Mishimoto Electric Fans in Your 67-72 C10?

[mosel70]

My 396 is getting above warm on the temp needle in my 1970 C10 here in Las Vegas. I already have Mishimoto's three-core aluminum radiator. I'm considering getting their dual electric fan that comes with an adjustable fan controller. Their dual fan setup is specifically made for the 67-72 C10 radiator.

Does anyone have experience with this fan? There are no reviews on the web.

https://www.mishimoto.com/chevrolet-...oud-67-72.html

[engineer_gregh]

I converted my big block 402 to twin electric fans. It runs cooler and I got a bump in performance as the engine is no longer turning the mechanical fan. You may want to consider upgrading your alternator to an internally regulated one with more amps to account for the load. I used the electric fan set up for a Griffin radiator. The Griffin radiator is/was a piece of SH!# but the fans are dual 1600 CFM and work well with my 4 row stock brass radiator.

[weq92f]

Man those are not cheap. 375 for the radiator and 360 for the shroud and fans.

If you've already got the rad. then maybe using their fans is your solution.

There are similar spec'd rad+shroud+fan systems under 500 out there. Quality is King though so these Mishimoto models may well be worth the $$.

-klb

[webfoot]

If you have that big of an aluminum radiator I think something else is amiss.

What is "above warm", into the red?

Are you running a clutch fan and shroud?

If so it could more likely be the factory gauge assuming that is what you are using, mine was going full hot when driving and would immediately settle down at idle, I installed an aftermarket gauge and the thing sticks at 190. Verify temps with an IR temp gun, mine was all hunkydory even when reading hot so I had that thing pegged as wrong all along.

[mosel70]

Sorry that I forgot to add that last summer I put in a new 150 amp alternator when mine went bad. Also put in a Optima AGM battery. The MIO-MMRAD-CK-67X radiator from Summit was only $298 w/tax and specifically made for 67-72 C10s. I ordered the Mishimoto dual fans from Jegs today. 2600 cfm total.

http://www.jegs.com/i/Mishimoto/690/...PROBE/10002/-1

Much lower price than Mishimoto and it comes with the adjustable controller installed. Only $287 w/tax (military discount helped a little). I'll post again here once the fans are installed to let you know if they work well. Ship date is 19 May 2017.

I also recently put in a new temp gauge so I know it's working. Engine temp good until it's in the 90s outside and then it's half to three quarters towards hot on the needle after about 5 minutes at idle.

So what's the best way to know exactly engine temp is by degree?

[mosel70]

I am running a stock clutch fan and shroud that covers the entire radiator.

[webfoot]

Next thing I'd check is your timing before throwing any more money at the cooling system.

[engineer_gregh]

I installed an old fashioned $20 temp gauge from one of the local parts stores just so I would know for sure what my engine temp is at all times. I spent in excess of $5K building the motor and wasn't going to take any chances on over heating it. My engine is the original 402 and it's .30 over with a Comp Cam 268H. It would start to overheat in 5 minutes or less with the mechanical fan, clutch, and shroud. I did a lot of research, the big blocks with hotter cams and headers are going to run hotter than a stock setup, period!! Adding the electric fans is absolutely the right decision. Timing does matter but based on my personal experience, you're not going to cool a big block with any performance modes like a hotter cam and headers in summer heat at idle with a stock cooling system.

[Mike_The_Grad]

Just throwing this out there, but have you "burped" your cooling system real well? I had no clue it was necessary when I freshened up my motor. I found out pretty quick my ole factory gauge still works spot on as does the sender. I had a couple of air pockets built up that would send my needle almost full tilt after about 30 minutes driving. Not knowing it was air at first, I pulled the thermostat thinking it was stuck. It worked just fine on the stove in a pot of water. So I read that you can drill a couple of 1 1/16" holes just inside the sealing surface of the thermostat. It helps purge most of the air as you fill the system as long as you give it time. Another thing I did to burp mine was to back down one of the loading docks behind my work and pop the rad cap while it idled. Those docks had a nice incline to them and worked perfectly for getting those last little air pockets out.

[weq92f]

My daily driver has a bleed screw at the highest point of all cooling lines ( it also has an electric water pump that has a bleed feature! ). It typically takes a few heat cycles to get all the air out following this...

get up to temp
open the bleed screw until coolant comes out, then close it.

drive and watch the temp.

periodically open the bleed screw to allow air to escape.

let cool and repeat.

[Gromit]

One disadvantage of the stock fan setup (and advantage of the electric fans) is without that whole stock fan and clutch assembly being in the way you have more room to put a wrench on the crank pulley nut to turn the motor exactly onto top dead center on the #1 cylinder for adjusting valves and setting initial timing.

My personal opinion it is major pain to remove the fan and fan clutch just to get room to get a wrench in there to turn over the motor by hand in fine increments.

Those remote starter switch works for that too but they are no fun either; so I guess I just want to point out that the electric fans have at least this one other nice thing going for them to justify the expense.

[mosel70]

Well, last Saturday I was sitting in the long line at the garbage dump, temp outside was only 80 degrees. With trans in gear and RPM at about 700 rpm, I noticed my temp gauge went from the middle range to near red. I then placed trans into park and with RPM at about 1500, the temp needle went back to mid range. I had my newly bought IR temp gun with me. At mid-range, the radiator hose just off the thermostat read 178 degrees. At near red, the temp gun read 212 degrees.

My Mishimoto dual electric fans with controller I mentioned above (05-09) arrive Tuesday from Jegs. Las Vegas heat is about to arrive. I'll let you know how they do.

