Coolant does not flow with thermostat installed

[klinton994]

I have a 1971 Mach 1, 351c 2V motor. The car recently overheated, and was expelling coolant out of the over flow tube. I have had the car for two years, without any overheating problems prior to this.

I inspected the oil and it looks fine, and no moisture out of the tail pipes after warm up. I removed and inspected all of the spark plugs, to see if the had a washed out look. All looked find. Leading me to believe it is not a head gasket.

I first checked the thermostat, only to find the previous owner had removed the thermostat, as well as the water restrictor plate.

I have done the following.

Checked the quality of the oil and it looks fine.

No moisture from tail pipes after warm up.

Purchased and installed the water restrictor plate offered by west coast classic cougars, along with a 180 thermostat for a Windsor motor. (a non Cleveland thermostat is required with this restrictor plate)

Removed and replaced water pump. Verifying no play in shaft and no internal damage.

Had the radiator serviced.

New upper, lower, and heater hoses.

I have drilled a 1/16" hole into the thermostat, installed the thermostat while leaving the upper hose disconnected. I then added water until I could see water coming out of the thermostat housing. I did this to verify I did not have an air pocket at the thermostat.

I then connected the upper hose to the thermostat housing. I filled the upper hose with water before attaching it to the radiator. Again trying to eliminate any air pockets.

At this time, the car is overheating within five minutes of start up, at an idle. The factory gauge is in the middle of the operating temperature range. However, the engine begins to emit a knocking sound that I'm associating with over heating.

With the thermostat OUT, and the restrictor plate installed, I can see coolant flowing through the radiator. When I increase the rpm's the coolant flows even more.

With the thermostat INSTALLED, along with the restrictor plate, I see no coolant flow in the radiator, and I get the overheating as described above within a few minutes. The coolant drops several inches in the radiator, then rises and spills out of the radiator.

Any help is appreciated.

I filled the radiator last night, and checked it this morning while cold. The water level is within an inch or so from top of radiator.

Could anyone explain or help solve the problem of no water flow with the thermostat installed

thanks,

 

[rocket366]

Test thermostat to see if it opens and when by putting it in a

pot of water on the stove and verify with a meat thermometer.

Paul

 

[klinton994]

Test thermostat to see if it opens and when by putting it in a

pot of water on the stove and verify with a meat thermometer.

Paul

I did bench test the thermostat with a heat gun to verify it opened and closed. I have not yet tried it in boiling water.

 

[Carolina_Mountain_Mustangs]

Is the restrictor plate some sort of custom made one and not like the original? Why did you not go with original style? I know they are hard to find but you can get them. I also drill the small hole in all thermostats to let the air out so no pocket that will do no harm.

Like Paul said test the thermostat to make sure it does work. If it is ok then do pressure check for blown head gasket.

 

[basstrix]

I have a 1971 Mach 1, 351c 2V motor. The car recently overheated, and was expelling coolant out of the over flow tube. I have had the car for two years, without any overheating problems prior to this.

I inspected the oil and it looks fine, and no moisture out of the tail pipes after warm up. I removed and inspected all of the spark plugs, to see if the had a washed out look. All looked find. Leading me to believe it is not a head gasket.

I first checked the thermostat, only to find the previous owner had removed the thermostat, as well as the water restrictor plate.

I have done the following.

Checked the quality of the oil and it looks fine.

No moisture from tail pipes after warm up.

Purchased and installed the water restrictor plate offered by west coast classic cougars, along with a 180 thermostat for a Windsor motor. (a non Cleveland thermostat is required with this restrictor plate)

Removed and replaced water pump. Verifying no play in shaft and no internal damage.

Had the radiator serviced.

New upper, lower, and heater hoses.

I have drilled a 1/16" hole into the thermostat, installed the thermostat while leaving the upper hose disconnected. I then added water until I could see water coming out of the thermostat housing. I did this to verify I did not have an air pocket at the thermostat.

I then connected the upper hose to the thermostat housing. I filled the upper hose with water before attaching it to the radiator. Again trying to eliminate any air pockets.

Although it's not uncommon, it is not good to run an engine w/o a thermostat. The fact that the previous owner was running w/o one is bothersome. There may be some issue this was masking, such as a cracked head. Over the 2 years that you ran the car, did you have to add coolant?

