overheating '78 TA
 

1978 Trans Am 400, 4speed runs hot. Car has Holley Sniper Quadrajet, Holley Hyperspark distributor, Holley in tank fuel pump. New 4 core radiator. New fan clutch. New hoses with spring in lower hose. New 180 thermostat [2nd one]. New water pump, divider plate and bushings. Tight clearance between plate and impeller. Lowered timing from 18 to 17. Total timing set at 32. Car got up to 245 at 60 mph. Dropped to 222 at lower speed. Just replaced head gaskets today and test drove close to home. Temp got up to 225 without ac on. Will pull thermostat tomorrow and test but this is a high end stat and did same on other stat as well. Flushed cooling system before changing head gaskets. Not sure what to do next. Any ideas?

Cast impeller? Lean mixture? what gauge are you using?

I else heard the 301 water pump can be used, but the impeller is way smaller, ive never had 2 side by side to compare. Maybe someone else has.

Cast impeller. Reading to fuel injection screen for temp but when it reads 220 so does the factory gage. I richened up the mixture and test drove it with no change.

Check your balancer for correct TDC. If old balancer, outer ring may have slipped causing you to run retarted timing. I would also run a 160 thermostat.

You alluded to new head gaskets, I'm curious why the head gaskets were changed earlier?

If there was compression gases getting into the cooling system it's possible that it wasn't head gaskets, and instead was a cracked cylinder head, and is still getting compression gases into the cooling system, causing it to still overheat.

A simple way to test for compression gases getting into the cooling system is to take an old water bottle and fill it most of the way up with water, submerge the end of the radiator overflow tube in the water, then observe to see as the engine idles and warms up if you get bubbles from the end of the overflow hose.

You'll never get it to run cool if the upper portion of the water jackets are being filled with gases as the engine is running.

Not saying that this is your problem, but it seems you've tried most of the common cures for Pontiac V8s to cure overheating. Just a suggestion for diagnosing a problem that I've run into in the past.

Something sure isn't right. You would think that cruising temp would be lower than at lower speeds. At temps that high I would expect that you would be puking coolant all the time..

What are the details on the engine? Compression ratio, cam, intake manifold, heads? Where is the temp sensor mounted?

Would definitely check that the balancer is ok and TDC is correct. The initial timing should be fine, but you can for sure add some more total timing to around 36 degrees.....more at light cruise conditions. What is your target AFR on the sniper and are you tuning with a laptop or just the handheld?

Does that distributor have a vacuum advance?

If the short block is a fresh build, it could be excessively tight, causing it to run hotter than normal due to increased friction. If it was redone, how much were the cylinders bored?

Agreed. Seen this many times. Engine starts to run cooler after miles are put on. Check basics 1`st. But sometimes it`s just a tight motor on a fresh rebuild. Mostly pistons and rings causing excess heat.

Overheating, e,ectricsl, carb issues, so on, are tough on a forum to fix. Get a good mechanic

Less likely but have seen too much engine sealer used in a build clog a radiator. Be a good idea to get it flow checked.

Both 265/301 and 350P/400 use 9796349 impeller plate, and 482171 pump to housing gasket.

HOWEVER,

265/301 use 12309445 water pump. 350P/400 use 12300305 water pump. It is most likely the impeller is the only difference. They will bolt up fine.

265/301 pump:

https://i.ebayimg.com/images/g/9VIAA...hD/s-l1600.jpg

https://i.ebayimg.com/images/g/qDYAA...hF/s-l1600.jpg


350P/400 pump:

https://www.carpartsdiscount.com/doc...301280-bot.jpg

oops...didn't read entire posts...

