yes - another running hot question. Freshly rebuilt 350, nothing crazy and mostly stock. Mild cam. Pertronix distributor. All timed and running great.
Still has the break in additive in the oil.

Idling, the temp rises to 220-230. Driving is no issue. Temp comes right back down to 190 deg or so. Just replaced the old 4 blade fan to an 8 blade. Made no difference.

The radiator is OEM that I had boiled out and restored. I was hoping to keep everything mostly original on the car but not opposed to swapping it out for something better.
I don't have all the radiator insulation seals installed yet and will do so but not sure if that will make a huge difference. I believe its a 180 degree thermostat.
I know its opening at about the right temp and verified with IR thermometer.

What new radiators would you guys recommend for this? Its an automatic trans.

I know these cars ran great in the 70's all with OEM stuff and was wanting to keep it mostly that way as designed, but I need to get the temp down.
I had a 72 in high school and drove the beans out if it until I graduated college - all oem. Honestly, the only thing I had to do to that car was oil changes and tune ups!
Should have kept that car.

Thanks for any recommendations on this.

 

Are you running an HEI or a Pertronics points replacement type distributor? What are your timing settings and is the vac advance hooked to manifold vacuum? How far is your new fan from the radiator and is it a fixed fan? Is there a shroud installed? With the temps being normal while cruising, this is not a radiator issue.

 

Distributor is a HEI from Summit. https://www.summitracing.com/parts/sum-850006

Running a fan shroud from Fusick. The original one was lost in the rebuild process.
I had the original 4 blade fixed fan on it and just swapped to an 7 blade/clutch. Clutch is the short version.

I will recheck the timing settings later when I get home. Will also verify manifold vacuum on the vac advance port as well as the distance
of the fan to the radiator. Thanks..

 

With a fan clutch and shroud the fan needs to be sticking halfway out of the opening. Post a picture of the fan/shroud setup from a couple of angles.

 

Autocity classics has a good price on a new Aluminum rad with the big tubes.

 

The stock radiator was a two row. The clutch fan should be more than adequate.There are a lot of other possible overheating causes, including timing (especially vacuum advance at idle) and jetting (E10 burns leaner and thus hotter than straight gasoline).

 

You had the radiator cleaned but how do you know what is still left behind and buildup in the tubes? I would get a new radiator.

 

Thanks... those prices are definitely reasonable.

What should I be aiming at for intial timing at idle? IIRC it was set at somewhere 10°-12° I will check it again tonight with vac advance line off and on to see whats happening there.
Will check vac level as well and make sure its coming off the manifold vac port.

You're right - I have no idea. Its more the fact that the temp goes down while driving that led me down the path that the radiator wasn't that bad. Could be
faulty logic on my part.

 

Initial timing depends on a number of factors. What are the mechanical and vacuum advance curves in the distributor? Is vacuum advance connected to ported or manifold vacuum? What grade of gasoline are you using?
You have an aftermarket distributor, so any factory initial timing specs are meaningless. Ideally you would want to set total timing first, which will define your initial timing. If that initial timing doesn't work for your combo, you need to change the mechanical advance curve to hold total timing while allowing more or less initial as needed.

 

Your logic is correct. A new radiator isn't going to help as you said it's fine while driving, which is where the larger heat load is and apparently the current radiator is able to shed the heat effectively.

Ignition timing and idle air flow are where I would start.

 

I am running that one, the 9+ to 1 compression Olds 403 never got above 190 with it. A shroud should also be considered as well. Get the rad side seals in place as well.

 

The saga continues with trying get the temps under control.

So far, i put in a new radiator, 7 blade clutch and fan. Timing is spot on, carb had an issue so its been rebuilt (even new bushings).

Car is running great - better than before I started all this, but sitting at idle, the temperature still climbs up to 220 deg an beyond.
No issue at all when driving it. Goes right down to 195 or so. When its sitting at idle and temp climbs up, higher rpm also brings down
the temp.

