Where did the air correction jets go?

[milesdzyn]

Okay here is one for you tech guys. As most of you know I am in the middle of doing a complete restoration on my 73 712M. I was removing the carbs in preperation of pulling the motor off the chassis when I noticed the front carb was missing the air correction jets and the washers that are supposed to hold them from backing their way out.

It looks like the last person that worked on these forgot to replace the washers and the Air correction jets worked their way out and went? down into the cylinder? Didn't find them inside the carbs.



The thing is the carbs got balanced and tuned and passed smog twice. Ran smooth for a year and a half, with no signs of troubles, and are super clean inside and only a little dust on the ouside. Compression is still good on the 1st and 2nd cylinders. There is no dings or scratches on the butterflies.

Just can't emagine someone forgetting to replace the parts on a rebuild. Now I have to pull of the heads to see if there is any sort of damage to the Heads, Pistons, Valve seats and Valves.

It just blows my mind that I was able to get the carbs to run so smooth with one of the two missing parts. Any thoughts?

I guess it would be nice if they were just not put in, hate to think of the possible damages.

Miles

[M Wehrman]

There is no way a motor could process something of that size and not "tell"you about it. They are probably still sitting on a workbench somewhere!
Mark

[todds112]

In my parts catalog there is a list of different carbs. One several of them the air correction jets say, "not for these models" or something along those lines.

It shows a metal tag attached to the carb with different numbers on them. This tells you what model or variant I guess.

[Jim LaGuardia]

No need to pull the head, just find someone with a boroscope, or put the cylinder near TDC and use a pen light to see top of piston(easy with body off). Damage should be easily seen.

[rla001]

Hi Miles,

I lost one about 3 years ago, The only place that I se that it can go is into the engine. My engine has been running fine since then though so I saw no need to go spending big $ to track it down. I had enough other opportunities to spend money on my truck.

It was kind of funny when it happened I was half way up some big shelf road pass in the San Juan’s and as I gained altitude it got rougher and rougher until it finally sputtered and died. I tried several times to restart it with no luck and so decided to tear into it. When I got the air plenum off and looked down into the front carb it was immediately apparent why it did not run. The whole atomizer assembly and the air correction jet was loose and the other was gone. I tightened things back down but figured it would never run with out the jet. In frustration I hit the bump rail with the pinz hammer as I was packing up my tools. My brother who was not relishing the thought of strapping me up the shelf road and having me coast down the other side ask me to try it one more time. Bloody thing fired up and ran better then it had in days. The people behind me to this day believe that it was the hammer hit on the side of the truck that fixed it. $5 for the hammer and $999 to know where to hit it

Rich A.

[lindenengineering]

Miles
Don't worry about it. For sure they fell into the cylinders and got ingested, pumped out and clattered through the exhaust. Be rest assured if they had done damage you would have known about it along time ago!
Let me tell you a little story.

As an apprentice we had a senior apprentice tech called Charlie.
Charlie liked to thump the younger guys, kindda of hard. A new inductee Malcom, took unknown to us, to whack the head stud threads of a Leyland diesel big truck engine with a hammer making head nut install difficult. Having wasted about 6 hours of shop time chasing threads and pissing off the foreman he rebuilt the engine only to have Malcom drop 5/16 nuts into the inlet manifold. Charlie ended up with a knocking noise whilst on roadtest. With a very testy foreman in the shop (as a business owner I can now sympathise) Charlie has to revise the engine that amounted to about 24 hrs of labour.

On rebuild, he experienced the same nuts in the manifold problem --again! and was threatened with the sack (fired). So poor old Charlie fixed it again!

On road test it developed yet other knock) nut on the piston! So the foreman Bill Bryce came out into the yard in a furious temper; saying "I've had enough of this for "F--K sake, floored the pedal and buried the nut into the piston crown to loose the noise and deliver the truck about 2 weeks late!

The errant head stud thread basher and nut flicker only came to light about a week later when he was caught doing the same to another truck engine being repaired by guess who --- a very subdued Charlie!
Motto keep yer hands to yerself.
Dennis

[milesdzyn]

Thanks for the replies guys. I do have a borescope so I'll check things out on monday.

Just one more question: My carbs that were on the Pinz had one jet size out of order from the stock setup. And my backup set of carbs seem to be set up for high altitude with all the jets swaped out. Listed below: "*" indicates stock option number.

On Pinz.............Back-up set
"60"....................55.................Slow running jet
"140".................125.................Main jet
130..................."110"...............Slow running air jet
"230"..................170................Air correction jet

As you can see the carb set on my pinz has only one of the jets not as stock, with 130 instead of 110 Slow running air jets. Think I should swap them for the right ones? or just leave them, have to clean the carbs anyways.

Also are my back-up carbs, set up correct for high altitude, if so I'll pull those jets and keep them as a high altitude set just in case. I want to rebuild my back-ups with the standard jet set up.

Miles