IC 392 BAD Mileage, mistery detonation/pinging

Here's the latest and greatest-
vacuum testing:
at a up to operating temperature idle of 750 rpm in park, 20"
in gear, foot on break, 600 rpm, 19"
at 65 mph, 2700 rpm, 12"
accelerating real hard from a stand still, 1, 2, 3rd gear, by new tires burnout, 5-6" vacuum.

Drove with the vacuum advance disconnected and the hose plugged, noise still present, extremely rough idle. Didn't really work out...


Here's the distributor numbers, tag was a red metal tag with a single screw affixing it to the distributor, reads"prestolite
1d114002w249 (the d is a maybe... 11 is questionable also) zeros might letter "o"s.

Carb id, carter thermoquad four barrel: number on driver side aluminum tag- 1700009c1
9g 09


hope this helps.
 
I really appreciate all the help everyone, I'm trying to accomodate all the "have you tried this yet?" and answer as many questions as possible. I have done my home work, read all the threads mentioned. Actually, half of the threads mentioned I had already searched and read before I started asking questions. Pretty busy day today, started a new job, don't have the time to fool around like I used to. Bad economy and a democratic president are bad for my kind of work. I took pictures this morning, as soon as I figure out how to post them, I will. Thanks for the help guys, have patience.
 
cbmind

Driver side vacuum

cbmind

Firewall vacuum

cbmind

Front of the engine vacuum hoses



cbmind



Passenger side vacuum hoses


cbmind

Distributor w/ vacuum advance, no cap or rotor installed.


I know, I know, couldn't resist. Had an edelbrock 1406 laying around, brand new, for my 65 lemans, decided to put it on here instead. I know I shouldn't have, but the idle is smooth now, acceleration is crisp and brisk, no stumbling as with the thermoquad. Egr valve is not hooked up, vacuum advance is plumbed into the thermo switch on pass rear block, the day after I bought it in calaforna, I had inspected and it passed with flying colors. I assume ( ass out of you and me...) that all emissions eguipment was working, but probably am mistaken. I have not physically pulled the distributor out and checked the shaft end play to verify wether or not the bushings are good, however when I had the cap and rotor, and "dust boot" off, I wiggled the shaft to and fro, did not check with a feeler guage, but I'm guessing (here we go again) hair under a 1/16th, or -.0625"
 
 
Just got done "powertiming" run's like a scalded ape. Can't hear the racket anymore, checked timing with my regular inductive timing light, at 4 degrees. Fyi. I'm going to run with it till the weekend and see what happens. Pull the plugs and take a look at them, big thanks to everyone. I didn't follow word for word, ignition/ carb thing, guess I'm stubborn, but everyon'es input is greatly appreciated. Thanks again.
 
Real texians (as in at least 5th gen) do know shit don't they???

Do not let that tq carb get away. And we're not "blaming" that carb for your issues which are multiple in actuality. But any carburetor running this e10 shit (and we now have no choice in that matter) will have a normal service life of about two years when used in daily service and not allowed to "sit" for an extended period of inactivity.

I'll post an analysis of your prestolite distributor when I've finished the research.
 
That ain't no tq on there....it's an edlebrock...probably a 1406

the distributor is a perstolite :mad5: ..........which in my mind presents a whole new set of problems. I'd kick that thing to the curb and get a Holley with a pertronix II. Opinions vary on repolacements.

Yeah I know throwing parts at a problem without proper diagnosis is a waste of money. For me some things just gotta go and the prestolite is one of them.
 
Tim...cb already posted that the tq carb originally discussed was swapped for the edelbrock 1406 just yesterday, and an "adapter" to do so can be seen in the pics!

And any distributor is the best one as long as it works as designed and the advance specs are matched to the motor it's being used in! While I am a Holley distributor fan for some IH schnizz just because they are more numerous, I work with just as many rotten prestolites and delcos as I do holleys. And the delco cast iron unit is far easier to service and repair when needed. Anyone with a "dial-back" timing light and a shop tach (accurate) can "tune" a delco using commonly available/inexpensive parts to do so.

Parts is parts...as long as parts are correct for the application and actually function as intended.

Imho, the prestolite electronic trigger unit is far superior technically to any other "electronic" distributor of that genre, the chrysler electronic sparker was equivalent in durability/performance.
 
Ok cb...first distributor data...

The prestolite number ya posted is "kinda" correct, good enough for me to make an id.

Attached is a spec sheet for several prestolite electronic sparkers right from a mts 2313 manual (late Scout II). By ciphering the number you posted, use the column on the far right for specs for your distributor when it was installed new. Notice the considerable specification differences in that distributor as compared to the 304 and 345 variations. And this is not all of 'em that were produced. This goes back to what I preach to you kids all the time...this stuff is not "all the same"!

Print this doc and retain for your IH service data collection.

And most especially, use a non-magnetic thickness gauge and verify the electronic trigger "air gap", it must be 0.008" before making any adjustments downstream.

