Weber intake manifold and potential cooling issue

The intake below is a 289 FoMoCo aluminum manifold (C6AE 9425-A) for the Weber 48IDA carbs, and the only head to manifold water inlets are the front two; all the other water inlets from the heads are blanked, and there was never any provision for getting the water from the rear of the heads out. I used to figure the engineers at Ford knew best, but I have come to think that the heat buildup in the rear of the heads could lead to steam pockets, poor cooling overall, and detonation. It just seems odd.

The only way I can see to get around that would be to drill passages through the manifold interior to the area of the water passages in the heads and run tubing from there to the existing outlets at the manifold front. That seems like a big potential source of failures in itself, and I'd hate to come up with a failure prone solution to a non-existent problem.

Thoughts?
 

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Ron Earp

Admin
I did what you suggest on a manifold that I had which was similar to the one pictured with no water outlets. Worked great. My lines from the rear were fairly small, something like AN-4 or so.
 
The center ports are for the exhaust cross over. The rear coolant passages are also "blank" on my original 'Cobra' high rise 4v manifold.

Have you measured /observed hot spots on the rear of your heads?

Its been a long time since I had an original cast iron manifold around. I don't remember a rear coolant crossover on them. The SB heads are reversable, so you have to have a way to block off the back.
 
John, this is a very common development, but do not use pipes greater size than -3, as the purpose is only to burp any air / steam pockets back to the expansion tank, if you use any larger pipes you are likely to divert the correct flow of coolant water within the system. I have pictures of system if required, Frank
 
John, this is a very common development, but do not use pipes greater size than -3, as the purpose is only to burp any air / steam pockets back to the expansion tank, if you use any larger pipes you are likely to divert the correct flow of coolant water within the system. I have pictures of system if required, Frank

X2

I would not modify an original though, that's like painting a mustache on the Mona Lisa.

Use a repop manifold and link bank to bank with a -6 or -8 tee that has the middle section -3. If you can not find one (they are rare) weld up the middle port on a 6 or 8 and drill to -3. In this way you achieve the best of both, help balance coolant flow bank to bank and get the added advantage of an air bleed.
 
The fundamental error that led me to ask the question was thinking coolant flow through the manifold was necessary. After more reading, I think this is what seems to be the case.

1. The rear water port in the 289 head was there to permit them to be interchangeable left to right. The only time the two rear ports are connected ordinarily is to permit fitment of an additional water temp sensor, not for circulation of the coolant, since flow is through the heads from the rear to front. (For some reason, I had thought there was circulation through most intake manifolds.) Frank, I'm assuming your caution to use small tubing if connecting the front and rear head passages is to avoid diverting very much coolant from around the 2-3, 5-6 cylinder water jackets. Is that close?


2. The "steam holes" aren't actually for steam, they're to allow the heads to "burp" air when coolant is added. most say an important passage from block to heads, heads to manifold, not at all.


3. Mark R Is correct in that the holes I miss-identified (and show blocked off on the manifold center) are exhaust crossover ports which improve warm-up of the manifold. (Why that would be helpful in a pre smog-controlled era is not at all clear to me though). Anyway, I confused them with the infamous steam holes, so Ron, may I edit and re-label the photo to avoid misleading anyone in the future?

Finally, there seems to be a wide opinion concerning the need for the steam holes or drilling the block on any particular small block to match the position of the holes in 302, 351W, Boss, Cleveland, or aftermarket heads. That seems to be a 6 to 7 and pick 'em sort of thing.

And Scot- I'd absolutely never modify it unless it were a common practice at JW in the day, like brazing the oil pickup tube to the pump. But now then, what do you have against women with facial hair?

John
 
There is an advantage to bleed off the two rear waterways, they will help to purge the heads of air pockets while the thermostat is closed. They are normally used to feed the heater matrix in a road going car and depending on how the engine is installed could be of benefit. I always think of an engine as an upside down bottle and any method to rid the system of air pockets has to be a plus.

Bob
 
There is an advantage to bleed off the two rear waterways, they will help to purge the heads of air pockets while the thermostat is closed. They are normally used to feed the heater matrix in a road going car and depending on how the engine is installed could be of benefit. I always think of an engine as an upside down bottle and any method to rid the system of air pockets has to be a plus.

