350 TBI overheating issues

[toyotaspeed90]

if the head gasket is blown, there are 3 ways the water is coming out. 1) into the oil where you'll have a milkshake, 2) into the cooling system, where you'll have bubbles at minimum (after all, upon detonation you have 1500 psi in the cylinders that's now in the water system), or 3) outside the block where you'd easily see it.

You forgot #4.... head gasket is blown, and it's exiting out the tailpipe as smoke. I'm well aware of all of that. Kinda looking for FJ40/350 specific issues

If you just admitted his engine is back into the firewall, that's the culprit. Heat dissipates out the back side of the engine, hits the firewall, and bounces right back into the engine before the non-existent prop wash can blow it out of the engine compartment. This happens 1,000 percent of the time when a motor is crammed into the firewall, and unfortunately the only remedy is re-motor mounting, along with the cost of modified drive shafts and exhaust. You can modify everything else until you turn green, but nothing else will be the remedy- - - sorry.

This is a concern I have. I feel there might be another remedy, but my guess is most FJ40 owners would consider it heresy.... (Cut the inner fenders to allow airflow... and if needed, use over frame headers to divert heat)

 

[yotafj]

Think you should pressure test cooling system before you tear it apart, but I think you need a thermostat that would match the high flow water pump for proper cooling. Also the newer motors came with cross flow cooling not down flow which changes cooling capacity and dynamics of the system as all the hot coolant is at the top of the radiator and could cause coolant to go out the cap or out the overflow tub on the catch can. My 347 stroker ran hot with the stock radiator so I changed it out to a cross flow by Griffen and had them put duel electric fans on it, run a 195 thermostat and never had a issue after that, a second fan on a toggle switch while the other has on a sensor that mounted in radiator hose and was automatic. If the engine is to far back the cfm is not there to cool to the motors needs. Sounds like there's a lot to look into but placement is everything like was said above and before. Do some research on the radiator diffrences also

 

[reddingcruiser]

^^ Jim, motor against the firewall sounds like the old "I saved money by not having to modify the drive lines " argument! Putting the motor in the 'traditional ' location saves a lot of grief.

And yes, I will agree that with some effort you can stick a reworked radiator in the stock location, but if you live in a hot, dry region or at high elevations you are more likely to have heating issues under load at low RPM's.

 

[reddingcruiser]

No fenders cut, Warn 8274 out front, 700R4 with oil cooler out front with larger aluminum cross flow radiator w/shroud. Runs 180 in city traffic when outside Temps are 100+ (which they are often, here )

 

[SuperBuickGuy]

I play a lot with race cars (and a SBC C3 Corvette - which are bottom breathers); and the biggest help on any vehicle is keeping the air out from under the car. Air gets out of the engine compartment by there being low-pressure behind the radiator. On our lifted rigs, we have trouble with this because many times the air travels to the axle then up to the engine compartment... blanking that space (between the radiator and the front of the engine/axle) via a skid plate or similar forces more air through the radiator and helps draw the air out once it's inside the engine compartment. Basically, the air stalls at the radiator. Only have half the radiator covered by a fan, or have cheap, electric fans and you will have temp problems.

if the traditional stuff doesn't work, wrap the exhaust, put an oil cooler on the motor. We have run Bonneville in 100 degree weather with the radiator completely blocked - and not overheated. I've run turbo motors on nothing but an oil cooler and full-fill hardblock in the motor. There is even talk now that an aluminum motor with proper coatings on the pistons, heads, and exhaust doesn't need any other cooling.... which is kind of funny, historically speaking, since it all started as air-cooled, then went to liquid cooled to allow for more hp... after all, energy transfered to water is wasted.

another thing to look at - air takes the path of least resistence. If you have lots of space above and below the radiator, the air will go around the radiator. Be certain that there is a block between the hood and the top of the radiator. Many people take that off thinking its unecessary or they take off the shrouds between the sides of the radiator and the grill.. all of those are great recipes for over heating.

 

[reddingcruiser]

2x on exhaust wrap. And your feet will appreciate it.

 

[RWBeringer4x4]

The rest of the world needs a bigger radiator for Chevotas, not sure what made your customer think he could use the stock rad????

