Topic: Correct 68 S Code C-6 Dual Vacuum Advance

[69SCJQ4.30]

FWIW:

My early 1967 w/ 390/C-6/Thermactor engine is a single-advance unit.

OP:
Your carb has the correct spacers  - so that answered that...

If the engine is overheating and stalling after a fresh rebuild - "could it be something binding internally."  Did you test turn the engine crank by hand? Does the starter 'struggle' (slow-cranking) when hot?

If the motor was rebuilt how far over standard is the bore? Did you have the cylinder walls sonic tested? I have heard FEs compared to all other ford blocks can have the worst core shift in there castings.

[jwc66k]

Not that it makes that much differance but the C8OF-D is for the automatic and the C8OF-C is for the manual according to the service manual. C8OF-D is not for both.

When I was gathering data for the distributor spreadsheet I asked members of the forum for copies of pages that contained information. Attached are the pages of the 68 service manual that I got (and I thank those who assisted again). There is no reference to a C8OF-C distributor. If you have access to a different revision of the 68 service manual, please post it and I will incorporate that information in the spreadsheet. This difference will also be of interest to those with a 68 390 S code engine.
Jim

[jwc66k]

The correct vacuum for 4 speed is the HP6 dual port and the automatic single port is the common C5AZ-12370-A

This is also identified as Motorcraft DD-190. However, the current vacuum advance unit sold is NOT the same as the original. The original had a screw in fitting for the advance vacuum line, one with a female threaded fitting for steel lines (64-66), and an attached male tube fitting for rubber vacuum lines (67 on). The unit could be adjusted for different "curves" by configuring internal washers, springs and stops. The current offering is a sealed unit with a male metal tube fitting and no provisions for internal adjustments. Be advised.
Jim

[Bob Gaines]

When I was gathering data for the distributor spreadsheet I asked members of the forum for copies of pages that contained information. Attached are the pages of the 68 service manual that I got (and I thank those who assisted again). There is no reference to a C8OF-C distributor. If you have access to a different revision of the 68 service manual, please post it and I will incorporate that information in the spreadsheet. This difference will also be of interest to those with a 68 390 S code engine.
Jim

Try reply #7 . 1968 service specifications manual. I had mentioned conflicting information before.

[jwc66k]

Try reply #7 . 1968 service specifications manual. I had mentioned conflicting information before.

Excellent, thanks. I missed it on the first go around. I will incorporate the info in the spreadsheet and will re-issue it soon.
Jim

[68 S Code]

Daisy the engine is not binding. It was rebuilt by Jim C up in Greenbay. Jeff and Bob know his work I'm sure. No issue with starter.

Bob in my copy of the service manual purchased new in the late 80's the C80F-D is listed for both 390 GT auto and manual. The C8OF-C doesn't appear anywhere.

OK last night I pulled the smog pump to check the timing. With the vacuum advance disconnected both the nipple and vacuum line plugged and ideling at about 750 rpm and warmed up I've got 10 degrees BTC showing. A smidgen high compared to the 6 degrees listed in the book. This is using the straight section at the top of the pointer not the hooked bottom.

Dwell is at 26 1/2

Seems to be idling OK.

What effect could the belly pan on the underside of the intake have?

[68 S Code]

Someone mentioned the location of the vacuum advance unit. It is at 7 o'clock. Number 1 on distributor cap is approx 7-8 minutes.

[Bob Gaines]

I would make sure your radiator is not clogged up and then put in a mr gasket high flow 160 degree thermostat (O Reilly's ,Summit racing etc.) .The high flow style moves more water then a typical auto parts store or even OEM unit.  You can try a synthetic oil which may be worth a few degrees less. You have what we typically call big blockitis . 30 over  and beyond engines are known for this. All of the steps you are taking are helpful to the goal and it may be a combination of things causing your over heating. 

[68 S Code]

Currently I have Brad Penn break-in oil for the first 500 miles on the recommendation of Jim. The thermostat suggestion I'll take into consideration. I did verify last weekend that the t-stat was opening because i could see water rushing across the top tank at a good rate while burping out air. Did have a volcanic eruption of coolant after shutting down the motor which made a tremendous mess. Thankfully my son was not standing over the top of the front of the motor. Never had that happen before on any car.

[sportyworty]

C80F 12127-C is a small block distributor not FE

[Bob Gaines]

Currently I have Brad Penn break-in oil for the first 500 miles on the recommendation of Jim. The thermostat suggestion I'll take into consideration. I did verify last weekend that the t-stat was opening because i could see water rushing across the top tank at a good rate while burping out air. Did have a volcanic eruption of coolant after shutting down the motor which made a tremendous mess. Thankfully my son was not standing over the top of the front of the motor. Never had that happen before on any car.

