400 getting warm with A/C
 

I’m really trying not to beat a dead horse, especially as of late, but I also didn’t want to hijack anyone else’s thread.

My 77 T/A has a ‘69 400 in it. Nothing crazy about it. Milled 6x4 heads with 8.8 CR, Comp XE 262 cam. I’ve never had a problem with engine temp in the past. I’ve had it for 11 years. Not sure what kind of radiator is in it but I don’t think it’s aluminum.

In preparation for adding A/C to my car this year I got curious about actual temp compared to my factory gauge this year so I installed a mechanical gauge temporarily. Turn out my factory gauge was reading high due to the sender and my engine was only running around 160° at idle and in town and near 170° on the expressway. I live in NW Ohio and I do drive the car with temps into the 50s so I thought that engine temp might be too cool. I swapped out what I found to be a 160 tstat for a 180. Even on 90+ degree days, my temps stayed around 180 idle/in town and 190 on the highway.

Now I’ve added A/C and the temps above with the 180 tstat are consistent with the exception of at idle. They creeped up near 210 once. As soon as I start moving they drop. I realized my fan clutch was a standard duty so I replaced it with a heavy duty this weekend.

Today it’s about 80° ambient. All was the same as above except at idle which still crept up to 200-205 at idle before I shut the air off and took it around the block to cool it off a little faster. It did take a while, maybe 8-10minites, to get that warm at idle, longer than with the SD fan but, I still feel like I’m missing something.

Before I throw parts at it I wanted some other opinions. The thing ran as cool as can be on the hottest days so I was surprised the A/C made the difference it did.

It does, not only is the condenser blocking the radiator but is is also hotter than ambient, why you need a tight shroud and a seven blade clutched fan (or good electric fans). The rise at idle is common for a marginal system since not getting any additional air flow. Also think the non AC radiator only had two rows. Mine has four. I'd go back to the 160F thermostat and possibly look into a bigger radiator.

I do have a tight fitting shroud but only a 5 blade fan. I wonder if that would make a difference.

The car was originally an AC car but the radiator was newish when I bought it. Maybe a dumb question but is there a way I can tell if I have a 4 row radiator?

7 blade will make a difference, particularly at idle. I can usually just look in the radiator cap or feel with finger, number of tubes is pretty obvious.

Ah yea, I see that now. Never knew exactly what 4 row meant or entailed. Never needed to know lol. I looked at mine and it’s a 4 row actually so I suppose that’s good. Just gotta figure out what I’m missing otherwise maybe beginning with a 7 blade fan

What is the diameter of the water pump pulley and the crank pulley as air cars water pumps run faster than non ac ?
Water pump pulley should be 6-1/2" diameter and crank pulley should be 8" diameter for ac

You know, I’m not sure. I’ll have to try to check after work tonight.

Crank is definitely 8”. WP pulley is probably 6 1/2. It’s not as easy to measure accurately on the car but I’m guessing my measurement is close enough compared to whatever the non-ac size is.

Your car will have a cross flow rad. Because the tubes are horizontal, sediment can & does form over time in the lower tubes. So rad capacity is reduced. I would remove the rad & take it to a rad shop for professional cleaning, where they should remove the tanks & rod out the tubes.

Good point. I may look into that.

Is the increase in temp (with or without ac) something to be expected? I don’t remember it doing that in years past although it could. Makes me wonder, if it’s not an airflow problem (highway speeds) could it be a coolant flow problem as in a dying water pump?

do you have the ac idle increase solenoid on the carb & working? i think ac cars bumped the idle up a bit with the ac on to increase air flow & coolant circulation. just a suggestion to verify.

a 7 blade fan should help quite a bit to increase air flow. & definitely at least try a radiator flush additive &/or back flush the radiator & heater core & add new coolant before taking it out to be disassembled &/or cleaned if its not needed. when adding new coolant consider dropping the anti freeze percentage & add a coolant additive like water wetter or hyper cool.

if this isnt a daily driver in extreme winter temps or is stored in a garage that doesnt get too far below freezing, having higher water % will help cooling, just be sure to verify the mixture & keep it in a safe temp range... 50/50 is good to like -20 or -30 or so, not too many places ever see that cold of a temp.

I do not have the idle solenoid yet but I’m going to order one. Just haven’t yet. The “tests” I’ve done at idle have been with the rpm either set or held by my foot a little higher.

