leak, but I checked those pretty good; I can't find any leaks.


Brian
Author:  SlantSixDan [ Mon Nov 28, 2016 9:05 pm ]
Post subject:  Re: misfire
Quote:
Supposing it sounds like a misfire...what is the leading or most likely cause of a misfire?
An RPM-dependent engine vibration can be caused by an RPM-dependent misfire, which can be caused by an ignition secondary short to ground when distributor parts align just right (just wrong). You've got a centrifugal advance mechanism in the distributor that is RPM-sensitive, and you've also got moving parts in the vacuum advance system. So if the exhaust note changes during the vibration speed range—or heck, even if you're not sure it does—first try disconnecting the vacuum advance hose (plug it off so as not to create a vacuum leak into the carburetor) and repeat the test. If no change, put back the vacuum advance hose and see if you can suss out a misfire using a timing light. The problem with the timing light method is that you can get a misfire that doesn't happen to affect cylinder № 1 and not see it unless/until you put the timing light sensor on the plug wire of one of the cylinders affected by the issue.
Author:  Killer6 [ Mon Nov 28, 2016 10:39 pm ]
Post subject: 
Quote:
Remove all belts off the engine and run it briefly to see if anything changes. Could be related to fan (bent) or other accessories.
Absolutely try this, easy, and I had a tweaked fan blade give Me
all kinds of grief on a 383 one time.
Author:  '67 Dart 270 [ Tue Nov 29, 2016 8:21 am ]
Post subject:  timing light
So, with the timing light method, I assumed that I would just put the inductor on each wire and observe the light pattern, looking for anything odd. But, what I'm hearing regarding a dizzy rotational misfire possibility, that could be a random misfire spread across all cylinders, is that correct Dan? If that's true, then it would be hard to diagnose with a timing light, is that what you're saying Dan?

Killer6, yes, the belt test is easy peasy, I won't miss that one.

Brian
Author:  Killer6 [ Tue Nov 29, 2016 6:24 pm ]
Post subject: 
I will throw these things at you, then see where you are at.
1)You run a compression&leakdown test on this since re-assembly?
2)Does the vibration change in gear sitting still holding the brakes as
you bring the engine thru' that RPM range?Disappear?
3)The timing on EI jumping around that much makes me wonder.Adv.
weight springs intact/correct? Yeah, reading each ign. cable is a
great way to spot a problem, incl. the coil wire. The coil itself can
do crazy things.
4)The character of this vibration seem very steady/rhythmic? Or erratic
but constant?
Author:  '67 Dart 270 [ Tue Nov 29, 2016 8:48 pm ]
Post subject: 
Quote:
I will throw these things at you, then see where you are at.
1)You run a compression&leakdown test on this since re-assembly?
2)Does the vibration change in gear sitting still holding the brakes as
you bring the engine thru' that RPM range?Disappear?
3)The timing on EI jumping around that much makes me wonder.Adv.
weight springs intact/correct? Yeah, reading each ign. cable is a
great way to spot a problem, incl. the coil wire. The coil itself can
do crazy things.
4)The character of this vibration seem very steady/rhythmic? Or erratic
but constant?
no compression test yet, but the vibration is the same as before the rebuild, so I don't think that's the issue. I will run a compression test now that I've broken her in, as a baseline.

Haven't tried the in gear brake test, but will.

I have a spring kit in it, they looked fine when I had the distributor apart; I checked again, they are in place and intact, they are the same springs as before the vibration issue ever existed.

Steady, intensity increases between 1200 and 1600 rpm, but it seems to be there the whole time/rpm range.

Granted a timing/spark issue would make the timing mark "jumpy" but would not also a mechanical vibration, i.e. the engine actually vibrating make the timing mark look jumpy?

Brian
Author:  DusterIdiot [ Tue Nov 29, 2016 9:23 pm ]
Post subject:  Not really...
Quote:
the engine actually vibrating make the timing mark look jumpy?
Only if it was running realllly rough, and I mean the powertrain is rockin'... if the timing mark is bouncing around enough for you to see it with the strobe of a timing light, you have a timing issue... either the distributor springs are too light and the weights are bouncing back and forth.... you can also catch this if the timing chain is loose and as the idle goes back and forth in rpm it can bounce... have you run it with a vacuum gauge at the RPM noted to see if the needle bounces or there is any indicator of a variance?

