350 TBI overheating issues

[toyotaspeed90]

This is not my rig, as such I don't have photos.

'68 or '69 FJ40 with a 350, factory 4 speed (and I believe a twin stick orion, now).

Either driving around town when the weather gets nicer and/or while wheeling, the vehicle overheats. This past weekend it reached 260+ (I can't vouch for why he's been driving it like this... but in any event).

The 350 is pretty close to the firewall, it has cast manifolds inside the frame rails, no modifications to the fenders (other than dual batteries, one on each side).

The factory radiator was "serviced" and to be in good condition. It has an electric puller fan mounted. He's changed the tstat (I believe with a 180) and coolant several times. In attempt to pull in more air he mounted a couple small fans as pullers on the hood vents.

I've read that some SBC's tend to overheat in FJ40's... primarily due to lack of airflow through the engine bay. It seems that with dual batteries, a/c converted as air pump (and pieces to go with that) and a few other things, this could be the issue.... along with a factory radiator.

Before he starts buying/throwing parts at it - I've recommended he get the thicker 3" Champion Radiator (he isn't convinced it will be easy since my rig took a ton of modifications to make it fit, but that's due to engine placement too far forward in min) and a new water pump.

Any thoughts from those who may have had issues in the past and the ways you resolved it/them?

 

[SuperBuickGuy]

how's the condition of the motor? running rich, running lean, poor spark management could all contribute. I can only guess whether or not it's a recent swap or a problem that just started occurring. But I'd start with the tune before I looked at inadequate cooling. If there is cooling problems that defy solution, your motor has an oil-cooler provision. Oil cooling does wonders to staunch overheating issues.

also, engine driven fans move far more air than electric fans. if that doesn't do it, make sure you have a good shroud too.

 

[sadam_husain]

what sort of electric fan is he using is it pulling enough air through the radiator has he got a sealed shroud so its drawing though the radiator core and not from around the sides of the fan

 

[Josie'sLandCruiser]

Hi all,

Does it have a fan shroud? Gotta have one!

A larger capacity radiator would be a good idea too.

Good luck,

Alan

 

[yotafj]

Check the air fuel ratio first like was said above, if that's good I would check the water pump. Pull the cap and see if the water is moving at all when you rev it up without a thermostat in it. If there has been mods to the motor you would need to see if the radiator that's in it is sufficient to what's been done to the motor to properly cool it. Don't know how to do the math but Griffen radiator has it on there Web site. I would look into a aluminum radiator as they get rid of heat a lot faster

 

[Downey]

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

 

[reddingcruiser]

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?

 

[Romer]

I run a Griffin radiator and a 3600 cfm electric fan. The fan is set to come on when the temp hits 180 deg. The only time it has overheated is when the fan control wire came off the sender and it never turned on.

 

[swamp-thing]

X2 I've run both a 400 sbc and a 350 sbc in FJ40 -- fan shroud is an absolute MUST have item.

Hi all,

Does it have a fan shroud? Gotta have one!

A larger capacity radiator would be a good idea too.

Good luck,

Alan

 

[shawnfj40]

Getta Betta Rade atter and shroud it. Mechanical or Electric fans will both work just make sure your moving air over the largest surface you can. A big tell will be to find if it only heats up while idling or low speeds and runs cooler at high speeds, that is a shroud issue. If it always runs hot its more than likely the radiator design.

 

[toyotaspeed90]

(Not a customer, not my vehicle... this is a friends vehicle... he wants me to help him because he sees what I'm doing with mine and he's at his wits end.)

His was built by someone else and purchased years ago, but he has done modifications to the vehicle (the engine is a stock TBI 350). He seems to think 220-230* is normal, so I'm guessing that's the way he got it... and something else could be contributing to the issues.

There is a shroud that covers the entire radiator. He is not currently set up with an oil cooler (I've already recommended he pick up the 3" champion radiator and use the AT trans cooler as an oil cooler, he's thinking about it).

He's been having issues, he claims running rich but when following him there's no signs of it (no smell, no smoke). He says there's a flat spot of power under load (I haven't driven it yet). He has replaced (he's a parts replacer) TPS sensor, map sensor, oxygen sensor, coolant temp sensor (engine)... His wires look good but his coil and plugs look old, I recommended he look into those, at the very least to replace plugs.

 

[Downey]

Not necessarily related to overheating, but is your customer running an 02 Sensor and Vehicle Speed Sensor??
Directly related to overheating, is your customer's fan blade totally covered by fan shroud?? If so, air will cavitate (whirl wind) inside the shroud, blow back out the grille, and there will be very little prop wash to blow heat out of the engine compartment. Shroud should only come up to front edge of the fan blade (per SAE test results).

 

[toyotaspeed90]

ha, still not a customer.

