Overheating above 1,000 rpm

Fresh 545 with dual 4 tunnel ram, aluminum heads, Comp Cams Big Mutha Thumper cam and valve train runs 185 when idle or around 1,000 rpm. Does fine idling down street, however the faster I go the faster the temperature climbs. Can not go more than 20 mph or it overheats.  Timing at 12 degrees initial.  Aluminum radiator with dual fans.  This is backwards to me, usually a car runs cooler at speed and overheats when going slow. Going 40mph it hit 215 in a minute, slowed down to 10mph and back to 185 within a couple of minutes. Any suggestions

545FORD wrote:Fresh 545 with dual 4 tunnel ram, aluminum heads, Comp Cams Big Mutha Thumper cam and valve train runs 185 when idle or around 1,000 rpm. Does fine idling down street, however the faster I go the faster the temperature climbs. Can not go more than 20 mph or it overheats.  Timing at 12 degrees initial.  Aluminum radiator with dual fans.  This is backwards to me, usually a car runs cooler at speed and overheats when going slow. Going 40mph it hit 215 in a minute, slowed down to 10mph and back to 185 within a couple of minutes. Any suggestions

Are you certain that one head gasket is not installed back-wards ...?
That is the usual symptom.

Are you sure the heads was torque right just went through the same problem with my 69 had a head gasket leaking back into the radiator as soon as I would speed up my temperature would start climbing. I had a brain fart when I installed my AFR heads only torqued them to 70lb should have been 105lb plus my thermostat was sticking replaced head gaskets and thermostat and my problem was solved

rmcomprandy wrote:

545FORD wrote:Fresh 545 with dual 4 tunnel ram, aluminum heads, Comp Cams Big Mutha Thumper cam and valve train runs 185 when idle or around 1,000 rpm. Does fine idling down street, however the faster I go the faster the temperature climbs. Can not go more than 20 mph or it overheats.  Timing at 12 degrees initial.  Aluminum radiator with dual fans.  This is backwards to me, usually a car runs cooler at speed and overheats when going slow. Going 40mph it hit 215 in a minute, slowed down to 10mph and back to 185 within a couple of minutes. Any suggestions

Are you certain that one head gasket is not installed back-wards ...?
That is the usual symptom.

I am leaning towards your head gasket suggestion. Built the engine a couple years ago and I am usually very careful, but who knows. I found a good explanation about this on the internet.........
Most gaskets have the word "front" stamped on them. that edge of the gasket needs to be at the front of the engine for coolant to flow properly.
The water pump pumps the coolant into the front of the block. The FRONT of the head gaskets is blocked off so the coolant will travel all the way to the back of the block. It THEN enters the heads, and travels from the back of them to the front, where it exits the water neck and goes to the top of the radiator.
If the head gaskets were installed backwards (open side to the front) the coolant would simply go in the front of the block, flow straight up to the heads and exit the water neck. It would not cool the back of the engine. So yes, the water would flow, but no where it was needed. Next step is to see if I have a difference in temperature between the front and rear of heads.

Drivers side head temperature by each exhaust port is about the same.
Pass side head temperature about 30 degrees hotter on #4 port versus #1 port
Will keep testing other things to rule them out, but this is looking like the culprit.
I will also check to see if the head gasket is letting blow back into cooling system as 69F100 suggested.
I haven't ruled out timing too retarded as that can cause this sympton too.
Everything is new, radiator, hoses, aluminum water pump, expansion tank, dual electric fans (which have the highest cfm I could find on Summit Racing)Already tried another new thermostat, so I don't think I have any part failure issues.

The problem is, your engine is under the cab of the truck, and all the air is flowing away from it!!
Just kidding it's very likely the head gaskets.

Is there a spring in the lower rad hose. Without it they collapse when the water pump rpm comes up.

545FORD wrote:Fresh 545 with dual 4 tunnel ram, aluminum heads, Comp Cams Big Mutha Thumper cam and valve train runs 185 when idle or around 1,000 rpm. Does fine idling down street, however the faster I go the faster the temperature climbs. Can not go more than 20 mph or it overheats.  Timing at 12 degrees initial.  Aluminum radiator with dual fans.  This is backwards to me, usually a car runs cooler at speed and overheats when going slow. Going 40mph it hit 215 in a minute, slowed down to 10mph and back to 185 within a couple of minutes. Any suggestions

whats the total timing? these need min of 4500 cfm fans. best to rum them on inside as pullers, not pushers

Seriously, with your rad cap off, squeeze your lower rad hose. If you can collapse it by hand, that’s your problem.