I am assuming you started with a cold engine and took the cap off before the engine warmed up to watch for the thermostat to open. You NEVER want to remove the cap on a warmed up or hot engine because you risk being scalded by boiling hot water.  Sometimes inside the water jacket there is a area that becomes too close the the cylinder wall after over boring . When you shut off the engine and the water stops circulating . That small point in the water jacket wall heats the water in that area up and to where the water boils in that area. This does not happen on a normal engine. The boiling water causes expansion/pressure and the added pressure in the water jacket causes the water to gush out the top of the radiator if the cap is off or out the overflow if the pressure cap is on after it exceeds the cap rating.This is more pronounced with the cap off because the added pressure that the cap provides raises the temperature that water will boil at. Once water gets to a point it will boil it is all over . The boiling cause the water to turn to gas and it expands exponentially . Race pressure caps have a 25 lb rating compared to the 13 lb of a typical stock cap. The higher pressure raises the boiling point more. Once the water boils inside you get expansion that results in hundreds of pounds of pressure. It shouldn't happen at all and worries me that you may have the thin wall problem. The symptom you describe typically is not indicative of a timing symptom. It sounds more and more like the thin wall big block symptom . In the thin wall scenario the high flow 160 thermostat,big radiator ,conservative timing ,synthetic oil to reduce friction may help some.  I hope I am mistaken about the root cause for your sake.

[jwc66k]

C80F 12127-C is a small block distributor not FE

Bob Gaines post #7 show the application to be for a 390 in a "Distributor Application" document. That part number appears in the 75 MPC with a valid service replacement part number for a 390. It is real Ford part number. That being said, I believe that Ford produced preliminary design documents and the referenced document, "Ford Service Specifications", is just that, preliminary. The 1968 Ford Service Manual and the 75 MPC do not list that distributor as being used. It could have been produced and used on a few cars, but it disappeared for dealer service.
Jim

[sportyworty]

It is a very common distributor. They were used on 302 2V automatics in 1968. Lots of F code cars just not Mustangs. I have a few here in the pile. Must be a print error. The part number in Ebay's search shows 5 currently listed.

[68 S Code]

Bob, the engine was cold after replacing the Vacuume Advance Control Valve. I left the cap off and warmed up the engine to allow any trapped air out and to verify the t-stat was working as well as the water pump. The block was standard bore before the rebuild and I was not notified that any additional boring was required over the standard amount that would have been required. I spoke with a close friend who is heavy into old Mopars and runs a few auto repair shops and he said the volcano was simply an air pocket that let go when I shut down the motor. As to the radiator I verified it this morning that it is a 3 row core. From the appearance of the fins on the core it appears (but i am not 100% certain) that it may have been re-cored but my memory isn't what it used to be. It would have occurred about 6 years ago. So results from today's tests are below with some odd results. By the way I tried to restart it about 2 hours later last night to try some more tests and she would not re-fire. Even tried starter fluid and nothing. Nothing else was touched in anticipation of further testing today

Yesterday my base timing was 10* BTC with the vacuum advance hose removed and plugged and engine idled at approx 750 rpm.
This morning after a 5 min warm-up the base timing is 2* and my idle is about 750  rpm. Wait another 5 min and still stuck at 2. We increase rpm to 2000 and mechanical advance is 25 degrees which seems a bit high (14-17 per spec). Plug the vacuum line into advance and idle increases to 1200 rpm and vacuum advance reads 40 degrees. The 40 is within spec but why did the rpm climb?
So we adjust the distributor back to 10* and measure mechanical advance by raising rpm to 2000 and now we are at 25 degrees. That's a big jump so we now plug the vacuum line into advance and engine is screaming at 1700 rpm. Raise it a touch to 2000 rpm and vacuum advance reading is 50 degrees.

During the entire warm up process i am using an infrared gun (ok a cheapie harbor freight I admit but better than nothing) to get some temps of the intake manifold flat spot right below the carb on the drivers side. After 1 min 110*, 3 min 133*, 4 min 170*, 5 min 185*, 7 min 219*, 12 min 230* and finally after 21 min 270*. Turn engine off and 275 degrees. So I shoot the top of the radiator, RH side of tank at upper hose 212, middle at cap 188 and LH side 209 degrees. So no big surprise that engine doesn't want to re-fire if intake is 270 degrees. Can anyone test their FE for intake manifold temps? It was about 80 degrees with 68% humidity. Today's ethanol blend fuels have a boiling point of 140 I am told.

I'm at a loss.

[jwc66k]

It is a very common distributor. They were used on 302 2V automatics in 1968. Lots of F code cars just not Mustangs. I have a few here in the pile. Must be a print error. The part number in Ebay's search shows 5 currently listed.

Yes, it is a small block distributor. It does show up in my original spreadsheet as being used in 1968 for 289 2V and 302 2V engines for both Mustang and Cougar. A glance at the 75 MPC shows other applications. Based on that, I agree that the "Distributor Application" document is in error.
Jim