Bob

Like I said before, I don't remember ever seeing a SB ford with a coolant fitting, or cross-over onthe rear water ports. I see the doing surgery on your vintage parts. Maybe use an infared temp sensor to see if there are any hot/cold spots on the head. ... just a thought.

If you really want a purge/cross over, There might be a better way that does not compramise your intake manifold. I will take a closer look at my '67, but maybe one of the expansion plugs on the back of the head would work.

The center exhaust crossover has been around for a long time. The oldest SB ford I ever worked on was a pre-'64 260, (5-bolt) and it had the ehaust cross-over as well. FWIW, Many aftermarket intake manifold gaskets come with a small thin metal block-off shim to insert between the head and gasket to eliminate the cross-over.
 
If you look at the 302 air gap manifold you will see the tappings for the rear waterways, one would have a pipe screwed into it as a feed for the heater matrix and the other a temp gauge. This is always a pumped open circuit which helps keep the engine purged. More importantly they are a bridged crossover which will purge both heads which is basically what Ron has done.

http://www.ebay.com/itm/SBF-Ford-30...r_Truck_Parts_Accessories&hash=item58a02373f4


Bob
 
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I too had these thoughts of a potential hot-spot bubble in the system (back of the head). I own both the Cobra Weber manifold and the C6AE. I had both sides of the Cobra manifold drilled and tapped for a (3/8 NPT) radiator petcock. (see pic)
As it turns out, in retrospect I should have never don’t that. It is totally un-necessary. If you think about it, the head gasket is blocked towards the front block to head surface. The direction of coolant flow is; water pump to front of block flowing towards the back (flywheel) up through the head then forward out of the front of the head. No issues what so ever. The next time the manifold comes off, I’ll have the holes plugged and welded closed.

Cheers,
~Earl J
 

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Little need for the mod in a mustang or similar where the engine is mounted 'nose high' and the radiator top tank is higher than the thermostat.
However on a rear mounted car like the GT40 where there are possibly purge issues due to the low radiator and in some cases a 'nose down' mount due to transaxle choice its a handy option to build into your manifold/engine combo.
 

Jim Rosenthal

Supporter
When we installed the engine (302) in my Cobra, it overheated almost immediately. It turned out that the engine builder had installed the head gaskets wrong and that the usual flow of water from back to front was not occurring. Once we pulled the heads and oriented the gaskets correctly, everything was fine.

Mid engine cars like GT40s are unusual in that the cooling system consists in a sense of two high spots connected by a low spot- the coolant tubes running through the car's tunnel. So there has to be a way to burp both ends. The radiator gets burped (on my car) via a fitting at the top of the right hand side of it. The engine has a 4 AN line from (I think) the highest point on the intake manifold which goes to the expansion tank. No overheating to date. There are photos in some of the books of GT40s with their rear ends up on jacks to allow the trapped air to bleed out of the top of the intake manifold.
 
Mid engine cars like GT40s are unusual in that the cooling system consists in a sense of two high spots connected by a low spot- the coolant tubes running through the car's tunnel. So there has to be a way to burp both ends. The radiator gets burped (on my car) via a fitting at the top of the right hand side of it. The engine has a 4 AN line from (I think) the highest point on the intake manifold which goes to the expansion tank. No overheating to date. There are photos in some of the books of GT40s with their rear ends up on jacks to allow the trapped air to bleed out of the top of the intake manifold.

Interesting... I didn’t know that about GT40’s or for that matter any rear engine car (I’m sure this would include Pantera’s as well) and I didn’t visualize it until your post. That being the case, If it were me I’d vent out of the back of the manifold with a “Y” going toward the front and into an expansion tank (mounted on the bulkhead) then plumbed into one of the inlet ports to the water pump (drivers side front) provided there was room. All this can be done discretely hiding the line I would think. I’m sure someone has done something similar.
~Earl J
 
If you do the rear coolant exit, it doesn't take a very large hole. I have done with and without, using an electric water pump, I could view the coolant exiting the rear fitting, a .040 or .060 hole is plenty, can't remember the exact size I used. Tapped the pipe fitting and installed a plug, then drilled the plug to size.
 

Jim Rosenthal

Supporter
It just needs to be big enough to burp the air out. The air will collect at the highest point and if you vent it out, the engine will cool just fine.
 
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