Topic: 1966 289 A code, auto, with smog, a/c and Autolite 6ZE hot idle compensator

[socalgt]

Would there be a hot idle compensator valve(in a hose) on this car since there already is one in the original Autolite carb?

[67350#1242]

I think only 2BBL cars with A/C got the compensator in the hose.   No need for 2 of them.

[jwc66k]

I do not believe that any factory 4100 carburetor used on a 66 Mustang had a hot idle compensator built it for A/C use. If compensator was installed, it would be in the PCV circuit.
Jim

[69cobrajetrugae2]

The 4100 that I rebuilt has a hot idle compensator.

The application was for a 64 390 PI but it was on a hot 302 in a 65 fastback that we acquired. What a wonderful carburetor!

I ran tests on the compensator and as I recall it opened at 160F to 180F and closed at 130F.  When it opens the compensator causes a vacuum leak right down the center of the carburetor which adds air to compensate for the rich mixture which occurs when an engine is turned off and the fuel changes state in the bowls flooding the engine.  Usually this happens at high altitudes due to less atmospheric pressure and a hill climb and turning the car off at a rest stop so the engine heat sink percolates the fuel.

 Summer vacations for my family always included a stop at Bishop for food and gas and I remember the open hoods and the air cleaner lids removed.

When the car is moving it's unlikely the carburetor inlet will see 160F but with the AC on in traffic tie ups with the draw of the AC compressor and the retarded smog timing, it's possible.  It's also possible that the engine will stall if it is rich to begin with.

 This condition is mistakenly attributed to vapor lock which I think is very rare.  The vapor lock would not stay in the line like a pea, it would want to change state back to a liquid as soon as the vapor cooled slightly and thus free the line.

 An engine with a true vapor lock will present as the car running out of gas, no smell of fuel with the air cleaner removed would be the symptom. After a 30 minutes sit the car would start up and continue running as if nothing happened.

[jwc66k]

Again, not factory. It's typical of carburetor rebuild shops to "just have" one rebuilt that will work "just fine" on your 66. The shop then sells your old original for two to three times what you paid for the replacement. Oh, they use your old tag on the replacement. Nice.
Jim

[67350#1242]

The 4100's on thermactor cars - C6ZF-D  and C6ZF-E had the hot idle compensator built into the air horn as the OP states.

[jwc66k]

The 4100's on thermactor cars - C6ZF-D  and C6ZF-E had the hot idle compensator built into the air horn as the OP states.

You are correct. After a bit of looking in the MPC, those two California smog carburetors have built in hot idle compensators. The base numbers, 9B532 and 9B567 for hot idle compensators, are listed as being used on them.

It's typical of carburetor rebuild shops to "just have" one rebuilt that will work "just fine" on your 66.

When I bought my 65 GT Fastback with an AT, it had a C6ZF-9500-D carburetor without a hot idle compensator. I bought a C5ZF-D to replace it, and swapped the C6ZF-D for some other stuff. Never gave a thought about it. When I bought my 66 Hardtop "A" code, it had a 4100 1.12 for a 390 with a hot idle compensator so I'm familiar with the item. I bought a rebuilt carburetor from Pony Carbs as a replacement. The vacuum "tube" in the top cover for the secondary actuation circuit on the 390 4100 was broke at the center of the carb so it was tossed in a junk pile. 
The point is - DON'T believe what you see as accurate, check. In this case, the MPC is your friend (if you have and take the time).
Jim

[67350#1242]

I expect a lot of mixing and matching was done at the rebuilders, especially the big production operations over the years.  It is probably good advise to also check the numbers on the bottom of the booster venturis to see if they match the original spec since they are detachable parts.
Kurt.

[socalgt]

The Bob Mannel book indicates all automatics had a spacer in the PCV to Carb hose and it was replaced with the compensator valve if a/c was installed.  I just don't want to hunt one down and install it if it wasn't used in conjunction with the Autolite 4100 6ZF(California emission carb) that already has one.

[lancelot66]

I did both, based primarily on what I found in Bob's book & reference. The compensator in the carb was always there but the one in the PCV was long gone when I purchased this car in '87. The one in the PVC, as I understand the research, adjusts engine idle when it's overheating because of outside conditions and A/C running. In SO CAL, when I lived down there, it certainly was experienced but I had no idea at that time this was used by Ford. I have not since that time, exposed or driven our car under these same conditions, but I'm ready for it now, especially if we drive over to Eastern Washington in the summer or on steep grades in general. Should be interesting...!

[67350#1242]

IMHO if they both open up, you will be overcompensating - only one is needed.
Not sure about 66 but found reference to the in line compensator for 67 in the shop manual page 8-72.  States for 2V AC cars only.  Probably because the 2100 carb had no provision for the compensator, whereas the 4300 4V did.

[lancelot66]

My comments, research and findings are limited to SOCALGT's original post topic (1966), since our car is setup originally the same (and is once again). I think if you read Jim's previous comments on this thread, you can derive the two compensator's addressed two different aspects of an A Code 1.08, thermactor emissions and  A/C (running). Bob Mannel's book is pretty clear on it also. I have no idea how or if '67 cars changed in regards to any of this. I'm looking forward to seeing how it improves the overall engine performance during the next drive in hot weather or when stuck idling, bumper to bumper, start and stop, out on a hot freeway...

[socalgt]

The book did say that "all" automatic cars in '66 had the spacer in the pvc hose, replaced with the compensator valve if a/c was added...so...I'll put in in.  I found an original pcv hose with the valve in still in it.

[jwc66k]

The book did say that "all" automatic cars in '66 had the spacer

What book? I've owned several 66 Mustangs, all "A" (ok, one "K") code automatics, all San Jose, all DSO 71 or 72, all without A/C and none had the spacer in the PCV line.
Jim

[J_Speegle]

Sorry for the delay...Bob Mannel  Mustang and Ford, small block V8.....6K13...special fitting at the PCV hose on all automatics, replaced with the hot idle compensator valve if a/c installed.  I got the part in case it was original to my car.  I'd rather not install it if it was not, per my postings.

Appears that you may not need it



If you read the next page you will see that that system and layout was "which quickly superseded"

This arrangement/attachment spot is different from many original examples where that hose goes to the pump since they used the other two port Thermactor valve. In that version the air cleaner attachment does the job of the PVC attachment


Bob's book makes reference to one system replacing the other  the first is noted on page 6-39 where you can see in the pictures the layout I'm referring to. (additional pictures below)  Because of this not all cars would have received the block for the compensator. So without the block there was no place for the compensator on those cars which it appears make up the majority of production

Both of the following (could post more) are A code, auto, thermactor cars.

6R07A1147xx   so it was pretty early in production when the change was made




6R07A190xxx