Hey guys, I need to get this ironed out before I install the big block.

I've always had cooling issues with my current 350. I'm pushing the timing as far as I can (24* initial I think, vac can unhooked), original fan blade with new stock clutch (blade has a couple of nicks but nothing bad), original shroud, rubber(?) side pieces in place to cover the gaps, new water pump (for AC) when I did the engine refresh.

Mostly I have trouble sitting in traffic, with it coming back down once moving which should tell me that I have an air-movement issue. But I did have trouble a while back on a 98* day, running about 80 mph in upstate NY (I was the slow one, lol), with three people in the car. It's bad enough that I won't even run the AC any more.

As far as temps; I get nervous around 215, but it'll creep up to 220 before I pull over.
I checked today and I have good flow, from what I could tell. I could see it flowing with the cap off. The lower hose was barely warm with the upper hose hot enough not to hold on to for more than a second or two. This was just letting it idle up to temp (about 180*).
I have this single row radiator (1.25" pipe) with a 180* thermostat:

https://shop.advanceautoparts.com/p/...auc0YzSpZzQnOp

Looking for reviews for this radiator I saw a Chevelle dude was using it with a 454 and no trouble. So there's that.

I'm sure I could use a better radiator but I feel like I have an airflow issue as well. I do have the AC condenser in front of the radiator and it has a trans cooler on that. I have a 16 lb cap that runs into an overflow tank (which I understand is unnecessary). I tested the fan clutch also and it seems to do what it's supposed to. Light drag when cold, a lot more drag when hot.

Call me crazy but I don't think this is going to get better when I drop in the 455.

 

I run dual electric fans, moroso water pump drive, aluminum radiator . car rarely hits 210 and I'm making long drives with 3.90 gears around 4k rpms . look at the radiators from champion they are nice and work well and are affordable.

the fans are pretty big so I pretty much don't need shrouds before everyone starts telling me how badly I need them. This set up works well. Used griffin radiator 100 bucks, 20 dollar fan units from a 9c1 caprice. The picture is before I fabbed all the mounting points but its layed out the same way.

 

Yeah, I remember you knocking that together. I just really don't want electric fans. At least, not unless I can get this ironed out.

 

I know nobody likes flexfans but this one gets very good reviews and seems to have solved a lot of over heating issues.

https://www.summitracing.com/parts/flx-1817

 

You need a better radiator imo. I would do a solid spacer on the stock fan before a felx fan.

 

I had to resort to one of these after trying 4 or 5 fan clutches (centrifugal & thermostatic) which would not move enough air at low speed on a '65 442. The flex fans may have their downsides, but it's moving more air for me and hasn't self-destructed yet.

 

Although that radiator works fine for me, I do not have a/c. You probably need to run a bigger one. Also, the initial timing setting you threw out there may be a bit high. Lets wait and see what your temps are with this new engine before making a bunch of changes.

 

How many blades is on your fan? It should be 6 or 7 blades and yes it will get much hotter with a 455. I never got much above 200 with a 4 blade factory fixed Non A/C fan, which moves a lot of air, no shroud and a recored brass factory two core rad with my 9 to 1 350. It was idling in traffic, nothing a $150 shroud wouldn't help. I know with the 403 stroker I will need a shroud and a much better radiator. I was thinking this in the two row with 1" tubes. I had the 3 row in my Gbody, good quality but marginal cooling with my 403. A guy with a 10 to 1 403 had very good results with their G body 4 row which is much narrower.
http://shop.championcooling.com/Perf...upreme-SKU-161

 

I have the 4 blade fixed fan with spacer on my 350 in my 70S. GM part number 405442.
https://gbodyforum.com/threads/mecha...upgrade.60566/
Frank on the G body site swapped his clutch fan for the 4 blade fixed fan. I have since switched back to the 4 blade mechanical fan in that thread. The relay in the fan controller died again. I moved it over to the G body, going for maximum mileage and manually wired it with a toggle switch. I am going to run two controllers due to the amperage draw on start up with a manual back up. I find relays die at the worst times.

