Old School 327 running hot

[ZooMad75]

OK resident old guys, let me run a mechanical puzzle we've been fighting at the shop.

Here's the backstory. The patient in question is a 1966 El Camino. Friend of the owner of the shop. The guy has dumped a metric truckload of money into this little elky. Full on restomod with shaved firewall, full Ridetech suspension, slick body/paint. The 327 has been fully rebuilt by a local shop (I don't know who it was) and is running Holley Sniper EFI. The car runs decent. However, the complaint has been the engine runs hot. The 327 has a full aftermarket accessory drive system that uses two serp belts, though the water pump does spin in the conventional direction as a V-belt. It had an aftermarket aluminum radiator and electric fan setup.

Since he got the car back from the builder the car has run hot in traffic. Our shop didn't build it, but because it's the owner's buddy and our collective knowledge between all of us we told him we'd figure it out. After checking the basics, we felt the radiator was a little undersized and the single fan setup wasn't moving enough air. We picked up a larger Cold Case unit and dual fan setup. We had also confirmed with the accessory drive company that the water pump was the right one for it. The car was running cooler for longer but still managed to get hot. We had the guy bring down the control screen for the Holley to compare the water temp reading with the Dakota digital gauges since there were two temp senders in the intake. Sure enough, they matched. But having the control allowed us to verify the timing was on the lower side of the scale and it was trending lean too. So we added some timing and fattened it up a little. We had also swapped out the 195-degree t-stat for a 160-degree version. The engine ran better and ran cool on the same test drive we had taken it out on before that it got hot on.

We let the guy take it home and it was looking up, but he called about a half mile from his house saying it climbed up to 220 again. He probably drove 15 miles or so in traffic before it got hot. So it came back yesterday to re-check some stuff. Coolant is moving quite well with the cap off. We confirmed the t-stat is opening quickly. The odd thing is the driver-side bank gets noticeably hotter than the other side. Like the valve cover is hot to the touch when the other side is still a lot cooler. I know not to go off of surface temps, but it is certainly odd that the whole head and valve cover get noticeably hotter than the other side, something is not right.

I had a talk with the owner of the car on the phone today and I was curious about what took place during the 327 rebuild. Mainly I wanted to know if the block got bored and if so how much of and overbore did it get? The guy thought it had been bored but wasn't sure by how much. Here's why I was so curious about that. I can remember my Dad talking with others about 327's back in the day. One of the common issues they would talk about was being careful on boring out 327's. The theory was that there wasn't much meat in the cylinder walls to allow for a big overbore and if one did they would run hot.

So that's the main thing I think is wrong with it. There is no mechanical reason this engine is getting hot so fast. I don't know if the stuff I heard about 327's having thin cylinder walls is an old gearhead tail or a legit issue. My guess is if it is a real issue whoever machined the block didn't have the insight to know the limits of the block because they might have been born well after the last 327 came off the assembly line in the sixties. Not knowing any better they needed more material removed to clean up the bores since it probably had been punched out before.

What is the thoughts of the brainpower here? Tagging known semi-old farts: @ktmoutfront @Bent77 @6872xtc @500$k5 @folkenheath @Capt Ron anybody I didn't think of and may have some practical 327 knowledge chime in.

 

[Wes Harden]

Unless the casting shifted I doubt the over bore is an issue. unless they went .080" but I doubt that very much. I ran 68 LJ 327 at .030 over in 66 chevy II, using stock rad and fixed 4 blade fan.
Have one head get hotter than the other is odd. I immediately thought flow restriction. Can't say if a gasket being install incorrectly would cause this. Head gasket upside down ? I have never done this or had an engine with improperly installed head gasket. I believe it would get hot on that bank.
1 thing that is different, and may not matter with your customers belt system, 327 from gm had a short water pump and smaller balancer.
I would hope any engine shop worth its tools would do a thorough cleaning of the block, including the water jackets. If the solution isn't found, popping a left side freeze plug and bore scope inspection of water jacket might be in order. Another possibility exhaust restriction on left side ? Has the rad been checked for exhaust gases, very minor head crack ? While I do like running a low t stat in old school engines (no computers) with the efi you could go up a little from 160°, maybe 170° to keep the hot coolant in rad a little longer. 170° is the current t stat in my 77 burb atm.