[Mike_The_Grad]

I guess I should have mentioned in my post earlier that I have a 4-row "Monster Core" Champion Cooling all aluminum radiator with a mechanical 7-blade flex fan and no fan clutch. My temp indicator runs just where the solid band starts on the gauge you have there, once I got all the air pockets burped out.

[webfoot]

Is that an original temp gauge?

What is your timing set at? Not enough advance can build up a lot of extra heat.

[mosel70]

New fans did not solve the overheating issue. With needle in mid-red (new gauge/sensor), upper T-stat hose 208 degrees and lower rad hose 217 degrees and it starts idling rough . I'll recheck all timing next and post results.

[67 chevelle]

Try some purple ice in your coolant , it has worked for me in the past on modified big blocks , make sure your timing is correct , and make sure you are not running lean . all these contribute to running hot .

[Mike_The_Grad]

You said that with your truck idling in gear the RPM's were at 700, and when you put the truck into park the RPM's jumped to 1500? If that is true, something with your timing is off. If you are running a Vacuum Advance canister on your distributor, what vacuum source are you using to supply it? If it's connected to the carburetor, is it a ported vacuum or full manifold vacuum source? These things can effect your engine's timing. Also, if you have vacuum leaks they can cause a lean Air/Fuel mixture ratio which leads to higher combustion chamber temps and higher coolant temps.

There shouldn't be such a large change in RPM's between Park or Neutral and the drive gears. Ideally, it should change less than a couple hundred RPM's.

I'm mostly familiar with small blocks and not sure if the same applies to big blocks though. Each engine and transmission setup is different especially when larger than stock cams, ignition types, and accessories are involved.

[Shinysideup]

Timing, Fuel mixture, Vacuum leaks are all possibilities here. I agree with the others the fan never was the issue. Baseline your tune before spending more $$.

[Jayred]

https://www.summitracing.com/parts/rnb-620-118

$74 for fan and shroud, 2 speed something like 2500 cfm? I bought a new aluminum dual pass fancy as **** and left my crappy china fans in and I can run any temp I want here in Phoenix. I was going to upgrade to this Dorman but I didn't need to. Something else may be up with yours if your still running hot with the new rad. Do your headers look cherry red after a few minutes at idle? Lol. Pull some timing, bleed the system, AFR? No need to throw money at mishimoto

[hjewell2]

Originally Posted by mosel70

New fans did not solve the overheating issue. With needle in mid-red (new gauge/sensor), upper T-stat hose 208 degrees and lower rad hose 217 degrees and it starts idling rough . I'll recheck all timing next and post results.

V8 motor needs at least 3000 CFM I see your dual fans are rated 1300

[mosel70]

Great replies, thanks!! My dual fans have a total of 2600 CFM. I put Purple Ice in today and also checked idle mixture screws. No vacuum leaks. Still overheats.
The rpm increased when the idle mixture screws were all the way in, but as I screwed them out one turn the rpm dropped a bit but after that virtually no rpm change. Odd, I don't know what to do about that. Whether 2 turns out, or 3, or 4, or 5, it still overheats when at idle (~800 rpm). I noticed driving home yesterday that the temp needle initially stayed under mid range while driving in town and only increased each time I came to a red light. But it wouldn't go back down when driving ~45 in traffic.

I think my last two theories are timing is way off as many of you suggested or TH400 trans torque converter is going bad. I'll have a shop in town check my total timing first. Need to get this overheat thing buried. It's gonna be 115 degrees out this week in Vegas! Many thanks for the great tips!

[Mike_The_Grad]

Try hooking up a vacuum gauge to a direct manifold vacuum port, they only cost about $25-$30 @ harbor freight and come in handy for these older engines. They can be a little tricky to read sometimes, but there is a ton of info on here or Google about reading the results. Ideally, a constant steady needle in the 17-22" range is what a engine with no vacuum leaks looks like. Obviously if you have a large cam like the Comp Cam 268h, your reading would be lower than those values. For that you would have to check what Comp Cams lists the vacuum this cam produces. Idle mixture screw adjustment won't tell you if you have a vacuum leak. You should be able to kill your engine when you "lightly seat" one of the mixture screws at idle, and the engine should definitely die when you seat both of the screws at idle. That tells me you may have multiple issues causing your high temp issues.

I say this because I had this exact thing happening with my freshly rebuilt SBC. My timing curve was off and my vacuum advance canister had a ruptured diapraghm creating a vacuum leak. It was hard to figure out the diapraghm was ruptured because when you set engine timing you plug off the port that supplies vacuum to the vacuum advance and plug it back in after the timing is set. When you have the shop check your timing, ask them to hook up a vacuum pump to the vacuum canister and verify that the diapraghm is holding a vacuum.

[Shinysideup]

/\ well stated,good advice!

[demian5]

On my dads BB 68 Chevelle with MT, we installed a huge aluminum radiator and dual fans and a shroud. We were actually able to disconnect one of the fans as only one was needed. Made all the difference. Both fans really drag the charging system down.

[demian5]

Originally Posted by mosel70

New fans did not solve the overheating issue. With needle in mid-red (new gauge/sensor), upper T-stat hose 208 degrees and lower rad hose 217 degrees and it starts idling rough . I'll recheck all timing next and post results.

Random observations and thoughts:
I see no mention of the installed t stat temp or if you even have one, or just a restrictor. The coolant needs to stay in the radiator long enough to cool it down. I like a good 180 in my older vehicles. 195 in newer stuff.
Is it bubbling over when you turn it off?
What temp does it run at speed on the road?
Does it ping under acceleration? (if timing is too advanced, it should sound like marbles in a glass jar under even light accel).
Does it diesel when you turn it off?
is the water pump good?
Do you have something blocking your air flow?