 

I'm sure this is true. At the time I was anxious to get her on the road. AND I was out of chashola, lol. And the spacer; move the fan closer to the rad?

Is your flex fan noisy? The reviews of the one I listed surprisingly said it was very quiet. A flex fan eliminates the clutch, yes? Did you use a spacer? If so, how thick?

Yeah Eric, like I said, I'm pushing the timing, lol. But no detonation. Remember, this small block has maybe 8.2:1 CR at best (if memory serves) so can take a lot of initial.

I think it's a 6 blade, I'll have to check. Those are pretty fair prices on those radiators. Not sure I'll spring for the dual pass though, lol.

 

My biggest fear right now is overheating during the break-in of the new big block. I should have solved this before cannibalizing the small block for parts. But I can run the 20 minute break-in in stages, yes? 10 minutes, shut down and cool (if needed), and another ten minutes. It doesn't have to be a continuous 20 minutes, does it?

 

FWIW, when we broke in my 400G the builder insisted on running it continuously.

 

my big block chevelle has a 3 core alum. radiator, flexfan and a fan shroud, runs 180 all day long. I would install a bigger radiator, and make sure you are using a shroud. I also have my fan aboit 1 inch away from the radiator. I think that rad. is too small, just my 2 cents.

 

There are many threads on this to read but from what I remember;
put a light behind the radiator and look though it to check for blockage that prevents flow.
Check on each side of the radiator for seals between radiator and core support. They force the air into the radiator.
Make sure the shroud is in place and fan blades are close to even with or sticking out of the shroud 1/2 inch. Too far in or out reduces suction through the radiator.
How many rows in the radiator?
use a temp gun and scan around the radiator looking for cold spots ( clogged rows).
Check the bottom radiator hose has a spring in it by squeezing it ( while cold). If it squeezed easy it may be sucking shut while driving.
Check the fan clutch for leaking oil and that it doesn't spin free.
Test or replace the radiator cap.
Is the air dam present under the front bumper?
is all the air purged out of the cooling system?
there may be more I don't remember.

 

Duly noted. Thanks, man.

I'm coming to that conclusion also. I'm looking at my options. Anyone try one from Eastwood?

Gary, notes taken:

Make sure the shroud is in place and fan blades are close to even with or sticking out of the shroud 1/2 inch. Too far in or out reduces suction through the radiator. I didn't know this about the placement
How many rows in the radiator? Too few
use a temp gun and scan around the radiator looking for cold spots ( clogged rows). Noted
Check the bottom radiator hose has a spring in it by squeezing it ( while cold). If it squeezed easy it may be sucking shut while driving. I put new hoses on it during the freshen but the hose did not come with a spring. I find one
Check the fan clutch for leaking oil and that it doesn't spin free. Good to go on this one
Test or replace the radiator cap. New 16 lb cap
Is the air dam present under the front bumper? It sure is. I cleaned it up and made it beautiful. Defiantly a waste of time, lol.
is all the air purged out of the cooling system? Should be. It's been in the car for a few years.
there may be more I don't remember.

 

I agree with needing a bigger radiator. When you do the switch eBay has the hose spring for about 7.00. You may not need one, just letting you know where to get one in case.

 

hi, just adding in my .002 here. The 350 usually came with a two core rad with ac.I have increased mine from the two core to a three and most of the time it runs middle of the gauge , I myself do not like to run the ac for long periods when running on the highway on hot days as it runs up near the top of the guage(I am using 3.73 gears also). I am in the process of doing the swap to 455 as well in mine and I just bit the bullet and went for the 4 core . I found that with timing olds's will like 32-34 total (no vac advance Included ) . I ended up with my 350 at around 9.2 compression and 93 fuel at 18 initial and 32 total.

 

Both of my 350 AC cars (70 and 71) came with 3 core radiators. Never had any cooling issues during 90+ degree summers (Louisiana Gulf Coast) with the AC on and hot rodding or freeway cruising.

