Got the carb leaned out a little, swapped the vaccum advance to a vacuum port rather than a timed port, runs super now, but in 4 miles the temp climbed to 200+. Note - Temp here was 97 degrees.

I am suspecting the thermostat is a 190. Thinking of going to a 160. Motor is a 400, Holley 750, Hooker Headers, Crane Cam.
Regular Mech fan, with a shroud, and a single Elec Fan.

Comments, Ideas?

200 + in Az (or Texas) when its 97F outside is pretty normal....I`d drive it farther to see how the 200 holds....205-210 would be ok too...but not more...I`d first rich it up some...the 190 TStat is fine...

my first question on 400 engine, do you have all the fillers? 1) lower air baffle 2) X fillers 3) Masticated or rubber fillers

the single electric fan , puller or pusher? if pusher , you`re probably blocking more air than getting benefits...i`d get rid of the pusher fan (my car had one when I got it...no benefit,just blockage)as long as youre 40 mph , no fan necessary anyway , just for slow speeds...

Just for starters.... 19" fan? Is the fan in the correct location in the shroud? 200-220 isn't overheating.

Welcome to the world of Pontiac ownership. They are notorious from running hot.

You will find a LOT of discussion about thermostats, blueprinting water pumps, water pump divider plates, the use of aluminum radiators, HD clutch fans, fan shrouds and adding the metal and rubber baffles that were standard on 400 and A/C cars.

I went will all of the above as I was originally putting my car together in the Phoenix area. Pushing 100 already? Man, I do not miss that.

I have been battling this issue for the last 7 years. I have done everything and tried everything. Guess what it turned out to be. My fan. As Jim mentioned above, make sure you have the correct fan. I JUST recently found I had the wrong fan (16", 5 blade, non-clutch fan. Installed a 19", 7 blade w/ clutch. Proplem solved immediately!!!!!!!!!!!!!

PS It was almost 90 here on Sunday and we purposely drove the car all over, let it sit and idle etc. and she never ran warm let alone hot

Describe the temps? what is a proper temp for a 400

Automatics usually run between 180-210. 4 speeds usually sit right at what the thermostat is.

it all depends on outside temps too...Michigan car will likely run cooler than Florida, Az ot Tx cars..

my car runs 190F 6 mo of the year, then as it gets to be 90 outside it goes to 205-210 dep on days...
last friday drove to Corpus...205 all the 200 miles in 87-88 F weather...cooled over the weekend...73F out on the way home, stayed at 190 for 3 hrs straight...

Just for reference, the temp warning lamp on our cars would not light up until temp reached 240 degrees.

Thanks all for the replies. There is what appears to be a small coolant leak around the thermostat housing. So I will clean that up, check mech fan size and look at the elec fan as well.

I may upgrade the radiator at a later date.

Well tonite checked the fan, it is a 19" with a clutch and it looks new. Yanked the theromstat and it is already a 160. Cleaned it all up and replaced it with a new one.
Gonna run it hard tomorrow.

Radiataor appears to be a 2 core. Checked at NAPA and the have a 3 core. Does anyone have a link on a 4 core? Do not really want to go thru all the BS of putting a 4 core alum in.

I run a 4 row (non-aluminum) desert cooler from Ames, with heavy duty clutch fan and all the proper fillers and still push 210 on hot days in traffic (with 4 sp). I'm not a fan of low thermostats. Whether you have a 160 or 190, they are both going to be wide open at 200F anyway. And the motor will run too cold on cool days. You have a 2 row rad? Was your car a 6 cyl?

Heres my standard op after having FB's since 75.

Aluminum radiator with 2-1" wide rows of tubes. 4 tubes works nearly as well.
160-170-180 stat depending on street-street/strip. Most mild hp built Pontiac's run best at 185-195*.
Drill 2-1/8th holes in stat.
Have all the core sppt baffles.
Shroud with 19" clutch or flex fan(make sure its at least 1/3 to 1/2 way into shroud. Not all the way in or out or it wont pull thru radiator well.
Plug coolant bypass to x-over from tmg cvr.
Remove r/r htr hose fttg and plug head.
Plug heater inlet nipple at tmg cvr.
For racing, run a hose under intake from both back heads up to x-over.
Use a big HD(small tube) aux cooler in front of rad for trany(ALL CARS).

From your original post i would suspect timing.
Especially with a aftrmrkt cam.
I have found most are ground 2-4* advanced/retarded depending on profile.
Have a Crower RAIV w/87cc E-heads in mine.
Set it up to RAIV specs, and could only get 12.40's(110 mph) with temps creeping to 210-220 between rounds(180 stat).
Other guys are dip'n down to 11.80's/12.10's(112-113 mph) w/nearly the same set up with alittle more c.r and rear gear.
Decided the heck with initial idle tmg, and set it to 38* @ 3500 rpm(disconnected vacuum can).
Idled alittle ruffer, but temp stayed @ 190-195.
BAM! Ran a 12.20 @ 112 mph.
Further testing showed it wanted 42-44* initial @ idle, but didnt chance it cause it was 87 octane.

So play with tmg and jetting some more after your sure the cooling system is correct.
Check your plugs after a high rpm run as soon as possible. Dont let it idle long.
They should be a light tan color.
White is to lean and will make it run hotter.
Black is to rich.

Thanks Poncho

I havn't checked timing yet.

Poncho, from my experience with my bird, your advise is dead on. I've been through each and every one of those steps myself and I now have finally beaten the running hot syndrome. I am running a two core alluminum rad, 19" 7 blade clutch fan, ALL baffles/fillers, 190 thermostat, and one bottle of Royal Purple watter wetter type product. And finallly have the timing set correctly for the new roller cam. All in all, I am now running 190 max. Even the other day when it was darn near 90 I let the car sit and idle and it didn't even hit 180. All of this after 8 years of running hot every season!

Hey Poncho,
How did you plug that bypass to the cross-over?
(I like your ideas except for disconnecting the heater hoses, I need my heater to work up here.)

Do you mean 42-44 total at 3500 rpm or 12-14 initial at idle?

Allen hex "internal" pipe plug from hardware store.
Dont remember exact size, but can check tonight.
I just took a tap with to match'm up.
Not sure how much good it did, but figured it couldnt hurt.

Dolp!
From beer belly memory(as 69Fbody says) with other cars in between.
And why before and after notes are so important...make a note to self to take better notes...
16-18 initial with vacuum can disconnected(which is set to give another 10-12).
42-44 total.
400 block/455 crank/87cc E-hds/Crower RA-IV/1.65 roller rkrs.

Another prob found was the "used" Demon 850 needle/seats were altered, and would'nt adjust properly,
Replaced them with std holley's, and went down five jet sizes since then.
Idles better, but havent been able to test yet.

Thanks Poncho,
I'm going to keep your list for when I actually get the car running.

so, how "hot" is Hot now? And, did you check for the fillers?



is this still true? and if you drive it 60 miles...then what?
if it stays at 200+ in 97F your fine!

Bjorn's right.
All Pontiac's used 195* stat's from the factory, so 210-220 is normal.
I like 190* average myself.