340 cooling

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mad dog

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Good afternoon FABO, I know this topic has been discussed, i spent the morning reading about engines runnin hot and over heating problems.
That being said my 340 is at the machine shop now and i should see it by spring, My question to the 340 gurus here is ...Can someone tell me a sure fire recipe for cooling this 340 before it becomes an issue, My 340 will be a stock rebuild with the Oregon cams in the 1968 4-speed specs. My radiator is fresh from the radiator shop, totally re-cored by an old school guy its the 2998 945 22" w/ac, 3 core. i also have a factory shroud and 18" fan.
I would like advice on what water pump,thermostat, clutch unit for my fan and any other componet, id like to get this right the first time.
Would a flowkooler water pump be beneficial?
I know people will say stick to factory cooling which is fine but if i can improve on the cooling design thats even better.
seems in the past i spend my time staring at the temp gauge instead of enjoying the ride..any suggestions will be appreciated...Rich
 
this: 1963-1969 MOPAR Dodge Plymouth 273 318 340 Poly wedge water pump

with this: The original Robertshaw 330 series hi flow thermostats

and something like this: Mancini Racing Restoration Fan #2863216

NB you can accomplish the same thing with pretty much any 70's 80's V8 fan and a clutch of your choosing, just check the size to be sure it fits in the shroud.

also, 100% get an aftermarket gauge in there someplace so you *know* what temp it's running and not: oh, it's two needles before the upper left top of the H
 
Is the engine overbored, and by how much? Stock compression ratio, or lower/higher? Aluminum or iron heads?
Notice my questions are not cooling-system oriented, yet they are some of the biggest factors involving cooling system performance. Which is why so many people have issues even though they've got all the "best" cooling system parts...
And the biggest factor: ignition timing. You won't hear me say this very often, but you need to throw the FSM out when setting your timing (with today's gas). Make sure you've got plenty of advance dialed in, as too retarded will contribute greatly to overheating, and no amount of trick water pumps, electric fans and fancy aluminum radiators will make it go away until you get the tune right.
Since your build is pretty much stock, I think your parts selection so far is spot on. Just make sure you use quality parts as you rebuild. Think of it this way: The factory designed these things to work (with regular maintenance) for 100K miles, in various conditions from Death Valley to northern Alaska. No "overkill" parts necessary.
To answer your question, the Flowkooler is a nice unit, probably not necessary for you but it sure isn't going to hurt!
 
junkyardhero said:
this: 1963-1969 MOPAR Dodge Plymouth 273 318 340 Poly wedge water pump

with this: The original Robertshaw 330 series hi flow thermostats

and something like this: Mancini Racing Restoration Fan #2863216

NB you can accomplish the same thing with pretty much any 70's 80's V8 fan and a clutch of your choosing, just check the size to be sure it fits in the shroud.

also, 100% get an aftermarket gauge in there someplace so you *know* what temp it's running and not: oh, it's two needles before the upper left top of the H
Click to expand...

This ^^^^^^

Only thing I would have done is for a high density core when they did your radiator. Those have more fins and rows per inch…. Maybe you already had one put in when you did the radiator.
 
Stock heavy duty cooling or AC cooling components is all you need

You may have noticed in all the "my engine overheats" posts the common denominators.

AL radiators, electric fans, crappy designed shrouds.

The cooling system is a system and all the parts need to be designed to work with each other.
 
mad dog said:
Good afternoon FABO, I know this topic has been discussed, i spent the morning reading about engines runnin hot and over heating problems.
That being said my 340 is at the machine shop now and i should see it by spring, My question to the 340 gurus here is ...Can someone tell me a sure fire recipe for cooling this 340 before it becomes an issue, My 340 will be a stock rebuild with the Oregon cams in the 1968 4-speed specs. My radiator is fresh from the radiator shop, totally re-cored by an old school guy its the 2998 945 22" w/ac, 3 core. i also have a factory shroud and 18" fan.
I would like advice on what water pump,thermostat, clutch unit for my fan and any other componet, id like to get this right the first time.
Would a flowkooler water pump be beneficial?
I know people will say stick to factory cooling which is fine but if i can improve on the cooling design thats even better.
seems in the past i spend my time staring at the temp gauge instead of enjoying the ride..any suggestions will be appreciated...Rich
Click to expand...

