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Engines running hot…they sure can be a struggle to overcome.

Upon building the RockHer II a few years back, we chose a 4.3 vortec v-6 engine because we knew that under extreme conditions of low oil pressure and high heat, that engine is VERY forgiving. When we set up the cooling system, we chose a radiator that was smaller than normal, but built by Ron Davis Racing Radiators with their recommended double-pass cooling and wide cross-tubes. They said that radiator, combined with a proper shroud and a SPAL cooling fan would handle the cooling, but would be right on the edge. They asked me if I couldn’t go a little bigger in the radiator, I said no, we’ll run with it.

The radiator arrived and it was excellent in craftsmanship, the built-in shroud was a nice touch, and the SPAL fan pushed some serious air, considering its compact size. SPAL was concerned that our exhaust came within an inch of the fan motor…I told them I would keep an eye on things. To this day, we’re still running that same fan. That’s a testimonial to SPAL for sure.

For a water pump, we chose Reid Racing’s electric remote pump as we knew we would be running in the upper ranges of normal temps and wanted to be able to circulate water with the fan on, while the engine was off. That Reid pump was just the ticket. Keep in mind, we had a pretty healthy built 4.3 for the RockHer…bored to the max, BIG valves, short fill on the block, rev limit at 5600, 320 ish HP, 320ish torque…balanced/blueprinted/not even close to stock inside…

After we finished the RockHer and began competing with it, we noticed we were running in the 230 degree range, even on cool days. We began filling the rad to the very top and put a 36psi cap on to kep the coolant from boiling at that temp and the engine survived just fine…still, it was running about 10 degrees warmer than we’d hoped.

Then, all of the sudden after 6 months of competition, it began running at 230 to 250 degrees…??? H’mmm…well, something is up, but what? The gauge or temp sending unit? Change them and no difference. We swap the electric water pump…no change. We check the fan, still pulling at full power. We wrap the exhaust to keep the underhood temps cooler, still no difference. Rad is clean inside so that can’t be it. Nothing stuck in the hoses and no other ideas coming to us…it MUST be the engine.

We pull the race motor and put in a stock engine…that will definitely make the difference. A ton of work, but hey, something’s up, it’s gotta be the engine. NO DICE…STILL running VERY hot!!!????? We end up installing an external “mist” system to assist the radiator through evaporation and although it does help, it is problematic as the mist nozzles keep plugging up. About 1.5 years of frustration and the engine running at SCORCHING temps we are at wit’s end and ready to install a new cooling system with a bigger radiator. 250 degrees will not keep that engine running much longer. They are tough engines, but not indestructible.

SEMA 2008…some guy is hovering over the front of the RockHer as it is displayed in the Stage 8 Locking Fasteners booth. He looks at me and asks if the rig runs hot. Say what??? “ YES, IT DOES, What makes you ask?”

His response: “I’m looking at your muffler. Did you know that in short mufflers, like 13” and under body lengths, that most anything but a resonator style holds in a ton of EGT?”

Then it dawns on me. It ran warm from the start…we ran a super-short flowmaster with the internal chevron baffles in it. It ran 230 ish. Then, because that exhaust was so loud, we built our own muffler based on information we found on numerous websites. That was when it started running at 250. It never dawned on us that Exhaust Gas Temps were WAY higher because of the designs of the mufflers but this guy, who is an engineer at MagnaFlow, knew our problem without us ever meeting him before, telling him we had issues, or even seeing the vehicle run. He was just walking by and noticed what we were running and decided it was something worth telling us. We decided to give his suggestion a try and picked up one of the MagnaFlow 8” body mufflers. The sound levels were between the muffler we built and the Flowmaster, so we’re happy enough there…but the real deal is the RockHer ran 210 to 220 all weekend at the Tucson comp, with an occasional jump to 225, versus running at 230+ all of the time.

AMAZING that something so simple was our issue…
 

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So what kind of internal design is best at scavenging heat? I would assume it's the mufflers that flow the best?

I use a typical 3-tube fiberglass packed muffler, and have the same problems running hot, despite all my best efforts.
 