The extra work to eliminate air pockets is, in my opinion, unnecessary. Even after all of that, I would have run the engine with the radiator cap off until coolant is seen flowing through the radiator core....at this time, top it off and replace the cap. There is a bit of a learning curve to modulating throttle as coolant level rises to prevent or minimize the mess caused by coolant overflowing from the filler neck.

At this time, the car is overheating within five minutes of start up, at an idle. The factory gauge is in the middle of the operating temperature range. However, the engine begins to emit a knocking sound that I'm associating with over heating.

I can't say that I've ever associated a knocking sound with overheating. What makes you think the knocking is from overheat? If the cooling system is in good condition, you should be able to run the engine at a fast idle with the radiator cap off. If it's overheating this will definitely not be possible. The coolant temperature needs to be verified to be sure you're not chasing the wrong issue.

The knocking sound is troublesome...perhaps from detonation as the engine warms up?

With the thermostat OUT, and the restrictor plate installed, I can see coolant flowing through the radiator. When I increase the rpm's the coolant flows even more.

This is normal. Behavior will be the same with thermostat installed AND after the thermostat is fully open.

With the thermostat INSTALLED, along with the restrictor plate, I see no coolant flow in the radiator, and I get the overheating as described above within a few minutes. The coolant drops several inches in the radiator, then rises and spills out of the radiator.

Aside from this knocking noise, what you're describing is normal for an engine that is coming up to temperature. The rise and fall of coolant level is due to the thermostat opening and closing as engine comes up to temperature. It may take a few cycles of this before the thermostat fully opens, but once it does, you should see steady flow through the radiator.

I filled the radiator last night, and checked it this morning while cold. The water level is within an inch or so from top of radiator.

Could anyone explain or help solve the problem of no water flow with the thermostat installed

thanks,

As previous poster said, test the thermostat.

Something caused the engine to all of a sudden expel coolant from the overflow and there's some strange knocking sound. Start by checking the radiator's "pressure cap". You can borrow a tester from the parts stores and it should also have an adapter to pressurize your cooling system. Once you verify the pressure cap is ok you need to pressurize the system and let it sit with the plugs removed for a half an hour. After sitting under pressure, crank the engine and watch for signs of coolant expelling from the spark plug holes. This will tell you if you have a leak allowing coolant to reach a cylinder.

The knocking may be associated with excessive ignition advance....possibly due to one of the thermal switches. Disconnect and plug the vacuum hoses going to the distributor to eliminate this as a possible cause....also verify base timing is set properly.

 

[will e]

Bench test the thermostat again. While it is still open try placing it in the block. You will have to do this pretty quick. You are looking to see if it falls into place or if the thermostat is hitting your block off plate.

I apologize for going back to the basics. Are you sure you didn't have a restrictor plate? Are you sure you installed the block off plate correctly? I have never attempted to install or remove the restrictor plate so I don't know how easy it would be to install incorrectly.

 

[Don C]

Interesting problem. Definitely test or replace your cap, even with new hoses if your radiator does not pressurize the lower hose can collapse. Most do not come with the spring in the lower hose, anymore. If the inner layer of the lower hose separates it can also restrict the flow.

This was the only thing I could think of that hadn't already been covered.

I agree with David's question about the restrictor plate. I know that some of the Pantera guys came up with it and swear by it but I believe the original style restrictor plate and Cleveland specific thermostat are the best way for all-around cooling performance.

http://www.7173mustangs.com/thread-351c-cooling-system

 

[klinton994]

Test thermostat to see if it opens and when by putting it in a

pot of water on the stove and verify with a meat thermometer.

Paul

I tested the thermostat in water with a thermometer. My 180 deg. thermostat was open at 160 deg. based on the thermometer.

 

[klinton994]

Bench test the thermostat again. While it is still open try placing it in the block. You will have to do this pretty quick. You are looking to see if it falls into place or if the thermostat is hitting your block off plate.

I apologize for going back to the basics. Are you sure you didn't have a restrictor plate? Are you sure you installed the block off plate correctly? I have never attempted to install or remove the restrictor plate so I don't know how easy it would be to install incorrectly.

I took the thermostat, still in the pot of hot water, out to the car and placed it into the block. It fell right into place. The block of plate I installed fit right into a casting within the block, with no effort. At tapped it in with a socket.

 

[klinton994]

Interesting problem. Definitely test or replace your cap, even with new hoses if your radiator does not pressurize the lower hose can collapse. Most do not come with the spring in the lower hose, anymore. If the inner layer of the lower hose separates it can also restrict the flow.

This was the only thing I could think of that hadn't already been covered.

