I bought a 68 302 blind not running so I tore it down spec it all out had heads magnafluxed and cleaned up re done motor shop said they were good to go. Put motor in my truck through in hei and edelbrock carb got it runnin and timed but now having temp issues and water boiling over withing 2 min. Thought maybe had a air bubble but have tryed bleeding it multiple times. Has new thermostat and water pump on also. Next step is to pull out thermostat and try it to see what happens. Looking for more ideas though. Hope some one can make since of what I'm trying to explain.

 

Can you detect hydrocarbons in the cooling system?
Head gaskets on backwards?
Are you sure you got a water pump for v-belt drive? (I'm pretty sure serp belt pump runs opposite direction.)

 

Check that the thermostat not in backwards. The spring goes into engine not facing into the thermostat housing.
Many people make this mistake.
orich

 

head gasket check . at the front of head you should have to tabs sticking out between head and block . if the tabs are at the back then gaskets are in backwards .

 

2 minutes is pretty darn quick for a boil. Made me wonder if it is actually hot boiling or did you fill the radiator all the way to the top rather than leaving it down a couple in. for expansion.

I'd say in 15 or 20 min you could have a hot boil, there should be about 4 1/2 gallons of coolant to bring to boil. As long as you can see the coolant inside the radiator you are good to go.


John

 

JO makes a good point , what temp is at in 2 minutes ? if she's just pushing water out you might just have a Bad or wrong cap on the radiator .

 

2x with Johns thoughts!
Yeah we sometimes assume guys know the basics and we look past them for the problems..

Orich

 

The engine has been swapped, 302 introduced in 1969 F100's.

 

Run it with the radiator cap off and see if it percolates (bubbles of gas/air coming up). If it does then you are pushing hot gasses into the water jacket, and that can make it boil quick. There can be many reasons for this: backward gasket(s), cracked block/head, warped head etc. Start with the basics like above. Look for 'why' then 'where.' Not to be a defeatist, but a two minute boil sounds like exhaust gasses in the water jacket.
Here's hoping for the best for you.
Also, does the lower radiator hose have a spring inside? Is the hose collapsing?
Good Luck.

 

Any updates OP?

 

Hey guys sorry haven't got back on to read anything. This all sounds like very useful tips I'm going check out tonight or tomorrow. The engine is out of mustang 302 block 289 hipo intake and heads and manifolds. So there not suppose to be full to the top of radiator? And I'll double check those head gaskets and thermostat but I just followed my engine book for that motor. Thanks guys for info I'll do some more digging around on it.

 

Note!
Now if you have the add on or if theirs one of those after market recovery tank system, then yes fill the rad full as long as there's no coolant in the recovery tank as it would over flow from the tank..
Orich

 

If they really are Hipo heads I'd sell them and get a nice pair of aluminum ones with the proceeds!

 

What are those heads worth?

 

The only trouble with aftermarket aluminum heads is they will not give you the longevity run as iron heads do.

Great for drag racing motor tho!

Orich