Oil Cooler Question

[srgould41]

I have been fighting overheating ever since going to EFI and 36" tires (305 SBC). The best cooling so far is via an aluminum radiator and electric fan. Still not enough, though. There are times when I can't get under 210*. SuperBuickGuy mentioned using an oil cooler as an additional cooling method. I have avoided it so far, but that may be in my future. The very next step is to louver my inner fenders for increased air flow, but I don't personally think it will help much. Never know, though.

The question I have is actually about the oil temp and the radiator. My radiator has a built in fluid cooling circuit for a transmission. I use an external cooler for that so never needed to use it. This gives me two choices. Is there any benefit to using the radiator circuit for an engine oil cooler? I don't know what temp the oil normally is and running it through the radiator might not do much for me and could raise temps even more I guess. A second option would be to run the trans fluid through the radiator instead of the huge plate type cooler I currently have in front of the radiator. Then use the plate cooler for the oil instead. The trans may benefit as it usually runs about 120*.

Thoughts?

 

[toyotaspeed90]

The real question is whether or not the radiator has the capacity to cool the excess heat from the oil as well.

I was planning the same... if you have a champion radiator you will need a few special fittings (I'll have to dig around to see what they are) for the radiator to then use AN for a cooler.

Using coolant to cool oil is actually far more efficient than air, and it also helps get the system up to temp faster as well. Toyota used this method on many vehicles.

However it's usually easier and cheaper to just get an external cooler. You can get them in just about any needed size.

I would question, though, why going EFI has caused you to run hotter than with the carb.
EFI should be easier to manage, and if the only change besides tires was EFI - then I would think there's something in the tune...

 

[srgould41]

I went from an over rich carb to a fully tuned EFI. Much leaner now.

The real question is whether or not the radiator has the capacity to cool the excess heat from the oil as well.

I was planning the same... if you have a champion radiator you will need a few special fittings (I'll have to dig around to see what they are) for the radiator to then use AN for a cooler.

Using coolant to cool oil is actually far more efficient than air, and it also helps get the system up to temp faster as well. Toyota used this method on many vehicles.

However it's usually easier and cheaper to just get an external cooler. You can get them in just about any needed size.

I would question, though, why going EFI has caused you to run hotter than with the carb.
EFI should be easier to manage, and if the only change besides tires was EFI - then I would think there's something in the tune...

 

[toyotaspeed90]

I also just saw that last statement- if the trans runs at 120*... then the cooler you have is doing a better job than the radiator would, as it would only be able to cool as low as the fluid inside of it - meaning the trans fluid would get warmer in the radiator cooler.

I wonder, how big is this cooler and is it causing some heating of the radiator?

I have a huge thread about this for my 40 for things I've done/tried.... the recommendation of others always comessage back to.... huge mechanical fan with a shroud... and for me, that means moving the engine back several inches (which that piece is easy enough, it's everything else that becomes a problem). I tend to disagree and think there must be another way....

It's a long read if you have time....

SBC Running Hot

 

[toyotaspeed90]

I went from an over rich carb to a fully tuned EFI. Much leaner now.

If its actually lean (not just leaner and closer to stoich, but still rich).... Lean runs hotter.....

 

[Mace]

Show us a pic of your setup please.

Running an engine oil cooler in a radiator won't do much to help you. If you ran hot while running rich, in WA, you need to address some inherent flaws in your cooling system. Even more so if you already have an aluminum radiator.

 

[srgould41]

I will go take a look.

Actually now that I looked I realized I had read your post before, just not the most recent posts. Is it back on the road yet?

SBC Running Hot

 

[Gumby]

What Mace said. You have a flaw in your set up that adding a bandaid to won't fix. thousands of sbc 40s cool fine. A 305 shouldnt have any problems. Oil coolers and louvers shouldn't be needed.

I run a 400hp LQ9 FJ45 with a 4 core brass radiator and clutch fan and it gets a little hot while wheeling. like 220*, nothing horrible. Romping on it around town never gets hot.

Most GM stock EFI likes to run at 195-210. You shouldn't run a t-stat other than 195 in most of them. If you have a 195 t-stat and a gauge that reads at the head you could see 210 and not have a problem at all. Check with a thermal gun.

What is the type of EFI you are using? What are your long term fuel trim numbers? You could be running too lean.

 

[Gumby]

Did you swap the whole EFI engine over? Are you running the serp belt or the V belt? The serp belt water pump turns backwards. i would suspect if that was the problem you'd be overheating much worse.

 

[toyotaspeed90]

Mine is sort of on the road... as much as it has ever been under my ownership and has been in the last 30 years (no, not a joke or exaggeration). As you can imagine, there are a lot of other things going on with that vehicle other than cooling issues.

... I've had some great luck with what's going on, but I still think I personally have tuning issues with mine - I've already proven (at least here at home) that the radiator and fan I currently have is able to cool the system. My 2 core aluminum Champion radiator was not up for the task, and the PS/trans cooler was adding heat soak, so I completely redid those as well.

With the new, much larger radiator, I did a test - I purposely ran it up to about 220 or 230 without the fan on and a high idle, then kicked the fan on with no other changes - and, although slowly, the needle moved downwards. Once I actually moved it back and forth a couple times in the driveway to actually get movement flow through the radiator, the needle dropped further.