Couldn't agree more! I fought this battle on my first SBC conversion 35 years ago, thinking I could keep the stock radiator. Yes, fall and winter were manageable but spring and summer were marginal at best.

It's not rocket science (well, it sort of is), but it's all about transferring engine heat to the outside air. The more surface area you have to facilitate this transfer the easier it is to manage the coolant temperature. Fan shrouds, larger coolant capacities and clutch-controlled mechanical fans will improve efficiency.

With a properly engineered system, space in the engine compartment is not that much of a factor. Any Big Block Corvette owners out there?

I don't think this is necessarily true. Granted, I have a smaller 283, but I'm running a stock radiator, no shroud, and a rigid steel belt driven fan, and the engine stays cool. That said, the engine is literally jammed up against the radiator (fan is about 1/4 inch away) which may contribute to the coolness. I've seen plenty of folks here who used the stock radiator and a shroud with success...although I'm not sure how many of them had the radiator re-cored.

I've read about a number of folks (as others have mentioned) who mounted the engine too far back. Heat deflects off the firewall and back into the engine, making it virtually impossible to cool. @Downey has been chiming in on his thread, and I don't have his manual in front of me, but I think it called for about 2 inches or so between the passenger side valve cover and the firewall to allow for adequate airflow.

When I move the engine back to its proper/final mounting location (with proper rear clearance from the firewall), I'm probably going to keep the rigid fan, or maybe go to flex (but stay clutch-less), and add a shroud. I haven't decided on an aluminum radiator, or a stock brass radiator (possibly re-cored).

It's tough to say what the real issue is without pictures, but as others have said, I'd start with the fuel air mixture and the location relative to the firewall. They seem to be the two biggest problems, from my reading.

 

[SuperBuickGuy]

I think the most important thing in this thread is that there isn't just one thing it could be - everyone's suggestions could be the issue or it could be a combination of a number of things, but that's hot rodding.

 

[Howard705]

I have had TBI 350 water pump I installed in the past that wouldn't cool right- the impeller was for opposite direction rotation. IDK exactly what the application was but was boxed wrong. Finally saw when removed etc. I have carbed 350 /stock radiator/no shroud/clutch fan- cools fine most of the time. Hottest it gets is in summer cranking high speed. bigger rad would help there. on trails is 180. I have LT1 350 in one haven't had the fan in it for a few years. Don't drive it too often but stays cool (stat open temp) at any speed except extended idling. In winter it will idle forever when the hood is up in a breeze before it gets to 180.

 

[Howard705]

Think was serpentine vs/V belt rotation.

 

[SuperBuickGuy]

serpentine turns the opposite direction as the prior motors. With that said, cars like the Caprice had a hybrid system that used the older pump.

 

[patrickhrco]

It’s been a few years, what was the final fix for this?

 

[RWBeringer4x4]

I’m not the original poster but for what it’s worth, I swapped the 283 mentioned in this thread to a 350 (gen 1, carbureted) and moved the engine to the “traditional” location (it was previously very far forward). I run a 17” rigid, belt driven fan, a CSF reproduction 4-core brass OEM radiator, and a custom fan shroud with slightly too much blade clearance (maybe 1.5” around the edges), and a 180C thermostat. The fan blades are probably 1/2-2/3 covered by the shroud.

It definitely runs hotter than the 283 did, but on hot, dead still 95 degree days this summer it would creep up to 210-215 (third gauge hash mark) crawling in traffic but didn’t seem to venture much beyond that. Enough to make me nervous, but from my understanding, probably not enough to hurt anything.

I’ve confirmed with an IR thermometer that this shot from the manual is about correct:

I was shocked at how much ambient temperature affects cooling. At 90 degrees, my truck will heat up to around 215 at idle. At 80 degrees outside, I don’t see much past 195 at idle. Now that it’s fall and we’ve had a couple days in the high 60’s, the truck stays at 180, and gets even cooler (160ish) when driving around.

In short, a stock 4-core radiator is barely adequate, but it DOES cool the 350. I doubt the older 3 core radiators could do it. I might be able to get improvement by going to an 18” fan or making some other tweaks.

