350 conversion overheating issues (1 Viewer)

[Bluecrew]

I’m new to the forum but looking forward to the insight provided. I have a 1970 FJ40 with a 350 (355 really with forged pistons) conversion and TH 350 transmission... stock transfer case.
I’m sure this topic isn’t new but I’m looking for help keeping this engine cool. It’s spring and the engine hasn’t gotten over 210 but I’m worried about summer. I’ve just put a new aluminum core radiator with electric fan but still having issues... a few min after I shut the engine off, fluid spews from the overflow line.
Transmission also having (infrequent) shifting issues getting into 3rd gear... that keeps the RPM’s a little high (3k) when cruising down the road and wondering if these two issues are linked? Any thoughts would be appreciated.

 

[Downey]

The coolest running Chevota I ever owned had an 18" diameter, 7 blade, air conditioning fan on a fan clutch, rig ran so cool I never added a fan shroud. Elec. fans seldom create the hurricane inside the engine compartment necessary to blow out the engine heat. No sure, but I believe auto trannys have a modulator valve that makes them shift, if valve is going out on you that could be the problem ???

 

[Bluecrew]

The coolest running Chevota I ever owned had an 18" diameter, 7 blade, air conditioning fan on a fan clutch, rig ran so cool I never added a fan shroud. Elec. fans seldom create the hurricane inside the engine compartment necessary to blow out the engine heat. No sure, but I believe auto trannys have a modulator valve that makes them shift, if valve is going out on you that could be the problem ???

 

[Bluecrew]

Appreciate it Downey... the hard part is the space needed to handle an 18 inch fan. Power steering and lower radiator hose prevented me from a setup like that. Engine is just too low (compared to center radiator core). The electric fan is working now... just have to wait and see how it handles the summer temps. It is moving air... I just added a coolant trap to see if I can keep from dropping puddles around town. Checked the Tranny and was a little low of fluid... hope that was the issue... had been awhile since I last checked.

 

[Skreddy]

First; are you topping off coolant every time it pukes? If yes, STOP! It could just be your setup telling you it’s full and there’s no room for expansion.
Second; Downey pointed it out, but rethink the electric fan. Not sure which ones you have but Ford windstar fans are popular for cooling with chevy muscle cars. I personally like clutch fans. I have a 7 blade from a mid 70’s chevy truck with an hd clutch on my big block Chevelle pushing 600 hp and can drive in summer traffic all day.
Third; depending on the V8 install, it may be really hard to cool. If installed too far rearward, there’s just no room for the air to escape. Depending where your exhaust goes can help or hinder this. Also, do you have a thermostat? What temp? Timing good? Carb tuned well? All those little things add heat.

 

[pb4ugo]

We probably need to see some pics of your setup. Temps are always going to spike when the engine is turned off, because coolant flow has stopped. Running 3k rpm is pretty extreme. I personally like engine driven fans with a good fan shroud, but theres a lot of folks on this site that have found good electric fans to work. Yrs ago the Taurus fan was the 1 to get, others have found good aftrmkt fans to work too. Not all electric fans are equal. Engine placement is critical too, for air movement under the hood. P/S should not interfere with mechanical fans. Use the search function in the 40 section to help find answers and look in the FAQ's. Your setup is not the 1st one, its was actually a fairly common swap, and Downey probably helped guide a lot of folks in their setups.

 

[Downey]

With the new info you supplied it certainly sounds like the radiator was not lowered during your conversion. The reason guys move the radiator rearward is because they put in a much shorter engine and the radiator is now too far from the fan blade. The reason guys move the radiator downward is because the Chevy fan in now not centered on the radiator surface, the fan is so low that it will cut through the path of the lower radiator hose, and this keeps you from running a larger diameter fan that pulls more air. Finally, my own opinion is electric fans lack the horse power to create a hurricane inside the engine compartment, and that hurricane is exactly what blows heat out of the engine compartment.

 

[Bluecrew]

With the new info you supplied it certainly sounds like the radiator was not lowered during your conversion. The reason guys move the radiator rearward is because they put in a much shorter engine and the radiator is now too far from the fan blade. The reason guys move the radiator downward is because the Chevy fan in now not centered on the radiator surface, the fan is so low that it will cut through the path of the lower radiator hose, and this keeps you from running a larger diameter fan that pulls more air. Finally, my own opinion is electric fans lack the horse power to create a hurricane inside the engine compartment, and that hurricane is exactly what blows heat out of the engine compartment.

Exactly right... the radiator should have been lowered and if this current setup doesn’t get me thru summer... Or even if it does, lowering makes sense. Im not set up for this kind of fabrication but there are enough around here in OC that I shouldn’t have a problem as long as I have the design.

 

[Bluecrew]

First; are you topping off coolant every time it pukes? If yes, STOP! It could just be your setup telling you it’s full and there’s no room for expansion.
Second; Downey pointed it out, but rethink the electric fan. Not sure which ones you have but Ford windstar fans are popular for cooling with chevy muscle cars. I personally like clutch fans. I have a 7 blade from a mid 70’s chevy truck with an hd clutch on my big block Chevelle pushing 600 hp and can drive in summer traffic all day.
Third; depending on the V8 install, it may be really hard to cool. If installed too far rearward, there’s just no room for the air to escape. Depending where your exhaust goes can help or hinder this. Also, do you have a thermostat? What temp? Timing good? Carb tuned well? All those little things add heat.

