Overheating big block - could use some suggestions...?
 

I'm fighting with the big block in my 1970, it's getting upwards of 230 on the gauge.... And I could use some suggestions... :ack:

The PO bought the car at auction so didn't know the person that built it.

Here's what I've got:

- 454 GM Replacement shortblock, found a metal plate on it, it's p/n 12498778. Shows it's a 454 HO short block, 9.5:1 with 110cc heads
- Edelbrock High Compression O port heads, 60499, 100cc combustion chambers
- Edelbrock Performer RPM Air Gap intake manifold, Proform 950 CFM Carb.
- Unknown Hydraulic roller and roller rockers
- Factory BBC exhaust manifolds
- '69 style sidepipes

March Performance Serpentine kit for corvette with an Edelbrock high flow water pump
BeCool aluminum radiator, looks like an older one before they revised the intake hose position (it really sucks trying to get the hose on)
BeCool Dual SPAL fans with correct relays and Dakota Digital fan controller
180 degree high flow thermostat

The PO had put some strange puke tank connected to the radiator, I've pulled that and put the correct 1970 surge tank for a small block in it, didn't want to shell out for a big block one - the holes were there for the big block one - it's just missing.

I have the vacuum advance hooked up to manifold vacuum at the carb (not timed)

It will slowly climb to about 230 and then try to keep going... No oil in the water, no water in the oil.

It was missing all of the fan shroud seals, I just ordered a set of factory style ones from Willcox. Wouldn't think this would be an issue with the full becool shroud/spal fans.

Since the big block isn't crazy, it would sure seem that the BeCool radiator with the properly shrouded twin electric fans should keep it cool?




Thoughts? Comments?


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Does it get hot at highway speeds or around town? Are you required to have a front license plate? I'd look at timing, maybe jump up a size or 2 on carb jets just to make sure it's not lean. My 69 BB will get warm on the highway, or it did until I removed the front license plate and bracket. And it'll crawl up around 210* setting in traffic.

It gets hot driving <45 mph or so, I live in the suburbs, since it's overheating just poking around I haven't taken it over to the freeway.

I already yanked the front license plate/plate mount. It does have a transmission cooler/fan in that area, the transmission fluid is not routed through the radiator cooler that's built into it.

I'll double check the timing. The exhaust doesn't make my eyes water, which is usually a decent indicator that the mixture is ok/fat, plugs look good.

The car was a complete mess when I got it, no end of "bubba" crap to get it through the Mecum auction where the PO got it.

Correct fan rotation?? Lower radiator hose collapsing? Dub once had a post about some after market radiators had the lower rad. outlet partially blocked by the trans cooler inner tank faulty design. Just some ideas.

first, double check the actual temp. 50 year old gauge and sender? or possibly worse, a new sender that isn't right for the gauge? pump rotation. serpentines run backwards. the spoiler-diverter-splitter under front bumper. is it there? lastly go bubba. remove the thermostat to see what temp you get without.

Chin spoiler in place?

I have a NewVintage USA 1969 style electronic temperature gauge (i've replaced the center gauge pod gauges), the short chin spoiler is in place. It's wired correctly, and I've actually tried moving the gauge sender from the driver's side head to the heater outlet hose. No change, so I'm going to move it back to the head.

The water pump question is a good one, while I would suspect that the right pump is on the engine, I've not verified, it's polished like the rest of the March accessories. Bubba did have his way with installing the serpentine kit, I wound up having to buy a new mounting plate as one of the idler pulleys was installed incorrectly so it ate the mounting plate.

Yesterday's mods to get it to cool off:

- Installed the vacuum advance (It was missing) to manifold vacuum
- Ordered radiator seals from Willcox

I've never run into something like this, it's a head scratcher.... :rolleyes: Keep the suggestions coming, I really appreciate it.

I drove it after hooking up the vacuum advance and adjusting the carb last nigh t, it still got hot - however didn't realize it had already puked up bunch of coolant.

