Should there be some restriction in the heater hose connection at the back of the intake? I have a 455 that I just have a 3/4 pipe to 3/4 hose barb connector. I have had overheating problems since I set this system up. I finally gave up and took it to a mechanic friend to experiment on and find the answer. AFTER, installing a VERY expensive electric, inline water pump (not much difference), he has come up with the idea that that most of the coolant is flowing through the heater core and not the radiator. When he pinched off the heater hoses....the engine did not overheat! He and I BOTH have a hard time with this concept, but it seems to work. Any explanations? Anyone?

 

All I hear is crickets! LOL! Surely someone understands the thermodynamics of the cooling system. I don't but some of you are pretty darn smart!

 

The factory used a heater fitting in the rear of the intake that was restricted.

 

Yeah, I've read about that. But all I've read was to keep excess pressure off the heater core. But would a full, unrestricted 3/4 line "bypass" most of the water from the radiator to the heater core? That seems to be what is happening. The heater core (according to infrared readings) gets MUCH hotter than the radiator.

 

For the last 20 years or so I had an unrestricted fitting on the heater core and my engine never overheated. Can't say your situation is the same, just saying that I didn't have overheating issues.

 

I guess I should have described the ENTIRE situation with my truck. This 455 is connected to the transaxle and frame cradle from a 1984 Buick Riveria. This was "grafted" to the rear of a 1985 S10 pickup. Resulting in a mid-engine rear drive vehicle. As part of the build, the radiator was left in the stock location and replaced with an aluminum radiator designed for a Corvette LS1 conversion. So, I believe the radiator is large enough, since it is designed to cool well over 400hp. To do this, of course, required piping the coolant flow to the front via 1 1/4 and 1 1/2 pipes. I have also installed an electric water pump chasing this overheating problem. The water pump seemed to help some, but not enough. Still had the problem until we tried shutting off the heater core flow. It appears that for whatever reason, the coolant is flowing through the heater core (at least primarily) instead of the radiator. And since there is NO restriction normally in the 3/4 line leading to the heater core, does any of this make sense?

 

What a neat truck, would like to see pics of that. I guess it may be easier for the coolant to flow thru the heater core than go up to the radiator??

 

Here it is.

 

Suggestion... put a ball valve in the line that runs to the heater core. When its hot you probably don't need need heat, shut it off. You want a little open it a little. If you drive it in the winter or cold temperatures open it up. BTW I'm running a used edelbrock 04B. The previous owner used it in a GMC motor home... It came with a non stock fitting in the fitting for the heater core lines. Some one had welded a washer over the end restricting the flow maybe 75%. Works fine like that me. Cool Truck ! Tom

 

Tangokilo,
I made something similar the the fitting you are talking about yesterday. I took a 3/4 pipe to 3/4 hose adapter and welded a piece of steel across the opening. I then drilled a 1/4 inch hole in it. I'll try it out this week and let you guys know. I'd still like someone to explain the "why" of this, though.

 

Those pictures were with the 307 in it. The 455 provides just a little more grunt!

 

I agree. You have a totally non-factory setup so you're gonna need to tailor the system to achieve proper coolant flow.

 

Neat truck. Good luck with the problem, I'll bet you'll get it figured out looking at what you have done already.

 

I MAY have found the answer! I now believe that because my radiator is lower than much of the intake manifold, that two things are happening. One - it is near impossible to get all of the air out and to completely fill the cooling system. Two - that the above fact results in the coolant "flashing" to steam as if passes the VERY hot area around the valves. This steam is then trapped at the higher parts of the engine and coolant line (specifically the thermostat housing and the front of the intake manifold), and the problem keeps growing with each "pulse" of the coolant. Eventually, the steam or super heated air gets into the water pump and it essentially stops pumping. Then of course, the engine overheats very quickly. I have read about "steam tubes" on modern, high-performance engines like the LS-1. I have ordered a pressure canister to make a place for the steam to condense and return the now liquid back into the system. This canister and the "tap" in the coolant line will the at the highest point in the system. What do you guys think of my theory and solution? I will have the parts in by the weekend and will let you all know the results.

 

A lot of European cars address the problem of a low fitting radiator by installing a small bore (think vacuum tube diameter) between the top of the radiator and the high point of the engine cooling system, probably the thermostat elbow in your case, running through a header tank. The tank is normally the filling point for the cooling system, and the pressure cap located there.
The aim is to allow air to vent, but not allow coolant to flow in significant quantity to lengthen the warming up process.

Roger.

 

I had exactly this problem with my 215-powered Vega decades ago. I solved it with a Corvette header tank mounted as the high point of the system. Overheating problem solved.

 

Joe, beat me to it. Corvettes had this problem because the radiators were installed below the waterneck. They added the tank as installed on Joe's car above everything to eliminate this problem.

 

That photo is not my car, just a picture I stole off the web.

 

You guys are giving me hope! This problem has been driving me crazy for months! I'll know by the weekend.