[rudytadow]

Hello,
Is bypassing the heater core to the rear of intake going to comprimise the motor from cooling properly? My heater core is shot and I have no time right now, putting away for winter - will deal with next spring. I'm taking a 3/4" x 5/8" reducer to run my 3/4" heater hose line from the bottom of water pump to the 5/8" nipple on the back of the intake. 65 LeMans 326 V8 with A/C (not hooked up) 2 spd with Edelbrock Performer Pontiac intake.
Thanks.
Rudy

[rudytadow]

Hello,
Is bypassing the heater core to the rear of intake going to comprimise the motor from cooling properly? My heater core is shot and I have no time right now, putting away for winter - will deal with next spring. I'm taking a 3/4" x 5/8" reducer to run my 3/4" heater hose line from the bottom of water pump to the 5/8" nipple on the back of the intake. 65 LeMans 326 V8 with A/C (not hooked up) 2 spd with Edelbrock Performer Pontiac intake.
Thanks.
Rudy

[wheelspin]

Rudy,

This is commonly done for your described purpose and to eliminate hot air inside of the car due to a failed water temp valve. There is no negative affect on engine cooling, save loosing the small radiator effect of the heater and that's only when it's being operated.

Les

66 GTO Coupe,455/trips,700r/2500stall,12bolt/3.08,1.79/13.01/104.5
68GP daily driver under restoration
--------------------------
Better lucky than good

[engineer]

i disagree. You are putting hot water from the rear of the engine, bypassing the heater core and then putting that hot water into the water pump directly. the heater core removes the heat from the water before returning it to the pump. No heater, no heat removal, so return water is still hot and it mixes with cooled water from the radiator at the pump, thereby heating up the water now going to the engine. Ask me how I know, since i bypassed a heater on the highway due to a leak, and then about 5 miles down the road, the engine overheats. Plugged off both lines, so no flow back to pump. Overheating problems solved.

[wheelspin]

Engineer,

Check out my post, I agree that the heater core provides additional cooling, but only when the water valve is opened. The heater outlet in the rear of the head is effectively "capped" when this valve is closed and the suction side of the water pump is open to the heater core.

If your car overheated due only to the heater core being bypassed, it would seem that your cooling system may be marginal. I can't see how a small amount of hot coolant introduced into the cold side (suction) of the water pump could be signifigant. I am glad that you found a solution to your overheating problem, many don't.

Les

66 GTO Coupe,455/trips,700r/2500stall,12bolt/3.08,1.79/13.01/104.5
68GP daily driver under restoration
--------------------------
Better lucky than good

[george kujanski]

Perhaps there was trapped air or just not enuf coolant in the system after the mishap. I also don't see how it would make a big difference at all.

George

[mike nixon]

rudy, i've done this "fix" repeatedly in the past with no problems.

the only way i could see this causing a problem would be if there was an air pocket in the head.

the heater can provide extra cooling in a overheat situation but should radiate much at all if it's in the off position.


mike

[wheelspin]

Rudy,

Mike and George bring up a good point re air trapped in coolant passages. This is one of the best reasons to utilize a coolant recovery system. As the system cycles between cold and hot temps any air trapped in the cooling system is automatically purged into the recovery bottle.

Les

66 GTO Coupe,455/trips,700r/2500stall,12bolt/3.08,1.79/13.01/104.5
68GP daily driver under restoration
--------------------------
Better lucky than good

[67 455 Bird ragtop]

Depending on how much work you want to do here is what I did. I removed the heater core, plugged the outlet on the timing cover fo the heater hose, and routed the water from the back of BOTH heads using the 301 nipples mack to the water crossover. Many have done this with excellent cooling results. Below is a pic of my setup before I put my intake on.

Honest dad, that 455 on the side of the block is a serial number

[mike nixon]

67 that's a common mod for circle track cars and is good for some temp reduction on the street also.


mike

[rudytadow]

67 455 Bird nice mod for cooling. However, I have an old motor with an aftermarket intake and really don't know how or attempt and potentially costly modification to the old girl. How can I avoid or know if there is an air pocket in the head as you guys have mentioned since I certianly don't want to find out the hard way and have it overheat. I'm currently replacing the fan clutch. The only thing about the one I bought that I don't like is that the mounting flange has four open "U" shape cut outs in place of thru holes for the mounting bolts to attach the clutch to the water pump. It came with new bolts and split washers. What is the purpose or advantage to using the split washer over a solid washer?

