[alanmay0]

Well as you know I posted that I was having a big problem with my 1867 GTO overheating. Well the problem still continues. As you know the engine was just recently rebuilt. I have a large cold case aluminum radiator with two 12 inch fans. I have the kooler water pump. I have hammered the water pump spacer to take up the gab between the impeller and the spacer. I am running a 160 thermostat, The water pump is working because when i turn on the heater it blow very hot air. I can also see if flowing with the radiator cap off. i have used the thing that detects exhaust gas in the radiator 3 times all negative. After driving on the highway for about 8 miles the engine, as tested with a lazar heat tester , registers about 240 at the thermostat housing, the same in the center of the intake manifold. It also shows about a 20 25 degree temp change between the top radiator hose and the bottom radiator hose. I believe that this indicates that the fans and radiator are removing heat, just not enough. Well some one suggested that I might try getting an adjustable cam timing gear so that I could retard the cam timing by 4 degrees??
Well today I took the heads off hoping to find a bad gasket or something, but to my eyes I say nothing that would cause the overheating problem. This problem persist weather i am driving so setting still. The temp just gradually climbs and climbs and climbs. It never cools down just climbs. Heaven forbid if I turn on the AC. I have attached four pictures of the engine with the heads off. so that maybe someone smarter than i might see something to indicate what my over heating problem is. Thanks

[JLMounce]

Here’s something to temporarily try. Plug the back of the head where it would typically exit to the heater core. Then, plug the heater core return on the water pump.

Part of what could be happening is that the circulation of hot water heads back to the water pump, then to the engine and bypasses the radiator.

I’m not an expert on this but it’s my understanding that there is supposed to be a check valve to restrict water flow through the heater core on AC cars, except when the heater is on.

If closing off the heater core loop helps, that may help to pinpoint where the issues are.

Does your engine ping at all? Those pistons are notorious for being a factor in hot running and ping prone engines.

[johnta1]

You have AC?

Take the condenser out if it's in front of radiator?

What pressure is the radiator cap?
Is it sealing?

Is the fan shroud good and fan in correctly?

Of course you have made sure the radiator is full and air out of system?

[25stevem]

The difference in the look of the heads from one
Bank to the other if you did not wipe stuff off is night and day, in fact I don’t think I recall ever seeing a more drastic difference!!

Either one bank is running very clean ( good oil control) and maybe very lean also, or the other bank is rich and oily.

[Murf]

I’m confused. I the other thread I & others suggested trying a mechanical fan & shroud. You didn’t mention it in this post.

Did you try it? What were the results?

Starting a new thread may or may not be a good idea. I think a lot of the same ground will get plowed again.

Good luck!
Murf

[alanmay0]

No pinging, this is not a factory ac car. AC was added. The way it works now is that the water leaves the water pump travels through the heater hose to the heater core and then out into the back of the passenger side head and eventually back to the radiator and the cycle continues again. At least this is what I think happens. thanks

[alanmay0]

I think one show was in full light and the other is a shadow picture without enough light. Not really that much difference. The fan shroud was what butler performance send me with the radiator and the twin electric fans. Unknown pressure cap, it does not say. What pressure cap should I have? why would I want to take the ac condenser off of the car. That would be a nightmare let alone the cost to reinstall and recharge the system.

[alanmay0]

Yes I did remove this cold case radiator and install another large aluminum radiator along with a 7 blade clutch fan and a shroud. now difference still the temp went up gradually to the actual engine temp of 240 using lasar temp meter

[redhawk44]

Got to agree with 25SteveM, looks like one side is rich and the other is lean. I noticed you said no pinging, what's the timing set at?

[Schurkey]

I don't know where to start.

1. You have the worst pistons ever made for Pontiac engines. What is the piston to wall clearance? What is the distance to the top of the block, and how thick are your head gaskets?
2. Describe, in detail, your ignition timing curve, including the vacuum advance.
3. Describe, in detail, your carburetor/fuel injection, including what tuning has been done to it.
4. Describe your procedure for getting the idle mixture screws adjusted properly.
5. It take REAL electric fans to equal an average fan/fan clutch/shroud system. How many amps do your fans draw when both are running?
6. WHY would you install a 160 thermostat? What brand? Have you dropped it into a pot of water on the stove, to verify that it opens when it should?
7. There is no such thing as a "Laser heat tester". There are infra-red thermometers that use a low-power laser as an aiming guide. Infra-red thermometers are notoriously inaccurate due to the emissivity of the item they're testing the temperature of, and also the size of the area they're testing the temperature of.
8. Have you ever lifted the car up to verify that the brakes aren't dragging? Is the engine under abnormal load?
9. Your description of coolant flow through the radiator core is exactly backwards. The cylinder head outlet supplies heated coolant to the heater core, which returns to the engine via a nipple on the water pump inlet.
10. Is there any chance you have an exhaust blockage on one side of a dual exhaust, that would force exhaust through the exhaust crossover in the intake manifold?
11. Have you ever verified your cam timing? Was the camshaft "degreed" when it was installed? Or were the timing marks set "dot-to-dot" and that was it?



