340 running hot

[Johnny Dart]

Just curious, Was it a Mopar Performance pump, with the description it was for iron heads/drag racing: this one as shown p5249558, or remember the part# and brand?

View attachment 1715033286

Not saying that this is your exact problem, just pointing something out in regards to water pumps.
6 vein pumps are for AC cars, 8 vein pumps are for non AC cars. Seems like it would be the opposite,right ? They also use different size water pump pulleys.
If you are using a 6 vein AC pump, with a non AC water pump pulley, it can effect your cooling.
On a non AC car, always run an 8 vein pump with the correct non AC pulley.

 

[12many]

I installed a high volume water pump but I don't know how to tell if it is what you are recommending.

I know of a guy with a 360 in an A100 van who for about 1/2 a year was fighting something similar. He checked everything, verified parts as correct, pulley ratio, you name it, new aluminum radiator, the works, did every test imaginable, new and hi perf/flow everything, still ran too hot. Guy was at wit's end. He took another look at the new 6 blade MP pump he was using, assumed to be fine, turns out that after installing an 8 blade w/plate on the vanes it solved the problem. I know some here will disagree, and it may not be the case here, but rule out nothing.

 

[12many]

vintage-vans.forumotion.com/t52684-runs-hot-out-of-ideas Yes it is a van with a unique engine bay but like I said, rule out nothing.

 

[1968FormulaS340]

a 195 is not going to make it run cooler.

Yes, but is isn't going to make it run hotter. He is over 195 already.

 

[70orangeswinger]

a 195 is not going to make it run cooler.

Fan shroud is in place, vacuum advance is hooked up but never tested. I will have to pull the water pump to make sure all is well there. Thanks everyone for all the knowledge you have given me. I will print this off and go through everything listed to try and solve my problem Thanks again.

 

[red67gts]

I had an impeller slipping on shaft on a new pump one time. Wasn't a mopar but it ran me crazy for a while thinking since it was a new pump that it was good

 

[1plydust]

Engine runs hot all the time, even hotter in traffic. If you are driving for any amount of time at around 35 mph it cools down to 180-190. I have replaced the tstat twice and am now running a 165 degree. I tested the cap and it appears OK

My 1994 5.2 Dodge B250 van would run cooler below about 50 mph but would start overheating at hwy speeds, tried cap thermostat. water pump and poured water into radiator with bottom hose off and water came out so i though the radiator was ok so finally i got a radiator off a van like mine and it was a used one but the temp now runs as normal as a new vehicle even in hot weather or hills and traffic. The cores can still flow water but be restricted with build up and slow flow down which keeps it in the engine longer than normal, so at higher speed it causes temp problems.

 

[j par]

Yep a systematic recheck of all the obvious stuff. It's all relatively easy stuff, but it is "where" it is...

 

[Rapid Robert]

Yep a systematic recheck of all the obvious stuff. It's all relatively easy stuff, but it is "where" it is...

Agreed, it is where it is & for sure let us know what that ends up being!

 

[j par]

I found the last guys overheating problem, the motor that I just bought that i'm reconditioning..

 

[RustyRatRod]

Nobody ever said the 195 stat will fix it. The 195 stat is a huge mistake. Huge. This lower stat myth needs to be pounded into oblivion once and for all. It's one big part of the problem. Running a 160 stat is the same as running none, because once the engine reaches 160, it's open all the time. It increases the wear on the engine many times more. All of this has been beat to death so much, it's pathetic. I am to the point where I will read these and just laugh and move on. No one gives a **** about anybody's 30 plus year experience. All most of you younger guys want to do is cram the biggest wheel under your ****, do a 3G Hemi or LS swap. Pitiful.

 

[MOPAROFFICIAL]

I would run an 8 blade water pump and no smaller than a 18" fan if no shroud is used.
Despite the culprit..the 8 blade pump will not move too much but will move more at lower speeds than the 6 blade more efficiently cooling the engine....btw it won't matter if you run a 165 or185 stat....but I'm not into the 195 stats, higher average temp..
Things that help with "cooling system related" low speed cooling issues..are fan shrouds, bigger fans, water pumps with more blades...assuming the radiator is functioning and up to the task aka correctly sized. High speed issues "cooling system related", collapsing bottom hose, too small a radiator, fan belt slippage, clogged radiator tubes, bad head gasket or cap bla bla...you can search. Good luck!