This car was completely gone through over the last few years. To me it looks like the fan is about halfway in the shroud. I'm wondering about the pulleys and
the possibility that they're not right. Water pump pulley is KN. Not sure what the crank is - but I believe is a 2 groove. The car in non-A/C, auto, ps, pb.

What am i missing? It seems that the coolant isn't flowing enough. What pulleys should i be using (1972 350ci). Appreciate any advice.

 

You say the timing is spot on, but what is it set to? Are you using the vac advance, and is it connected to ported or manifold vacuum?

 

These guys are steering you right, I just want to put my .02 on the radiator. If you decide to do something with it I highly recommend having the original re-cored and not going to the ugly aftermarket aluminum radiators. If you must go aluminum, please paint it black. Nothing worse than seeing an old car that they are trying to maintain the original look but then have an aluminum radiator.

If you need a bigger than 2 row radiator because of aftermarket upgrades in the engine, find a copper 3 or 4 row.

 

My Autocity aluminum dual 1 1/8" core cooled the 9+ to 1 403 with ease and if painted black would look stock, stamped tanks. I assume you put all the flaps back in place to direct flow? What radiator did you go with? Honestly even a 1 core aluminum plastic replacement rad should be no issue. I used the factory 2 core that was recored at some point with slightly under driven aluminum pulleys, factory four blade, no shroud and never saw above 195 in my 70 Cutlass S. What pistons did you use in the rebuild? Again, total timing should be 34 to 38 and try vacuum advance off manifold. If it is Pertronix aftermarket distributor, the timing curve can be changed with springs and 3 different limiters. Sorry to see this issue, beautiful car and the 350 usually doesn't run hot. I went through hot running with my G body but it was the opposite, mostly at speed. The GN rad surround finally fixed it. Good luck.

 

Overheating at idle - that generally indicates its not the radiator as almost any radiator has enough heat rejection capacity to handle a motor at idle. When radiators are not sufficient, the car will overheat at highway speeds when lots of heat being generated by the motor.

Anyway, overheating at idle is usually an airflow problem. You could try augmenting airflow at idle with fans etc to confirm (do you have access to a bigger fan you can put in front of grill and blow air through?). Are all the factory baffles in place? Air will try to go around the radiator and the factory baffles make sure the fan is able to just suck air through the radiator and not around the radiator.

 

Was it bored with new pistons as part of "nothing crazy"?

 

Checking on the portion about the vacuum source... will get back to you on this.

I went with a Cold Case GMA43A, 2 row, 1.25" tubes, painted black with Eastwood thermally conductive rad paint. Added 7 blade fan with clutch. Fan sits about halfway into the shroud.
This car underwent complete restoration during the time period of about 10 years. The original guy that tore the car apart absconded with a bunch of $$ and left parts scattered all over the place. There is
a better than probable chance that some parts may not be correct for the car like pulleys, water pump, .... I managed to get it all back together but battling these last details.


Thank you - I know there are a few of the insulators missing and I'm putting them back on. See above for the radiator I put in. I dontt have all the info on the motor rebuild as they went out of business during covid. I know it was bored out with new pistons but it was not done to pump up the HP, just mostly as close to stock as possible with a mild cam.
Distributor is a Summit HEI 850006 (much to my dismay as it interferes with the OAI air cleaner). I till tackle that problem another time. For now, i just need to get the idling temp down.

This is interesting and I am wondering if its either an airflow issue or coolant flow issue (ie... wrong pulleys and maybe wrong water pump). The new fan (7 blade/clutch) I put on is the same OD as the original 4 blade fixed fan.
Looking closer into the baffle point you and others brought up. I know there are a few missing and will solve that asap as soon as I verify the timing again.

I really appreciate all the comments from you guys and will make sure I get all the answers and make this a worthwhile conversation. I know your time is valuable.
Dave...