I agree with David's question about the restrictor plate. I know that some of the Pantera guys came up with it and swear by it but I believe the original style restrictor plate and Cleveland specific thermostat are the best way for all-around cooling performance.

http://www.7173mustangs.com/thread-351c-cooling-system

I'm not an experienced gear head, but after viewing the illustration of the 351c cooling system I'm beginning to wonder about this after market restriction plate. I know some swear buy it. Help me to understand this correctly.

The stock restriction plate, has a fairly large orifice that I assume allows water to circulate throughout the orifice, the heads and block, via the by pass. Upon the engine reaching operating temperature, the thermostat does two things. It expands and blocks the orifice in the restriction plate, and at the same time opens at the top of the thermostat to allow the water to begin circulating through the radiator.

With the aftermarket restriction plate, the hole is extremely small. Am I correct in assuming that with the aftermarket plate, water does not circulate through the head and blocks, but remains stagnant until the thermostat opens and allows water to circulate.

With my temperature gauge reading in the middle of the operating temperature area, my thermostat has still not opened.

 

[Mister 4x4]

I had the opposite issue - with the stock thermostat plate (with the big hole for the Cleveland-specific thermostat), it was overheating because it never allowed the coolant to flow to the radiator - just kept recirculating through the engine and never got cooled, or more like, only part of it actually got cooled and most of the hot coolant just kept circulating back into the engine, rather than only being able to go through the thermostat back to the radiator. Looking at the thermostats I had purchased though, my parts guys let me know and sold me nothing but Windsor thermostats, so it wasn't working right anyway.

I pulled the stock 'restrictor' plate, installed the West Coast Cougar's plate along with a new Windsor thermostat, and have never seen anything past the spot between 'E' on the 'TEMP' gauge.

When you looked down the hole, if you did not see the plate with the word "TOP" on it, then you did not have the stock plate, as you mentioned. (I know what you said, just covering the bases here )

The one on the left, is the West Coast Cougar restrictor plate (as you already know), which based on your words, you installed correctly (I also tapped mine with a fat socket just to be sure it was seated properly).

Your synopsis of the WCCP plate is correct, except that the coolant always bypasses the thermostat at that point, staying circulating inside the engine until the thermostat opens and flows back to the radiator. It's more of a traditional design, since the Cleveland's design was something of an experiment, hoping that the coolant would be able to flow back through the block with the thermostat closed, to 'warm up' the engine quicker. Which, it still pretty much does, just not through the thermostat housing.

I know I'm probably regurgitating everything you already know... sorry for that. I honestly can't think of what's not working for you with this set-up. You could still have some air trapped in the system, or maybe your water pump hoses aren't plumbed properly preventing the circulation from flowing properly (the previous owner DID actually remove the thermostat, after all). Are you getting heat when you turn on the heater? If not, that could be an indicator of the water pump and/or thermostat system not being plumbed correctly or clogged. Maybe the water pump itself isn't working properly as well. If the radiator is partially clogged, that could reduce circulation also. The cap itself being defective is a simple thing that's caused a lot of folks to tear their systems apart thinking something else was the issue.

Start simple:

• check the heater to see if it's working
  
• check the cap to see if it's sealing properly
  
• try a laser thermometer and shoot the various hot spots on the engine
  
• check the temp sensor for proper readings (with the thermometer)
  

Just coming off the top of my head. Hopefully, something helps. Good luck and keep us posted - we like to hear how these things turn out.

EDIT: I re-read your initial post a little more closely. I think the radiator cap and checking the heater are about the only things you haven't tried yet. Sorry for all of that 'Captain Obvious' stuff. Just hoping something pops out more than anything.

 

[Stanglover]

If you haven't already done so, read some of the related threads at the bottom of this page. I went through some issues with the T/stat. There is some useful stuff there that might help solve your problem. I'm not sure exactly where it is posted, but there is a diagram of the coolant flow through the engine. It may be included in one of the posts. If I find it, I'll get back and or repost it.

From what I found, check that the bottom hose is NOT collapsing. If you can squeeze it with your hand, you need to get a "spring" installed.

Stanglover.

Edit: I did a quick look-see and found the diagram, but I can't find where I got it (yet). In the meantime, Google "351C cooling system" Look at Images of cooling system. There may be some helpful info there. There are links to other forums with good info. Hope this helps some.

