Detecting detonation, among other things

[kyleandhisIH]

Well I guess I figured it was time to make a new thread about my recent experiences with my own binder. The 304 still starts and runs well, nothing terribly erratic going on, no causes for immediate alarm. Still yet, I have no idea what to think about my "timing issue." to rehash, my motor seems to run best when the indicator reads 20 > 25 deg, on a light with no dial-back setting. Btdc. I have re-stabbed per the instructions handed to me in several places on this forum, and still I end up "chasing" the 20>25 degree point around, because that's just where it runs best. Three times now, I have used a long-shaft screwdriver to verify top dead center. Each time, I do my best to install the wires in a way that #8 is right in line with the rotor. From this point, I usually get it running ragged (which ends up being anywhere from 0 > 10deg) and then I play with timing until it becomes smooth and runs with nearly zero hiccups. Put the light back on, and guess what? I'm anywhere from 20 to 30 degrees registered on the light, so I'm convinced something just isn't right.

One of these "issues" May very well be this amateur mechanic. I can't say I've ever heard detonation, the only pings I recall come from dropped bolts hitting the exhaust, and the only knocking I've heard was due to the double-hump sump starvation issue. I have tried to advance the ignition to the point that it detonates while driving around in a rather obnoxious stomp-on-it manner. So far, I don't think this motor knows how to detonate. I have a very slight exhaust leak, which hinders my ability to hear when the motor is idling at its easiest. I don't currently have the tools to chop and fix the "professional" exhaust job that broke my flange gasket and prevented correct installation of another, so I'm living with a slight ticking noise of escaping pulses. Still yet, there's no way such a tiny exhaust leak could cover up a solid pinging, is there? I don't even notice the leak at cruise speed, and no irregular or scary sounds can be had during any kind of driving.

I got a little worried that maybe I was just missing the knock, so I backed off my timing until the point where the motor started to sound rough and show wider "pulsing" on vacuum sourced from the #8 runner (brake booster fitting), and this pulsating has nothing to do with the booster... It's just the motor itself. So I try to "time" it to where the pulsating is most consistent and less erratic & jumpy. Right now it sits at around 15 degrees advance, And tip-in makes this thing feel like a turd, no matter how many hours I spend setting and re-setting idle mixture and verifying good, strong accel pump shot. It wants more timing, it drives better with more timing, but I'm inexperienced and a little afraid of losing what is still the most valuable thing I can claim to own.

The idle speed also tends to wander. What I mean is that if I release my manual choke a minute into warm-up, it will idle at ~600rpm. After fully hot, it will idle at roughly 750. Based on advice from this place, I simply lean the idle mixture (after everything gets nice and hot) 45 degrees at a time until speed begins to drop, and then I back up (enrich) 45 degrees for safety's sake. I still have the egr installed, and verified functional/not sticking. I don't rightly know if I still have vacuum going to it, but I definitely eliminated anything else coming from the vacuum tree on my manifold. I check the egr just about every time to make sure it's not playing with my head, but every time it responds with a sickly change in idle quality, which disappears when I release the diaphragm.

I know that my binder-driving habits (maybe a few times a month) are not enough to damage this vehicle and I doubt I've caused any serious harm. I still can't help but worry that I am leaving it in an improper tune. I have spent too many hot summer days leaning over a hot engine bay, trying the same things over and over, and getting the same results. Once I think I've verified proper ignition setpoint, I try to verify that the carburetor is idling and responding in the way I'd like. But then, no matter what kind of fiddling I do afterwards, the vehicle acts like it's not in proper tune. I realize 3.56 gears are going to dog the hell out of even a fluid-linked powerplant, but I just expect more than coughing and sputtering like the stereotypical antiquated vehicle.

Tomorrow I plan on once again checking firing order (which is a number sequence I'll never forget) as well as the relationship between tdc and the odd numbers I'm receiving from the timing light. I hate to basically post a lot of the same info I've already shared with this forum, but I don't know what else to do. I don't have connections, and I surely know nobody who has dealt with this stuff before.

Thanks in advance.

 

[Rock Tractor]

I think your dist. Is just one tooth off. So try installing it one tooth off. Maybe you think you are putting it in right, but you could be doing it just one tooth off.

