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Head cooling on cylinder #5 - solutions?

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rossman    18

The internal path to the thermostat is still there, right?  I thought that the point of this was to removed dead flow zones, hot spots.  So, total flow is maintained, but there's a side current introduced.

 

Seems like flow control valves in each port might help, to balance flow.  To avoid creating a dead zone somewhere else..  

 

My very stale recollection of the thread was that it recommended improving flow thru the back of the head thus removing dead flow zones.  So my solution is to improve coolant flow across the head to the bypass lines that short circuit directly to the thermostat.  On my setup I added a spacer between the thermostat valve and the lower thermostat housing.  I then ran aluminum tube from it to several locations near 3, 4, 5, 6, as 83turbo280zx did.  Basic calculations comparing the cross sectional area of the tubes to the upper radiator hose show that the small tubes combined are less than 1/4 the area of the large outlet to the thermostat.  Based on that I assumed that my setup wouldn't cause dead flow zones in the front of the head.  I also plugged the coolant bypass in the block and opened up the head gasket to allow more flow into the head along it's length. All that said, I'm still running very conservative timing advance.  

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83turbo280zx    11

My very stale recollection of the thread was that it recommended improving flow thru the back of the head thus removing dead flow zones.  So my solution is to improve coolant flow across the head to the bypass lines that short circuit directly to the thermostat.  On my setup I added a spacer between the thermostat valve and the lower thermostat housing.  I then ran aluminum tube from it to several locations near 3, 4, 5, 6, as 83turbo280zx did.  Basic calculations comparing the cross sectional area of the tubes to the upper radiator hose show that the small tubes combined are less than 1/4 the area of the large outlet to the thermostat.  Based on that I assumed that my setup wouldn't cause dead flow zones in the front of the head.  I also plugged the coolant bypass in the block and opened up the head gasket to allow more flow into the head along it's length. All that said, I'm still running very conservative timing advance.  

 

Just out of curiosity, how much timing advance are you running? I'm at 26 full advance, 18psi boost, ported, polised, deshrouded p90 with dished pistons.

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rossman    18
Posted (edited)

I set it at only 22 degrees at red line with 10 lbs of boost. The car is pretty fast even with such a mild tune. The engine is far from stock - custom high lift longish duration cam, ported head, 8.5:1 flat tops, larger intake valve, etc. I only played with the tune for drivability. One day I'll start bumping up the timing and boost but right now I have other issues to tend to.

Edited by rossman

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83turbo280zx    11

I set it at only 22 degrees at red line with 10 lbs of boost. The car is pretty fast even with such a mild tune. The engine is far from stock - custom high lift longish duration cam, ported head, 8.5 psi flat tops, larger intake valve, etc. I only played with the tune for drivability. One day I'll start bumping up the timing and boost but right now I have other issues to tend to.

Nice! My old setup was dished pistons with a N42 head, I couldn't get more than 9 degrees timing at full boost (18psi), so once i got up to 26 degrees on this p90 i started to get nervous lol, no knock from what I can hear, motor is still together haha. I'm gonna push the boost to 25psi with water/meth and see how much more timing I can get, probably at that point a dyno will benefit hugely, only so much you can do on a street tune.

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