 

[Mister 4x4]

This is one of the threads that might be helpful, as well as the one I originated when first considering the WCCP "Pantera Mod."

http://www.7173mustangs.com/thread-351-cleveland-thermostat-restrictor

I think this might be the diagram you're thinking about (found on Page 5, along with P/Ns for proper Cleveland-specific thermostats).

Basically, with the WCCP plate installed, it permanently covers the bottom pathway forcing the flow through the upper pathway and out through the thermostat when opened... rather than allowing it to simply recirculate back into the block through the bottom pathway.

The Cleveland-specific thermostat's plunger reaches all the way down to the opening of the factory restrictor plate and seals it when opened, which is the same effect.

The reason it never worked for the previous owner is most likely because they were provided with Windsor style thermostats and the system never worked properly again after that change.

 

[Stanglover]

Yes, that was one of them. I bought Stant 13468 180 Deg & 13469, 192 Deg. The 294 numbers were not available from RockAuto. I started with the 192, but have now changed to the 180 and it runs really well with that one.

I scanned the first 2 pages of the diagram and info I'm thinking about, 5 pages in all. Maybe it will jog someone's memory as to where I got it 'cos I can't remember. This getting old really sucks sometimes!!

 

[Mister 4x4]

It was right below the other one in that thread I originated - right where you left 'em. :whistling:

 

[klinton994]

I have a 1971 Mach 1, 351c 2V motor. The car recently overheated, and was expelling coolant out of the over flow tube. I have had the car for two years, without any overheating problems prior to this.

I inspected the oil and it looks fine, and no moisture out of the tail pipes after warm up. I removed and inspected all of the spark plugs, to see if the had a washed out look. All looked find. Leading me to believe it is not a head gasket.

I first checked the thermostat, only to find the previous owner had removed the thermostat, as well as the water restrictor plate.

I have done the following.

Checked the quality of the oil and it looks fine.

No moisture from tail pipes after warm up.

Purchased and installed the water restrictor plate offered by west coast classic cougars, along with a 180 thermostat for a Windsor motor. (a non Cleveland thermostat is required with this restrictor plate)

Removed and replaced water pump. Verifying no play in shaft and no internal damage.

Had the radiator serviced.

New upper, lower, and heater hoses.

I have drilled a 1/16" hole into the thermostat, installed the thermostat while leaving the upper hose disconnected. I then added water until I could see water coming out of the thermostat housing. I did this to verify I did not have an air pocket at the thermostat.

I then connected the upper hose to the thermostat housing. I filled the upper hose with water before attaching it to the radiator. Again trying to eliminate any air pockets.

Although it's not uncommon, it is not good to run an engine w/o a thermostat. The fact that the previous owner was running w/o one is bothersome. There may be some issue this was masking, such as a cracked head. Over the 2 years that you ran the car, did you have to add coolant?

The extra work to eliminate air pockets is, in my opinion, unnecessary. Even after all of that, I would have run the engine with the radiator cap off until coolant is seen flowing through the radiator core....at this time, top it off and replace the cap. There is a bit of a learning curve to modulating throttle as coolant level rises to prevent or minimize the mess caused by coolant overflowing from the filler neck.

At this time, the car is overheating within five minutes of start up, at an idle. The factory gauge is in the middle of the operating temperature range. However, the engine begins to emit a knocking sound that I'm associating with over heating.

I can't say that I've ever associated a knocking sound with overheating. What makes you think the knocking is from overheat? If the cooling system is in good condition, you should be able to run the engine at a fast idle with the radiator cap off. If it's overheating this will definitely not be possible. The coolant temperature needs to be verified to be sure you're not chasing the wrong issue.

The knocking sound is troublesome...perhaps from detonation as the engine warms up?

With the thermostat OUT, and the restrictor plate installed, I can see coolant flowing through the radiator. When I increase the rpm's the coolant flows even more.

This is normal. Behavior will be the same with thermostat installed AND after the thermostat is fully open.

With the thermostat INSTALLED, along with the restrictor plate, I see no coolant flow in the radiator, and I get the overheating as described above within a few minutes. The coolant drops several inches in the radiator, then rises and spills out of the radiator.

Aside from this knocking noise, what you're describing is normal for an engine that is coming up to temperature. The rise and fall of coolant level is due to the thermostat opening and closing as engine comes up to temperature. It may take a few cycles of this before the thermostat fully opens, but once it does, you should see steady flow through the radiator.

I filled the radiator last night, and checked it this morning while cold. The water level is within an inch or so from top of radiator.

