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.