[68RT]

If the thermostat is working properly, it is not the cause of the higher temperatures. Thermostats limit the MINIMUM temp. Make sure you do not have a collapsing lower hose or coolant flow restriction. When you are cruising, what is your speed? If it is lower speeds, then you might have a fan or ducting problem. Not sure if it pertains to the 340 but there was two different rotational direction water pumps and if they get mixed up, you have heating issues too.

 

[scatpack70]

Hey, thanks for your help. The motor is newly rebuilt by others and the hoses look brand new too. I know that doesn't mean they are but I'm assuming they are. I don't know about if there is a coolant flow restriction or not, I guess I could take one of the hoses off one at a time and see how it flows. My cruising speed was about 55mph to 60, not real fast. It has a flex fan installed right now, not a viscous type or clutch fan. The fan appears to be OK. I have no idea about the water pump thing, I'd have to ask a real mechanic about that. I was just curious about the temp. It's probably OK, it's just that I have an automatic transmission and I didn't think the higher temps would do it any good. I'll keep an eye on it. Thanks alot for your help.

 

[dana44]

I thought the reverse flow water pump was used on the serpentine belt pumps, belt pumps all turn the same direction, but I could be wrong on that, something else I might learn.

With that said, if there is an overflow canister and it appears to allow overflow to go out and return with the same amount, check the flow across the top of the radiator to make sure it is good. Suggest turning the heater on full blast without the fan on to allow flow through the heater core (and release any air in there), some have a valve, some don't, also. Watch the flow of fluid with the cap off, it may take a few minutes for it to warm up, but you should see it flow across. If it doesn't it could be a plugged radiator or restricted flow through the radiator. If this is good, then, as said, ducting, or the stopping of air going around the radiator between the radiator support and the radiator edges top and sides will help ensure it isn't bypassing the radiator. The radiator cap itself can allow the temp to rise also, preventing the pressure from building properly, so take it a little bit through the paces, take the speed up higher than 60, say up to 75-80, see if the temp stays at 205. If it does she should be OK, if it keeps climbing and goes above 215, do the stuff noted above and what 68RT said, and the only last thing that would have her run a little warmer than you like is running the carb lean. How does the temp do running around in town? If it is up in town also, then start with the flow things and then go to the carb running lean. What carb and intake are you running?

 

[scatpack70]

Hey Dana, I will definitely check all those listed above. Running around town is about the same temp as before (205) maybe closer to 210. The carb is not running lean,if anything it is too rich. I'm running an Edelbrock Performer dual plane intake with a 575 cfm Speed Demon carb. There is no shroud around the radiator either, maybe I should get one. What did you mean by 'the stopping of air around the radiator'? You mean air inside the radiator that shouldn't be there? Thanks.

 

[dana44]

The radiator bolts to the radiator support. Many times this radiator support has holes in it, a gap between the radiator and the radiator support, the support and the top of the radiator so when you close the hood there is a gap. The reason a radiator won't cool as much as it possibly can is because the holes and gaps allow the pressure in front of the radiator to be close to the pressure behind the radiator and the normally forced through the radiator air doesn't have to pull as much heat from the radiator core, thus she warms up higher than she should. Start with simple duct tape if you want, and tape over any gap where wires pass through the radiator support, along the edges of the radiator, and the hood should actually have a piece of rubber flap that goes along the edge of the hood and against the top edge of the radiator support. The more of these things closed up to force the air to pass through the heat of the radiator core, the cooler she will run if it is flow as the problem.

To the carb, how many turns are the two needles turned out? Or how far can they be turned in before she starts stumbling? This is the fastest way to determine rich or lean, similar setup as a Holley, so let me know where they are and then I can tell you if it is lean, rich or OK. Start warmed up, at idle, see how far you can turn them in, like quarter turn at a time side to side, before the idle starts to stumble. At that point, shut her off and gently turn them in the rest of the way until they bottom out gently, but record the amount of turns and part turns you move them before you return them back where they were.

 

[68RT]

I thought the reverse flow water pump was used on the serpentine belt pumps, belt pumps all turn the same direction, but I could be wrong on that, something else I might learn.

With that said, if there is an overflow canister and it appears to allow overflow to go out and return with the same amount, check the flow across the top of the radiator to make sure it is good. Suggest turning the heater on full blast without the fan on to allow flow through the heater core (and release any air in there), some have a valve, some don't, also. Watch the flow of fluid with the cap off, it may take a few minutes for it to warm up, but you should see it flow across. If it doesn't it could be a plugged radiator or restricted flow through the radiator. If this is good, then, as said, ducting, or the stopping of air going around the radiator between the radiator support and the radiator edges top and sides will help ensure it isn't bypassing the radiator. The radiator cap itself can allow the temp to rise also, preventing the pressure from building properly, so take it a little bit through the paces, take the speed up higher than 60, say up to 75-80, see if the temp stays at 205. If it does she should be OK, if it keeps climbing and goes above 215, do the stuff noted above and what 68RT said, and the only last thing that would have her run a little warmer than you like is running the carb lean. How does the temp do running around in town? If it is up in town also, then start with the flow things and then go to the carb running lean. What carb and intake are you running?

Serpentine pumps do turn the opposite direction and there have been problems with getting the two mixed up as they both bolt up the same. It has come up before here on ALLPAR before as a cause of overheating. The only way to know is to pull the pump and look at the impellar for proper vane angles.

