Sup guys I have a rebuilt 70 455 and i just put everything in the car and started my engine break in. As the engine is warming up temp would warm to about 190 after like 5-10 min. IT would sit at 190 and then start to bounce up to like 210, then back to 190. As I watch it.. it starts to heat to 210-230 and higher bouncing up and down... it will continue to do that and hit like 250 and i turn it off. Then i can hear the engine boiling....the whole time iam running the engine at like 1500-1700 rpm for the cam break in. Could there be air in the system? HOw do i remove it? any ideas

 

It is not uncommon for a new/tight engine to run a little warm especially if its stationary. A large box fan running at front would prob help. Also make sure cooling system is up to snuff.

 

X2 on the above!
Anti-freeze and/or 'water wetter' could be a considerable help, too!
Did you 'burp' the systen for air pockets?

 

X3 plus burp the system. run with the radiator cap of until warm water starts circulating. It might shoot some hot coolant up and out as the air escapes so be careful and stay out of the way.

 

i am not sure how much affect it has but i have always jacked the front of the car up on blocks to help the air find it's way to the radiator. and the big fan is a must.

 

A box fan works great. And when it gets too hot I hose down the radiator with water.

 

Sup guys I have a rebuilt 70 455 and i just put everything in the car and started my engine break in. As the engine is warming up temp would warm to about 190 after like 5-10 min. IT would sit at 190 and then start to bounce up to like 210, then back to 190. As I watch it.. it starts to heat to 210-230 and higher bouncing up and down... it will continue to do that and hit like 250 and i turn it off. Then i can hear the engine boiling....the whole time iam running the engine at like 1500-1700 rpm for the cam break in. Could there be air in the system? HOw do i remove it? any ideas

 

I know its normal for engine break in to get hot, but not over 210 and so. Are you using a 4 core radiator? If you have a flex fan was it working properly before the rebuild? 455 burn REAL hot, make sure your thermostat isn't stuck either.

 

Besides all the normal stuff like water pump, fan clutch, etc.....How did you fill the engine anti-freeze?. I know a newly rebuilt tight engine will run a little hotter, but I would think only a few degrees. I had the same problem on my Chevelle 396 years ago so I did my 70 455 SX differently. 20 years ago..... I put all the hoses, etc. on the Chevelle and filled everything thinking it would circulate around and fill the air pockets and then I add more coolant as needed. Mine shot up high on temp and I heard bubbling like yours. I think I had an air lock/steam pocket and the water pump just pulled water around but left the pocket. I popped a heater hose off and heard a sucking sound and then refilled everything to insure no air pockets and it worked fine after.

This past month, before I broke in the 455, I left off the heater hose on the back of the intake and filled to insure the block was full. Then I put the hose on and continued filling to fill radiator and everything else. It worked perfectly - 190F temp the whole time with a 180 thermostat.

Not sure if this is your problem, but give it a try.

 

A good water pump,and a 3-core radiator,will be plenty for a 455.The only thing I would try is to remove your T-stat altogether,and try it again.If it is still getting hot,and you don't have any other issues,like water in the oil,or oil in the water,then the tolerances are too tight.

 

Definetely make sure the fan clutch is working. When it is running hot, there should be a loud roar of air movement from the fan. When the temps get back to 180 or so, it may disengage, but should engage again when temp climbs.

 

Make sure the fan clutch is working if equipped - you must hear a loud roar of air movement then temp is up there. It will be louder than the engine itself.

 

Hose.

 

i have a flex fan and new 180 t-stat..... putting in new rad. the other one is kinda old. Also going to check for air in the system.

 

Sometimes the flex fans are not good for higher speed engine speeds while vehicle is stationary. By design, they move the most air at idle, and flex at higher engine speeds to cut drag. Try either a high velocity fan in front of the car blowing into the radiator, or do what another member here did - set up a water spray nozzel to heavily mist the radiator.

 

What I do to try to get the air out, is,I fill the engine up first, in the thermostate housing. When the engine is full, than install the thermostate, and housing. Then fill the radiator. I also don't lock the cap all the way on, so if there is any air still in there it can come out, I check it all the time as it is warming up, to see if I need to add more water, and usally do add more. Also in the breakin, I run plain water, no anti freeze, so if there is a leak, it will not be as big a problem. Also I turn on the heater, so if there is air in it, it will come out. I also put a big box fan in front off car to help push air in.

 

I also, fill the block from the thermo on the intake, then the radiator. And yes, I have used fans before. Mine is a thermo clutch, as I hated the noise of the flex fan. Also, I run an aluminum radiator. 180 all day no matter what temp.

 

I would never use a flex fan either, I seen one once flex the fin right into the hood, good idea is to grab the upper rad hose and pump it by squeezing it, helps with stuck air some times. and turn the heater on low allows for circulation if there a valve allows some excess heat to disapiate too.

