The car: 74 Challenger, 318 with mild upgrade and freshened up ('69 block), 340/360 cam from Comp, NON-hp AVS, dual exhaust thru late model Magnum manifolds.

The sit-rep: Only driven short periods (less than 10 miles) since break-in maybe 500 miles ago (maybe less - speedo not reliable) but didn't seem to run overly hot except in the hottest stop and go traffic. seemed to idle at normal op temp in the driveway for fairly long periods (15 min or longer. Upon trying to stop an exhaust leak, I pulled the threads out on one of the out board bolts. Not having a offset drill, I resigned to pulling the head and doing on the bench. It also gave me the opportunity to install the Holley intake, replacing the '67 273 cast iron one I was running. After getting it back together, and running a thermostat this time around, I notice it heating up right away. I pulled the thermostat and it caused it to heat up slower but heat up all the same. It didn't seem overly hot, but temps have been cool lately; 80s. I dove it to a show, Sunday about 15 miles away and it was alarmingly hot by the time I got there. Not as bad returning as it was raining then. I know I need another gauge but my Sunpro was reading 250*+. I say I need a new one because it never pegs down to 0 and you have to tap it as it sticks a little. (Stock doesn't work)

Can I assume the top end of the gauge reads fairly close? Or can I subtract the difference of about 140* that is the bottom end even tapping and its not really and issue. I have been chasing dizzy timing because timing light issues but have it just where it doesn't ping, but dead-stop hesitation is a problem I'm hoping is in the carb. Temp seems un affected by timing

Thoughts? Would the aluminum manifold be a factor (I thought it would be a + as less heat sink). There isn't a great deal of coolant noise when I shut it off after its hot (internal boiling or back-flow into the overflow.)

Thank,
Scott

Have you confirmed the temp with an inferred thermometer? Tell us about the cooling system.

250 degree, it would be puking it's guts out at that temp.

I would confirm the accuracy of your gauge as well.

Cooling sys is 22" Aluminum 2 row core from Radiator Express. 16" electric fan stock water pump. No stat. It seem to run hotter with a new 195* so I took it out. Heater core is by-passed until I get a new one.

I had similar thought. Seems to run pretty good, albeit it needs a little more fine tuning. On hard accel, it seems to be starving for fuel. Lines too small for 4 barrel??

Hello Scott, always good to hear from my Omaha brother. if I read it right it was pretty much OK ex in very hot weather stop & go? then a new head gasket with the head R&R now it is running way hotter? that would point me toward that gasket or its install. I would get a known good mech gauge & see where you are really at for temp but with your current gauge it was OK before & now it ain't. EDIT was ANYTHING else changed/altered/adjusted in the swap?

Lines too small for 4 barrel??

No not even close, not with a hydro cammed 318, look at float level,pump pressure, ect...

A couple of questions for understanding. Does it heat at steady speed? (>40 MPH?).

Also, what type of fan and shroud do you have. Can you post a pic?

I wonder about the 16" electric fan. Aftermarket fans in that size often lack air flow capacity. Almost guaranteed heating at low speed and the shrouds they use may block airflow at higher speed.

Also FWIW the boiling point of pressurized 50/50 antifreeze is over 250F. I agree good idea to check or change the gauge but it could be right.

Update: Temp reading may not be too far off; Wouldn't start. Analysis: Timing has jumped. stretchy chain too. crank moves 30* - 40* before distributor moves

Robert, I'll drive out a see you in person one day when this think can make it LOL. Only thing that changed, is, I swapped a stock cast-iron intake for an aluminum Holly intake.

Heats up gradually at any speed stop and go or freeway speed

Just the shroud that is integral to the fan. I have it installed to suck rather than blow anticipating a condenser for air-conditioning.

Timing could be a heating issue.

So could the the electric fan and shroud. Can you post a picture of the fan/shroud setup?

More info/update on that

New timing set but that's about as far as I've gotten. My daily (03 Durango 4.7) is down with a rod knocking. Priorities (rolling eyes)
Anyway, someone asked me if I was sure I had gaskets installed correctly. I was pretty certain I had but of course, I started second guessing myself. So i pulled the intake and realized the metal gaskets can't be reversed front to back due to the dimpled locating holes and they are a mirror image left to right; (Correct?) And the head gaskets cant be reversed due to the locator pins in the block.(Yes?)
So I guess the next step is to revisit the fan shroud. Thought I still had stock one but must have lost it when I moved. Custom fab time (after the durango is running )

I had battled a high coolant temp issue for a while (stock system with shroud). The temperature would slowly creep up to 220-230 no matter how the car was driven (highway, stop and go). Turned out rust/crud from the engine (which had been tanked when rebuilt) slowly clogged my new radiator. I had the radiator rodded out, put in a TEFBA filter to prevent the radiator from getting clogged again and the temps are normal now. I did see significant crud when the filter was first installed, and it is still trapping small crud particles. Just something to consider when all else fails.

I tell people about running a screen,filter all the time, no one listens , Baffling

Hey CSK, could we have more info on your filter as to make and where placed?

Thanks, Joe

You can get the TEFBA filter on ebay - for what it is its not cheap and is an obvious non-stock item in the engine bay (not a problem if you don't care about non-stock appearance), but it is easy to clean the screen. I've read some have placed a screen material or even pantyhose in/around the return inlet on the radiator and then placed the hose over the screen and inlet to hold it in place. A drawback with this approach is cleaning the screen is a little more difficult/messy, but it is cheap and effective.

GANO FILTER HERE

See the double clamps on my upper hose.

You never answered his question , did it puke coolant ? If it didn't then it wasn't 250 degrees, as indicated by that POS sunpro gauge.

Do you have the stock factory temp gauge setup still connected?