Could anyone explain or help solve the problem of no water flow with the thermostat installed

thanks,

As previous poster said, test the thermostat.

Something caused the engine to all of a sudden expel coolant from the overflow and there's some strange knocking sound. Start by checking the radiator's "pressure cap". You can borrow a tester from the parts stores and it should also have an adapter to pressurize your cooling system. Once you verify the pressure cap is ok you need to pressurize the system and let it sit with the plugs removed for a half an hour. After sitting under pressure, crank the engine and watch for signs of coolant expelling from the spark plug holes. This will tell you if you have a leak allowing coolant to reach a cylinder.

The knocking may be associated with excessive ignition advance....possibly due to one of the thermal switches. Disconnect and plug the vacuum hoses going to the distributor to eliminate this as a possible cause....also verify base timing is set properly.

Basstrix,

I pressure tested the cap today and it was fine. I also removed the spark plugs and pressure tested the cooling system for thirty minutes. After thirty minutes my wife turned over the motor. I am more than pleased to report that no coolant exited the spark plug locations.

I added approximately a gallon of water to the radiator this morning to bring it up to the top. I took the car out for thirty to forty minutes of combined in town driving. The needle typically rested to the lower side of the normal operating temperature area of the gauge. While waiting in a drive through line, the needle did creep up towards the letter "P" on the temp gauge.

While on the test drive, I turned the car off on two different occasions. Each time the car was more difficult to start. Requiring me to press the accelerator pedal to the floor.

During the drive, I did notice the knocking sound at one intersection. However, upon returning home, and parking in the drive way, I did not hear the knocking sound.

Allowing the car to cool down, I then checked the water level in the radiator. It had dropped down several inches. Close to where the upper transmission cooling line is located.

I will top of the radiator tomorrow and give it another test run.

I'm still a bit curious as to why I would not see the water circulating in the radiator with the thermostat installed, and the temperature gauge in the operating temp range.

With the thermostat out, I could see the water circulating.

Thanks for the input and help

 

[Don C]

Yes, that was one of them. I bought Stant 13468 180 Deg & 13469, 192 Deg. The 294 numbers were not available from RockAuto. I started with the 192, but have now changed to the 180 and it runs really well with that one.

I scanned the first 2 pages of the diagram and info I'm thinking about, 5 pages in all. Maybe it will jog someone's memory as to where I got it 'cos I can't remember. This getting old really sucks sometimes!!

Here it is:

http://www.7173mustangs.com/thread-351c-cooling-system

 

[basstrix]

I have a 1971 Mach 1, 351c 2V motor. The car recently overheated, and was expelling coolant out of the over flow tube. I have had the car for two years, without any overheating problems prior to this.

I inspected the oil and it looks fine, and no moisture out of the tail pipes after warm up. I removed and inspected all of the spark plugs, to see if the had a washed out look. All looked find. Leading me to believe it is not a head gasket.

I first checked the thermostat, only to find the previous owner had removed the thermostat, as well as the water restrictor plate.

I have done the following.

Checked the quality of the oil and it looks fine.

No moisture from tail pipes after warm up.

Purchased and installed the water restrictor plate offered by west coast classic cougars, along with a 180 thermostat for a Windsor motor. (a non Cleveland thermostat is required with this restrictor plate)

Removed and replaced water pump. Verifying no play in shaft and no internal damage.

Had the radiator serviced.

New upper, lower, and heater hoses.

I have drilled a 1/16" hole into the thermostat, installed the thermostat while leaving the upper hose disconnected. I then added water until I could see water coming out of the thermostat housing. I did this to verify I did not have an air pocket at the thermostat.

I then connected the upper hose to the thermostat housing. I filled the upper hose with water before attaching it to the radiator. Again trying to eliminate any air pockets.

Although it's not uncommon, it is not good to run an engine w/o a thermostat. The fact that the previous owner was running w/o one is bothersome. There may be some issue this was masking, such as a cracked head. Over the 2 years that you ran the car, did you have to add coolant?

The extra work to eliminate air pockets is, in my opinion, unnecessary. Even after all of that, I would have run the engine with the radiator cap off until coolant is seen flowing through the radiator core....at this time, top it off and replace the cap. There is a bit of a learning curve to modulating throttle as coolant level rises to prevent or minimize the mess caused by coolant overflowing from the filler neck.

At this time, the car is overheating within five minutes of start up, at an idle. The factory gauge is in the middle of the operating temperature range. However, the engine begins to emit a knocking sound that I'm associating with over heating.