 

[dana44]

Isn't the reverse pump have a problem attaching the pulley on the front? Or was there a period where V belts were used on the same reverse direction pumps?

 

[scatpack70]

Hey guys, thanks for getting back. Dana I think I understand what you're talking about now on the air space around the radiator, and everything looks pretty sealed up around it. I think it's OK. As far as the carb goes, I adjusted the four mixture screws one full turn out. When I got the car, the screws were a turn and a half or so out and I had lots of smoke and poor performance. I had to lower the float levels also, they were way too high. Now with the screws one turn out, it runs better but not great.I was going to try doing the adjustments with a vacuum gauge while in gear, but I haven't had time. I'll try your suggestions on the carb and the radiator this weekend. Thanks a bunch.

 

[dana44]

OK. If they are good at 1 to 1.5 turns out, she is good, higher float level not so good, so good thing you caught that. The other thing is, what is your advance look like?

Total, including mechanical advance (usually 28 degrees), should be no more than 36-38 degrees, too much advance (put 10 degrees at the harmonic balancer) can hurt both mileage and have her heat up a little bit extra. It's that radiator support that is the biggie, holes that allow air to get into the engine bay without going through the radiator can add a few degrees whether a person realizes it or not.

 

[CudaPete]

You need a shroud.

 

[tazdevil]

Absolutely get a shroud. Make sure the fan blades are half way in to the shroud.On timing, set initial to 8 degrees at idle. Get a dial back timing light, and check advance at 3000RPM. It should run at around 34-36 degrees. If it exceeds that number, remove the vacuum hose and insert an allen wrench that fits the socket inside the vacuum can. Turn the wrench clockwise and check advance again, repeat until you do not excced 34 degrees.
Cured my identical heat issues for sure.

 

[scatpack70]

Thanks for the info Taz, I've realized that I mispoke earlier in the post. There is a shroud on the radiator, it's just so thin I guess I didn't notice it. In fact, the blades barely go into the shroud at all, maybe I should find another one. When I turn on the heater and the fan, it does stabilize the temp or bring it down just slightly. I took a look at the radiator flow with the cap off and up to temp. and it looks OK. I took the car out and drove it at highway speeds (70 mph) for 5 minutes or so and the temp. stayed around 197-200 until I slowed down to around 45, then it creeped up 205 or so. With the elec.fan it seems to be OK though, it doesn't get any higher than 210, does that seem reasonable? As far as the timing,I can't set the initial down to 8 degrees at idle, not even down to 12 degrees for that matter, the engine won't idle it just stumbles. I just put a recurve kit in the distributor with the soft and medium springs thinking I could bring the initial timing down a bit, but with this camshaft I guess it just won't run that way (280 dur. 474 lift.) I've got it adjusted to 16-17 degrees initial right now and it runs OK but it makes the overall timing 40 degrees at 3000 rpm and I guess it makes it run hot.It's kind of hard for me to figure out right now, I talked to Dana 44 on the other string about the timing and he gave some ideas and I'll do the best I can. For the temp. I'll find another shroud and see how it goes, maybe a viscous fan might help too. Thanks

 

[dana44]

What kind of radiator cap do you have? Does it also have an overflow canister to catch overflow? I drove around for years in my old 68 Charger with a radiator cap that for some reason didn't go against the face of the rubber to clamp it down hard enough to keep the pressure up where it needed, and as long as the temp wasn't above 90 degrees outside I was OK, I didn't know the cap was incorrect for the radiator until later in life. You may try a 16psi cap without the lever and an overflow canister, on top of everything else done. If you have a flex fan (also), since they flatten out at higher rpm, they do tend to make her run hotter, too. Still need to get that advance backed off a little bit more, too much advance does make them run warmer, which is also why slower rpm made the temp go down. I had that same thing with my 318 Barracuda (gas mileage suffered, too).

 

[scatpack70]

Hey Dana, looks like a 16 psi cap without a lever on the radiator and it's in good shape but no overflow canister. I'm looking into getting another shroud and perhaps another fan also. I managed to back the timing down a little bit this weekend and when we took it out for a spin yesterday it ran quite well and fairly cool,(190-197) but it was cool weather anyway, about 50 degrees or so. I think we're pretty good for now, at least until I get the other equip. Thanks a bunch for your help. I'll go more into detail about the timing on the other string. Steve.

 

[dana44]

Get an overflow canister on her, that will keep fluid returning so you don't have to check it every time you go to drive her for starters.

Fan, make sure it isn't a flex fan, and a clutch fan is always a plus. Mopar made some very good 5, 6 and even seven blade fans over the years, but a clutch portion can help with that better shroud.

 

[scatpack70]

I'll look into it, those are some good ideas. I'll let you know what I can find. Thanks again.

 

[scatpack70]

Hey guys, I had another question about the Dart referring to the radiator fan. I've got a good fan on the car right now, its a MP six blade cooling fan. I'm thinking of getting a thermo controlled clutch unit for it like you guys suggested. My question is, do I need to buy a unit specifically for the 340 engine? or can it be a unit that just has the same bolt pattern from any vehicle or engine? The thing is, the new ones on the Moparts website are kind of pricy and I wanted to know if I can just get one from the junk yard. But from what vehicles would mine be compatible? What do you guys think?

 

[scatpack70]

Almost forgot, does anyone know where I can find the correct radiator overflow canister for the '70 Dart swinger?

 

[CudaPete]

I beleive in 1970 the overflow canister was ......the ground