 

[1-ton]

I would hope any engine shop worth its tools would do a thorough cleaning of the block, including the water jackets.

That is what I was thinking...crusted up old 327 block with crud in the water jackets. One way to figure that problem out is with a infrared temp gun. Use a infrared temp gun to Point it at different areas of the block to see if it is hotter in one area than another. Before I take any block to a machine shop I use a steel rod, and a garden hose with a spray nozzle to blow out any crud in water jackets because you cannot trust a machine shop to go any further than pressure hot washing the block in their washer tank, which does not get out baked in crud out of water jackets. I even ran a garden hose with a spray nozzle through the water jackets of my new crate engine, and I was surprised at how much iron dust came out of it from the manufacturing process. My TBI crate engine runs rock solid at 190 Degrees unless it is real hot out, and may get up to 210 degrees, which is still within factory specs.

 

[CT-BLAZER]

Uncomfortable, not knowing if that block was ACID dipped before and after machining...

Blocked water flow I e. Black mud or a piece of shop rag can screw circulation.

??? Was radiator sized appropriately for BTU generation? Including fans and a full shroud..

Has the radiator actually been flow tested?

Has the block / coolant been tested for hydrocarbons leaking into the coolant?

? When are the electric fans set to turn in? Do they turn on by H2O temp of radiator?

Time for testing ....pricey, but run it on the Dyno & watch temps in controlled environment

 

[6872xtc]

I like the suggestion of using the temp gun to have more proof of the temperature imbalance. Maybe it could be possible to prove that the water pump is pushing coolant to both sides well enough to keep the temperatures balanced at the front of the block.
I get suspicious of water pumps after fighting a brand new one years ago on my big block. Everyone kept telling me that it should be good since I bought new, and it wasn't after months of trying multiple other things to fix the cooling issue. Fixed it with a different brand new water pump. Seems like another member had an issue a few years back too, but it was a big block too. Still, man made parts on this engine as well.

What intake manifold? If dual plane, could it be running lean on the bank that is getting hot? Is that also the bank that has the 02 sensor? Maybe it shows in the AFR?
I am wondering if one side of the Sniper is going lean. Possible injector issue?

 

[Capt Ron]

I like the suggestion of using the temp gun to have more proof of the temperature imbalance. Maybe it could be possible to prove that the water pump is pushing coolant to both sides well enough to keep the temperatures balanced at the front of the block.
I get suspicious of water pumps after fighting a brand new one years ago on my big block. Everyone kept telling me that it should be good since I bought new, and it wasn't after months of trying multiple other things to fix the cooling issue. Fixed it with a different brand new water pump. Seems like another member had an issue a few years back too, but it was a big block too. Still, man made parts on this engine as well.

What intake manifold? If dual plane, could it be running lean on the bank that is getting hot? Is that also the bank that has the 02 sensor? Maybe it shows in the AFR?
I am wondering if one side of the Sniper is going lean. Possible injector issue?

These are my thoughts as well. A temp gun front to back on the hot side should help narrow it down a bit and I have seen more then one weak/defective new pump cause problems like yours.

 

[GWeakland620]

I know I’m not an old fart, but my background is old engines as that’s what my dad taught me with. He always told me that 327’s were an engine that you had to be careful on. He said it was safe to bore .030, but never a good idea to go .060 as the walls didn’t have the thickness to cool themselves.

That being said, we had a 327 in a late 60’s el Camino that had overheating issues too. It ended up being crud in the water jacket from a PO putting an insane ton of stop leak in it.

 

[mrk5]

Could there be anything restricting the exhaust on that one side? My 64 had a butterfly valve in one side just below the rams horn exhaust manifold that I reinstalled incorrectly causing it to be stuck mostly closed. It would overheat the engine, especially at highway speeds.