 

[kyleandhisIH]

I think your dist. Is just one tooth off. So try installing it one tooth off. Maybe you think you are putting it in right, but you could be doing it just one tooth off.

The way to jump over one tooth is 1/8 turn counterclockwise? I'll go try this again now, since it does seem like the most reasonable explanation. I just got done driving it with a little more advance (28>30 indicated) and it made quite a difference in driveability.

Edit:
skipped the distributor one tooth ccw, verified that the rotor was roughly 22deg behind its previous position, rotated distributor to where the engine seemed to idle the smoothest - checked with light, and saw 25 btdc indicated. Again.

Maybe I need to stop worrying about the number and figure out some way of determining the best setting? I've tried power timing it, but again, I still haven't heard any pings or knocks that would indicate too much advance.

I guess at this point if I can get it to consistently idle in the same place from day to day, I'd be happy. The idle has never sounded smooth as silk, though, and random occasional hiccuping noises ruin what otherwise sounds fair enough. I'm also witnessing 700rpm @ park transitioning to ~525rpm @ drive. A sticker on the valve cover describes an "80 rpm" drop, and I'm assuming once I finally get everything situated I should eventually see a little higher in-gear idle speed as such?

 

[Robert Kenney]

It has nothing to do with where you stab the distributer. That only changes the indexing of the distributer with respect to the engine. You will still have to time it to the #8 piston.

Detonation/pinging usually sounds like glass pieces rattling around. You will hear it. The clattering/rattling a diesel makes it for all intents and purposes detonation. If your engine is experiencing pinging it will under heavy load like wot and at the rpm where peak torque occurs (2500-3000).

Open both windows and drive near a block wall or parked cars. The ping will bounce off of the wall and be very obvious when it happens as you advance the throttle.

Keep turning in more timing till ping just starts and see where you have the timing.

 

[kyleandhisIH]

it has nothing to do with where you stab the distributer. That only changes the indexing of the distributer with respect to the engine. You will still have to time it to the #8 piston.

Detonation/pinging usually sounds like glass pieces rattling around. You will hear it. The clattering/rattling a diesel makes it for all intents and purposes detonation. If your engine is experiencing pinging it will under heavy load like wot and at the rpm where peak torque occurs (2500-3000).

Open both windows and drive near a block wall or parked cars. The ping will bounce off of the wall and be very obvious when it happens as you advance the throttle.

Keep turning in more timing till ping just starts and see where you have the timing.

The only reason I'm reluctant to drive by parked cars or a wall/building is due to the rather rural nature of my region, and the fact that the nearest wall, or series of parked cars, is in a city overrun with bored police. Not to mention it's several miles just to get there.

I just took a trip down some different roads around my home looking for barns, vehicles, whatever. And any witnesses to my last trial probably think I'm crazy. I feel like I'm kinda abusing the thing just trying to figure out the timing, what with doing wot accel at 55, 65, 75... It's surprising how fast you can fly around in these bricks. :d I now see why everyone says the sv304 spins up real fast.

Regardless, I still can't hear anything significant. The only change I noticed while advancing this last run was that the full-load exhaust note changed to a "bogged" noise, like the motor wasn't producing the power that it made at the 28 > 30 range. I know I'm well above that right now, as I started there at the beginning of the run, and kept bumping more advance in as I worked my way home. Haven't put the light on to find out, but the idle is very erratic and odd sounding, so I'll probably just back it off to the high 20's and focus on fuel delivery.

 

[Michael Mayben]

Any engine will detonate (or "ping" if you prefer) if the base timing is advanced too far for the octane rating of the fuel being burned. And each cylinder will go into detonation at a slightly different point as compared to the others as that is controlled by variables such as distributor wear/tolerances, carbon accumulation in the combustion chamber, variations in all sixteen cam lobe profiles, cylinder head/combustion chamber temperature variation, length of the various intake runners on a dual plane intake manifold, etc.

Since you have an auto trans, simply "power-brake" it (no more than 15 seconds at a time followed by a five minute cool-down with the engine running and trans in neutral (not park). Keep advancing the timing until it rattles, you will hear it as it's very noticeable. I have 80% hearing loss and I can hear it all the time when present!