 

Initial timing at 12⁰, total timing at 34-35⁰ and it is connected to ported vac off the carb.

 

Try connecting it to manifold vac, you'll have to lower your idle speed.

 

When you say halfway, are you saying that it should be on the closer side to the radiator side of the shroud? (like the left image of the pic). That's actually how it is now.

It is not like the right image above.

 

Right image, fan blade half in/half out. Also seal if not done already the forward edge of the shroud. The mission is to make any and all air pulled by the fan to go THROUGH the rad, not allowing any air to get around the edges.

Use an infrared to shoot numerous points in the rad for cool spots indicating a blockage but that should manifest on the highway vs at idle.

 

Here's a few shots of the front of the engine.

I need to verify that I have the correct water pump and pulleys. Any ideas on what diameter pulleys need to be on it (crank and pump)?
They are both 2 groove pulleys now. Pump pulley is ~ 7"

Also, what is the correct water pump? The manual shows a 5.072" height pump for an A body without A/C but I haven't been able to locate one. The one on the car is about 6" now estimated (hard to measure).

As I mentioned earlier, at idle the temp creeps up to 220+, revving the engine brings it down indicating that more flow of air or coolant is helping. What's the best way to separate the two issues to identify the problem?

 

Will take a look at that. Thanks.

 

No one makes the correct 5.1" pump with the smaller inlet used on the 1971-72 cars. Short of rebuilding an original, the only option is Airtex AW773. This pump requires use of the larger 1968-70 lower radiator hose and a bushing at the radiator end to fit the smaller outlet bung. With the 5.1" pump the pulleys should be 405462 KN for the water pump and 405459 KJ for the crank.

 

Maybe consider swapping water pump with an after market high flow one ?

 

Are those fan paddles facing the correct way to pull air from the front to back? I can't tell from the picture.

 

Joe, since your knee deep what hose reducer would be used? Ty

 

 

You are missing these.

 

Yes, he is those two pieces and there should be the side rubber pieces against the radiator as well. March has a set of more overdriven aluminum pulleys supposedly for the 5.25" water pump. They are available in a black anodized coating to look more stock but will set you back over $300 for 3 piece set with the optional coating. It is either that or go to a 5.6" or 6" pump and matching pulleys from a member here. CVF also has a couple of different aluminum sets but only for the 5.6" and 6" water pumps.
https://marchperformance.com/oldsmob...e-16083-c.html

 

The lower splash sheild from the bumper to the core suport is missing also.

 

How many miles since the rebuild? A freshly rebuilt engine will run somewhat hotter because it is still tight.

 

I love these overheating threads. 🤣

Is the oil cooked yet?

 

Yes - they are correct.

Yes - I know those are missing but at idle does it really make a lot of difference? We do have a shroud and the rubber seals on the side of the radiator.

Looking into that - thanks.

Its been about 200-250 miles. Not much as I dont want it to overheat. Runs pretty cool while driving.

Heck no - not even close - i hope!

This is next on the list. Looking into this now. Flowkooler is the only one that I've found so far.

 

Thanks for the link. I may try those if this high-flow pump still has issues. I was looking for something like this. Appreciate it.

 

I hate to say it but the aftermarket water pump is not going to help.

 

I have not re-read this thread but by chance did you check and see that the timing mark on the balancer is really top dead center? If it is not and you are timing by the mark, your timing is off.

 

Yes - good suggestion. There is an aftermarket harmonic balancer with graduation marks. We did verify that TDC was with the zeroes in alignment on that and the timing plate.

 

I'm about out of ideas for things that can cause this overheating issue. I know the motor is still tight from the rebuild. New radiator, thermostat, 7 bladed fan, clutch. Shroud is new too. No - i dont have all the
seals on it but I dont think they really contribute much sitting still in my driveway. Sealing up between the radiator and shroud as well as fan placement in the shroud seems to be more critical to me.
Heck - i read some back posts here that 350 cars didn't even have shrouds from the factory.