WILD GUESSES
You don't have nearly enough airflow, because the electric fans don't have the snort to move enough air.
The shroud for the electric fans doesn't have openable flaps or louvers to allow air flow at higher speed.
Not enough ignition advance in the normal driving range
Fuel system too lean in the normal driving range
When you get this figured-out, using a 160 thermostat will be way too cold.

[Radman]

Are you running stock exhaust manifolds? If so make sure that the heat riser valve is not stuck in the closed position.

[alanmay0]

total advance 31 degrees

[alanmay0]

yep it is stuck open

[68WarDog]

At this point, you may want to consider pulling the engine and doing a thorough analysis. Replace the pistons after zero decking the block. Way too many unknown variables to properly diagnose your overheating problems.

[tom s]

IMO,31 degrees is not much timing with iron heads and pump gas.Pretty much all of mine are 36-38 degrees.Tom

[25stevem]

Is there a shop you can get to that can pressure test the heads and and check them to confirm that they are level within .003”?

If not then your at the point where you clean up all 4
deck surfaces as best you can , bolt everything back on , fill the system up water with the 8 plugs out and do a pressure test.

If this checks good then I need to ask if you have ever done a compression test , if you have under 140 psi then the cam may be retarded and the motor simply can’t pump all the exh gasses out effectively.

Also as stated above 31 degrees total without vacuum advance is no where near enough with those closed chamber 670 heads!
In this case the lack of timing will have the same effect as the cam timing being off.

[Schurkey]

Originally Posted by Schurkey

2. Describe, in detail, your ignition timing curve, including the vacuum advance.
WILD GUESSES
Not enough ignition advance in the normal driving range

Originally Posted by alanmay0

total advance 31 degrees

That's what you think is "described in detail???

How much does the vacuum advance add?

Originally Posted by tom s

IMO,31 degrees is not much timing with iron heads and pump gas.Pretty much all of mine are 36-38 degrees.Tom

Originally Posted by 25stevem

Also as stated above 31 degrees total without vacuum advance is no where near enough with those closed chamber 670 heads!

[Murf]

I saw you addressed pulley sizes in the other post. Are you using a stock v belt setup? No serpentine belt setup? It made me wonder when you described coolant flow that isn’t right.

Has it every blew coolant out, rattled or made the hammering sound of coolant boiling in the system?

Murf

[Schurkey]

Originally Posted by Murf

I saw you addressed pulley sizes in the other post. Are you using a stock v belt setup? No serpentine belt setup? It made me wonder when you described coolant flow that isn’t right.

Even if the water pump was spinning backwards due to a mis-matched belt drive system, the coolant flow would be the same...just much less efficiently pumped.

[alanmay0]

Well you are way above my pay grade when it comes to this engine. I will not be able to answer all of your questions simply because i do not know the answers to some of them. You are correct i was referring to the infra red device. I have no clue what the piston clearance is. These are the pistons that came with the car. I am not an expert on pistons. I have it rebuilt and the guy used the same pistons and did not mention anything to me about how good or bad they are so i am stuck with them. all i can tell you about the time is that the total timing is set to 31 degrees per butler performance. As for the carb adjustments i started out about 3 turn out then used a tach to achieve the highest rpms and left it at that. The idle was set when he car was idling at about 600 rpms. don't know the amps per fan at the moment but they are rated at 280 CFM each. I have a separate relay for each fan. The fans come on at about 160 degrees. I do not know the brand of the thermostat but i did check it and it does open at 160 degrees. also I can tell it opens because the water starts to flow in the radiator when the stat opens and i can check the temp with the infra red device at the thermostat housing. Yes the car in on the hoist often. and the brakes are fine and not dragging. Thanks for this suggestion though it is a new one. No exhaust blockage. total new exhaust just made for this car 3 weeks ago. I have not verified the cam timing nor do i know how to do this. I'm sure when rebuilt it was set dot to dot. One member on this web site suggested setting the cam timing to 4 degrees retard due to the fact that he used this to cool a 67 GTO that he could cool no other way. What are your thoughts on this and how do i check the cam timing?? You may be on to something with Your number 9 suggestion or comment . Attached is a picture of the way the heater water hoses run in my car. As you can see the heater hose leaving the water pump goes into the top tube of the heater core and the bottom tube then goes to the nipple on the back of the passenger side head, see S curved hose. Would having these switched cause a slow temp rise?? Also what temp thermostat should I be using? a 190. You are correct the electric fan shroud does not have flaps that open at high speed. I will contact Butler Performance and ask about this. Please let me know if I have the heater hose connected correctly and it not would or could it cause my problem?? thanks