overheating

[Greg Howarth]

ok , my '73 will run for 20 minutes and over heat.

here's what I've done .

my son and I have just installed 2x10" fans (pulling .

the engine is brand new so that should not be the problem.

plus I had this same problem when I got the car.

I had the radiator checked out and they said it was fine. I'm beginning to wonder.

Another thing I'm thinking the air flow is terrible and that is a factor.

If anyone has any ideas please let me know.

Thanks

[Gunslinger]

Under what conditions does it overheat? Does it overheat only at highway speed? Idling only? That can make for different causes.

First...make sure it's actually overheating and not a bad sending unit or gauge.

If it's at highway speeds it could be the lower radiator hose collapsing under pressure. If at idle only it could be lack of airflow, a bad fan clutch, inadequate coolant or an air pocket in the cooling lines due to not having been bled properly. The radiator may be in good shape internally but the fins could be clogged from bugs, debris, etc.

Other issues could be a bad radiator cap, improper ignition timing, a bad sending unit or gauge.

Determine what conditions the overheating occurs and find the cause and fix that. Adding fans won't hurt but it won't address the actual problem.

[wildfelr]

Happy 4 th of july ....RQB3263 Bill Gregg.......While iI never had a true "overheating" problem on my 81 /305 ...I still gor nervous if it allroached 200 degrees...so I did a bunch of things and it now rarely gets to 180 and never over 190 stuck in a 20 mile traffic jam in georgia last week ...I have pics that i can email you ...my cell number is 386-466-6434 in florida...Here is the list....depolute the engine completely, remove and block EGR valve, remove thermostatic valve from right exhaust manifold.(may req minor welding), , check ign. timing, install dual 10" fans with full alum shroud and 180 on 165 off thermo switch from thermo houseing, install 160 degree thermostat w/ 6 3/16 inch holes drilled in flange, remove trans cooler from radiator and relocate alum. tubular double pass cooler under radiator, install air intake spoiler/scoop (pics avail). space hood latches up 1/2 inch for summer operation,,install 3000cfm fan on A/C condenser wired thru relay from A/C compressor power wire, ...I did all these things and it works ...call me for pics ....BILL RQB3263

[wildfelr]

yup....First thing may be to replace the gauge and sending unit (I use Autometer) ..also before I forget it ....While you got it up on the rack...rap on the mufflers....if they rattle replace them, something broke loose inside and may be restricting ex flow ...I did these also..new engines will run a little hotter for a thousand miles or so then normal...after break-in switch to Rotella T 15w40 oil forever....RQB3263

[Avanti83]

As others have asked, what do you mean by overheating? At idle, or road speed and the indicated temperature. My 83 has a fairly strong 355 and it runs all day about 190 -200 on the gauge, 190 thermostat and temps as high as 95. It has a SS flex fan in the shroud for cooling.

Do the fans work?

It could also be a bubble of air in the new engines cooling system, one thing that can help is to drill about a 1/8" hole in the thermostat flange to let the air bleed out.

You may want to replace the thermostat.

BUT!!!! If it's a 400, be sure they used the correct head gaskets. The 400 needs to bleed off the steam created by enlarging the bore and the correct head gaskets have the holes to allow that to happen.

Bob

Edited July 4, 2015 by Avanti83

[Greg Howarth]

Thank You for everyone's interest and idea's.

The engine is a brand new 350/ 325 hp.

Wen I bought the car a little over a year ago on ebay , I was told and the car had not run in 5 years.

So last November I sent the car to a car shop and had a lot of work done on it.

Now in defense of the guy who worked on the car I told him I had pulled the radiator and had it checked out.

They said it was good, so we didn't pay much attention to it .The engine doesn't have 30 miles on it.

Gunslinger suggested that the airways may be clogged, I kind of think that may have a lot to do with it.

So here's my plan tomorrow I'm

going to order a new radiator with 3 rows instead of 2 rows that will give me more cooling capacity.

tat's the plan ,any other idea's let me know.

Thanks

[Gunslinger]

If you replace the entire radiator or have it recored, ask for the unit with the most fins per inch...it will be much more efficient at transferring heat.

[warren55]

My 400 never gets over 190, even though the heat coming from the engine compartment is intense! I've had to pull my radiator twice now (had it recored and it leaked the first time....), so I know how much fun that isn't!

While you have it out, I would consider looking at your fan clutch unless you've eliminated the fan? Also, is your shroud intact? You said you put two electric fans on it, so not sure what your setup there is.

And, even though it is a new motor I'd look at the thermostat and finally the gauge. You can check temps with an infrared thermometer while it's running and see where you are at different points in the cooling system. Those are pretty cheap anymore.