I just finished my restoration. All original car, rebuilt the 400w ith .30 overbore, new everything and new be cool aluminum radiator which is way over kill for this car (should be anyway). I took her out on her maiden voyage tonight, after a five mile trip, I returned home, the gauge was showing 225 degress and she started to spew coolant from the overflow line. Funny thing is, it didn't overheat before the rebuild and I upgraded the old cruddy three core tank? Does anyone know what it couild be?

Just in case anyone was wondering, yes, I enjoyed the hell out of my 5 mile trip, it's been a long time coming, now to fix this overheating problem.

if you have a new waterpump, did you check to see that the divider plate is as close to the fins as possible? it seems the consensus that tweaking the plate closer can help alot. there is also a pump with a cast iron impellor which is supposed to be better. do a search in tech help on 'divider plate' and you should get some good hits.

once it's running cooler, the antifreeze will still spew out a little if the radiator is filled all the way to the top.

Check your oil level, your timing and your mixture. Adjust the timing a little or richen the mixture a little if necessary, and keep your foot out of it until the cam breaks in. Pull the plugs and turn the engine by hand to see if you have anything dragging or tight. A brand new rebuild will run a little hotter than it will once it's broken in, but 225 is too hot. Also, your coolant mixture should not boil over at that temp if you are mixing 50/50 antifreeze and water.

Sure that your temp gauge is correct?

You may have had an air pocket in your block. Make sure you purge all the air when filling coolant. A little drooling is normal no matter what your mixture. If you have true boiling and steaming it could be the air pocket.
Jim

Thanks for the tips fellas, I'll try all of the recommedations and see where I get. You guys are the best!

68Bird400, my rebuilt 400 was running very hot last month, so I bought an aluminum radiator and an electric 16-inch push fan on the front. Previous temps went over 220, but now, in the heat of Tennessee summer, it never goes past 200. In the early morning hours on the way to work (35-40 minutes) it stays at 190 or so. Only in the afternoon sun does it get near 200. BLUF, these blocks run hot and you might as well get used to it, I suppose. :rolleyes:

The cast impellars are supposed to work better, but the aftermarket stamped impellars do fine, too. Sounds like it may be a timing problem. What is your timing set at?

Fresh rebuild, it is possible that the tolerances are still a little tight as well.

Good luck! I JUST cured my overheating problem at idle. Turns out the impellar would spin freely on the pump shaft. I would get some coolant flow until the engine started getting warm, then it would bubble and spew. The water mixture was boiling in the heads.

Fixed the pump and now there are no ill effects. Runs at 180 in 98 degree Tx heat and high humidity.

How did you diagnose the water pump issue? Off car or on?

I've got a new water pump and divider plates coming tomorrow from Ames. The bearing got toasted in the old one. I am going to try to minimize the divider plate to impeller gap and see if that helps the cooling.

Actually, you can diagnose the water pump problem wither way. With the engine idling and operating temperature you can open the radiator cap and look inside (BE CAREFUL!! The coolant is HOT! Don't put your face right over the filler neck. Shine a flash light down in the neck) There should be a constant flow of coolant if you rev the engine a little the coolant flow should increase.

Otherwise you can use a mechanics stethescope and listen to the water pump housing.

All sounds familiar..I had posted here last fall with my 350 HO rebuild probs and I was running 225 as well. I installed a new aftermarket 4 row radiator and put in the metal sheilds on top of the radiator and it runs around 205 now. As the engine is breaking in it seems to be running cooler. I will attempt a rally gauge conversion next week to get a better reading. I will say this take your car into a service shop and have them take a heat gun to the engine that way you will know Exactly what temp your at. By the way my 350 HO has no take off power, I can't even burn rubber....seems like I gained HP at higher speeds only when I upgraded my 350 to the HO.

pmdclasics,

Now that just doesn't make any sense at all and you've got alot of us wondering about your rebuild!

I don't know your tranny or rear setup but a rebuilt HO should allow for much rubber burning in several gears, depending upon your commitment to puncing the pedal and your use of the clutch (if you have a manual tranny). What do you think has caused your issues with low end power?

Might be to much cam. I am going to have the rebuilder drive my car so he can get an idea of what is up.