If it’s a factory 340 car is should have a 26 inch radiator.

Get a high flow water pump. Flowkooler or Milodon.

Stewart Components thermostat.

Mechanical fan. No tricky clutch fans or any of that crapola.

You need to verify by measuring that the water pump is turning 1:1 (crank speed) at the minimum.

Never ever under drive a water pump unless you are shifting at 8500 rpm plus.

If you can turn the water pump 15 or 20% over driven I would do it so fast your head would spin.

Most over heating issues come from turning the water pump too slow.

Edit: if you can get the fan within an inch of the radiator skip the shroud.

If you can’t get the fan that close then you’ll need a shroud. Most of them are straight junk. I avoid them whenever I can.
 
Recommend Cold Case radiator based on performance on my 340. This is a 1970 motor and I drive the Dart to shows as much as 200 miles away (400 miles round trip). Had problems on and off for a few years. Switched to this recommended set up 10 years ago and no issues since. Radiator is set up for the stock fan shroud. Use a Robertshaw style thermostat - I use 180 degree. Use an 8 fin impeller (stock for AC cars) water pump and stock pulleys. Hayden makes a short shaft clutch fan specifically for A-bodies to resolve spacing issues, and yes the type of fan that Mancini sells (maybe look for a used one or at least a better price). Cold Case is a sponsor here and you can get a FABO discount by calling in your order.
 
Newbomb Turk said:
Well, now I’m questioning my memory
Click to expand...
Screenshot_20250119-145441.png
 

Newbomb Turk said:
Well…****. I was going off my memory. I thought all 340 cars got a 26 inch radiator.

I could be mistaken though.
Click to expand...

I don’t think any got 26”. Unless that’s an 73-up deal.

In 1970 the radiator tops changed to a square “bigger” look. Also in 1970, they introduced the aluminum water pump
 
Newbomb Turk said:
Well…****. I was going off my memory. I thought all 340 cars got a 26 inch radiator.

I could be mistaken though.
Click to expand...

Newbomb Turk said:
Well, now I’m questioning my memory.

Maybe it was 70 and up 340’s that got the big radiator.

I’m going to have to look into it.
Click to expand...

mind like a steel trap: rusty and illegal in 50 states!

i know for certain that 69 and earlier didn't get anything bigger than 22" but if it's a 70+ there could be some xtra-special xtra-heavy duty thing where they got 26's, but to my knowledge everybody got 22's until like 73/74
 
autoxcuda said:
I don’t think any got 26”. Unless that’s an 73-up deal.

In 1970 the radiator tops changed to a square “bigger” look. Also in 1970, they introduced the aluminum water pump
Click to expand...


My first car was a 72 Demon 340. It had the big radiator.

My 73 Demon 340 has the big radiator.

I’m trying to think of all the 340 cars over the years that I was around and I can’t think of one that didn’t have a 26 inch radiator.

It’s very possible I’m not remembering correctly. I know several 318 cars that had a towing package or something (maybe it was AC) and they all had the big radiator.

Hmmmmm…
 
73 was first year for 26" radiators in A bodies

70-72 max size was 22" with AC

The tune up that was mentioned will be numero uno in whether you can keep temps under control. Set the engine timing at idle around 14-18 BTDC to start with and run it. Limit mechanical to stay inbounds for total/
 
Last edited:
The car in question is a 73 Duster 6 cyl that i cloned into a 71 Duster, the 340 is a 69 but im dressing it like a 71 340
i was looking at the Robert shaw thermostats, what temp would you guys recommend? Also what flowkooler would i need, the 1701-3 or the 1700
 
Professor Fate, i cant answer your engine questions yet, machinest hasnt gotten back to me yet..but point well taken..thank you
 
crackedback said:
73 was first year for 26" radiators in A bodies

70-72 max size was 22" with AC

The tune up that was mentioned will be numero uno in whether you can keep temps under control. Set the engine timing at idle around 14-18 BTDC to start with and run it. Limit mechanical to stay inbounds for total/
Click to expand...


My 72 Demon had a 26 inch radiator. It was an early 72.
 
73 parts book (see how the smallest of details changes the direction of the conversation!)

26 was for the win!

1737326596970.png


1737326671108.png

1737326702475.png

1737326723277.png
 
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