There was no observable difference in the flow from the Gates pump and the "hi flow" model I selected. There may have been fewer bubbles observed while revving the engine, but again, the difference was so slight so as to have me really wondering if there is a real difference, or if I am just hoping. The bottom line is that it still overheats.

I believe I have the wrong fan, based on the fact that I have ordered two good quality Hayden fan clutches (severe duty and a heavy duty units) and neither of them will accept my fan blade at the mounting point. The mounting bolt size, bolt circle diameter and the center hole did not match the Hayden units, which were identical. My fan blade has no Ford numbers, it's an unevenly distributed 5 blade design with a 2" inclination to the blades. I didn't measure the fan diameter but it's about 2" smaller than the shroud aperture. I attempted to bind up the fan clutch to see if it pulled more air while locked up, but I could not create a non-destructive method of binding it, so I reused the used fan assembly without changes.

I'm hoping you guys can help me out by describing or photographing the correct fan for this truck. Again, it's a 1979 400M that was fitted with A/C, however the system no longer exists except for the evaporator and housing. If there is a part number available, that will help me as well. If anyone has a known good fan for sale, I'll buy it, along with the 4 mounting bolts. I have a new fan clutch waiting to be tested!

Also, can any of you confirm the water pump pulley diameter for a comparison? That would be greatly appreciated.

Thanks,

Rick

 

Thanks Cole, I have proven there is observable flow through the radiator at all times and temperatures. The T-stat is currently removed. Installing it only holds up the flow until the opening point is reached. When I cure the massive heat build up in the radiator, I'll install the proper T-stat.

Thanks Smiffy. The felpro gaskets did not have the mentioned tabs. I wish they did so I can set aside that 1% of doubt remaining in my mind that I did the job right. For now I'll have to go with the memory that I was careful and did it right.

Hello Ken, I checked the shroud and found only the upper area had a gap. I filled the gap with a section of bicycle tube stapled shut and fitted in the gap. I then filled the tube with expanding foam. It works and the seal is 100%.

Your post indicates I should switch to non-ported (manifold) vacuum for the advancer? I am running 6* initial advance, and ported vacuum from the fitting just ahead of the choke linkage on the passenger side of the 2bbl Autolite carburetor. This port does not provide a vacuum signal at idle. It starts vacuum at about 1100 rpm and along with the module creates about 30* total advance when the engine is revved.

There are a couple of other unused ported vacuum fittings with caps on the carburetor, both up front, but I have not measured their operations. Is one of those the correct port?

Thank you,

Rick

 

Rick - I don't know about anything earlier than 80, but the 80-82's with a/c had a pulley of 5 15/16", and w/o a/c it was 6 61/64". And an a/c fan should be D8TZ 8600-A and be 19" in diameter.

 

You might want to get a shop manual and look at theory of operation of the distributor for your year model motor......meanwhile, try this...........

.....with no vacuum advance (disconnected & plugged) how much total advance can you get from centrifigual advance only? On most modern V8's, this should be about 30-32 degrees by 2800 - 3000 rpm as the factory advance curve. If you get this much advance, the motor should run fine at acceleration. If not, you need to find out why you can't get this much centrifigual advance (see 1st sentence above).

Is there a vacuum port BELOW the throttle blades? If yes, using it would allow you to add vacuum advance (about 12 degrees) at idle and cruise when the motor has high vacuum. Using a port above the throttle blades only adds vacuum during acceleration (this is what centrifigual advance should be doing).

If there is no vacuum port below the throttle blades, try manifold vacuum.
Manifold vacuum will add advance at idle and cruise when you have a high engine vacuum.....If this adds too much advance, you will get pinging just as you begin to accelerate from cruising speeds. Then you try to adjust the spring tension inside the vacuum canister (allen wrench into the port and turn the set screw in/out) to add/remove advance. You should have about 20 degrees total advance at idle and about 42 at 3000 rpm cruise.

Ford distributors before 1957 used ported vacuum to get distributor advance.....beginning in 1957, they have centrifigual advance in the distributor and worked as described above.

 

I disagree. Ported vacuum is very close to the same as manifold vacuum as soon as the throttles start to open, and is the same at cruise and WOT. And a port below the throttle plates IS manifold vacuum.

 

I expected that someone would disagree.....ported vs manifold vacuum has been debated since 1957. The object is not to find a source that delivers the same vacuum all the time. It is to use vacuum to change distributor advance as engine requirements change.

Ported vacuum will not add advance at idle. Thus the motor runs hotter at idle speed since you can't have enough initial advance to make it happy.

Ported vacuum will not decrease advance when you increase throttle at cruise speed. Thus the motor will ping when you have enough advance to make it efficient.

Since this motor isn't running correctly with ported vacuum, why don't we let 'em try manifold vacuum and see if it solves his problem.

 

Ported vacuum, historically, has referred to a carb port that is above the thorttle plates that produces vacuum when the throttle is opened and air is flowing past the port. when the throttle is closed (idle) there is no vacuum at this port........this is what was described in the posts above.

Manifold vacuum, historically, has referred to the carb port (if there was one) below the throttle plates. This port produces vacuum when the throttle is closed and at cruise. Under acceleration, when motor vacuum drops, this port does not produce enough vacuum to operate the vacuum advance.

You are correct in that, a port below the throttle blades produces the same vacuum as exist in the manifold.

