350 Heating Problem Help (1 Viewer)

[ianacole]

I need some help with a mild overheating problem.

Technical info:

• '75 40 with a 350 swap - purchased 1 month ago with the swap already done
• No idea of the year of the motor (haven't cleaned the area with the casting numbers yet).
• Stock radiator
• Fan is on the motor
• Holley carburetor, 4bbl.

Assumptions:

• People have run 350s without heating issues
• The temperature gauge is functioning properly/reading correctly
• This thread won't deteriorate into a Stock vs. Swap bash fest

Problem:

• When driving the temperature slowly climbs. If I have a long drive without a lot of stops, and a "coolish" day, the temperature will hang out at ~170. However, if I have stop and go driving (~3 minute wait at a light with ~5 minute driving cycles) it will climb to ~190. Prolonged stops cause the temp to climb over 200. I have ~45 minute drive home and by the time I arrive the temperature has been at 190 for a good 10 minutes.
• When the temperature hits ~190, the truck starts hesitating when applying the gas (vapor lock?).

Fix actions:

• I've built a fan shroud for it as it came without one. This helped slow the temperature climb, but not halt it.
• I plan on replacing the water pump with a high flow, short rise pump
• I plan on replacing the thermostat with a 172 degree unit
• I plan on pulling the radiator and checking for obstructions
• I have a Flex-a-light Black Magic fan that I'm hoping to install if the short water pump nets me enough room

Questions:

• Anything else that I should look at/consider?
• Can I use high pressure (1750 psi) sprayer to dislodge any sediment or blockage in the radiator?
• Should I look at trying to flush the block with the high pressure sprayer also (is this even possible without completely disassembling the motor)?
• What have others with 350s done for their cooling?

Thanks!

Ian

 

[JJS]

Are you running a clutch fan? A full-time fan tends to work better in this application. It's up for debate, but some people think it works better than an electric, i.e., Taurus fan.

How much spacing is between the face of the fan and the radiator? It shouldn't be over 3" in this application.

Swap in a 160* (172* would likely also be fine) t-stat.

That's all I got off the top of my head.

If this doesn't work, you may have to look into an aftermarket radiator. If there's no luck there, you may need a higher volume water pump, but that's unlikely.

 

[camcruiser13]

as far as your temps those arent high, but its the hesitatoin thats got me concerned, maybe just my rig but it hangs out around 190-210 all the time. maybe my gauge is off, but i ve never had a problem with that being to hot. hell my new dodge runs at 215 all the time.

i run a taurus fan and stock radiator.

seem like your temp climbs when their is less air flow ie stop lights

 

[ianacole]

Spacing is about 2.5", hoping to get 4 so I can install the black magic. Great question on the fan - I'm not sure. I cannot grab the fan and turn it with my hand, but it does have a big radiator looking thing attached to it. Thanks for the suggestion on the turdmostat - I hadn't thought about the 160*.

Thanks!!!

 

[JJS]

Spacing is about 2.5", hoping to get 4 so I can install the black magic. Great question on the fan - I'm not sure. I cannot grab the fan and turn it with my hand, but it does have a big radiator looking thing attached to it. Thanks for the suggestion on the turdmostat - I hadn't thought about the 160*.

Thanks!!!

It sounds like it's a clutch fan. If you have the electric already, by all means give it a shot.

 

[ianacole]

as far as your temps those arent high, but its the hesitatoin thats got me concerned, maybe just my rig but it hangs out around 190-210 all the time. maybe my gauge is off, but i ve never had a problem with that being to hot. hell my new dodge runs at 215 all the time.

i run a taurus fan and stock radiator.

seem like your temp climbs when their is less air flow ie stop lights

I need to put an IR gauge on the block to verify the accuracy of my temp gauge. I had read a number of threads through the search that identified operating up to ~230 being acceptable, which is why I'm concerned.

I wouldn't be so concerned with the temp climbing at stop lights if it dropped back to "normal" operating temp when i get to driving again, but it only drops marginally. The hesitation also concerns me.

One thing that I did forget to mention is that it has a mechanical fuel pump. I've been contemplating going to an electric.

 

[dgangle]

Do A Search This Has Been Beet To F#$%ing Death

Ahh, the predictable and expected V8 cooling thread. A little earlier this year than most. It hit 74 here yesterday so I knew it was coming.

News flash.......
Your radiator is too small, plain and simple. Anything other than replacing it with something bigger than the stock I-6 rad is going to be a waste of time and money no mater how one justifies it. You are not in unchartered waters here.

https://forum.ih8mud.com/showthread.php?t=105975

see posts 3 & 5

 

[ianacole]

It sounds like it's a clutch fan. If you have the electric already, by all means give it a shot.

