Additional Coolant Routing

[68Formula]

On the Pontiac V8, behind the middle two exhaust valves on each bank there is an ajoining exhaust passage that leads up the the intake manifold. The idea is when the either of the two valves open it sends hot exhaust up to the manifold for faster warmup and driving in cold climates. Most people simply fill this with aluminum.

I want to keep detonation at bay using pump gas (as low an octane as I can get away with). So, since I am still using the heatercore my plan was to tap the rear of the heads using -6AN fittings, and the tee them into the heater core. This would better balance the heads at the two rear cylinder banks.

Now the heads I bought already have had the center exhaust ports welded shut at the valves. So unlike filling with aluminum, it's an empty cavity. I thought maybe I could take this to my advantage.

Here is my idea. Cut the heat crossover of the intake from the plenum flush to the intake flange. Bore out the exhaust hole in the flange so it's round, and then tap a pipe thread in it. (This could also be done by tapping into the head and just cutting off the flange completely, but since I'm cutting so much of the manifold I'd rather do that). Now run coolant lines from this (each side) to the front water crossover. Then drill from the water jackets in the head to the exhaust crossover, thus making it part of the wet cooilng system. My theory, this would keep the center two cylinder ports (which seems would normally be the hottest) more even with the outter two cylinders.

This would be quite a bit of work I know, but the cost is relatively small so I find the idea very interesting.

1. First question (since I don't have a head available to look at), is there even a jacket close enough to drill in a connection?
2. Will this work as I think it will?
3. Is there a way to do it better?

[Scott Parkhurst]

This can be done. SBC guys have been tapping into the spot between the center exhaust port on the heads for years, but the trick is to make the line small so the hole you have to drill is small (with all the heat in the area, cracking is a real concren).

On SBCs, I've seen -4 AN lines used (connected to a steel fitting that's actually screwed into the steel head. Aluminum heads use aluminum fittings so everything expands and contracts at an almost-constant rate and seals).

I'd still check with a dedicated Pontiac shop (like Butler) and ask them about the water jacket in that area. Because the Pontiac exhaust ports make that nice 120-degree turn after the exhaust valve, the water jacketing might be minimal there- if any exists at all.

On the Chevys I've seen with it, this was a hardcore race deal and obviously it's not become a mainstream mod. The use of a reverse-cooling design has become prevalent at the Engine Masters Challenge to fight detonation. You could do a little of both with your idea, but you'll have to ask the Pontiac guys if you'll even hit water by drilling between those center ports. I know there's a head bolt there, and I don't know how close or far the water jacket is from that point.

Best of luck with it, and let us know what you learn!

~SP~

[MonzaRacer]

If you are going to run high compression then you need all the help you can get with shrt duration cams and cast iron heads.
Shoot for about 180-190 cranking compression and try evans cooluing product NPG-R for coolant. Its expensive but you wont have corrosion to deal with or boiling(375 degree boiling point with no pressure on cooling system.
Evans Cooling 18889902665. As for using 2 exits on back of heads, there really is no need as I have never gotten a Pontiac to run super hot unless it was messed up (as mine was with high compression and short duration cam, rattled like a pig over 3500rpm with 256 duration and 10.5 to 1 heads).

[68Formula]

If you are going to run high compression then you need all the help you can get with shrt duration cams and cast iron heads.
Shoot for about 180-190 cranking compression and try evans cooluing product NPG-R for coolant. Its expensive but you wont have corrosion to deal with or boiling(375 degree boiling point with no pressure on cooling system.
Evans Cooling 18889902665. As for using 2 exits on back of heads, there really is no need as I have never gotten a Pontiac to run super hot unless it was messed up (as mine was with high compression and short duration cam, rattled like a pig over 3500rpm with 256 duration and 10.5 to 1 heads).

Was that a 400ci with 256° @ .05" or .006" lift? (Although really after 3500rpm the cam won't be bleed off cylinder pressure anyways). Was that iron heads and 93 octane? What was your total timing?