BritishV8 Forum

Overheating in these conversions is 90% related to airflow problems.  Bigger, high powered (and power equals heat) engine crowding a small engine bay.  Look at the space around the original little 4-banger compared to what you have done. So...is the air hitting the front of the radiator getting through it without restriction?  Are the fan(s) running at the proper speed?  Do you have the radiator "sealed" to the front bulkhead so that other airflow is not bypassing it, and "pressurizing" the engine bay so the radiator's backside doesn't want to allow airflow?

Heat soak is what happens once you shut off or stop moving, but your fan arrangement should partially compensate for this.  My 1994 GM factory manuals for the 3.4 and 5.7 engines state that the PCM will cause the cooling fan(s) to switch on at low speed at 220F and high speed at about 240F.  That was what GM's engineers designed, so they did not consider those to be alarming temperatures.  Toss the boutique coolant and go back to standard Ethylene Glycol (Prestone green/yellow) or DexCool at a 50/50 mix.  If your cooling system is up to snuff, install the GM recommended 92C thermostat. And run 5W30 synthetic oil.

I have a 240 Volvo and see guys on that BB complaining occasionally about overheating.  First question to them is "did you remove the splash shield under the engine?"  Answer is often "yes".  They don't understand that the clever Swedes put that there not only to keep water out of the alternator, but to increase airflow through the rad by preventing air at highway speeds from washing up behind the front bumper/airdam and pressurizing the engine bay.  So airflow through there is extremely important to cooling efficiency....(to state the obvious).

Drilling a little hole in the thermostat flange is a way to bleed off any trapped air and let it get to the upper portions of the rad.  99% of the time it makes no difference,as the opening of the thermostat will do this anyway.

Since I don't require the extreme protection of anti-freeze, freezing or boil-over, I never use a 50/50 mix. Anti-freeze reduces the heat transfer efficiency of water. Therefore, I find that a 30/70  or even a 25/75  works for me & does a better job with engine cooling. LBC Winter drivers should stick with the 50/50, though.

MGBV8 - fair enough if you never see cold temps. The anti-corrosion additives in antifreeze do deplete over time and if you are using a weak mix, you should consider draining it and refilling with fresh stuff more often than if you used 50/50.

Hi,

Running late to the party and restating some things that have already been said but some cars such as Sunbeam Tigers, so I have read, have issues due mostly to air flow more than radiator size. I think the same holds true for any small engine bay.

Small fans, fans that are running the wrong way (blowing forward instead of with the air pressure going backwards), fans that the blades are 1" or further away from the cooling fins (no matter how good the shrouding- I question yours by appearance) and other air moving across the fins is a big portion of the issues.

The Original Fuel Injected version of this engine does run happy all the time above 220* but if you have the engine set up with a cooler thermostat, yup, it should run cooler.

Although I see many very good factory and aftermarket water temp gauges, I would say at least a third of the overheat complaints we hear about are a combination of a gauge that is not set up right or individuals who are not used to seeing the stock gauge go so far. For most gauges, this just needs an extra resistor of size 'X' in line.

My car and many that we build run stock radiators for the late model MGB. We sell a retrofit kit for the late model radiator to fit into the 1962-1976 MGB. This fits fantastic, looks stock and has no problem running hot. The biggest difference is the cooling fan used. Cheap cooling fans will allow overheating with almost no regard to how good of radiator installed in the MGB or other small engine bay car.

-BMC.

Just A Thought, Did You Check To See, If You Had A Counter Clockwise Water Pump Or Clockwise. I May Have Missed That Topic Here??

Bob B, We met in CS. I am running 3.4V6 like yours, 66 B no hood lovers and FI. 195 degree thermostat, stock water pump, 50/50 mix coolant. I put a wireless grill therm. sensor under the hood with the display unit on the console, went for a slow speed trip in traffic. Engine temp gauge shows between 195-220. At 220 fans come ON, then OFF at about 195-200. Engine area shows between 170-185, when the fans come temp will rise to 190-195 then start to cool down. When I shut engine off and watch the temp. it will go to about 195-200 for a short time then start to drop.
Like Bob W. and Brian Mc wrote, GM don't consider 220 hot on this engine. When setting at idle my engine bay temp seldom goes over 175, my ambient is about 70, granted it has not gotten hot, but it will, I will check again later.
I have reset my fan control to ON at 220 and OFF at 200. I would rather be ahead on the temps than to try to catch-up.
charles

When I put my 3.4l in my car, it ran hot. 10 miles or so I had to stop.  I had the Evans like I said. I did 2 things. First I swapped out the Evans. I imediatly got 20-30 miles but was still getting too hot.

One thing I noticed was the water temp would come up and stabalize like it should with the thermostat. Then the oil temp would come up...and it would keep on going. The oil temp would then pull the water temp.

I then put in a small oil cooler under the front valance and have had stable water and oil temps ever since:

Great tip Gary. One thing the factory did better than most of us is to keep tabs on the engine oil temps and the OEM oil cooler was there for good reasons. The piston takes as much heat as the head (nearly) and almost all of that heat goes into the oil. To get to the coolant it then has to migrate back through the block. American engines have for many decades used exactly that approach but the more efficient method is to cool the oil.

Jim

When I put the cooler under the front valance, I did not know how well it would work since it was not in dirrect airflow. I was suprised how well it did work.

Usually the oil is significantly hotter than the engine coolant, sometimes quite a lot hotter. That means the cooler will be just that much more efficient.

Jim

I also think the air is rolling around the valance getting more airflow then one might expect.

Good idea Gary so where on the engine does the oil lines run from to and from the oil cooler

I have a remote filter adapter on the block. I put the remote filter inside the front fender well:





I used to have it in the engine bay but moved it when I cleaned some things up in the engine bay. You can see it on the right on one of the picutres before I did more work in the engine bay:




It just looks better with it in the well:

Not only that, it's less mess when you do a filter change.

Jim

You know the remote filter block also gave me a good place to hook up the oil temp gauge.