I have a cheap temp gauge - and another thing I noticed is a roughly 10% variance in reading based on whether the engine is running or not (to say that - there's a variance in reading from voltages - when the vehicle is shut off the needle immediately drops 10-15*, start it right back up and it'll move back up - it isn't based on coolant movement/stagnant, otherwise the temp would increase).

I've also known that mine isn't running quite right. A "rebuilt" quadrajet (and unknown if it even is the right one for that engine) and unknown timing - and I haven't seen any vacuum variances when messing with the idle adjustments tells me something is wrong. I'm carb stupid, and replacing the parts internally on the carb is about the extent of my carb understanding goes (though to be fair, I was able to clean and "rebuild" a Marvel Shebler unit on a 1965 International Harvester tractor to get it running for the first time in 4 years....). My next step will be to check timing and back it off a couple degrees. At that point, it will be - drive it and if I destroy the engine, so be it - I'll find a truck or suburban with a good 350 and EFI for under $1k and just swap the engine and harness all at once. For my rig that now means... a little tinkering with the engine but focusing on things that I've otherwise ignored as I attempted previously to tackle the "cooling" issues.

In my readings/studying - I didn't fully trust that the only way to cool a SBC 40 is based on engine placement and a large fan - same reason that you can run a BBC in a rat rod with an electric fan without massive cooling issues, a trophy truck can make gobs of power with a radiator that has electric fans, or that a mid engined car works at all... Yes, it is a tried and true method, but can't be the only one.

However, 40 specific - I was reading a bit and how surface area of the radiator is more important than number of rows on a stock-sized radiator- and also not necessarily the quantity of rows, but the size of the tubes in the rows. The radiator I went with was a universal unit from Summit Racing (the biggest downsides are that you have to fabricate your own mounts entirely, and there's no drain), 2 core with large tubes (either .75" or 1", I don't recall.... they were significantly larger than the Champion radiator), cross flow, and about the max size that would fit in a 40.

The 195 t-stat is always an interesting topic. This is somewhat of a broad statement - but if you're running EFI, a 195 makes sense because the coolant sensors are expecting a certain operating temperature range, and if too cool could be running overly rich. However, I've seen it many times that the 195 t-stat is required to properly cool the system - but that isn't the case. Chevy used to sell their vehicles with t-stats in SBC cars (including corvettes) with as low as 160* - this was because the system was able to take the extra burden of the heat, run it lean with advanced timing and make more power. They actually went with higher temp t-stats when the EPA starting cracking down - chevy actually did it more for meeting pollution standards. (That isn't to say, though, that their systems then weren't designed to work best with a 195 t-stat)

 

[srgould41]

Hiya Gumby. The engine is an '83. I ran at 180 all day long when I was using a Qjet and mechanical fan with a limited shroud. Of course it was running so rich it blew back smoke all the time. I installed a factory TBI then tuned it with a professional tuner over a couple months. I left it slightly rich, more so at low RPM. I tuned it to overcome low vacuum from a cam. I went to 36" tires at the same time. Trail rides after that had me boiling over and so started the odyssey. I am now running an electric fan with a 100% shroud. Pulls air great at idle where the mechanical fan would not. Most times I run to 195 where the fan kicks on and drops it to 175 then turns off. However, on hot days it will stay up at 210 to 215. Not the end of the world, but I worked hard to get the temps down and would like to keep them under 195 like the system should do.

 

[Mace]

210/215 is not overheating for that motor..

 

[srgould41]

Not anymore, no. Maybe I should restate my original post as "fighting higher than I like temps" . It started as overheating, actually boiling over. I do't mind seeing it hit 210 or more, I just don't want to see it stay there. My last trip I did not test the air flow by opening and hood to see what happened. Maybe that is the next step to see if I need more venting ability before I blindly add louvers. I need a road trip anyway, it has not been out of the garage in 2 months. No time off lately.

210/215 is not overheating for that motor..

 

[srgould41]

I was wrong. It had not run in 3 months and the battery was dead. Poor 40, so neglected.

 

[toyotaspeed90]

40.... 3 months.... and neglected.....

that's not neglected....

try 30 years.....

 

[Chris Wilcox]

You need to dump heat to air, not to glycol if you want to make a marked improvement. Dumping it to the glycol isn't going to work if the radiator is already at it's limit. I didn't read all the posts above but is it possible your thermostat is hotter than you like or maybe your temp gauge is inaccurate?

 

[srgould41]

After reading the other comments it was obvious that was a bad idea. If I do add the cooler I would use the radiator builtin for the trans and the current trans cooler for the oil.

My fan controller uses the same sender as the AutoMeter temp gauge. I had lots of bad luck with their quality, or lack there of. It does worry me. I was planning on a separate sender, but have no place left for one. The ones you push through the radiator fins have more bad reports than positive ones. So far my temp indications seem correct for the thermostat opening and regular running temp. I believe it is close.

You need to dump heat to air, not to glycol if you want to make a marked improvement. Dumping it to the glycol isn't going to work if the radiator is already at it's limit. I didn't read all the posts above but is it possible your thermostat is hotter than you like or maybe your temp gauge is inaccurate?