I’ll have to see if I can find a 7 blade fan. I didn’t realize in my short attempt to find one they don’t seem to be readily available unless I wasn’t looking in the right place. Any advice on where to find a fan would be appreciated.

I should look at my receipts I got with the car to see if I can tell when the radiator was purchased. It’s at least 11 years old. Coolants been changed a few times over the years from pulling the motor. The most recent time the motor was out was 2017. I’ve never tried flushing the radiator though. Like I said I’ve never had an ounce of an issue until I added AC into the mix.

I can look into the coolant mixture thing too but my garage is uninsulated and detached to it is quite cold. I’m in NW Ohio so we’re normally not too far into the negative but it does happen. The google shows 6 years ago being -20 for an all time low that year and 2019 was down to -10.

ok just checking on the solenoid, sounds like you mimic that with raising the idle though so that probably wont change the results.

pretty sure most places like our host ames sells the 7 blade fans but not positive. pretty sure i have a couple off of 2nd gen firebirds i would sell if they are the same size as yours, i will check & let you know.

-10-20 is pretty cold, im in northeast iowa & we see the same temps here but its usually for a long time in the dead of winter, set a record last year of -30 & was -teens to -20 lows for a week or more straight... i hate winter! but i do have a insulted garage that stays at or above freezing during those cold spells so i keep mine at about a 40% concentration & use hyper cool just because its cheap. never had any overheating issues with my cars, even back in the 90's with a partially clogged 4 core & a mild built 455. but each car/engine is different.

as for the flushing or cleaning, sounds like your radiator is new enough & you keep up on replacing coolant... i doubt its dirty or clogged enough to require professional cleaning. you can usually see the top few rows to see how much residue is on them or if they are filled with debris. i would just try a back flush if its close to time for a coolant change & see what comes out, im guessing you wont see any real signs of sediment or dirt to worry about flushing chemicals or cleaning it but always good to check. i have a stock 4 row in 2 of my cars that are 20+ years old & no signs of sediment or clogging & thats with probably less than suggested coolant changes but they dont see too many miles like a daily driver would.

chances are your radiator cleanliness isnt causing or contributing much to your cooling issues, its the new ac & condensor & possibly the 5 blade fan. & the temps you mention arent really that big of an issue, factory t-stats were 195 in most cars & they got up to 210 regularly in summer temps with ac on, as long as the temp drops pretty quick when moving you are probably fine... or shut off the ac for a few minutes if they get too high for your comfort.

What's up, b_hill! I'm finally on this forum, lol. Took my computer forever to finally get the sign-up "picture assembly" captcha working.

I think all the suggestions mentioned so far hold water. You got the correct overdrive WP pulley, you're covering the original function of the AC idle solenoid by boosting the idle to circulate coolant... only factor is the fan.

If you have an original shroud, I'd pick up an original 19" 7-blade fan and see if that helps. My temp rises super fast when I'm using the AC, too, but I think that's because I need to just adjust my idle-up solenoid. The car bogs down big time and the idle sounds like its at around 550-600ish and shaky, even when the solenoid is energized.

Is your car still equipped with the original radiator? If so, yes, it should be a 4-row. Air conditioning warranted mandatory Code VO2 HD cooling, which was a 4 row. Thing is, it may have met its service life if it can't cool anymore with the AC. If you decide to upgrade the rad, a lot of success has been made with the fat oversized 2 rows like Cold Case, Griffin, BeCool, etc.

And yes, a quick rise in temp is very much expected with the use of AC, and a rise to 210 with AC isn't that unheard of. The condenser puts off a lot of heat. What's more important is, does it stop there or does it keep rising?

Thanks 78w72. I’d probably be interested in a fan if you end up finding one.

Nuc what’s up man?!? Lol. I don’t have the correct shroud actually. For whatever reason the car had a 403 shroud when I bought it. Not correct obviously but functionally, I think it works.
No idea if the radiator is original and maybe re-cored but it’s awful clean inside and out.

I wouldn’t even say the temp rises quickly necessarily. I wasn’t paying close attention to how long I let it idle but I’d say conservatively, it was at least 5 minutes but probably longer. I also can’t say if it would creep past 210. It may have slightly but by that point I didn’t want to let it get much warmer so I took it around the block with the AC off to cool it down quickly.

i do have some 19" 7 blade fans, think i have some correct style 400 shrouds too. send me a PM if you want to work something out.

I sent you a PM. Thanks.