So the new 400 is in and running.. but I seem to have encountered a problem.
So you know what it is... it's in a 78 F250 4x4.

I test ran it a few times for 15-30 second without water before everything
was in the truck... fired right up ran great.

Got it all in and together ( rad, hoses, front clip etc).. ran it last weekend for a few mins.. but the water pump sprung a leak so I changed that today.

While letting it warm up today... it got hot. No temp sender or probe to tell you how hot..but hot enough to boil the water while idleling. No load( do driveshaft so I can't take it for a ride)...just idleling and some reving. Fiddled with the new carb ( Holley Avenger 670)... and checked timing.. dead on timed @ 12 BTDC... But water still boiling like mad. Thermostat is opening..and there is circulation...so I am a little confused as other then this new issue.. thing runs like a top. ( other then I need to build a heat shield for the new headders as that will be a problem in the future I can see already)


Anyone have any ideas for me

 

So the new 400 is in and running.. but I seem to have encountered a problem.
So you know what it is... it's in a 78 F250 4x4.

I test ran it a few times for 15-30 second without water before everything
was in the truck... fired right up ran great.

Got it all in and together ( rad, hoses, front clip etc).. ran it last weekend for a few mins.. but the water pump sprung a leak so I changed that today.

While letting it warm up today... it got hot. No temp sender or probe to tell you how hot..but hot enough to boil the water while idleling. No load( do driveshaft so I can't take it for a ride)...just idleling and some reving. Fiddled with the new carb ( Holley Avenger 670)... and checked timing.. dead on timed @ 12 BTDC... But water still boiling like mad. Thermostat is opening..and there is circulation...so I am a little confused as other then this new issue.. thing runs like a top. ( other then I need to build a heat shield for the new headders as that will be a problem in the future I can see already)


Anyone have any ideas for me

 

Howdy,
I know this may sound stupid, but, is your water pump pumping? And if so is it doing it at 100%?
-Chirs

 

That better NOT be just water in the cooling system

Should be at least 60%-40% coolant to water

The thermostat only starts to open at the pre-determined temp.

Cooling systems with proper ratio usually handle 220*F.

But are you sure it is boiling & not bubbling from a compression leak?

 

Head gasket leak, or missing fan shroud.

 

Sounds like a t-stat to me..........how do you know yours is opening? Was the radiator hot?

 

Ok a quick run down... yes plain water as I wanted to clear the system of any debris, check for leaks etc before throwing away $25 on antifreeze until i've determined it's all good.

Rad and cap came out of a running truck I parted out last weekend, no leaks,no overheating, plus i've felt the rad... no cold spots.

Yes there is a fan on it..no shroud. But again sitting in the shop, no load at idle I suspect you should not boil water.

Screwed around with the idle mixture screws on the new carb...but I am not sure that helped a whole bunch.

More burping then one would expect so I am starting to think a dreaded thing.. I am hoping the new headgaskets sealed up ok... I didn't really want to pull it all apart again. See the motor was a complete build up 10 years ago...ran for 1000 miles, then the truck was wrecked. The guy pulled and stored the motor. I picked it up a couple months ago.. tore it apart to check things out. You could eat off everything. So some new gaskets and back together she went. So as it's "sort of" been broken in.. I am not thinking it's so tight it should run that hot.

Yes it was primed with a drill and a shaft prior to running it.. several times.

Speaking of oil.. funny thing. If you are running hot enough to boil water, would your engine oil not be close to or equally as hot? I pulled the dipstick last night to check level and such..wiped it off with my fingers. Warm but not hot by any means...
I wonder what the heck that means....

As for today I will pull the stat... and let it flow free.. if it burps and boils right away I will likely have to go further. If not, check for vacuum leaks and such.

Any more thoughts? I will keep you posted

 

Sitting in the shop with no airflow will boil it over. Put a big box fan in front of it like they do at service shops. Without the fan shroud all the fan does is stir the air. Get a fan shroud and check the fan clutch.

If it starts bubbling and boiling immediately it is most likely a head gasket or a crack somewhere that is blowing combustion gas into the cooling system. Put a pressure tester on the cooling system and see if the pressure rises immediately. Be ready to vent the system very quickly or it can blow the hoses or radiator.

 

A newly rebuilt motor will generate a lot of excess heat due to the friction from all the new parts. It is normal for them to run hot for a while.

You cannot let it boil, if that is what it is doing. You should put box fans on it, and get that fan shroud installed. Get some anti-freeze into it as soon as possible,

 

are the head gaskets oriented to the "FRONT"? they are directional and you haven't mentioned that you are sure they are in right.

 

Ok so I changed all my variables and one would suggest I got completely different results( which I did)

Here is what I did

One: Pulled out the new stat... ran without one
Refilled with water only.

Two: Re Torqued intake manifold bolts( they were ok)

Three: Found and fixed a vacuum leak *(found at PB Booster hose- that may have had something to do with my problem)

Four: Installed Fan shroud

Five: Ran it outside ( Current outside temp today was -20 C or -2 to -5 F )

Six: Installed oil pressure and Water temp gauges to check it out

Well it ran fine ( like it did yesterday)...although a little rich ( suggests vacuum leak was present while adjusting mixture screws yesterday) so I will have to re adjust that again. But it stayed cool, luke warm actually. Oil press was great 65 lbs cold, stayed 25-30 warm. Water temp was inconclusive as new temp gauge was NFG ( bummer But I can tell you that watching the coolant circulate... there did not appear to be any bubbles to speak off ( the odd small one on occasion but I would think it was just venting some trapped air)... but nothing like yesterdays geyser of boiling watter.

Once I got that far... I Dumped the rad of water, filled it with two jugs of coolant and re ran it for 1/2 hour. Again runs good, not hot at all. Checked the current mixture, is now good to -30 C....so now if i leave it outside, it shouldn't freeze tonight I guess I will try installing the thermostat next weekend and give her another go. Wanna make up transmission lines to get that all plumbed up too.

Dumb question of the day... All of the above should make no difference that I am running her open headers should it( no exhaust on her yet).. ?

Marc

 

You will need the exhaust on it b4 you do final adjustments. Sounds like the missing shroud and no air circulation was the problem.