I can't say that I've ever associated a knocking sound with overheating. What makes you think the knocking is from overheat? If the cooling system is in good condition, you should be able to run the engine at a fast idle with the radiator cap off. If it's overheating this will definitely not be possible. The coolant temperature needs to be verified to be sure you're not chasing the wrong issue.

The knocking sound is troublesome...perhaps from detonation as the engine warms up?

With the thermostat OUT, and the restrictor plate installed, I can see coolant flowing through the radiator. When I increase the rpm's the coolant flows even more.

This is normal. Behavior will be the same with thermostat installed AND after the thermostat is fully open.

With the thermostat INSTALLED, along with the restrictor plate, I see no coolant flow in the radiator, and I get the overheating as described above within a few minutes. The coolant drops several inches in the radiator, then rises and spills out of the radiator.

Aside from this knocking noise, what you're describing is normal for an engine that is coming up to temperature. The rise and fall of coolant level is due to the thermostat opening and closing as engine comes up to temperature. It may take a few cycles of this before the thermostat fully opens, but once it does, you should see steady flow through the radiator.

I filled the radiator last night, and checked it this morning while cold. The water level is within an inch or so from top of radiator.

Could anyone explain or help solve the problem of no water flow with the thermostat installed

thanks,

As previous poster said, test the thermostat.

Something caused the engine to all of a sudden expel coolant from the overflow and there's some strange knocking sound. Start by checking the radiator's "pressure cap". You can borrow a tester from the parts stores and it should also have an adapter to pressurize your cooling system. Once you verify the pressure cap is ok you need to pressurize the system and let it sit with the plugs removed for a half an hour. After sitting under pressure, crank the engine and watch for signs of coolant expelling from the spark plug holes. This will tell you if you have a leak allowing coolant to reach a cylinder.

The knocking may be associated with excessive ignition advance....possibly due to one of the thermal switches. Disconnect and plug the vacuum hoses going to the distributor to eliminate this as a possible cause....also verify base timing is set properly.

Basstrix,

I pressure tested the cap today and it was fine. I also removed the spark plugs and pressure tested the cooling system for thirty minutes. After thirty minutes my wife turned over the motor. I am more than pleased to report that no coolant exited the spark plug locations.

I added approximately a gallon of water to the radiator this morning to bring it up to the top. I took the car out for thirty to forty minutes of combined in town driving. The needle typically rested to the lower side of the normal operating temperature area of the gauge. While waiting in a drive through line, the needle did creep up towards the letter "P" on the temp gauge.

While on the test drive, I turned the car off on two different occasions. Each time the car was more difficult to start. Requiring me to press the accelerator pedal to the floor.

During the drive, I did notice the knocking sound at one intersection. However, upon returning home, and parking in the drive way, I did not hear the knocking sound.

Allowing the car to cool down, I then checked the water level in the radiator. It had dropped down several inches. Close to where the upper transmission cooling line is located.

I will top of the radiator tomorrow and give it another test run.

I'm still a bit curious as to why I would not see the water circulating in the radiator with the thermostat installed, and the temperature gauge in the operating temp range.

With the thermostat out, I could see the water circulating.

Thanks for the input and help

Thanks for the follow-up and the lack of any signs of water blowing out of the spark plug holes after pressurizing the system is good news.

How long are you running the engine with radiator cap removed to observe coolant flowing through the radiator? This may take several cycles of the coolant rising and falling as the thermostat warms up. When the system is actually full, it may spill some coolant before the thermostat opens fully and you observe coolant flowing through the radiator core.

I am still puzzled with the knocking sound. Did you verify the base timing was correct with all vacuum hoses disconnected and plugged?

The progressively hard starting could be related to a slightly high float level or something similar...let's not confuse the issue for now. You're on the right track, as far as I can tell, let's figure out the knocking sound for the time being.

 

[Stanglover]

Yes, that was one of them. I bought Stant 13468 180 Deg & 13469, 192 Deg. The 294 numbers were not available from RockAuto. I started with the 192, but have now changed to the 180 and it runs really well with that one.

I scanned the first 2 pages of the diagram and info I'm thinking about, 5 pages in all. Maybe it will jog someone's memory as to where I got it 'cos I can't remember. This getting old really sucks sometimes!!

Here it is:

http://www.7173mustangs.com/thread-351c-cooling-system

Yep! I just knew someone would know where I found it. It's good info to have on file.

Thanks Don.