update
 

Engine is stock with 85k miles on it when I got the car. I replaced the head gaskets as I suspected compression getting into water jackets. I am using handheld to adjust specs. I do not have a laptop.
Today I pulled stat and checked. It did not open so bought another and checked before putting in. It opened fine. Test drove and still ran hot. Removed water pump and ran water thru block to check for blockage. Water flowed thru block, heads and out thru stat housing very well. Replaced the Flow Cooler water pump that I had on it with a conventional cast impeller water pump. Test drove and it is much better. So much for $135 Flow Cooler water pumps. Should be called Flow Hotter.
Still runs a little warmer than the '76 TA I unfortunately just sold.
The hyperspark Dist. is computer controlled. No vac adv. I did have it set for 36 total adv. but lowered it to see if that was cause of heating issue. Right now target AFR is idle 14.5, cruise 13.8, wot 13.0. Car runs very well but not sure what AFR should be set to. And should I set total timing back to 36.

I'm getting ready to install a FlowKooler 11-bolt. :(

Hopefully I'll have better luck. I've done a lot of research and the worst case scenarios I've generally seen with it are that people see no difference in temps. My old water pump was a stamped impeller A-1 Cardone unit and the clearance was friggin' .200"!! So I know when I put on the flowkooler, ill see SOME change lol

Glad your problem has improved!

the water pump to plate clearance should be adjusted by the plate itself, not how the water pump fits. meaning you could have fixed the .200 clearance, although the stamped impellers are not as good as the cast ones for longevity. even the cast impeller pumps can have different clearances that will need adjusted by bending the plate.

Oh, yeah, trust me I know LOL

I just wanted to put a better water pump on the car, anyway, since I already identified the water pump on the car as an A-1 Cardone unit before I took it off. This forum brought to light the inconsistencies and quality control with Cardone back in the 2000's and 2010's; so I figured, the one on my car is probably garbage, so let me get a better water pump while I'm at it. Most of the reviews on Summit for the Flowkooler are positive, Butler swears by it, and the GENERAL consensus on this board is neutral or positive—so I went for it.

The Flowkooler I got came with their divider plate, and right out the box, the clearance was around .075" with the gasket added. I got greedy and got it down to .050" as recommended in Jim Hand's book. Pretty happy with it there. I'm installing it soon, hopefully it gives me better coolant flow at idle. *Fingers crossed.*

just wanted to point that out since you didnt mention adjusting the plate. never used a flow kooler & honestly never had a problem with A1 cardone pumps when clearanced right, have one on a mild built 78 W72 for going on 12 years now, cant get the temps over 190 with a 180 t stat no matter how hard i try. same for a stock 81 301t. A1 pump & stock 4 core radiators on both that cool great.

i have a PRW brand aluminum pump with cnc'd impeller blades on a 500+hp stroker motor & a cheap price 3 row champion rad that also cools great in all conditions.

i realize every car/engine is different & its a mystery why some cars have such a problem cooling while others cool fine with lesser radiators & parts. has a lot to do with the tuning im sure. hope the flowcooler works out for you.

I appreciate it. :)

Honestly, my cooling problem isn't really that bad. At speed, or cruise my temp stayed only 10 or so degrees above stat temp, but on real hot days it would creep up in traffic or at idle slowly but surely over 15-20 mins. A couple times it got up to 215 or so. I live in SoFlo.

I figured it was a flow problem since even if at idle, if I rev the engine and spool up the water pump, the temp would start going down. And obviously it would go down when I start moving.

No matter what, my clearance was excessive with the old water pump. So not only will I be putting on a new pump with a better impeller, but also a very narrow clearance. I'm excited to see if it makes any difference.

im sure florida makes a big difference compared to most places, im in iowa & although we have terrible winters & mild spring/fall... the heat of the summer can be almost as bad as florida... mid 90's & terrible humidity but luckily it doesnt last that long during july & aug.

as much as the divider plate clearance is mentioned, some members on here say they never clearance the plate & have big gaps like your .200 & dont have any cooling issues. so its hit or miss & the rest of the system like tune, fan/shroud etc play a big part in how a car cools. i would imagine your new pump will help though.

nice looking 79, my 78 is a black W72 4 speed hardtop.