 

I'm not sure why people have issues with flexfans. I went for the 1309 and have not had any issues since I installed it. I tried several combinations of fan clutches, electric fans, and just never had any success. Went with the 1309 and it stays steady. I will admit, I hate the noise, I sound like a jet turbine and the fan is louder than my exhaust. So every once in a while I go back to experimenting again, but I seem to always end up back with the 1309. ( yes to all the obvious ... no hose cavitation, radiator flows well, good water pump, shroud, etc. )

 

So where are you guys getting your radiators? And is a 3 or 4 row rad thicker than stock? As in, will it fit in the saddles?
Am I going to have to spend $500 to get good temps? I'm looking at the Champion 4 row for $309 but they don't get the best reviews.

 

It’s too bad you missed out on that $59 Rockauto clearout on 4 core rads. I went from a two core to a four core with the stock 6 blade fan and kissed my overheating issues goodbye. You’ll also need a new top plate if you go 4 core.

 

The 2 core with 1" tubes should cool just as well as the four core. There should be measurements for both on their site. Replace the rad when you put the 455 in. I didn't with my 403, overheated 10 minutes into the cam break in. I repeat replace it.

 

Where would I get a new top plate? And just modify the lower saddles?

Will do, buddy. I'm working on it

 

Originally from GM on my cars, as in they were the factory installed radiators.

For "factory replacement" radiators, you have to ensure there are the same number of tubes and cooling fin-per-inch count (or at least that's what was needed before the copper-brass radiators were replaced with aluminum). Back then a lot of replacement copper-brass radiators had the same external dimensions, but the cores had fewer rows of tubes and fewer cooling fins, which resulted in some cars running hot even with a new radiator.

"Stock" depends upon the application. As I posted earlier, the AC cars had a 3 row radiator as stock, and a 455, HD cooling, etc. application could have a 4 row as stock.

So as far as I know, the 2 and 3 row radiators used the same width saddles and the 4 row radiators used wider saddles.

I once installed a 4 row radiator from my brother in law's 68 GTO in my 70 Supreme's 3 row saddles by flattening the top plate and the rear ends of the lower saddles. Later when I reinstalled the replacement radiator (original 3 row end tanks with 4 row high efficiency core) I bent the saddles back.

 

https://www.googleadservices.com/pag...41471842508405
Another option, it should out cool a 4 core radiator.

 

Thanks for the write-up, Ken. This is the same info I came up with during my research. But I was unable to find the specs for the original radiator (which I recycled years ago).

I checked and I am missing one of the rubber seals (like a thick piece of weather stripping) on the trans cooler side of the radiator.

Right now, I'm leaning towards this Champion 3 row:

https://www.ebay.com/itm/16151651601...witem=&vxp=mtr

 

I no longer have an original core, so I can't help you there. In the past I always recommended folks count the number of tubes and fins-per-inch on their existing radiator and compare that to the prospective new radiator, but that option is out for you unless someone has an original and can provide the numbers.

 

Cooling issues? Dimple tube core and SPAL #30102130 12" dual electric fans properly wired, problem solved .... I find it interesting that no one has addressed the heat exchanger itself as the starting point of cooling issues... thanks Erik

 

Huh? This whole thread has essentially been about radiators (aka heat exchangers).

 

The old saw is that, if one has overheating problems on the road, one has a coolant flow issue, and if one has overheating problems at idle, one has an airflow issue. Mac may well have both. I had overheating issues with the stock thermostat, so I went to a lower, 160 degree, Stant Superstat that gives better flow. At some point I need the original core rodded and repaired.


A note on thermostats. Newer cars have rock solid temperatures in the middle of the gauge. This is due to imprecise gauges and good radiators. How can a car under light load at 30 degrees have the same temp as a car under heavy load at 90 degrees? The thermostat is regulating the engine heat correctly by reducing coolant flow when it is cold, and opening when hot.


Ok, that's obvious. But, why do our old cars go all over the place with the gauge? Why does mine do 130 when it's cold, 160 in town on a normal day, and 210 on a hot day bombing down the road with a 160 degree thermostat? Answer is simple: the 160 stat is being overwhelmed by the coolant demand from the engine which the radiator cannot fully regulate. That 160 degree stat is wide open to the world and everybody and the radiator does the best it can to cool the engine.