 

[1plydust]

I found the last guys overheating problem, the motor that I just bought that i'm reconditioning..View attachment 1715033487

Yes, I had a block full of jell like crud in a late 60s 318 that caused it to run hot also!

 

[Marcohotrod]

an n9y is the stock plug for a 1968-71 340. does it have a CLUTCH fan?? sometimes they go bad and constantly slip. the 6 blade pump was initially used on A.C. and H.P. models, in the engine book by a Chrysler engineer "only the lower horsepower required A.C. pump was used in 1974-82 engines".

 

[67Mungo]

I’m a new classic Mopar owner and have been obsessed with this issue as well for a few months. 67 Barracuda / 340-4, 26” radiator and shroud & new 160 Deg stat. Was running around 220 which just seemed too high in normal conditions. Replaced with a heavy duty fan clutch and got me down to 210, but barely at my minimum threshold. Lone behold it’s the first 70 degree day in North Texas a couple months later and ran at 178 moving & 185 at a red light. Later in the day when it warmed to 85 outside ran a hair shy of 200. At least with my situation I’ve come to the following conclusion. Texas is hot. 95-105 degree days she’s going run close to 210-215. Fall and winter in the 80’s outside she’ll run where expected 180ish. Point is I underestimated to effect of ambient temperature with a mechanical fan on a 50 year old car. May be factor for some of y’all if in a hot climate.

 

[Dan the man]

I installed a high volume water pump but I don't know how to tell if it is what you are recommending.

A high volume water pump will cause it to run hotter as the water moves through the system to fast, not allowing it to cool.

 

[Dan the man]

Does it still have a Shroud on it?

JW

Fan blade proper distance from the radiator? Is the fan belt in good condition, does the belt have proper tension? If it didn't overheat before you rebuilt it then it's something that was done when the engine was put back together. Bad thermostat?

 

[jazak5]

an n9y is the stock plug for a 1968-71 340. does it have a CLUTCH fan?? sometimes they go bad and constantly slip. the 6 blade pump was initially used on A.C. and H.P. models, in the engine book by a Chrysler engineer "only the lower horsepower required A.C. pump was used in 1974-82 engines".

Yep ditch that factory fan clutch and go with a hyden HD/truck thermo clutch 90% lock up night and day >>> I saw a 20 degree drop between inlet /out let with a good lazer thermometer >>>>>same day/conditions

 

[RustyRatRod]

Nobody ever said the 195 stat will fix it. The 195 stat is a huge mistake. Huge. This lower stat myth needs to be pounded into oblivion once and for all. It's one big part of the problem. Running a 160 stat is the same as running none, because once the engine reaches 160, it's open all the time. It increases the wear on the engine many times more. All of this has been beat to death so much, it's pathetic. I am to the point where I will read these and just laugh and move on. No one gives a **** about anybody's 30 plus year experience. All most of you younger guys want to do is cram the biggest wheel under your ****, do a 3G Hemi or LS swap. Pitiful.

Glad this comment came back to the top, so I can clarify it due to recent experience. In tuning Vixen, I discovered that she responds best with a 160 high flow thermostat. That was a big part of why I was able to get her to run ping free on pump gas with 175 PSI cranking pressure. So it's all dependent on your combo and tune.

As has been said all over this forum, it's all in the tune.

 

[Bewy]

Nope, you want the coolant to flow faster, not slower [ post #41 ]. See link below.
Retarded ign timing &/or lean cruise mixture will cause hot running. W/pump. The gap between the impeller blades & the pump body should be minimal, almost touching. This ensures that the coolant captured by the blades has no escape route & that the coolant gets pumped into the engine.
Nothing pulls air like a 19+ inch, steep pitch, mech fan. Replace your clutch fan if old or questionable.

www.stewartcomponents.com

 

[RustyRatRod]

Nope, you want the coolant to flow faster, not slower [ post #41 ]. See link below.
Retarded ign timing &/or lean cruise mixture will cause hot running. W/pump. The gap between the impeller blades & the pump body should be minimal, almost touching. This ensures that the coolant captured by the blades has no escape route & that the coolant gets pumped into the engine.
Nothing pulls air like a 19+ inch, steep pitch, mech fan. Replace your clutch fan if old or questionable.

www.stewartcomponents.com

Exactly! Get it out of the engine as quickly as possible!

