Yup.
Mild 340 build runs hot
- Thread starter John Trickler
- Start date
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" my shroud was a hinderance." Let me guess,- Probably one of those flat aluminum pieces of **** that cover the radiator with less than 2" of air space, and had 2 holes for the "fans". There's a HUGE difference between a correctly shaped shroud and the flat aluminum box\plate.
When they put 5.9 in Jeeps, they had cooling problems, so they put silicone flaps on the shroud so when speed was going to shove more air than the fan was gonna pull, the pressure pushed the flaps open allowing full air flow. At stop, flaps were closed, allowing the 6000 CFM fan to do its job and pull air across ALL the radiators surface (because of the shroud).
They did also vent the hood right behind the radiator, in the low pressure area to help suck the heat out of the engine bay. Once the fan(s) and radiator do their job, the heat has to have somewhere to go.
Air dams below the radiator help to create higher air pressure in front of the radiator and simultaneously a low pressure area right behind it. 6th grade science showed us that you get flow from a high pressure side to the low side without any help at all.
Of course, all that is when the vehicle is moving. My guess is an airflow issue when you're at low or no speed. Fans and shroud.
When they put 5.9 in Jeeps, they had cooling problems, so they put silicone flaps on the shroud so when speed was going to shove more air than the fan was gonna pull, the pressure pushed the flaps open allowing full air flow. At stop, flaps were closed, allowing the 6000 CFM fan to do its job and pull air across ALL the radiators surface (because of the shroud).
They did also vent the hood right behind the radiator, in the low pressure area to help suck the heat out of the engine bay. Once the fan(s) and radiator do their job, the heat has to have somewhere to go.
Air dams below the radiator help to create higher air pressure in front of the radiator and simultaneously a low pressure area right behind it. 6th grade science showed us that you get flow from a high pressure side to the low side without any help at all.
Of course, all that is when the vehicle is moving. My guess is an airflow issue when you're at low or no speed. Fans and shroud.
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340six
King Of Bling
I never read the whole thread sorry.
I agree some sets are underdriven. I like High Flow pumps with the plate welded on the back of fins. Brass Rads and shroud.
Not enough octane and to much timming is also one thing to look at.
John Trickler
Well-Known Member
Yes, the 7 blade fan with a clutch worked great on my RR. I even have a spare fan. But it is not how I went on the Dart, not having the room. Thanks for the input.
Bro we can't change physics. Most likely the issue is the fan/shroud setup. Your car originally came with that. You could easily bolt those parts in and it would probably be cool as a cucumber. It would have the bling factor but it would stay cool....
I can tell what will reduce temps....
For reasons known only to Chrys, they used a huge bypass hose & fittings on the SB engine. Hot coolant returning to the rad to be cooled is being diverted just below the t'stat housing via the hose...to the inlet side of the pump. So the cooled coolant that is about to be pumped back into the engine is getting hot coolant mixed with it. The engine is getting warm coolant, not cold coolant!!
There were two reasons for this engineering:
- pressure relief in case the stat jammed shut
- reduce engine warm up time.
In the BB engine, the 'bypass' is a 1/2" hole in the housing below the stat, much smaller.
I would put a restriction in the bypass hose that has with a 1/2-5/8" hole in it. A garden hose brass fitting might do the job.....or put a restrictor in one of the fittings that the hose fits onto....
For reasons known only to Chrys, they used a huge bypass hose & fittings on the SB engine. Hot coolant returning to the rad to be cooled is being diverted just below the t'stat housing via the hose...to the inlet side of the pump. So the cooled coolant that is about to be pumped back into the engine is getting hot coolant mixed with it. The engine is getting warm coolant, not cold coolant!!
There were two reasons for this engineering:
- pressure relief in case the stat jammed shut
- reduce engine warm up time.
In the BB engine, the 'bypass' is a 1/2" hole in the housing below the stat, much smaller.
I would put a restriction in the bypass hose that has with a 1/2-5/8" hole in it. A garden hose brass fitting might do the job.....or put a restrictor in one of the fittings that the hose fits onto....
70SwingerGuy
Long Haired Freaky Person
Okay, so stupid question then, if those are the only two reasons for the bypass hose, why cant we just eliminate it altogether?
Because of reason #1: pressure relief. If the stat jams shut, the coolant is stuck in the engine...& heats up quickly....expands with the heat..... then pressure builds...& will find a way out...such as a blown Welsh plug. Ask me how I know....
Dartswinger70
Well-Known Member
Is the serp belt routed correctly, is the water pump spinning the right direction ? I ask cause you can install a serp belt a few different ways .
What bore and stroke gave you a 426. I Did a 4 inch stroke and a 4.165 bore That was a .125 over bore for a 428. X-block
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the 426 was made off a la360 1976 block don't remember the specs it was 2 strokes and a brain seizure ago . I WOULD NOT STROKE MY 340 BLOCKS
TXOval
340 stroked to 416
OP - did you ever try adjusting your fan ON - OFF temps?
autoxcuda
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The 7 blade fan doesn't fit because the radiator is spaced too far back.
I have a cheap champion 4 core and it fit with the short repro Hayden fan clutch. But every aftermarket radiator is different.
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John Trickler
Well-Known Member
Okay, update on my over heating saga. Took all of your input and started tracking down items. I ended up putting on a different water pump. The Milodon #16250 definitely moves some water. And I found a used 7-blade viscous fan and put it on. It definitely helped, I have not driven the car yet, but I know it's better, had a 40 degree drop across the radiator. I know the viscous clutch need replacing. Debating about putting a regular fan on instead.
cookietruck
Well-Known Member
On one of my vehicles, a flex fan ran about 5-10* cooler than a 7 or 8 blade fan (of same diameter) with viscous clutch.
70SwingerGuy
Long Haired Freaky Person
Same here. Mildly built 340 here also, factory rad and shroud, 5 blade fan runs a steady 165, when sitting in traffic more she'll creep up around 185 or so. Seems that when I read about overheating, there usually seems to be an aluminum rad, or electric fans, with maybe no shroud, and(possibly) a serpentine system involved.
Yup, the water pump is sooooooooooo important. Not the number of impeller blades or their shape, it is this.....
You are shovelling dirt with a spade that has a flat steel blade. Dirt falls off the the flat sides. You switch to a shovel that has a blade with curved sides; no dirt is lost The dirt represents coolant loss from too big a gap between the impeller & pump body. Obviously, the bigger that gap is, the more coolant just gets churned up inside the pump...but never gets captured to be pumped through the engine.
You are shovelling dirt with a spade that has a flat steel blade. Dirt falls off the the flat sides. You switch to a shovel that has a blade with curved sides; no dirt is lost The dirt represents coolant loss from too big a gap between the impeller & pump body. Obviously, the bigger that gap is, the more coolant just gets churned up inside the pump...but never gets captured to be pumped through the engine.
Wow, just wow. Shroud it and get the fan spaced to an inch or closer to the rad. It has always been lack of shroud for me.
Make one outta coat hanger?
gzig5
Well-Known Member
Music wire would probably work better, wrapped around a mandrel of some sort. Hanger material is pretty much dead soft. Won't hold shape under pressure.
Without googling, I don't know where to get a commercial one.
mopowers
Well-Known Member
I got mine at a mustang parts supply shop. It's a pretty common part. Cheap too.
Check Inline Tube..that's where I picked up some
Inertia
Well-Known Member
Stainless welding rod or piano wire .
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