Why does this matter? A lower thermostat, on a car which cannot regulate its temperature fully, will not help. My car was helped by a performance thermostat which flowed more, and also opened sooner and for longer, but it is just a bandaid. Unless your classic can hold a 180 temp, putting in a 160 will not move it to 160, and it might not even, then, as a hotter radiator cools more efficiently.


I would go for a new, bigger radiator first, hose spring, new hoses, new thermostat, 180 is ok, but maybe a performance flow one, and go from there.

 

The driving conditions of 60's & 70's are a bit different than today. The principals have stayed the same. Heat transfer needs circulation and airflow, address all aspects of the cooling system, that's why it's called a system, don't skimp anywhere or you'll be steamin' in today's stop n go driving environment...

 

No need to tell me about keeping a classic cool. I drive in 115+ ambient summer temps with the AC on and don't have any cooling issues, either in town with heavy rush hour traffic or humming down the highway at 70 MPH / 3000 RPM.

 

mac my 72 CS never had a cooling issue w the 350 and a stock like 3 core radiator.

When i put in the 455 (new t stat, hoses, waterpump, belts) I had to be careful 15 mins on the hiway (3k+ rpms) in 80+ degree temps would have me climbing up to 220, as soon as i got off the hiway and cruised down a 45-50mph road the temp cooled right down to 200ish.

Ive driven a couple thousand miles and only on hot days and hiway will it start running hotter than i want...my conclusion is the rad just doesnt have enough capacity.

I plan to get the champion 4 core mc161 just havent gotten around to it as the majority of my driving is secondary hiway or around town where the temps stay down even at 100 degrees ambient.

also funkwagon455 posted a pic of how he modified his 3 core top plate to look similar to a 4 core top plate and added the 4 core mounts to hold his 4 core rad ill see if i can find the pic an post it i intend to do the same to mine.

 

this thread has a couple pics of funks modification to a 3 core top plate

https://classicoldsmobile.com/forums...***-455-a.html

 

Fun 71 has it right, not to many people think about fins per inch. I had mine set up for the Woodward dream cruise. I had problems with sitting with the original set up with temp light coming on. 70 supreme 350 and A/C.

I had the original tanks cut off and recored with 14 fins per inch, up from 6 from the O.E.

Now I can sit on Woodward for hours without issues.

Pat

 

Luckily, I put in a "built" 200-4r so 70 mph puts me at about 2200 rpm, maybe 2300. The downside, I suppose, is the extra trans cooler on the front of the condenser.

I'll give this a read, thanks Retro. If that's the modified top plate, I can't see where it was done.

The Champion that I'm looking at, in fact all of them, I believe, have 14-16 fins per inch with 3/8" between tubes.
I think the sad thing is sitting for hours when it's supposed to be a "cruise"

 

I get it now. I actually read some of this thread earlier.

I think I'm going to go with the Champion three row and if it's not cooling quite enough, I'll pick up their electric fan package.

 

Get the 2 core with 1" tubes, it might even out cool the 4 core. The 455 can be tough to keep cool, why go marginal?

 

Yes, it's too bad that they don't limit that day to just the cruisers. Most business close down that are not fuel, bank and food. Of course Friday night is just as ugly. At least 50-60% is normal daily drivers mini vans with the doors open or pickups with people in the bed, IIRC that is illegal in this state.

Pat

 

A friend of mine with a '71 vert has the Champion 4 row and it fit with a little modification. So I just ordered one. Go big or go home?

I'm pretty sure it's illegal in Illinois as well. But it doesn't stop the kids from doing it. I remember hitchhiking in the 70s and riding in a lot of beds. But there were so fewer vehicles on the road back then and they weren't in such a hurry!
I've been wanting to do the Hotrod Power Tour but I hear it's mostly sitting in line. If I get my cooling issue solved, great. But I still don't like sitting still. I don't even like stop lights! Lol.