 

[Dan the man]

Nope, you want the coolant to flow faster, not slower [ post #41 ]. See link below.
Retarded ign timing &/or lean cruise mixture will cause hot running. W/pump. The gap between the impeller blades & the pump body should be minimal, almost touching. This ensures that the coolant captured by the blades has no escape route & that the coolant gets pumped into the engine.
Nothing pulls air like a 19+ inch, steep pitch, mech fan. Replace your clutch fan if old or questionable.

www.stewartcomponents.com

I've always read and been told that if the coolant

Exactly! Get it out of the engine as quickly as possible!

But if it doesn't spend enough time in the radiator where air can be drawn through, the coolant can not get cooled down, known fact.

 

[RustyRatRod]

I've always read and been told that if the coolant

But if it doesn't spend enough time in the radiator where air can be drawn through, the coolant can not get cooled down, known fact.

Known mistake.

 

[Dan the man]

Known mistake.

I could be miss informed on the topic. But it does make sense that if the coolant passes through the radiator to fast how can it get cooled down? Please explain this to me as I don't think I understand. If the engine ran cool enough before the engine was rebuilt is it possible that the cam timing could be wrong? If the owner reused the pulleys, fan blade, water pump, radiator then it would have to be ignition timing, camshaft installed incorrectly, radiator hoses clasped, clogged exhaust system. Is any of the items that I mentioned a possible cause for the problem? I don't mean to come off as a expert by no means. I'm trying to pay attention and not sound like a know it all because I'm not. I believe that I can learn different things everyday.

 

[RustyRatRod]

I could be miss informed on the topic. But it does make sense that if the coolant passes through the radiator to fast how can it get cooled down? Please explain this to me as I don't think I understand. If the engine ran cool enough before the engine was rebuilt is it possible that the cam timing could be wrong? If the owner reused the pulleys, fan blade, water pump, radiator then it would have to be ignition timing, camshaft installed incorrectly, radiator hoses clasped, clogged exhaust system. Is any of the items that I mentioned a possible cause for the problem? I don't mean to come off as a expert by no means. I'm trying to pay attention and not sound like a know it all because I'm not. I believe that I can learn different things everyday.

It's very simple. IF the radiator is optimal for the vehicle and combination, it will cool the coolant faster than the engine can heat it. I'm not just arguing theory, I PROVED it through my own experiences. Once with my 75 Ford F250. With no other mods, I flushed the system and installed a high flow 160 thermostat. The temp gauge barely moves off the first line, and it's right. Coolant coming out of the engine is about 170* and goin into the engine is about 88*.

With Vixen, once I installed a high flow 160, her temp coming out of the engine is about 167* and going into the engine about 79*

The two radiators in those vehicles slap GET IT DONE and that's the the key. Having the most efficient radiator possible. The reason for the 160* thermostat is this. If you allow the engine to get to say, 190 or 195, there's not much "cushion" before it reaches what I call the point of no return. That's when the cooling system just gets maxed out and cannot shed heat anymore. It's a little different for each cooling system, but once reached, the engine just keeps heating up. So, if you open the thermostat earlier, you don't allow the engine to get to that point.

The reason for the high flow thermostat is exactly what we're discussing. Getting the coolant out as quickly as possible. If you find yourself having to allow the coolant to stay in the radiator longer, it's because the radiator is not doing its job for "whatever" reason. Not big enough, partially stopped up, or "whatever". A good optimized radiator that does its job efficiently will shed heat very quickly and allow that coolant to get back into the engine so as not to allow the engine to reach the point of no return.

Generally speaking, a stock to mild engine is not as "picky" when it comes to everything working in conjunction. But when you couple high compression, a big cam, lots of initial timing all in a small compact space with a small frontal area for air flow, you need to optimize each and every part of the cooling system, and leaving the coolant in the radiator too long does not achieve that. Hope all of that made sense.