Yeah, in FL the humidity is almost year round. So I'll take any measure I can to keep this car near 'stat temp in all conditions. Point is, an inferior part with a big clearance was on the car, and that is a known issue with Pontiacs, so it's the first thing I tackled. These temps I told you about are WITHOUT AC, mind you. Pretty sure it's not an airflow problem. Using stock shroud, stock 19" 7-blader, a brand new Hayden 2747 HD clutch... heck, I even got some weather strip to seal the shroud against the radiator. At idle speed, a piece of cardboard will get sucked against the condenser. Pretty sure it's just insufficient coolant flow at low RPMs. Also using the original overdriven 6.5" AC water pump pulley.

And thank you so much! I've had 'er for almost a year and a half now. It's got its hangups like any 40+ year old car that hasn't been completely gone through, but it presents well. Like a step or two above a driver, if you will. Got any pics of your '78 to share?

Right now I'm a little concerned, though. I pulled the old water pump a few days ago, and like a dumb*ss, I didn't drain the cooling system thoroughly enough. Not only did I make a huge mess when the water pump came off, but as soon as I removed the two long 3/8" bolts that marry both the water pump and timing cover to the block, I saw a small coolant leak spring and dribble down behind the timing cover where it meets the block, right at where the coolant passage is on the timing cover-to-block gasket on the passenger side. I'm hoping it's only because I undid those bolts, and when I put on the new pump and snug everything back down, it'll seal it back up. I figure that undoing those bolts caused the tension/pressure from the intake-bypass connection where the donut o-ring and draw bolt is to overcome and unseat the timing cover toward the top just enough to spring the leak. It only takes .003-.005 for water to seep through afterall.

Really don't want to have to pull the timing cover and re-gasket it. If it does seal back up when I cinch everything down and refill with coolant, I'll do an oil change just in case before I start the car.

the a/c condenser can restrict flow, one member recently had a thread about overheating when he installed the condenser, said it was ok before that. but these cars stayed cool from the factory so the a/c parts shouldnt be related to your overheat.

i did see your post about the timing cover leaking. if the gasket is newer or in good condition & isnt ripped it should seal back up when you tighten it all back down.

heres a pic of my 78, 400 4 spd. no a/c.

Hmm, perhaps. Id hate to have to sack the AC tho.

Interestingly, I don't know if they're related but I noticed that the heating up in traffic or idle has occurred after any time I rev the engine to 3500-4000RPM and cause a belt to chirp that I've been dealing with. It could've been an issue the entire time I've owned the car, but I'd have never known since I VERY rarely wring the car out. I drive it like a granny and I'm delicate with it.. ill usually shift at 1800rpm. So I looked around and noticed my power steering pump was installed years ago without the .250" rear bracket spacer, causing it to bow downward and misalign the pulley so maybe that's the source of my chirp. Also using same width belts on alternator and PS pump even though the PS pump should be slightly wider. Anyway, like I said, I noticed the heating up occurs after that belt chirps... can you think of ANY relation? Maybe once the belt chirps, it starts slipping thereafter even though I can't hear it, causing the water pump not to flow coolant as well?

Man, is your 78' a beaut! I bought a 78' SE clone without t-tops back in 2008 site unseen off eBay and it was a disaster. Turned me off from old cars for years while I had a 2010 Camaro. In that time I developed a taste for the 79-81 body style and ended up getting this one last year from a guy a bit up the road. Went to go look at it first lol like a smart person.

i dont think a slipping or chirping p/s belt would cause overheating since the alt belt also drives the pump pulley separately. sounds like you have checked all the right things, see what the new w/p does & go from there.

thanks. it had the common gold decals but since it has a red interior i chose the silver/red bird that came on white & silver cars when it was repainted. a friend of mine has a 2010 rs/ss camaro with a mild cam & lots of bolt on goodies, its a nice modern car but not as fast as it should be for what it is with modern technology.