 

[ZooMad75]

Unless the casting shifted I doubt the over bore is an issue. unless they went .080" but I doubt that very much. I ran 68 LJ 327 at .030 over in 66 chevy II, using stock rad and fixed 4 blade fan.
Have one head get hotter than the other is odd. I immediately thought flow restriction. Can't say if a gasket being install incorrectly would cause this. Head gasket upside down ? I have never done this or had an engine with improperly installed head gasket. I believe it would get hot on that bank.
1 thing that is different, and may not matter with your customers belt system, 327 from gm had a short water pump and smaller balancer.
I would hope any engine shop worth its tools would do a thorough cleaning of the block, including the water jackets. If the solution isn't found, popping a left side freeze plug and bore scope inspection of water jacket might be in order. Another possibility exhaust restriction on left side ? Has the rad been checked for exhaust gases, very minor head crack ? While I do like running a low t stat in old school engines (no computers) with the efi you could go up a little from 160°, maybe 170° to keep the hot coolant in rad a little longer. 170° is the current t stat in my 77 burb atm.

Flow restriction is an idea that wasn't brought up. As far as the accessory drive goes, it's a solid setup that uses a long water pump. The belt for the pump runs in the traditional v-belt routing even though it's using a flat serpentine style belt. The long pump is also what precludes having mechanical fan as it would be right into the radiator. We did run a block test for presence of combustion gasses in the cooling system. That result was negative.

I have no clue who did the machine work to even research customer feedback. So I have no way vouch if the shop has a track record for solid work or crap. Not getting the block water jackets cleaned out is totally plausible.

I know I’m not an old fart, but my background is old engines as that’s what my dad taught me with. He always told me that 327’s were an engine that you had to be careful on. He said it was safe to bore .030, but never a good idea to go .060 as the walls didn’t have the thickness to cool themselves.

That being said, we had a 327 in a late 60’s el Camino that had overheating issues too. It ended up being crud in the water jacket from a PO putting an insane ton of stop leak in it.

Score one for the old theory about punching out the 327's too much. From my memory, .030" was about the max, .060" was the no-go zone.

That is what I was thinking...crusted up old 327 block with crud in the water jackets. One way to figure that problem out is with a infrared temp gun. Use a infrared temp gun to Point it at different areas of the block to see if it is hotter in one area than another. Before I take any block to a machine shop I use a steel rod, and a garden hose with a spray nozzle to blow out any crud in water jackets because you cannot trust a machine shop to go any further than pressure hot washing the block in their washer tank, which does not get out baked in crud out of water jackets. I even ran a garden hose with a spray nozzle through the water jackets of my new crate engine, and I was surprised at how much iron dust came out of it from the manufacturing process. My TBI crate engine runs rock solid at 190 Degrees unless it is real hot out, and may get up to 210 degrees, which is still within factory specs.

I'll grab my temp gun and take it to work Monday as that's a great idea. We can compare side to side as well.

Uncomfortable, not knowing if that block was ACID dipped before and after machining...

Blocked water flow I e. Black mud or a piece of shop rag can screw circulation.

??? Was radiator sized appropriately for BTU generation? Including fans and a full shroud..

Has the radiator actually been flow tested?

Has the block / coolant been tested for hydrocarbons leaking into the coolant?

? When are the electric fans set to turn in? Do they turn on by H2O temp of radiator?

Time for testing ....pricey, but run it on the Dyno & watch temps in controlled environment

No clue if the block was acid dipped or not. The Cold Case radiator is oversized for the application for sure. It came with a very nice shroud with two fans that is very tight fitting. The fans have a temp probe to trigger off the radiator temp plus a trigger from the a/c to turn on the second fan with a/c use. The main fan turns on at the correct set temp. Not sure what the guys set that trigger temp to come on at.

I like the suggestion of using the temp gun to have more proof of the temperature imbalance. Maybe it could be possible to prove that the water pump is pushing coolant to both sides well enough to keep the temperatures balanced at the front of the block.
I get suspicious of water pumps after fighting a brand new one years ago on my big block. Everyone kept telling me that it should be good since I bought new, and it wasn't after months of trying multiple other things to fix the cooling issue. Fixed it with a different brand new water pump. Seems like another member had an issue a few years back too, but it was a big block too. Still, man made parts on this engine as well.