Thanks.

Joe

[wheelspin]

Rudy,

See my post re coolant recovery system. This will eliminate trapped air.

The "U" shaped cutouts on your fan clutch are not a problem as the clutch registers to the water pump shaft. Use the flat washers to spread the load over the "U" shaped cutouts and place the split lockwashers over the flat in order to secure the fan clutch. Do not underestimate the damage that occurrs should this assembly come loose @ speed.

Les

66 GTO Coupe,455/trips,700r/2500stall,12bolt/3.08,1.79/13.01/104.5
68GP daily driver under restoration
--------------------------
Better lucky than good

[engineer]

some one needs to check something. Most of the older 65-67 A body cars do not have water valves in the heater hose lines. The ones on like 71-72 GPs only work if the AC is in the max. position. The idea of an air pocket in the system does not apply since that would mean the water pump with the bypass would be vapor locked, or cavitating which is not possible if you look at where the hot water return is compared to the suction on the timing chain cover. You are adding a lot of heat back into the pump. GM always had water flow through the heater. In fact, if an enigne is experiencing overheating, it is recommended to put the heat on high to help remove heat.

[lust4speed]

Since there is no air flow over the heater core when the air door is shut, the core reaches engine temperature and just becomes part of the plumbing without any heat transfer - so you should be able to just loop the heater hose with no loss in cooling since this is what is happening anyway during the summer.

And a question to ponder. Since you are short-cutting the normal cooling water route when you loop the heater hose outlet(s) to the manifold, why does this allow the engine to run cooler? The water would only be somewhat as hot since it has not done its full job on its way back through the head to the manifold crossover. Since our temp gauge is in the manifold, and it is getting cooler water from the short-cut, it will read cooler. But is the water at the front of the head actually running warmer since less volume is available across the front cylinders?

[RAJNWDY]

If you look at the picture again and then think about where the Water pump actually pulls water from, then you will see that he is feeding cooler water to both the front and the back of the heads at the same time. The water pump pulls from the block and with the cooler water going to the front and the back of the head I would think that all four corners of the block would run cooler then the center ie., 4,6,3,5. but I'm sure only slightly. I was going to do something like this on mine but I was going to feed both heads back to the water pump heater connection. remember that the water pump pushes water to the bottom of the radiator and then returns thru the upper hose back to the engine. I would be interested in tempetures taken at various points on the block to see whether there were (hot Spot's) in the block. Nice job though!!

[RAJNWDY]

Sorry, I went out and re read the proper cooling circuit of a Pontiac and I stand corrected as to proper flow. Please disregard last post as just being tired and not thinking properly

[engineer]

looked at my 1967 gto with Air cond. heater box today and there is always an air flow over the core even if the air door is in the full cold position. the air door has a stop built in so there is always air across the core and therefore it will remove heat even in the full AC position. It would be nice if people looked at what they have instead of just talking. Bypass the heater and the car overheats.

[skip65]

IF YOU HAVE HEAT COMING INTO YOUR INTERIOR ALL THE TIME YOUR A/C WOULD HAVE TO WORK EXTRA HARD,EVEN MORE ON HOT DAYS.THE HEATER CORE WAS NOT INCORPORATED INTO THE COOLING SYSTEM FOR ENGINE COOLING.IF YOU BYPASS HEATER CORE AND CAR OVERHEATS YOU HAVE A COOLING SYSTEM PROBLEM.

[lust4speed]

Funny, I don't have heat coming into my interior all the time. Wouldn't that be an asinine way for Pontiac to design an air conditioning system? My door does close all the way. Must get awful hot in your goat during the summer. Possibly it is time to fix your door.

[This message was edited by lust4speed on December 01, 2003 at 09:33 PM.]

[BOWE62]

I bypassed my heater core on my 67 goat temporarily while I waited for my new core to come in and did not notice any temp increase without it...And I live in Texas and drove it in 5 o'clock traffic and it was 99 degrees that way.

Greg Bower