I seem to be having a bit of overheating or overreacting, depending on my problem here. First off, I am running a crappy Sun manual temp gauge that likes to jump up to around 230 when I am stopped at a light for more than 3 or 4 mins. I am running a 16" SPAL fan with a 433162 radiator and a probe style therm switch at 195* on 185* off. I am running a 180* thermostat. While at cruising speed I am running 170 to 180* all day long, it is when I am idling too long at a light that the gauge starts bouncing. But as soon as I take off, it drops back down. During these spikes the fan does not kick on, so that makes me think that the gauge is crap. The gauge temp sender is currently in the intake on the pass side by the neck. This leads into my dilema. I am running Brodix IK200's and the temp sender holes are not pre-drilled (and I really hate to pull the heads to drill them out at this point). So, what I would like to do is pick up a good Autometer electric temp gauge and run the sending unit to the same place I currently have it and then get a new SPAL thermoswitch for my fan and put it on the other side of the intake. My concern is whether or not that is a good place to draw a reading for the switchs/sending units and also if it affects flow at all having the probe's in the intake passages. Any suggestions you guys have would help. I really hate to pull my heads, but if it comes to that, I suppose I will. Thanks guys

That is where mine is in my bb and the temp senson in the rad set at 190 on 175 off

I ran a mechanical Autometer water temp probe screwed into the 1/2" NPT boss on an Eldebrock Air Gap rpm with no problems. The fan temp sensor was in one of my heads but you can run them in the radiator.
I suspect your temp gauge is not calibrated very well....just replace it before you change anything else.

Thanks guys. I will pick up a new gauge on my way home today and see how that works. I will keep the probe in the radiator for now, if the new gauge reads right and I don't have any temp spikes.

The in-block temp is gonna be hotter than the probe type sensor reads for sure. I bet your mech. gauge is right, let us know what you find though. Your engine cares what the temp actually is in the engine, not so much what temp the outside of your radiator fin reads with a probe.

Throw away that POS electric fan and put on a mechanical/flex fan.

So, I went by Advance on my way home and they sold the one Autometer electric temp gauge they had. I am not a very patient person, so in an attempt to do something, I went home and wired up a manual overide toggle switch to atleast kick the thing on myself when the temp starts rising. I also looked for another thermostatic fan switch that is adjustable to temp down the controller and actually make it kick the fans on when it should, but they didn't have that either. Well I took the car out for a short drive (about 15 miles) and the temp holds right around 170 to 180 while at cruising speed and was staying below 190 at stops. Everything was going good until I went to turn down my alley to put her back in the garage and the temp jumped up to around 240 very quick. So I flipped the fan on and it cooled down fairly fast, but not sure why it spiked up so high that fast. I just feel like something else is wrong here or I like originally posted, maybe I am just overreacting. It has not ever actually blew the cap and steamed out. I just can't figure out why it would be running so hot at low speed other than my fan not kicking in when it is suppossed to. And even with the manual toggle switch, I am afraid I may not catch the temp increase soon enough. So here are the knowns, to help you guys help me:
38* total timing at 3000, vac adv plugged
180* Robert Shaw stat
probe style fan therm 195* on
Aluminum rad
16" SPAL
lower hose is stiff, not collapsing
Sunpro mechanical gauge, sending unit in intake next to neck
recirc'ing overflow tank

only thing that is not new is the water pump. It is a standard flow not a high flow, but at 375 hp I don't think I need an HD pump. Maybe I'm wrong. Any suggestions you guys have are always welcome. I know a lot of you all are running e-fans with no issues, so until I get an overwhelming "toss the e-fan and go back to the clutch", I plan to keep it. This is starting to get frustrating:(

vac adv pluggedI see that as part of your idling temp issue. What's the initial timing at idle? Late/retarded timing puts a LOT of heat into the cylinder head and exhaust, and it's usually worse at low speed, since the mech advance drops out.
The other possibility is that you are creating steam voids. If steam pools around the sensor, you'll see a rapid spike in temp that's not "real," at least not at first, but could become that way if not cooled off. BTW, does the temp spike stay high if you rev the engine up a bit?

When you say probe style fan switch, is the temp sensor mounted IN the coolant stream somewhere, or stuck to a fin?

Todd,
IIRC the initial timing is close to 12*. I am not really sure why the vac adv is plugged, my engine builder said to just leave it that way, since I have a DP and a 4 speed, it would be fine. I haven't tried to rev my engine when it spikes like that. I didn't think about a steam void. What I do notice is that when it begins to spike is right around 195ish and it goes really fast past that over to 240-250 then settles back at around 230, then I flipped the fan on and and it worked its way back down steady to 190, where I shut it down at. Something that was odd today was, as I was slowing down to make the last turn onto my street, it was initially at 180 and kept bouncing up to 190 and then back, about 5 or 6 times before the big heat spike. The probe is in the radiator fins about two fins down from the inlet hose.

Todd,
I think you may be right on with the vacuum advance. I read through a bunch of posts about it and I am begining to think that may be my culprit. Just to confirm though, the vac port i need to use is the little one on the front of carb plate right? looks like the only one it will fit on. I have the power brake booster plugged into the large one in the back. Also, on that point, I am confused about something else; I have my PCV ran to the intake vac port and my brake booster to the carb vac port, is that right? I don't know, I am confusing my self now:confused:

John,
The vac advance is probably only going to be a part of it, IMO. I'd definitely do that, and I prefer manifold vac for the vac advance- meaning vacuum that is present at idle as well as part throttle, and it disappears as you open the throttle and intake vac disappears. Just find a port on the carb that fits those conditions, hook it there. You'll need to know how much pull the can has- at 12 initial, 38 total, I wouldn't want much more than 12-14 deg tops. Be prepared for your idle to jump up several hundred RPM- you'll have to set it back a bit.
Maybe consider bringing the probe ON point down 10-15deg. The outside of the rad must be a good bit cooler than the water, and air blows directly on the probe when moving, so the fan controller needs to be set to accommodate for that. I've never played with one of those, but the engineer in me would want to plot the probe temp vs. engine coolant temp to see the delta between the two under various conditions, then decide where to put it.
On the steam voids- are you sure the system is full, and your 15lb rad cap is working correctly? Does the top hose feel full (squeeze it)? I always fill my radiator to the top, then push the top hose down, let it fill, top of the rad again, repeat a couple of times. Best way I could think of to get the air out of that hose. Some of the pros here may have an even better way...

Good luck!

Todd,
Thanks again for the help on this. How can I test how much vac my can is pulling? With a vacuum tester? or just trial and error? I know that I have a medium wieght advance kit, if that helps. Also, by push the top hose down, do you mean to try and burp out the air? I am running a 16 lb cap as well, should I get a 15lb? I am going to order a new temp switch for the fan control, cause the one on it right now is not adjustable, and I think that you are right with the outside air temp on the fins being too cool to kick the fan on.

Put it in the front passage between the heads that the thermostat is.

http://www.nastyz28.com/forum/gallery/data/587/medium/Race71_EngDrv.jpg

hhott71,
Are you talking about the red wire you have running up the block then under your top hose? I see you have your gauge(i think) in the port on top of the intake. That port is the only other one I have available on mine and my top hose runs directly over it. I have my gauge sender in the port on the opposite side on top of the intake. I do not have one on the front of my intake (performer RPM). I am considering getting a water neck that has a 3/8 NPT hole in it and putting it there, or putting my swivel neck back on and using that port that your gauge is in, but that passage on mine is very shallow. Thanks.