If I can gain enough clearance with a short water pump I hope to. It came with the truck, so I figure "what the hell if it will help."

 

[ianacole]

Ahh, the predictable and expected V8 cooling thread. A little earlier this year than most. It hit 74 here yesterday so I knew it was coming.



https://forum.ih8mud.com/showthread.php?t=105975

see posts 3 & 5

I actually did search and read through most of those. However, none of them specifically address my question about hesitation.

 

[dgangle]

...none of them specifically address my question about hesitation.

Me: dad, it hurts when I do this.

Dad: well don't do that then

if it only does it when it's hot, keep it cool and it won't hesitate

 

[JJS]

Ahh, the predictable and expected V8 cooling thread. A little earlier this year than most. It hit 74 here yesterday so I knew it was coming.

News flash.......
Your radiator is too small, plain and simple. Anything other than replacing it with something bigger than the stock I-6 rad is going to be a waste of time and money no mater how one justifies it. You are not in unchartered waters here.

https://forum.ih8mud.com/showthread.php?t=105975

see posts 3 & 5

There's definitely some truth to that. At best, your stock radiator is going to perform marginally well. I swapped mine out for an aluminum Griffin rad.

 

[ianacole]

Me: dad, it hurts when I do this.

Dad: well don't do that then

if it only does it when it's hot, keep it cool and it won't hesitate

Yah, but if normal operating temperature on a 350 is ~190-210, and should be able to run to 230 without issue, then it shouldn't be hesitating.

So, to use your analogy,

Me: Dad, it hurts when I breathe.

Dad: Well, Don't breathe then.

 

[ianacole]

There's definitely some truth to that. At best, your stock radiator is going to perform marginally well. I swapped mine out for an aluminum Griffin rad.

I have been thinking of swapping out the radiator, but hoping it wouldn't have to come to that. Did you go directly to Griffen for yours, or someone local?

 

[ranger]

You would be better off getting a radiator with larger surface area than spending alot of time and money trying to get the stock rad to cool the 350.
A high volume water pump will make the cooling worse, since the water will be pushed through the radiator quickly it will have less time to allow for heat transfer.

 

[camcruiser13]

dgangles got some good specs on the perfect size and where to get one fabbed up. or am i thinking someone else??

pm him he would love to help

 

[JJS]

I have been thinking of swapping out the radiator, but hoping it wouldn't have to come to that. Did you go directly to Griffen for yours, or someone local?

Summit.

 

[ianacole]

You would be better off getting a radiator with larger surface area than spending alot of time and money trying to get the stock rad to cool the 350.
A high volume water pump will make the cooling worse, since the water will be pushed through the radiator quickly it will have less time to allow for heat transfer.

Hmmmm, good point. Thank you!

Summit.

Thanks!

 

[pb4ugo]

The only time i had issues w/overheating w/the stk rad was when my 1st 350 was pushing 400+hp, or the 454. I have seen many SBCs run w/stk rad w/no problems.

You say hesitation, If the timing is too advanced it will overheat. I was working on a friends that was overheating, found the harmonic balancer was bad and was timed by the mark, which was advanced, new balancer timed right and no issues ever since, and no fan shroud. A Decent fan shroud will help, but hell my fan doesn't even stick into shroud. The postion of engine(not to close to the fire wall). A good fixed fan. mine has 5 or 6, 35* steel blades.(no flex fan) 160tstat ussually runs 160-180*, If hammered long and hard 200-210, but will cool down after. 180ish on the highway.
It's never been a concern in my current set up. Both cruzers listed below have stk rads.

 

[dgangle]

dgangles got some good specs on the perfect size and where to get one fabbed up. or am i thinking someone else??

pm him he would love to help

Yup, that's me. I am by no means the only person who has cooled a SBC sucessfully. Read the threads in the link I provided. They have all my dirty little secrets!

The timing issue is very important as well. 34-38 degrees total advance and call it good. Oh, and don't breathe then.

 

[ianacole]

Yup, that's me. I am by no means the only person who has cooled a SBC sucessfully. Read the threads in the link I provided. They have all my dirty little secrets!

The timing issue is very important as well. 34-38 degrees total advance and call it good. Oh, and don't breathe then.

Thanks, I'll go through them again with a fine tooth comb. I'm hoping that I can get away with using the stock radiator as my wife will s*** if I tell her I need to spend ~$600 on an aluminum one.

I've gone through the timing (not withstanding a harmonic balancer issue as pb4ugo referenced), and it is set at 8* at idle, then retarding ~0 when giving it gas without plugging the vacuum advance on the distributor. 34-38 seems really high, is that with the vacuum advance plugged?