What intake manifold? If dual plane, could it be running lean on the bank that is getting hot? Is that also the bank that has the 02 sensor? Maybe it shows in the AFR?
I am wondering if one side of the Sniper is going lean. Possible injector issue?

We have kicked around the idea that maybe the impeller on the pump is loose. I've run into that in the past and it was hard to prove for the same reason nobody wanted to condemn a new pump. The reason we haven't jumped on it is the fact we are seeing the block getting hotter on one side than the other.

Not sure which side the O2 sensor is on and if it's the same side as the one getting hotter. Overall fuel trim as we watched wasn't lean.

These are my thoughts as well. A temp gun front to back on the hot side should help narrow it down a bit and I have seen more then one weak/defective new pump cause problems like yours.

The temp gun will be in the truck to take to work. It would be great if we could prove an external issue and avoid having to take the engine out of the car.


You guys did what I expected by bringing up some ideas we hadn't thought about yet. Thanks. I'll keep you all posted on the findings.

 

[Wes Harden]

If you are seeing good flow across the road I expect the impeller is good

 

[ktmoutfront]

Early 327s were bored 283s. This is why they had problems with rebuilds. When I started reading the first post, that is what jumped to the front in my mind.

The heat gun on the block is how I check.

If it only gets hot in traffic, not at speed, I doubt it is blockage.

Overbore=bad build. I don't know why someone would build a 327 unless it was original to the vehicle and a show room rebuild.

The guy got screwed.

 

[82355]

Put a mechanical gauge on it and see if it is actually hot?

Martin

 

[70jimmy]

Pretty much all of what I was thinking has been brought up here. 30 over max is what I was always told also.

What condition is the lower radiator hose in, any chance it is collapsing reducing water flow? I know we used to get ones with springs or find springs and put them in.

Curios if plug condition provides any good info?

 

[CT-BLAZER]

Convection will move enough water to cool an engine.... In stop & go traffic you lose that action...

Unfortunately, have seen a car with no improoellers on the water pump..... Car only got hit on slow or stop & go city traffic

 

[Chickntrk]

Good point about the spring in the hose, hard to find a replacement hose with one in it anymore, I always take the old one out and put it in the new hose….although you would t think that would cause it to overheat only in traffic, maybe even more so at highway speed.

 

[Bent77]

Can’t confirm a lot of things unfortunately
Pump direction
Clean block
Correct head gaskets
Bore Size

Pretty normal to go .060 or more on a 66-67 block. A lot of those used the same jacket cores as the later 350 blocks. Remember the first 350 was a line bored 327 block. However, good machine shop not only mag checks, but has sonic tests as well

Also not mentioned, the O2 may say it’s not critically lean, but could have a bad injector, causing other issues

 

[Bent77]

Few extra thoughts

The cold case in my 69 doesn’t even turn the fans on this time of year

Pretty sure amongst the lot of you, there’s a complete set for pulleys. Pull everything and add a new pump of known correct rotation
It’s almost free, just some time. It’s a test I would do before pulling the heads

 

[70jimmy]

Couple more shots in the dark, are both fans spinning the proper direction?

Is there a coolant overflow reservoir and are the hoses to and from it open and not restricted?

Other than that, swap the water pump just for grins.

 

[mrk5]

If it is due to over boring, could the cooling system be built up to compensate?

My old 350 in the C10 would get really hot on the initial drive for the day and then cool back down. Every time it was a nail biter thinking it was going to stay up but it would always drop to normal operating temp. Didn't change with a new temperature sender or thermostat. Could this motor be doing the same thing?

 

[CT-BLAZER]

Couple more shots in the dark, are both fans spinning the proper direction?

Is there a coolant overflow reservoir and are the hoses to and from it open and not restricted?

Other than that, swap the water pump just for grins.

??? Is vehicle boiling over or is the gauge.just reading. 220,?

when it's hot, is the eggradiator evenly hot,?

I've seen over heating from a flex fan inversed...

And 350 heads mis matched to a 400 V-8

The newer vehicles have very tight soft gadgets sealing the radiator to the chassis ...All the air goes through the radiator passages


Time to tie it to a chassis Dyno, computer, run it checking it with a thermometer...a mechanical temp gage would be more comforting too me.