 

[LB LandCruiser]

I put an aluminum radiator in my 73 Fj40. I believe it was a Champion. Less than $300 I think. I have a non-clutch type fan on the water pump. Runs fine. I might hit 215 in traffic on a hot day, sitting at a stop light. Wheeling it has been fine.

 

[SuperBuickGuy]

I've never been above 195 with my '40.
Where are you measuring the temps? for example, on the back of my heads, it's 140 degrees, when it's 195 at the neck....

 

[RWBeringer4x4]

I put an aluminum radiator in my 73 Fj40. I believe it was a Champion. Less than $300 I think. I have a non-clutch type fan on the water pump. Runs fine. I might hit 215 in traffic on a hot day, sitting at a stop light. Wheeling it has been fine.

This is pretty much how mine behaves.

I've never been above 195 with my '40.
Where are you measuring the temps? for example, on the back of my heads, it's 140 degrees, when it's 195 at the neck....

I was kind of hoping you’d chime in here as I know you haven’t seen the temps many of us see. That said, I believe you’re running a pretty big radiator.

The temperature sender is mounted in the driver’s side head, in my case. I’ve never checked front vs back of head (I should try that) but temperatures are usually pretty uniform - if the gauge reads 210, I’m at 210, pretty much everywhere I’ve measured (neck, water pump, heads, block, etc.)

Most of the time, I’m at 190, it’s only when sitting in long lines of cars crawling along in 1st gear that I start to see temperatures elevate to the third mark on the gauge (210).

 

[SuperBuickGuy]

I'm not sure I'd be concerned at 210* 230? I'd be concerned. 210? many new cars run that warm normally.

as much as I avoid electric fans, it really does sound like you could install an electric fan that comes on at 200* (they have ranges that are more-or-less accurate). One thing, for sure, is I would have an override switch to turn it off for water crossings.

As for the radiator- Chinese something or another that is for an FJ40. I also run a clutch fan - which gets me more blades, I'm using a 7 blade right now and I also have a shroud. To date, it's never come fully on and I was wheeling high-altitude, 100 degree days last summer.

 

[AggiePE]

I run an 89 TBI 350 in my 40 and I had a lot of overheating issues at first. I installed a 3" champion radiator and a ford Taurus electric fan with a 180° switch. I no longer have overheating issues.

 

[RWBeringer4x4]

I'm not sure I'd be concerned at 210* 230? I'd be concerned. 210? many new cars run that warm normally.

as much as I avoid electric fans, it really does sound like you could install an electric fan that comes on at 200* (they have ranges that are more-or-less accurate). One thing, for sure, is I would have an override switch to turn it off for water crossings.

As for the radiator- Chinese something or another that is for an FJ40. I also run a clutch fan - which gets me more blades, I'm using a 7 blade right now and I also have a shroud. To date, it's never come fully on and I was wheeling high-altitude, 100 degree days last summer.

This has sort of been my opinion too. 210 seems acceptable to me, 220 I'd start to worry, and 230 I'd shut it down. Conveniently, 230 is the OEM temperature gauge "pegged" fully to the right, and I'm not sure my nerves would let me actually peg that gauge. I'd probably shut it down if it got much past the third hash mark. I don't have a fan clutch, but I do have a 7-blade, 17 inch rigid fan. I have an 18 inch fan available (that was on the 283) but it winds up dangerously close to the shroud and lower radiator hose.

I've tossed around the idea of trying to find a low-profile pusher fan I could put in front of the radiator and wire to a switch on the dash. I watch my gauges like a hawk so it wouldn't be a big deal to flip a switch to turn on a fan if more airflow was needed, but I think I only have about an inch of clearance to work with. Most of the low profile fans I've seen still need 2" or so, which would require me to modify my radiator mounts.

210 is not ideal, particularly because it makes the cab bloody hot on an already hot 90 degree day. I haven't overheated the engine yet though. I do worry that the slightest change (ie: mud plugging up the radiator fins, higher altitudes, etc.), extended low speed wheeling in high temperatures, etc. could cause the truck to boil over but I haven't found the urge to fix it yet.

 

[peesalot]

A stock radiator can cool a sbc just fine. My 40 has had an old school 307 and a LS, both used stock fj40 radiator, mechanical fan, and a good shroud.No oil coolers or other stuff.