Open questions:

- Correct head gaskets?
- Correct water pump (not likely the issue, as everything matches)
- Design issue with a "first gen" BeCool radiator (not likely either)

It had the wrong Fel-Pro intake manifold gaskets on it, which Edelbrock specifically says will not work. They were leaking as you might predict... I put the right intake manifold gaskets on it. Now it makes me question the head gaskets...There are two styles....

I'm going to try:

- verifying the timing is correct
- make sure the cooling system is refilled and then try it now that the advance is hooked up

Yea twin SPAL fans, they are pullers and pulling air through. You can put your hand in front of the engine and feel the airflow.

Interested in outcome here. I have similar issue w/ new 540 build with some similarities. I have a different March serpentine setup (more spread out), edelbrock reverse flow water pump, dewitt extra thick core, dewitt dual spal fan setup, seals installed, with and without thermostat, water wetter, tried timing at various increments up to 25* at idle, chin spoiler, radiator does not have transmission cooler built in, and still creeps hot just sitting there. All new components. I also have coolant transfer lines from the rear of the manifold up to the front to ensure no hot spots. With radiator cap off, the pump is moving a good amount of coolant the correct direction.

I'm currently in the process of building a custom fan shroud this weekend that covers the entire radiator (the dewitt/spal package only covers about 75%) and using 2 of the spal 30a fans (pn 30102800). Each fan pulls more air by itself at the pressure differential provided by a thick radiator plus condenser than the combined fans in the fan kit. So... hoping full radiator coverage combined with potential for 2x airflow will fix it. If not, I'm at a complete loss.

Can you take a picture of the "stock" SPAL fan next to the 30102800 fans for size comparisons? My concern there is the thickness of the built in fan "shroud" or frame. If it's a like for like swap for w hat's on the stock shroud - this is an interesting idea. Would love to hear how it goes.

The shroud and seals should help.
Replacing the vacuum advance and having that set up correctly should help.
Check the mechanical advance springs in the distributor to make sure they are the correct ones.
Make sure the lower radiator hose has the spring installed and the lower hose can’t collapse.
Drill a couple of small holes 1/8” in the thermostat to allow some water to pass and to help purge all air out of the cooling system.
Burp and purge all air out of the cooling system as it is common to get air trapped and overheating will result.
On a side note, your carb is too large, unless you are drag racing.
Running what you listed and normal street driving, you would find a better running engine with a 750cfm - 850cfm, in my opinion.

Spring is in the radiator hose, high flow thermostat already has bypass holes in it
I'll take some care to get all the air out of the system

The carb is too big, agreed - however need to sort this cooling mess out first, the PO stuck it on there. Once I have this cooling issue sorted, I'll probably swap it over to an 850 with a choke. No reason to run a 950 no choke carb on a mild to medium-built 454 on the street IMO.

The vacuum advance is working, engine RPM jumped when I plugged it in, had to back off the idle speed adjustment. As a side note, adding that greatly improved throttle response/drivability.

One different thought. I’ve recently had real grief with a malfunctioning high flow thermostat. Unlike yours, it’s on a small block, but I made a number of odd issues go away by replacing it. I had holes drilled in it too. You might try removing yours to see if this solves anything.

I don't think it is the correct radiator for that car. No cap on that year and engine. https://www.dewitts.com/collections/...inum-radiator#

You can always take the surge tank out and replace it with a overflow tank.

Probably overzealous in my 75% assessment seeing them side by side. Measures about half inch deeper which could be a challenge with your accessories. Airflow will undoubtedly be higher.

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I saw that as well, the Be Cool radiators all have a cap. The kit that's on the car appears to be the "BeCool Show & Go" with a puke tank. (well, I took the small puke tank out and replaced it with the much larger OEM style surge)

Wow, that is definitely going to move some air. You're right, I don't see that fitting in my car with the corvette specific (narrow) serpentine.

That radiator is not made to run with a surge tank. Made to use a overflow tank. I did not see you list the temp the fans come on and off. may be another issue.

Doesn't really matter, but the serpentine setup you have is not their corvette specific kit for C3s... but if it fits, it is good!

Hi, yes, it's the specific serpentine for the c3 corvette.

It's this one:

https://marchperformance.com/chevy/c...ntine-kit.html

I've had the "fortunate" experience of taking it all out and putting it all back in there.