A very interesting way to help cool a modern Pontiac engine. He presents an interesting solution. I've seen separating the water cross over from the rest of the intake manifold before, but what he does to it after that is quite brilliant.

FYI - this guy is quite the Pontiac geek. You might want to check out the rest of his YouTube channel.

Edited May 12, 20251 yr by Frosty

Here is another video with good cooling tips.

 

very interesting !

What’s the implications with extra heat on the back of the heads ? 
it’s certainly a good idea to flow water evenly through out the heads 

It contributes to possible over heating because coolant at the back of the head is significantly hotter than at the front. So it raises the overall average coolant temp.

Based on his data, his engine ran a lot cooler than before.

The "421" mod is cheap, and gets the job done well. There is no need to over engineer this solution. 

2 hours ago, Formulabruce said:

The "421" mod is cheap, and gets the job done well. There is no need to over engineer this solution. 

whats the "421" mod formulabruce ? 

Basically it forces water to middle and back of heads and the allows the coolant into the head at its hottest part, the dual exhaust ports, and the rear of the head. this forces coolant all over and makes the heat even. s req in plugs installed in first 3 coolant holes in front of head, and head drilled ( there already is a coolant hole in the gasket for this. Do this with heads off. I will have to make a video I Guess, but engine stays Stock, no plumbing to watch for leaks, heads may KEEP their paint !

2 hours ago, Formulabruce said:

Basically it forces water to middle and back of heads and the allows the coolant into the head at its hottest part, the dual exhaust ports, and the rear of the head. this forces coolant all over and makes the heat even. s req in plugs installed in first 3 coolant holes in front of head, and head drilled ( there already is a coolant hole in the gasket for this. Do this with heads off. I will have to make a video I Guess, but engine stays Stock, no plumbing to watch for leaks, heads may KEEP their paint !

I  would be keen to see that 👍

as I am building a stroker 400 and it sounds like a great improvement 

I found a little info on this mod 

here’s a picture. 

That's part of it yes, use gasket to locate holes. need a corresponding hole in block too. then use 1/4 plugs in the 3 front water outlets on block at deck. these should be recessed about 5 thousandth .  back when Pontiac v8 was developed, they had water pipes from the pump go right into the heads, with bigger holes at rear to keep the block temp more even. I have a 400 with plugs in place and middle hole at exhaust area, I'll get pics up soon. this is almost mandatory  for any CR over 9 or Iron headed high CR engine. Pontiac did this engineering ,  due to CR drop offs in the 70's the cooling wasn't as much as concern...

Edited June 6, 20251 yr by Formulabruce

I wonder if the blocked coolant passages I encountered during my rebuild have anything to do with a factory attempt to improve cooling? I know the previous owner had overheating problems and of course now it runs sweet - temp never strays from 180.

Lower cr, better tuning, lower t stat, cooler plugs all help.. have to see pics.