We are debating the same point.

 

6* BTDC initial timing is way too retarded for a 351M/400 - could be a reason you're running hot. Try 12* - 14* initial, if you're basically stock (no "bigger" cam, etc).

You also want total timing to be 36* - 38* and "all in" by 2500 - 3000 RPMs.

Ported or timed vacuum is also what you want and is what you have, I believe.

You said you've blocked off the heater core, yes? Dumb question - the hose you used to bypass the heater core isn't 'kinked' or blocked in any way, is it?

I have some prior arrangements to meet soon. When I get back, I'll check out those number you're looking for, if you haven't found them. (I have a 79 400, too)

 

Ken - We aren't debating the same point. If you look at a cross-section of a carb you will see that once the throttle plate opens the ported vacuum connection is effectively the same as manifold vacuum - there is nothing between them. Granted there is a point in the early opening of the throttle where there is a lessening difference, but as soon as the throttle is opened much at all the two vacuum sources provide the same vacuum.

Yes, there is an on-going debate, but it is all about which provides the best idle. However, at cruise and WOT the two are the same.

 

Isn't the problem we were trying to solve how to get more spark advance at idle to see if it solved an overheating problem?

Getting more advance at idle can only be done two ways........
#1 set more initial advance
#2 add advance with vacuum

There are limits to how much initial advance you can add before the engine begins to kick back against the starter. And there are limits to the amount of total advance an engine will accept.

More initial advance means you have to take out some of what the distributor/ignition module/ecm/pcm will add as rpm increases. Manifold vacuum advance will decrease as the engine is under acceleration (vacuum drops) and add back advance when the motor is in cruise and vacuum is high (and motor can use 50* total advance for best economy).

Ported advance, as you describe it, will not add advance at idle. It will add advance after the throttle starts to open and at cruise. Neither of these solve the advance at idle problem we were working on.

 

Ken - I was only responding to statements about various vacuum ports, trying to ensure that when people find this thread in future what they read is correct. We may be wandering around trying to solve an overheating problem, but need to ensure the information provided is correct.

 

ok. For future readers then.......there are two types of vacuum ports on a carb.
one type has vacuum at idle, the other does not (it has a vacuum signal that increases as the throttle is opened from the idle position).

my suggestion was/is that rchalmers3 try connecting his distributor to the port that has vacuum at idle and see if it solves his problem.

only takes a minute, doesn't cost anything, and he'll quickly know if that solves his problem.

rchalmers3....if this solves your problem and you wish to discuss vacuum at cruise, send me a personal message.

 

Well said. Thank you.

 

Thanks guys, I appreciate the discussion about the proper set up to advance the timing. There are as many (possibly more!) schemes for providing timing advance as there are manufacturers. I never did commit this engine application method to memory: that was what the repairs manuals are for. Now that I have this old Ford occupying my stable, I find that Mitchell On-line does not cover the 1979 model.... And I have not purchased a hard copy manual. I have been flying by the seat-of the pants a bit. And to be honest, I do not believe that timing would induce the amount heat I am seeing. Some heat yes, but this is excessive.

Having said that, I have no problem altering my original scheme, in fact I already did that just this morning.

I found there is one tap at the front of the EGR spacer, well below the throttle blades and having a slightly larger diameter nipple. The other vacuum tap is on the driver side front of the carb, along side the idle mixture screw. While it appears to be above the throttle shaft, it does produce a signal at idle. I used that one. I left the base timing alone and adjusted the idle speed to compensate for the added advance and subsequent rpm increase. I did not re-trim the idle mixture, thinking it was set to best idle before that there would be little change in fuel requirement.

Finally, I'll mention that all the temperature switching valves are eliminated from the engine. It's a detail I think we can all agree that the TSV's serve a purpose for emissions, and their absence does not impact this situation.

Right now I am observing on a warmed up engine:
6* base timing
15* mechanical advance when revved
26* total advance with vacuum advance connected at idle
approx 40* overall advance when revved (it gets too sporadic to measure well)

It still over heats and I believe I have found the reason why. Please cover your ears because I am about to shout:



THE FAN BLADE (and clutch) ARE FOR A COUNTER ROTATION APPLICATION.




I hope you guys don't kick me too hard for missing this detail. It *looks* and is sized correctly. I would have had to have compared my truck to another, in order to pick up on the airflow. There is airflow back over the engine. It must be doing a hell-of-a reversal inside the shroud! There is no air blowing through the front of the radiator. The lack of proper fan noise indicating lock up is understandable. The steady and excessive build up of heat is understandable. When I was spraying water over the radiator it did not blow off the radiator to indicate the airflow was an issue.

Somebody put the wrong blade on and forgot to tell me!!! I have been duped by the hands of others who were there before me. And it ain't the first time.

In sum, I do not yet have results proving I'm right. But for the first time I have identified a tangible error to be addressed. I have the smoking gun. As you guys can probably imagine, I'm thinking of the needless expenditure I incurred trying to solve an error in installation somebody else made. And I certainly wish I spotted it earlier.

I'll let you know the results about when I run the proper fan!

Thanks to all,

Rick

 

Maybe someone used the correct fan, but installed it backwards....is that what you're saying?

Fan diameter - 18.25"

pulley diameter - 7.0"

I'm having a bit of trouble with the pictures today....maybe you won't need them now....