 

Any time I've every had an engine over heat like that I'd shut it off and hit the radiator with water from the garden hose,then restart the engine,let it run a min.or two.this will cool it down quicker.Repeat if necessary.Remember temp gage is coolant temp engine is hotter.may be unnecessary but can't hurt.
railguy

 

I merged these two threads into one, to prevent some of us (like me) from posting duplicate answers and to ease the clutter.
It is never good practice to post duplicate threads in different forums.

 

I started the same way you did.

Same problem with engine brake-in.

did the whole 30 min in 3 times, between the cooling off period.

My problem was air in the engine ( next time i make a build in bleeder) and a faulty pressure cap.

pressure cap got to hold between 14 and 17 psi. a looser cap wil boil sooner.

mine did boil to whe i shut the engine, now it is solved.

Edelbrock intakes do have a 1/2 (gas) inch thread, ( over here a lpg/ gas thread) plumbing stuff
I bought my plug's at a store that suplies heating suplies.
And the next time i clean my coolant i mount a 1/2 bleeder from a radiator/convector/heater?

 

update on my problem..... noticed that there might be a little leak at the front of the radiator. Also noticed some uneven heat spots on the radiator when toughed by hand. i also noticed that my heater has been bypassed. The Radiator hoses are hella old and super soft. i got a 3 row radiator will that work for the 455?

 

The lower rad hose can collaspe as well if the wire support has rusted or knocked in from re-ing the motor or using a different hose not designed as a lower rad hose, best to put all new hoses and clamps on, cheap insurance vs overheating your new motor.

 

A 3-row should be fine, provided you don't turn on the air-conditioning, and the rest of the system is up-to-par!
Let's start from the beginning -
If it were me, I'd have replaced the water pump, thermostat, belts, all the hoses, anti-freeze, and had the radiator boiled out, cleaned and painted.
Especially on a fresh motor!
Of the above, what have you done, or, not done???
The only other things I can think of, causing all this is ;
Lean condition - MAJOR vacuum leak, are all hoses on???
Timing too advanced - Does it turn over alright, or turn hard??
I don't even want to ask - did you use proper break-in oil?? Something with zinc for camshaft break-in??? Or an additive??
We need some clues, as this should've been cured!!

 

From my understanding,

Water is sucked from bottom of radiator into the water pump and is pumped into the front of the block and around the cylinders were it can migrate under pressure through the holes in the head gasket and head.
It will then travel along and collect at the front and rear of each cylinder head and continue through the front of the intake manifold to the water neck just under the thermostat.
When the thermostat is open it flows directly back to the radiator.

Sooooo.......

Bottom of water pump hose goes to a bucket of cold water and a garden hose, and the water neck attaches to a hose dumping the hot water on the curb.

Cool water all the time.

No fans, thermostats, bells, or whistles. Just simplicity.

 

A 3-row is plenty for a 455,even with AC on,as long as it's not clogged.Make sure you have good hoses,and a good fan.As long as your water pump is working,it can be the standard cooling or heavy-duty cooling version.
You say your heater is bypassed?You mean it is not connected?If so,it sounds like the heater core started leaking,so they unhooked it.Maybe I read that wrong.

 

Drill an 1/8th to 3/16 inch inch hole in the outer edge of the thermostat and the air will bleed out through that when you're filling it.

 

ok iam back with a update. the whole cooling system is all new now. I started the engine and let it run with the rad. cap off so the air could escape and put it back on when no more bubbles came out. the temp would rise up to 190 at idle then i gave it a little gas to bring up the rpms and the temp would drop to 170 then back up. i think that my timing may be a little off and my air/fuel mix off too. so my next question how do i adjust those? i have a HEI distributor and a 750 carb.... the exhaust smells rich....... also i only let the motor run like 5-10 mins at a time so it doesn't overheat. i turn it off when it gets to 210

 

If you're breaking it in, it should not idle at all.
You must start it, and keep it at 3k rpm for 30 min or so.

 

Agreed! I always run mine between 2500 and 3000 up and down, hold a little and then the same, for the first 30 min. (or so). Never had a cam problem to date. However, now that I said It

 

This link will show you how to adjust your air mixture.
Good luck


http://www.youtube.com/watch?v=RUrCP_KPLYY

 

ok i think i have it under control.... i started the engine up and ran it around 2500 rpms and watched the temp go up to 190 and then back down to 170, it would go up and down the whole time but never went over 190 it also was a little cold today so i bet that helped............ Thanks for all the help everyone.

 

When I was 19 a friend of mine had his 74 Mustang engine rebuilt. It too then ran really hot. He asked if I would take a look since the guy who did the work basically said take a hike. I tried everything. I replaced the coolant. I removed the T-stat. I took off the hoses at various points in case there was an air pocket. Nothing worked.

Well, finally I figured out a solution. I found the temp sensor and put a small electronic resistor inline. Simply cut the wire to dash guage and twisted in the resistor. The guage read perfectly afterward. Friend never knew and drove around happily for a year or so before selling the car.