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The MagnaFlow we ended up with was a resonator style, with a straight thru tube with the holes in it, going thru into the outer body. Not sure what is in the outer body...if anything at all. Here's the page with the muffler we used: http://www.magnaflow.com/02product/02race.asp It looks like it's got a 6" long body, not an 8"///H'mmm, I need to measure that.
 

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Really cool tech, who knew something like that would effect engine temp.

Thanks for sharing Dustin.
 

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but this guy, who is an engineer at MagnaFlow, knew our problem without us ever meeting him before, telling him we had issues, or even seeing the vehicle run. He was just walking by and noticed what we were running and decided it was something worth telling us. We decided to give his suggestion a try
Nice of the guy to do this but even cooler you guess were willing to listen and give it a try. Not often you get free advise but even rarer that someone is willing to listen.
 

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Part of the reason I was able to run a 402 ci LS2 on a Scirocco radiator for so long (prior to this year's rebuild for KOH). Backpressure holds heat.

...and it doesn't hurt that resonator style sound pretty bad ass as well. :smokin:
 

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The MagnaFlow we ended up with was a resonator style, with a straight thru tube with the holes in it, going thru into the outer body. Not sure what is in the outer body...if anything at all. Here's the page with the muffler we used: http://www.magnaflow.com/02product/02race.asp It looks like it's got a 6" long body, not an 8"///H'mmm, I need to measure that.
Cool, good to hear I bought one of those Magnaflo's last week for the new buggy.

How does it sound? like a tractor?
 

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Thanks Dustin. I have an extreme space/shape limitation in my rig, I need to construct my own muffler with a straight through design.
 

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Very cool info! (no pun intended). I'm in the process of putting a 4.3 into my flatfender and trying to cram in a muffler around all the suspension links.

I've been happy with magnaflow resonator styles that I've run in the past (4" and 6" bodies). The only issue I have is that style isn't a spark arrestor, so for me, running at our state ORV parks like Silver Lake Sand Dunes, I need to have the SA. (They check with a rod in the tailpipe:eek::laughing:). Not a concern for racing, I'm guessing.
 

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By the way, with the vortec.... which of the fuel systems are you running as a base? Or is it not based on any of the TBI/CPI/MPFI oem stuff? Just curious what you'd done to support those power levels. Looking at putting together something in the 250hp-275hp range myself....
 

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Hey Dustin,
I just replaced my 2.5" exhuast running a Flowmaster 40. Before, I would hover in the the 220's. I would see about 230 quick. When I was in the boost, it was stupid with this set up. I just went to a 3" exhaust running a Magnaflow, and all problems are gone. I was able to get into the boost and keep it for a long period of time and my temps stayed at 210 or lower. Lower EGT's do wonders. And I thought a 2.5" would be large enough:shaking: Magnaflow is the shiznet!
 

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Keep in mind, we had a pretty healthy built 4.3 for the RockHer…bored to the max, BIG valves, short fill on the block, rev limit at 5600, 320 ish HP, 320ish torque…balanced/blueprinted/not even close to stock inside…


sorry I couldn't find anymore hp/tq for ya. LOL :laughing:thats alot for a mini me V8 you need to send it back so I can go through and freshen it up. its been a few years now.
 

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I'm running one of these, not a glass pack but a tube in a tube with oval louvered style holes punched inwards in to the direction of flow. Sounds Great, reasonable noise level and strait through. EDIT: oh ya, $14 :D

http://www.exhaustdirect.ca/ResNoNeck.html

No Idea about EGT's or overall performance but I had to find something to squeeze it between the floor and flat belly of my CJ9 project. .5" clearance under the drivers seat floor... Might get a bit warm :D
 

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that's great to hear Dustin.

-Tristan
 

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We had a small block Chevy with a similar issue.

We ran a set of custom headers with smaller longer primary tubes that were supposed to help build torque, all they did was help build heat.
 

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320hp from a 4.3L v6?? Pfffffsht, should be at least 450 :flipoff2:

nice, simple and cheap solution, unfortunately after you had already done a bunch of other stuff :Doh:
 
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