[2PLUSTWO]

I hope somebody can shed some light. I have just installed a 1969 428 into a 1965 Catalina 2+2. I had the motor professionally rebuilt by an guy who has rebuilt pontiac motors for me before without any incidents. When I was breaking in the motor the thing fired right up and sounded great but then the temp gauges started to rise quickly all the way to 230 and I shut it down. I let it cool and checked to see if the thermo was opening and sure enough it was wide open. There seems to be no flow. I removed the thermo and filled the block through the thermo housing, resecured and tried again. Well this time in about 3 min. the temp jumped right back to 230 and there was no flow in the radiator and it started to flow out of the radiator and started to boil. This time it blew the seam in the radiator. No cracks in block or heads... Head gasket???? I used fel-pro. I also checked the water pump plate to pump clearance checks good. Please advise.

[Pzr]

Right initial timing? (9 degrees for stock 67>70 maby more if engines hotted? (I used 12 degrees)
When I was breaking in my own I had to change the initial timing cause it got to hot.
Also, I filled up the radiator while a friend "mushed" the upper and lower coolant hose to get more air out. After that I had no problem getting a stable temp. But I guess the "breakin" is producing much more heat since everything's new. (In my case it was.)
(Now that my breakin is completed I've adjusted timing and vacuum again.)
What temp is the thermo opening at?

Hope someone with greater experience can answer too, the info above worked for me.

Hope you fix it. / P

[BVR421]

take the t stat all the way out and try it

[Bud Lyons]

Do you have the plates in the water pump? If you don't you won't get any water flow.

[george kujanski]

Does the '69 use a 11 bolt pump? if so, make sure the tubes that channel the coolant from the pump plate to the cylinder banks are in place.

George

[chiphead]

Yup,

The 11 bolt pump uses the single pump plate and the two replaceable inserts. If those parts are missing, the pump can't pump much water thru the engine. If no flow and the radiator isnt blocked, pull the pump. Check for the single divider plate, and the guide tubes. You need a good 4-core radiator too. A marginal radiator won't even wipe the sweat off a hot pontiac.

[2PLUSTWO]

Thanks for the reply! I do have my initial timing @12 degrees. I will turn it down to 9. I'm running a 160 thermo that I did check, it was wide open. The radiator is getting recored( I hope the radiator was plugged) and then I'm going to pressure test the system to see if the head is maybe cracked and pushing compression into the cooling. Also, i'm sorry I did not mention I am running a 1965 front cover and balancer. The correct plates are in place.
Thanks again.

[Brian D'Amico]

I can't believe this... I've been helping a good friend with his 69 GTO Convert the last 2 days and we just put in a newly rebuilt (76) 455 with 6X heads. During the break in, we experienced the EXACT SAME THING!!! We've checked the pump, replaced it with a cast impeller and set the timing to 9 degrees. We also removed the thermo. The only thing that is different is it's boiling over at 160!!! (That's if the guage is right) There is no flow through the rad and it's seems to have alot of presure in the hoses. We run it for about 5 minutes.. it gets to 160, then it boils over out of the overflow. My friend is going to re-check the timing again tomorrow. I hope someone can shed some light on these issues.. Pretty odd that we are experiencing the same thing!! I will be anxiously watching this post!!!

[Baron Von Zeppelin]

Sounds like you both have the same problem, air trapped in the water jackets. Drain everything out of the cooling system. Pull the thermostat and leave it out for now, and leave thermostat housing off for now. Leave the radiator cap off. Refill the sysytem this time pouring the antifreeze directly into the intake with a funnel where the thermostat was. When everything seems full (overflowing), replace thermostat housing WITHOUT THE THERMOSTAT. Connect your upper hose. Crank and inspect for radiator flowing. If all is well and staying cool, put the thermostat back in and drive.

When you fill an empty system through the radiator that is "closed off" by the thermostat, there is no where for the block to vent as the water tries to push into the block and heads. Sometimes this causes air pockets to trap which cause fast boil overs, sometimes you get lucky and it doesn't trap air. Hot water + Air = Steam. You don't want steam inside your cooling system.

Also, some water pump/timing covers are designed for vertical flowing radiators (64-67 type GTO radiator) some are designed for horizontal flow (68-72 GTO radiator) , the impellers are made different.

Good luck guys.

[chiphead]

On my 9.3:1 407, I had to core the thermostat. I put the thermostat back in, with poppet valve removed. That way the stat body acts as a slight restrictor, but it flows more than an open thermostat. Dropped my temps from 210 to 185-190. These motors gotta have flow.

Bryan, Try running engine with rad cap off, and turkey thermometer stuck in the filler neck. Watch what the turkey therm says, vs what the temp gauge says. You should see 5-10 degrees cooler on turkey therm than what the in-car gauge says. You should also see rapid water flow.

robertg

[Formulabruce]

lots of newer engines have a air pressure release on the uppermost part of the cooling, like the upper hose. Baron von Zepp is probably right.
Keep in mind the water "pump" is just a circulator, not much of a pump at all, and check the impeller to plate clearance!

[2PLUSTWO]

I would like to thank everybody for the quick replies. The radiator shop called today and told me the radiator was more than 3/4 blocked. I hope this takes care of the problem. This is the original 4 core radiator and I never had any problems before with any over heating, but it was dry for about a month. I guess that all the crap in the tubes dried up and clogged it. I'm going to install it tonight and try breaking the new motor in again. I would like to thank everybody once again!!!!! I will keep you all posted on the outcome.

[Brian D'Amico]

We are thinking we have a blown head gasket. This is why it is there is so much pressure in the rad. We'll investigate more after Woodward. Thanks for all the advice!!

[2PLUSTWO]

Well. Seems all is well. I recored the radiator and Tried it again and walla..... it working just fine. The funny thing is I never had an issue before until I removed the radiator and it sat dry for about 2 months. Just enough time to dry up and start to clog the passage ways. Thanks again everybody for your help!!!!

Mike

[Formyla]

Water doesnt boil at 160' so you must still have air in the system and the thermometer isnt in the water but in the air pocket.

I'd follow the Barons advise on how to fill it.