MG Sports Cars

I've been fighting an overheating problem with my SBC. The problem has been getting the heat out of the engine bay. I've tried replacing the sheet metal rad support with small tube mounts, cutting vent holes in the inner wings, lifting the back edge of the hood but once the heat starts building, the rad just can't shed it. Last night I wanted to head out but it was hot and sticky so I pulled off the hood - problem solved! except I'm running without a hood. I could easily see 230 degrees and have to pull over to let it cool down but last night the temp stayed at 190 - 200 even crawling in traffic.
So for the time being I'm going to be running without the hood until I get a hood filled with louvers to let the heat out

Warren, A puller fan with shroud will help too. I would run a 180 thermostat also. You can buy louver panels for your hood at RodLouvers.com. I plan to mount them upside down for a little more subtle look.

"I've tried replacing the sheet metal rad support with small tube mounts"

Every bit of air entering your engine bay should have to pass through your radiator core. It's no good to have air bypassing the core and instead going around or over your radiator. You want high pressure in front of the radiator core and low pressure below it. Louvers might help too, but getting maximum airflow across the core would be my first priority.

Is your radiator big enough?

"I would run a 180 thermostat also."

Run a thermostat. If you doubt its performance, check it in a pot of water on your stove to make sure it opens fully. As for the thermostat's temperature rating: that shouldn't have a significant effect on cooling performance because any properly functioning thermostat will be fully open way before you get to overheating temperature.

Warren, I have 26 louvres in my bonnet and they work very well when the car is moving slowly and the fans are on. Once moving I don't think they have much effect as my understanding is that it is a high pressure area near the screen and very little air will get in or out through them....untill my fans come on that is and then heat comes out through the louvres and then down through the screen air vent. So I always know when the fans come on as my feet get warm. Great in winter.

As Curtis says puller fans are better apparently by upto 30% more effective than a pusher and fill all the gaps around the radiator front panel so that air only goes through the radiator. I have a 3.9l Rover in mine with 2 revotec puller fans which keep it at normal eg 82c. I also run without an oil cooler as I don't do long motorway runs and it sat infront of the radiator. I also moved the oil filter to under the drivers wing to get a bit more heat out of the engine bay.

I have headers that go out through the wings, which I have wrapped down to where the 4 pipes meet and that seems to get lots of heat out. You can touch them without getting burnt.

I managed to cure the heat soak problem using an edelbrock heat sink gasket which is only 5/16" thick and works a treat. The car always starts straight away when hot.

Ian

Thanks for the suggestions but I think I have exhausted almost everything.
The thermostat is working, I have a pusher fan at the top and a puller at the bottom, 16lb rad cap, and the rad is recored and extends down to the bottom of the cross member. The rad does cool the engine as long as it is moving but eventually heat builds up in the engine bay with no where to go.
I did block off the front around the rad forcing air across the radiator core and it ran even hotter. Making up the the tubular rad supports from the suggestion in the How To Give Your MG V8 Power book, let air to be pushed in around the engine and let some heat out in traffic, but not enough.
A lot of people are telling me I need a bigger or aluminum or crossflow rad but just pulling the hood suggests to me I really need to vent the engine bay more.

We need more information on your setup. What kind of radiator, dimensions, photos of the mounting and baffleing, what kind of fan and how it is wired???

Another thing you might find usefull is a Magnehelic differential pressure gauge. You need one that measures in inches of water and you can pick them up pretty cheap on Ebay. I have a 0-1" and a 0-2" and paid less than $20 for them. The idea is you run tubes to two areas and measure the pressure drop. You could put one tube in front of the radiator and one in the engine compartment. You should see a significant difference when the car is moving - if not the air isn't flowing through the radiator. It is a good way to determine how effective your modifications are. You can also use it to determine where to put the louvers in your hood, you want to put them where the greatest differential occurs above and below the hood. Curtis did an article about using one to optimize a cold air induction system and that should show you the basics of using the gauge. Once you have one there are a lot of uses for it on the car.

You should also consider using an OEM electric puller fan from a domestic car. They move a lot more air than most aftermarket units









Edited 1 time(s). Last edit at 05/28/2014 01:11PM by Jim Stabe.

Ditch the pusher fan in front of the radiator and use that space to move the radiator forward so you can put a big, domestic OEM fan behind with a shroud that pulls air through the entire core. I would suggest either a Ford Taurus fan or one off a 1990's Volvo. Both fans move some serious air. If you use either of them you need to wire them with 10 gauge wire straight to the battery and a GOOD ground and run a 75 amp relay. Baffle the radiator so that all air entering the front has to go through the radiator or you are defeating your purpose

This is a Taurus fan



This is a Volvo fan

Quote:

Thanks for the suggestions but I think I have exhausted almost everything.

Oh? Is your exhaust coated? Ceramic coated headers or exhaust manifolds (& connecting pipe) will go a loooong way towards keeping heat out of the engine compartment.

No, I have stock exhaust manifolds. Guess the engine will be coming out again to get them off.

Warren, You could put a louvered panel in each fenderwell by the exhaust manifolds.

Don't quite think you've tried "everything" yet.
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A big motor in a small car is a formidable challenge, but rest assured there are solutions. Perhaps your louvers will do the trick. On the Roadmaster that oversize radiator sure takes care of that big 455 Buick though. Now with electronic fan control the temp holds rock solid at 190. I expect the 340 will do no less.

Jim

Warren,
Have you checked the water pump to make sure it is the right direction for the pump. Chevys have regular rotation and reverse rotation pumps depending if they are v-belt or black side drive of the flat belt.. . Easy to get them swapped around.

I put some big rad out of a Tahoe in my MGB/SBC. Plenty of cooling capacity with not much fan.

Cheers,
Bill