Another item to consider is possibly your carbs in that rpm range are in the transition circuit and need to have the circuit fattened up a little because the engine is wanting to be in the mains... not sure how that works on a weber... on a holley we would either open up the slot in the plate a bit, or plug/restrict the air bleed in the throat, so the main circuit comes on sooner and closes the gap.... For my Hpak engines I set the mains to engage about 1600 rpm instead of the stock setting which would be about 2000 rpm...

(I know that that was an issue when I worked with another member and this same dual carb setup on his 66 Dart... we also had to work with a lot of 'listening through the rubber hose' to make sure the carbs were synched to prevent some engine disco bumpin'...)


Some other food for thought....
Author:  '67 Dart 270 [ Tue Nov 29, 2016 11:36 pm ]
Post subject:  right....
I would think the same thing, DI, it seems like it would take a real earthquake to make that timing mark jittery...then again, let's say it's an imbalanced torque converter, might that vibration go all the way through the crank to the harmonic balancer and make the timing mark shaky?

I haven't run it with a vacuum gauge to see if it's bouncy, not this fresh rebuild that is, but I did run a vacuum gauge on the previous engine and the vacuum wasn't shaky at all, but the engine had that vibration.

The dizzy springs being too light seems unlikely, because these are the same springs as before the vibration issue. To be clear, I have swapped distributors before the rebuild and had the same vibration issue, both distributors had the same type springs, one blue one green for the same curve. So, same type springs but different actual springs and in different distributors. If the spring type were OK before the vibration problem, not likely two separate sets of the same type of springs in two different, but identically configured dizzys would both have identical problems. For this rebuild I used a freshly rebuilt distributor, new nylon gear as well. I did note some play in the dizzy shaft when installed, that is, the play between the nylon gear and the cam drive gear. Otherwise the dizzy shaft had no play, either vertically or lateral.

I don't think it's the carbs either, they were OK before the vibration problem, except for the lean mix that caused the head gasket issue, but I've fattened the mixture across the acceleration and load range since then and the vibration issue is the same.

Ain't the timing chain, it's new and double roller Aussie one, quite solid, no stretch.

That all said, let's assume it is ignition related for the sake of argument. What could happen during a head gasket failure, two cylinders communicating and the engine violently jerking, in the ignition system that would cause such a vibration? Keep in mind, I've swapped out nearly all of the ignition parts and had the same vibration issue both in the old engine and the new one.

I'll run some tests, timing light, listen to the exhaust, etc, etc., see if I can see any anomalies. Whatever this vibration is, I'll track it down eventually. Seems like the two main suspects are 1) the torque converter, simply because to me it feels like it's coming from the rear part of the engine and/or tranny (and the previous engine went through violent shaking), and 2) something in the electrical system, a misfire for some reason. I want to believe it's mechanical, but I can't ignore that shaky timing mark, that is something that I noticed right away after the head gasket failure was repaired, and now that I have a completely rebuilt engine (including balancing the crank, checking the main bores, new rods and pistons, matched weight on pistons and rods) it still is there. Tells me that something peripheral to the engine is at fault, not the innards. It is either electrical or mechanical and I'll find it....bear with me, and thanks for all the ideas, gives me lots of avenues to explore...

Brian
Author:  '67 Dart 270 [ Mon Dec 05, 2016 7:49 pm ]
Post subject:  dropping transmission
When dropping the transmission how does one support the engine? Do the motor mounts need to be loosened? Any helpful tips? jack under the oil pan?

Brian
Author:  '67 Dart 270 [ Mon Dec 05, 2016 7:53 pm ]
Post subject:  Fyi
I checked the FSM, it shows a cool little frame for supporting the engine, it says you should lift the engine slightly to remove the tranny. That's why I'm asking.

brian
Author:  Reed [ Mon Dec 05, 2016 8:59 pm ]
Post subject: 
A floor jack under the back of the oil pan has always worked for me.
Author:  Louise76 [ Mon Dec 05, 2016 9:30 pm ]
Post subject: 
I cheated on our 74 Scamp. Found two bolts on the back of the engine that looked like they could temporarily support the weight of the back of the engine. Made two steel straps to go from those two bolts on the engine and up to the face of the (sheet metal) firewall, where I drilled through the straps & firewall and installed bolts to basically suspend the back of the engine from the firewall, gently. While actually working under the engine & trans, I placed a safety block under the pan just in case I screwed up and a strap broke free. "Your ideas may vary."
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