You can even hear ping when whacking the throttle from idle with the trans in park if advanced too far. That is with hardly any load on the motor.

We've been chasing this strange timing Mark positioning now for well over a year...guess it's time for me to make a house call back east?? I don't know what else to recommend.

If...the distributor was one tooth off and the plug wires not re-positioned to compensate, then the engine would either kick back during starting or turn over very hard like a dying battery (too much advance), or simply run like shit with no power (too retarded). If it's one tooth off and the plug cables are not moved to compensate, then it would run like total shit no mater what and most likely spit back through the carb!

As for idle speed variation, make sure you have a strong throttle return spring mounted and that the throttle cable has a bit of "slack" in it's adjustment. Also, make sure the kickdown linkage is not binding anywhere, I delt with one of these last week that the kickdown rod was binding on a heater hose only when the motor torqued over on it's mounts! The kickdown stuff cannot be in contact with any other vehicle component and all the linkage must actually be "sloppy" in fitment.

 

[kyleandhisIH]

since you have an auto trans, simply "power-brake" it...

I'll have to find some video or instructional on power braking, I guess? I've never done it.

we've been chasing this strange timing Mark positioning now for well over a year...guess it's time for me to make a house call back east?? I don't know what else to recommend.

I guess today helped a lot, because I finally got the nerve to push indicated timing to 30* or better. I found out that it really runs well right about there, and the driveability difference is insane... I must have been trying to run at tdc or something when it indicated 22>24?

Indicated anomalies aside, it's a non-issue if it runs well, right?

As for idle speed variation, make sure you have a strong throttle return spring mounted and that the throttle cable has a bit of "slack" in it's adjustment. Also, make sure the kickdown linkage is not binding anywhere, I delt with one of these last week that the kickdown rod was binding on a heater hose only when the motor torqued over on it's mounts! The kickdown stuff cannot be in contact with any other vehicle component and all the linkage must actually be "sloppy" in fitment.

I actually just fooked around with the springs, and I really don't have a great place to mount them. Right now, a piece of baling wire is tightened well against the support for the left-side plug cables, which is mounted on the t-stat housing. The springs pull in what is almost a direct line with the travel of the throttle arm (they are still good and stretched at idle), and the only interference that the springs themselves see is a bit of a rub on the accel pump arm, but that's at wot.

I really have no other options for a mounting location, because any lower and they would really get into the pump arm. Any higher and they'd be interfering with the stud that connects throttle cable & sliding linkage to the throttle arm. I don't know if you remember the looks of this throttle arm, Mike, but it has a single square hole, and I'm guessing that's the only provision for return spring location. I am still using the ones that were with the mixer.

I also spent a lot of time figuring out how to best position the heater hose that runs to the left-side, because the po had it left in a position where the sliding throttle linkage was actually cutting the shit out of the hose. Somehow the hose is still in tact with a squared-off notch missing, and now it's well out of the way. I also had an issue with my odd hard fuel line, which resulted in a very brief wot start once. everything at this point has been verified clear of the linkages, and I'm pretty sure that cleaning up the timing to ~30* btdc has helped the idle become more consistent.


Unless it's imperative that I get the timing as close to the point of detonation as possible, I think I can be satisfied with the "new" wrong indication, and the associated improved street manners.

 

[Michael Mayben]

What matters is that the motor runs right! Leave it alone!

Power braking....

With the engine fully warmed, trans in drive, simply stomp the brake pedal hard and then hold the loud pedal on the floor! Do this with nothing in front of the rig in case the brakes won't hold firmly (fairly common on a Scout II). If in doubt, put the front bumper against a stout tree firmly rooted!

This generates extreme heat rise in the transmission, thus don't do it longer than 15 seconds and allow a cooldown period. It does not hurt anything, this is common "launch" practice for any autotrans vehicle used in drag racing. And a stock tf 727 circulates oil (pump charges all circuits) when it's in neutral, not park. And...whatever rpm is noted on the tach when doing this is the actual "stall speed" of the torque converter installed within a few hundred rpm, a redneck method of determining stall and if it's close that what the spec is for the vehicle system.