While all the above may create or contribute to overheating, the one point that jumps out is how QUICKLY it heats up. The fans only matter from a stop to 30 mph with wind faster than that pushing more air than the fans can. The fact it doesn't COOL down above 30 leads me to believe you have a coolant flow issue.
Have verified coolant circulation with the cap off? I have never had dual fans cool as efficiently as a ducted single fan. I have been very satisfied with Spal 16" fans (pulling) and the Black Magic fan. You can pull 5000 cfm with a small fan but it won't cool well due to the small surface area it's pulling air through.

Which water pump do you have? I have heard high volume pumps don't allow the coolant to stay in the radiator long enough to dissipate the heat.

Engine fires right up and sits around 180 degrees when idling or driving slower than 25 mph or under 1,500 rpm. Any more than that and temperature starts climbing very quickly to 220+. I slow down or sit and idle and temperature goes back to 180 fairly soon. Here is what I have: All parts are new except for the block which a reputable shop did the machining, balancing, and head work. Fresh 545 Stroker, . 30 over, 10.5 to 1 compression, Aluminum heads, Comp Cams valve train, Ford Racing gaskets, Dual Four Tunnel Ram with FiTech FI, new polished aluminum water pump I bought on ebay (maybe my problem???), stainless backing plate behind water pump, 180 degree thermostat (tried several), 13 psi rad cap, Griffin 2 – 1 ¼ core cross flow aluminum radiator, Derale dual puller fans 4,000 cfm, Pro Billet Magnetic Trigger Distributor with mechanical advance at 16 degree initial 35 total advance.
Hoses are new and not collapsing, have tried several different thermostats, have played with timing a few degrees both ways, originally had 2 new Holley 450’s but they kept giving me idiling fits so I switched to FiTech 2x4 1,200 hp FI system. If I turn fans off when idling the temperature climbs quickly but comes right back down when fans turned back on, so water must be flowing right. I thought it might be the head gaskets on wrong, so I took the heads off and found that both gaskets were on correctly with hole in the back and block off in front. I am out of ideas! Suggestions are welcome.

Try different timing and fuel ratios, see how it acts

Also try taking the fan off and drive it at speed and make sure the lower hose has a metal spring in it to keep
It from collapsing

Sounds like the radiator either has internal blockage or doesn't have enough capacity. When I put my Ranchero back on the road after many years of doing a complete resto on it, I had similar overheating issues, held temp at idle but overheated at speed. I found that rust scale from the engine made it's way into the radiator's cooling tubes, causing internal blockages. Once I back flushed the radiator a number of times(required removing it and using air compressor to force water backwards through radiator) it really helped with temperature control. Another thing I did was to install a "chin spoiler" under and just in front of radiator core support, this addition forces more air to go through radiator instead of under vehicle. Hope this is helpful in some way.

545FORD wrote:

rmcomprandy wrote:

545FORD wrote:Fresh 545 with dual 4 tunnel ram, aluminum heads, Comp Cams Big Mutha Thumper cam and valve train runs 185 when idle or around 1,000 rpm. Does fine idling down street, however the faster I go the faster the temperature climbs. Can not go more than 20 mph or it overheats.  Timing at 12 degrees initial.  Aluminum radiator with dual fans.  This is backwards to me, usually a car runs cooler at speed and overheats when going slow. Going 40mph it hit 215 in a minute, slowed down to 10mph and back to 185 within a couple of minutes. Any suggestions

Are you certain that one head gasket is not installed back-wards ...?
That is the usual symptom.

I am leaning towards your head gasket suggestion.  Built the engine a couple years ago and I am usually very careful, but who knows.  I found a good explanation about this on the internet.........
Most gaskets have the word "front" stamped on them. that edge of the gasket needs to be at the front of the engine for coolant to flow properly.
The water pump pumps the coolant into the front of the block. The FRONT of the head gaskets is blocked off so the coolant will travel all the way to the back of the block. It THEN enters the heads, and travels from the back of them to the front, where it exits the water neck and goes to the top of the radiator.
If the head gaskets were installed backwards (open side to the front) the coolant would simply go in the front of the block, flow straight up to the heads and exit the water neck. It would not cool the back of the engine. So yes, the water would flow, but no where it was needed.  Next  step is to see if I have a difference in temperature between the front and rear of heads.

With most Ford engine head gaskets there is a rounded lower corner and a square lower corner ...
this can usually be checked with the engine assembled; the square lower corner goes toward the front.

No spring in the lower rad hose causing it to collapse as soon as the rpm comes up.

This is an old thread. Is the OP still around to give update? Just curious what it was.

stanger68 wrote:This is an old thread. Is the OP still around to give update? Just curious what it was.

If you read the post you will see I posted an update on Jan 22 2023..........