[redfirebird]

I have been fighting an overheating problem on my 69 Firebird 4 speed. The spec on the motor are as follows.
I rebuilt the 455 2 years ago and 3000 miles I had it bored 30 over and decked the block. I am running 6X 4 heads 3 angle valve job done not shaved. I am running stock rocker and timing chain. My cam has duration of at 050 inch Lift: 224 int./234 exh. I have an Accell Distributor and Qjet carb off of a 1974 455 attached to a Edelbrock performer manifold. The oil pump is a Sealed power high-pressure oil pump. I am running headers with the Pypes exhaust system.

Things I have already done.
Replace fan blade with 5 blade and a new clutch (I do have a fan shroud)
Water down antifreeze to a -10 protection and I added Royal Purple Ice
Replaced radiator with four core
New water pump with new divider
Added electric cooling fan I use when idle or in town driving.
Replaced thermostat with a Robertshaw 180 degree
I installed a Dakota water sending unit and gauge
I set the timing to 8 degrees

Now the car runs great only problem is when I idle or drive slow 30 MPH I heat up over 230 degrees that is when I shut it down. If I increase my speed to 50 MPH the temp drops down to 190 to 200. I did notice when drive the interstate at 70MPH I heat up to 220. With the hood closed in my driveway the electric fan on I noticed my hood and fenders on both sides of the car in the middle of the wheel opening heats up to 140 degrees.

I am not sure what to try next I am considering replacing the fan blade and shroud with an electric unit off of a Lincoln. I have one installed on my other bird but have not driven on the road yet (getting ready to paint)
Any help would be appreciated.

[george kujanski]

Low speed heating is most likely not enuf air or coolant flow. You have a new pumpa nd plate, but did you minimize the impeller-to- plate clearance?

A 7 blade fan would move more air.

Did you check the gauge for accuracy? When it's not overhaeting but warmed up, the gauge should be at around the thermostst tem, i.e. 180.

George

[quicksilver97ta]

Do you have the 2 filler panels in place that go between the bumper support and top of the radiatior support? Also, there is a panel available to close off the area between the valance and the bottom of the radiator support as well. These items were originally available for 400 and a/c cars. They will force more air thru the radiator instead of going around it.

[redfirebird]

I did check the gauge for accuracy and it was right on and yes I do have top and bottom filler panels. I did minimize the impeller-to- plate clearance. I just feel and ton of heat coming off the motor when the hood is up. I keep wondering do I need adjust the cam. I set it up with both dots aligned. I am now wondering if I need to move it a little. I did not block the intake cross over off and there is a lot of heat there as well. As I said before I think this one has me beat.

[quicksilver97ta]

Can you elaborate on the radiator?

[redfirebird]

I purchased it from D&R Classic there catalog list it as follows "Radiator 23 inch 4 core Manual Trans Super Cooling"

[hal101]

someone told me to block the bypass from the timing cover to the manfold

and block the heater hose so hot water dose not go back to the motor without

going through the radiator

i don't know if it works just something i herd maby worth a try

[tempest455]

Did you burp the cooling system for air before the cap went back on?

[DOC]

I had similar issues w/ a new 4 core desert cooler w/ a mild 462 setup. I upgraded my motor to a Balanced 462, ported/shaved 6X-4 heads, Comp 284 cam, Torker intake, 850 QJET, 165 Thermostat. I added a generic aluminum 2 Core Summit radiator w/ a flexfan. I had to modify my shroud a little and now it does not see 1 degree over 180 in hot traffic w/ my AC running to running 75MPH down the interstae w/ AC Running. I did not do anything special to the waterpump or pulley setup. I did make sure everything was clean and new rubber sleeves installed in the timing cover but thats it. I have spent a lot of time looking for the perfect tune and I think thats where my success comes from. Dont forget, this means my AC condensor is in front of the radiator as well as a large tranny cooler. So, Not sure why it works well but it sure does....

Reccomendation, get an aluminum radiator setup....

[tempest455]

Ditto on above. I run a lot of comp and HP for the street. I had a custom 5 core copper/brass radiator and had cooling problems. I went to a 2 row aluminum and the temps dropped by over 20 deg.

[redfirebird]

I pulled the water pump over the weekend and found that this pump did not have the cast impeller must have my two cars confused anyway I just ordered a new Milodon water pump hope to install it later this week. I am also considering replacing the water pump pulley. Current pulley is an 8 inch may replace it with a 6 1/2. First I will go with just the new water pump but if that does not solve the problem on goes the smaller pulley.

[smagnotti]

Make sure your blades on the fan are half in and half out of your shroud, to move the maximum amout of air that your set up will allow.

[Indiangoat]

Isn't the timing suppose to be 9 deg BTDC. Also, if you think it might be heating up from lean fuel mixture, you could check the plugs for white residue and determine if the air fuel mixture is okay. Also, to confrm you could set and lock the choke into a postion that will keep the carb rich, then you could run it and see if it still heats up.

[redfirebird]

I just wanted to answer a few ideas and to let you know the new water pump will be going in tomorrow.

I wish I would have heard about the aluminum radiator sooner but I may be trying that next

I did burp the system for air no air in the system
The fan blade is in just over 1/2" and I was incorrect on the blade it is 7 fin blade
I did run timing at 9 went to 10 for a while and now tried 8

Thanks for the ideas I do appreciate the help

Keith

[n2ogpsj462]

seems like you have alot covered. is this a problem you have had since day one with the rebuild? or was it there before rebuild? my friends 390FE ford big block had the SAME EXACT problem. he threw tons of cash at the cooling system and nothing worked. turned out the incompetent machinist who bore his motor bored very tight piston to sidewall clearance. and my machinst actually brought that up because i was at his side most of the time with my machine work. if this is the case your motor will always run hot. cure on the FE unfortunately was a complete tear down and as long as your pistons arent scuffed to badly you can hone some clearance. this obviously is worse case senario just sharing an experience

[Dens71TA]

Originally Posted by redfirebird

I just wanted to answer a few ideas and to let you know the new water pump will be going in tomorrow.

Now would be a good time to inspect the rubber o-rings in the coolant tubes behind the divider plate for any cracking. That could possibly cause water to bypass the engine.

What size is your fan in relation to the shroud opening? My '71 T/A used to always run hot and would hit 230-240 degrees when sitting. It turns out somebody replaced the original 19.5" flex fan with an aftermarket one that only measured 17". I found the correct one in a salvage yard and now it hardly ever gets above 200 degrees.

[redfirebird]

The motor was new to me I bought a virgin motor tore it down and completed rebuilt it including cleaning the block and I replaced the rubber o ring's in the coolant tubes.

I installed the new water pump with only minor improvements I guess next I will replace the pulley on the water pump with a smaller pulley. One thing I am noticing with the radiator cap off and when the motor comes up to temp I don't see fast moving water I do see water coming from all core openings in the radiator but to me it seams slow that is why I plan on changing the pulley.


Keith

[dedsleds]

What's your compression? Maybe you have to run a higher octane in the summer, 1/2 race fuel 1/2 93 octane.

[redfirebird]

It works out to about 10.6 I run 93 octane

[DiamondJim]

10.6? Are you sure? 6X-4's? IMHO, If you are really running 10.6 with iron heads and 93 octane you have detonation problems. My motor is a 463, zero decked, 6X-4's(92cc), SRP's and .038 gasket, and is right at 9.9cr, FWIW. -Jim