And back in the day, if you sourced a replacement part distributor through an IH dealer, it would not have carried that exact same part number, service parts carried somewhat different numbers to denote..."service part", not oem part. Many reasons for that, not important here!
 

Attachments

  • Prestolite IDN 4002A Specs.PDF
    1.7 MB · Views: 668
Likewise, the IH p/n ya supplied for the tq carb is not accurate. If that number was on an aluminum tag under a screw head, those can be impossible to read correctly most of the time. But that was good enuff for a starting point, dealing in all this kinda shit is an investigative process!

The "c1" suffix tells me that was an oem carb, not a "service part replacement". I believe if ya look at it again, you will see that the first digit is really a "4", not a "1".

Here is a scan of the actual replacement parts list page for what I "think" is your carburetor, you can see all the variations that were used. And this is just for the "normal" versions, not the "low compression/export" stuff. This is directly from the IH parts list for '74/'75 pickall.

These tq carbs never had every small part available though ihc, if a carb required any other part, then it had to be replaced with new, that was a warranty/emissions requirement and not uncommon at all.

And the "kickdown" stuff for the tq when used in pickalls was completely different from the system I see in the pic of your engine bay, that has the Scout II kickdown linkage set up. Since you had to use that carb adapter, the linkage is now working at a fairly extreme angle (as compared to oem), so ya need to "re-adjust or at least verify the kickdown travel adjustments.

And with that carb adapter, hood clearance is really close to the air cleaner top!
 

Attachments

  • 74_75 392 TQ Carb App.PDF
    781.5 KB · Views: 615
Thanks for the hard work & homework. I used the carb adapter pn edelbrock 2696 and yesterday was able to get the throttle linkage adapter, pn edelbrock 1481. Corrected the angles somewhat. The previous owner put a 2" body lift on the traveler, only thing besides wheels and tires that isn't original (and now the carb...) so there's plenty of room for a tall air cleaner. The thermoquad is at my building in town, it'll be tomorrow before I can verify the numbers on the carburetor and distributor. I never doubted your displaced texan wisdom for a minute mr. Mayben:) I think part of my problem is solved, but I'm wondering something I forgot to mention before, when I pulled the old rj12yc plugs a couple weeks ago and replaced with a new set of 12s, they were white in color. Indicate a lean condition or poor timing? Also, when I pulled the rotor off the distributor yesterday, the "metallic bump" towards the end had wht kind of looked like welding slag hanging off of it. I'm guessing the metal bump partially melted. I replaced with an identical part the po gave me. The cap looked, fine, clean, no visible cracks.
 
Now we're gittin' there dude!

That weldin' slag on the tip of the rotor is a normal condition for a rotor with many rotations on it! That's caused by "arcing" from the rotor to the cap terminals along with metallic transfer, perfectly normal, that's why the need to be replaced periodically.

Rotors like that can be rejuvenated if need be by using a quality file or a product referred to as a "flextstone", (even emery cloth works well), those are used to dress breaker/contact points such as in distributors or in oldskool electro-mechanical voltage regulators, motor contactors, etc.

The sharper/cleaner the "edges" are of the rotor tip, the easier the path for electron flow, same as regards a spark plug.

While I'm not a fan of body lifts, they do make life with an air cleaner and all much more pleasant for a Scout II/traveler! Opens up a whole new range of air cleaner options!

If ya need a replacement distributor cap, don't let any parts house bs ya. The Holley cap and the presto cap do not interchange anywhere near correctly, they don't locate correctly, and they don't "index" correctly (very slight difference but enough to screw with timing in some cases)! I really think the male terminal configuration on the presto caps are far superior to the much more common female terminals as used on the Holley and delco caps.

I'm still looking at your pics as I see a few more areas ya might wanna look at, you May have already done so but I'll throw it out anyway prolly tomorrow.

For help with the tranny kickdown adjustment if needed, check this link, post #23:

http://www.forums.IHPartsAmerica.com/transmission-tech/588-torqueflite-727-guapo.html

Also...robertk called to my attention a point that I overlooked regarding that spec sheet for the distributors. All of that information is based upon the use of a some type of "distributor machine", such as an allen synchrograph or the old sun electric units. And the data is in "degrees of distributor rotation", not crankshaft rotation! You can see that notation up at the top of the page. The info he posted earlier regarding "typical" degree set points reflects crankshaft rotation!

If you want to screw with that thermoquad in the future, I can post a similar page of "specs" for those mixers as used in the IH apps, those would be specific by carb part number also. That kind of info is what differentiates the IH carbs from the mixers used in chrysler oem service...and of course the differences in the 49 staters vs. The kalifornikate units!

I also just came into possession in the last few days, of a large document originally prepped by carter just for the chrysler thermoquad product dealer mechanic training. I'll attempt to post that in a new thread just for tq info over in the carb tech sub-forum.
 
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