Scottsauto

Hey everybody I got a big problem!! I just built a 71 350 rocket for a customer and its running hot 230-240 and hotter some times. I've checked over every thing a 100 times. I received the motor in boxes I sent it out to the machine shop for a full check over and 30 over bore. I had no problems with the build. It has a new 3 core aluminum radiator and 17 inch plastic flexlite fan. New water pump and lower hose with a spring. At first it didn't make it 7 min into breakin before it boiled over. I checked for bad head gasket and its good. Second time I removed the tstat and filled the system in the tstat opening. And it ran cooler but if you looked in the radiator it would flow then stop flow then stop. If I pull the heater hose off the pump while its running it is not flowing. Any help would be great. Also my tune is rich with mild advance.

oldcutlass

What ignition system, and what did you set the dwell (if points) /timing to. How far is the fan from the radiator and what does the fan look like? There are some flex fans that just plain suck. What thermostat are you running? Is the car sitting in a shop with no airflow, I like to put a big fan in front to help airflow on a hot day.

Scottsauto

Hei set at 10 idle and 25 total. The fan is 2.5 inch away and the fan is the plastic flexlite and its pulling very good. I believe it's a 190 tstat

oldcutlass

OK, your timing is way to low, bump it up to around 34 total with the advance disconnected, around 17-18 initial. 36 is what most like. Make sure when the vacuum advance is connected you don't exceed 50 I try and keep it down around 46 on a performance engine. I also don't connect the vacuum advance until I get it set right.

Also is the HEI powered with full battery voltage, not going through the resistance wire?

Miles71

Let’s start with this Quote “If I pull the heater hose off the pump while its running it is not flowing.”
If you do not have water flowing out of the heater port on the water pump, then you have a serious problem.
Is the radiator full of liquid?
Make sure it is up to the full mark or approximately 2-3 inches below the filler neck.
If you still do not see water flowing out of the radiator tubes or out the heater hose from the
Pump port, and the tank is full as specified, then you have a bad pump!
Also, check to make sure you have a real pump and not one of those Very-low-volume pumps that
have the Stamped Impeller.

Try a high volume pump with an enclosed impeller (and heavy duty Felpro gasket only).
http://www.milodon.com/water-pumps/water-pumps.asp

With the thermostat removed for testing, you should see water flow at all times through the
radiator tubes (Looking down through the open radiator cap).
With the thermostat installed, you will still see water flow out the Heater port at all times
and water through the radiator-tubes only when the temperature exceeds the thermostat settings, such as 180F.
A bad pair of radiator hoses, would not stop water comming out of the Water-pumps heater port.
A radiator full of cement, would not stop water comming out of the Water-pumps heater port.
Is the water pump shaft connected and turning?

Scottsauto

Well I had the timing set higher and it pinged and ran on when I shut it off and it was hard to start. One thing I didn't say was its in an 84 cutlass so it had the factory hei power wire. Also it's not that performance it's 30 over with dish pistons, small cam,aluminum intake, with edelbrock carb.

oldcutlass

It's still a 71 engine, and I'm assuming it's set up as such, not computer controlled. Is the engine running lean?

On the thermostat I like the Stant 180 deg Superstat. It will usually keep the engine running around 190 in traffic.

Do you know what part number your using on the flex fan or can you post a picture of it? Why not use the factory clutch fan set up with a shroud?

Scottsauto

Just noticed a coolant leak. Put a pressure tester on and it coming out the shaft seal on the pump. I took the pump off and the impeller is not broken. But it is stamped steel. The problem is the motor shouldn't overheat like this with a stock pump right? The old pump had 5 fins and the new one I just got has 8.

oldcutlass

See what happens with the new pump. Also like I said I like to run a big box fan in front of the car when it's idling for long periods of time and during breakin on a hot day.

Please post a picture of the engine cooling fan setup.

Scottsauto

I would use the factory fan but the space is to small. The part number is 417 flex a lite. No it's not running lean. I set it rich trying to remove variables. And it's a customers car and its champagne taste on a bottle water budget. I hear you on the super stat but it seams to be working.

oldcutlass

If it's this fan:



Throw it in the trash as they don't work very well. It should have enough room to run a stock clutch fan setup.

I use these, Derale Flex fan spaced 3/4 in from radiator:

Scottsauto

Yea I used a box fan. I got through the breakin finally without it getting to hot. What do you think the temp increase would be on a tight new motor.

oldcutlass

A 195 degree thermostat starts to open at 195. It will maintain a 200-205 operating temp at speed. Breakin temps will vary based on outside air temp and available airflow. I would say around 210ish with the 195 thermo.

Scottsauto

Thanks for all the help guys ill update after I finish and run it for awhile

oldcutlass

Whats your oil pressure running at idle and through breakin?

Scottsauto

Never drops below 40 at idle and 55 at breakin

oldcutlass

That's great!

Good luck with it.

Miles71

The Stock 71 rocket 350 used a Cast water pump Impeller with 8 blades.

Redog

I was thinking the same thing. I agree this would be the best place to start

oldcutlass

I think all of that had been corrected this morning.

krooser

All I used for 20 years on my dirt cars was those black plastic fans from Flex-a-Lite... never had a heating problem.

oldcutlass

Come to Texas with it. Ambient outside air temps 100+ for days on end. The other problem I've seen with those plastic fans down here is they break apart and wedge fins in unwanted areas around the front of the engine compartment.

380 Racer

That sounds funny but really isn't.........but I bet it is very true .

Scottsauto

Fixed!! Runs 180 on the road and around 200-210 in traffic or at a long stop light. Thanks again guys for all the help.

72cutlassconv

So, was it the fan?

Octania

Please, elaborate!
What was the trick?
Timing sounds way retarded for that motor on HEI. If advancing it makes for pinging, then you can reduce the mechanical part of the advance and/or vacuum part using kits for such purposes.


Yea I used a box fan. I got through the breakin finally without it getting to hot. What do you think the temp increase would be on a tight new motor.
===============
I was going to suggest tight pistons.
Evidently forged piston makers and sellers recommend the clearance for factory CAST pistons, on the order of 0.002" piston to bore- that is not enough for forged pistons, say the experts. My 403 had been assembled with tight forged pistons, and it had scuffed skirts and scuffed bores. I had it honed out to 4-5 thou clearance over the objections of the machine shop, and it works just fine.


As for the heater hose at the water pump.... never heard of disconnecting that to ck flow- it's a secondary section of the cooling system. Oh, and evidently some of the above contributors think the pump is pressurized there? The heater hose, bypass hose, and inlet [lower radiator] hose all feed into the CENTER of the impeller cavity, which is the LOW pressure side of the pump. It should suck in at all those ports, and push out at the heater core by way of the right rear intake fitting, and at the thermostat housing after going thru all the cylinder and heads areas.