Yes on the O2 sensor, unknown on the VSS.... it's a 93 or so 350 swap with a factory computer - there is a CEL wired and only gets the CEL randomly while driving (hasn't been able to pull the code as once he stops, the light turns off). For fact I know it's OBD1.

It's a puller fan, the shroud I don't recall 100%, but I don't believe is covering the blades.

I was looking for other possibilities before I start to actually tear into his vehicle.... probably won't be until this weekend but already telling him he needs plugs, might pull the water pump to ensure it's working, check for HC's in the coolant (HG check).... it's very possible that he has a blown HG considering how hot he's let it get and continually drives it as such. The Autometer gauge he has maxes out at 260 and he has said "the needle has gone just a tiny bit further but not all the way", I'm not entirely convinced the autometer gauge will continue to rise much past that point.

 

[SuperBuickGuy]

there are some people who shouldn't own modified vehicles, maybe suggest he get a nice, new 4 runner? As he probably won't, here's what's next.

With that said, you have checked to be sure that the gauge is reading accurately? because if it is truly at 260* it runs really, really poorly. also at 260, it starts to burn wiring harnesses. The motor will diesel badly, it will misfire (because the fuel is pre-igniting)...

if it's a later GM head, they can crack. But, they also do run warmer than what anyone else would consider "normal" (210-215 range).

tell him to get a laser temp gauge and measure these things. 1) the exhaust manifold temperatures at the port, 2) the temperature of the thermostat housing, 3) the temperature of the top tank and the temperature of the bottom tank near where the water pump draws the water.
Here's the normal temperatures of those items - 1) 450-600*, 2) 200-220, 3) 190, 165

I suspect, the more you talk about it, that it's simply a screwy gauge.

 

[B y r o n]

For those of you who think a larger radiator is needed, that isn't necessarily the case. I've been running a built 350 for years without any over heating issues. That said I have done things to minimize that possibility.

I built a full shroud so that all air is pulled through the radiator.

I use a 5 blade stainless steel flex fan without a clutch.

I have a LARGE ( 8 row) oil cooler in front of the radiator to help cool the engine.

I just had a row blow in the original radiator after all these years. I had my choice of going to a 4 row or sticking with the high efficiency 3 row. 3 row is 2" deep, 4 row is 2-5/8" deep. The thicker radiator may have been needed if I had immediate plans to add AC but I don't. The thicker radiator also is harder to pull air through so that is also something to consider for those with weaker fans. Besides, I didn't want to re-fab the mounts for the oil and PS cooler and since I've not had any issues with the factory radiator I had it rebuilt with a high efficiency 3 row.

Proper planning can prevent overheating issues.

 

[toyotaspeed90]

Well - like I said in the original post, I have read that engine placement can impact engine temperature within a 40... (I didn't place mine but I have put in a different engine) mine is far different than his in terms of location... it's tight between the firewall and motor on his, and mine is really tight between (clutchless) the fan and the radiator. Cooling is one of the things I'm taking seriously with my vehicle - just a stock 350 but it will have the (thinner) Champion radiator, a decent sized PS cooler, an AT trans cooler, and I'll be using the radiator lower tank as an oil cooler. I'm hoping he listens....

With his rig I'm wondering if the engine is placed further back, and if that is in fact a contributing factor, how to possibly resolve it (at this point moving the engine isn't an option)

I know it's an early 90's motor, what year exactly I don't recall. I'll throw my laser temp gauge in varying spots and see how it behaves.

I have ridden in the vehicle when off road... and I don't think it's a faulty gauge. He is losing coolant (nothing out the tailpipe and nothing in the oil) - so I suspect it's boiling out... The cap is a 16lb cap and seems to have quite a bit of tension in it still....

 

[SuperBuickGuy]

without googling the ratio, raising the boiling point of water - I think it's a straight 1-to-1 ratio... thus, with a 16 lb cap, you're raising the boiling point to 228* if it is 260, it should be blowing past the cap and onto the ground. Further, you should have bubbles perking through the radiator and out the cap along with major boiling in the radiator and in the recovery tank.

 

[toyotaspeed90]

(I usually see it when it arrives at my house, not so much on the road)

Usually when we check coolant it's low in the rad and not in the overflow... hence why I think he's loosing coolant through boiling rather than a BHG (but still not ruling it out)

 

[SuperBuickGuy]

my first car was a 1962 Buick Skylark. It had a 215 aluminum motor in it that is, in my opinion, the most likely-to-blow-its-headgasket motor that was ever built. I had 3 head sets for it, one on the shelf, one in the car, and one at the machine shop. I could swap them in 4 hours and only needed to go to the toolbox once.
so I have a bit of subject matter expertise here... (though the melt the wire stuff is something my dad did to an IROC Camaro.. his line, I just need to get a little closer to home.. poof).

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.

 

[Downey]

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.