Appreciate the info.... I agree that topping off would be a bad idea. I just put in a collection tank so guessing how much coolant is left should prevent me from having to add as a prevent measure. I’ll post a few pics but Downey has it right... the radiator wasn’t lowered to match the engine and that how it still stands. I need to lower in order for me to go back to a mechanical fan. I’d love to run that 7 blade clutch fan you discussed... I just don’t trust the electric versions.

 

[Bluecrew]

We probably need to see some pics of your setup. Temps are always going to spike when the engine is turned off, because coolant flow has stopped. Running 3k rpm is pretty extreme. I personally like engine driven fans with a good fan shroud, but theres a lot of folks on this site that have found good electric fans to work. Yrs ago the Taurus fan was the 1 to get, others have found good aftrmkt fans to work too. Not all electric fans are equal. Engine placement is critical too, for air movement under the hood. P/S should not interfere with mechanical fans. Use the search function in the 40 section to help find answers and look in the FAQ's. Your setup is not the 1st one, its was actually a fairly common swap, and Downey probably helped guide a lot of folks in their setups.

Agreed.... too many of these conversations around... just not around here. The guy that installed my engine and mounts as well as my radiator guy; neither had seen this done before. Appreciate forums like this that can help a rookie like me work thru these issues.

 

[rumrebel]

Hey, Presently I'm in the middle of chev/auto swap in my 40 and to deal with perceived overheating I've up scaled my radiator by about 10 percent to a HJ75 diesel 4 core copper type ,(lose front PTO), running a fully shrouded 18" steel non clutch fan (early 327, 7 curved blade type. sucks a bit of HP but hey a 400's
'got a few to spare) and have brazed the thermostat permanently open. I don't know if you can get away with an open thermostat in your neck of the woods but works well in my climate. ( they do come in different temperature ranges which could help) the right radiator cap pressure is another factor with cooling, I agree with the other blokes, electric fans are fine for a 2 ltr rice burners not a 6ltr mountain machines but prefer non clutch type as they pull air at high revs and low speed when your working the motor hard also buy an in line anode for your radiator, electrolysis can be troublesome with older cars

 

[workingdog]

210 is not a problem. Why do you think you even have a problem? The puking. I would not assume that's from overheating. Most of the time, the expansion tank is not set up properly or is overfilled. That 350 is designed to run between 190 and 210 and goes up to 230 without any trouble, if the system hold pressure.

 

[B y r o n]

If your radiator was not moved back and lowered there are options. When I did my conversion I left the radiator in the stock location. I fabricated a shroud and cut the opening slightly larger than the 17" stainless flex fan. I also used a spacer between the fan and water pump to place the fan closer to the radiator. I also hooked up an overflow tank. It's been doing fine for many years.

You just need to look at the options and decide which is better for you.

 

[Vandal FJ]

The overflow tank is what cured this issue for me. Aluminum radiator and a 350... no more overheating.

 

[Bluecrew]

The overflow tank is what cured this issue for me. Aluminum radiator and a 350... no more overheating.

Haven’t overheated yet since putting the new aluminum core. Hoping the problem is solved.

 

[Bluecrew]

The overflow tank is what cured this issue for me. Aluminum radiator and a 350... no more overheating.

Did add an overflow as well... helps from dropping puddles everywhere

 

[Bluecrew]

210 is not a problem. Why do you think you even have a problem? The puking. I would not assume that's from overheating. Most of the time, the expansion tank is not set up properly or is overfilled. That 350 is designed to run between 190 and 210 and goes up to 230 without any trouble, if the system hold pressure.

210 is not a problem and if that’s the highest it gets they the summer months, I’ll consider this problem solved. I changed out to an aluminum core, and added an overflow tank. The old radiator was definitely an issue and temps would get to 250 in summer heat.... just not a healthy temp. I get nervous when that temp starts riding north of 210 but I really shouldn’t. Guess I’m just gun shy

 

[workingdog]

It took me a while to get comfortable with higher temps. But a modern V8 will hit 220 frequently, 230 some of the time under sustained load (like a long pull on a steep grade in summer). But, it should always come back down and never go past 230. But, that assumes the system is holding pressure. Being able to run at those temps assumes a pressurized system and good quality coolant. If you hit 230 and there's no pressure in the system, you're cooked.

 

[MrXIXX]

The overflow tank is what cured this issue for me. Aluminum radiator and a 350... no more overheating.

What temp thermostat are you running? I have a 79 350 in my 72 FJ40. Sniper EFI, 3 row aluminum radiator, 16in electric fan and a 180 thermostat. It runs at 190ish on the street with no issues whatsoever. When I drive on the freeway, the temp with start climbing to over 200. So far 217 is the highest I have seen after climbing a hill, the temp will start to decrease on the downhill side.