Thread: Zips riser

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Here is my latest Zips report.

It has taken about three weeks of waiting for parts and some fabrication but yesterday I was able to get another test of my 350 SBC heating problem. After setting up the Walker shroud (WS-70) for a '28-'29 Model A radiator (Walker Cobra with a bottom section for a trans cooler) I found the 17" fan tips were less than 1/2" from the bottom of the overhanging tank on the top of the radiator which worried me that motor vibration might lead to the fan hitting the bottom of that tank overhang. Thus after the usual shipping delays I purchased a 16" heavy duty flex fan and another blank shroud since the hole of the previous shroud is too large for the smaller fan. After a few days of messing around with the shroud I got it on and filled the radiator with 50/50 Prestone/water. I also drilled a 3/16" hole in the 160 degree thermostat and that was useful because I could hear the bubbles coming through that hole as the fluid filled the block so that eliminated a potential bubble-block. Then I released the bubble in the Zip pump with the usual amount of spilled coolant and topped off the coolant. I also added a full small bottle of "water wetter" which is supposed to lower the radiator boiling point by about 10 degrees F. I then fired up the engine and let it run at the 1500 rpm setting we used for the break-in run and timed the temperature response. The starting temperature of the garage was 62 F and with the garage door open and a small window fan blowing air through the garage the engine temp eventually boiled again at about 205 F. Pure water boils at 212 F but the temp gauge is not very precise. I shut the engine off when it reached 200 F but since the fan stiopped, the temp went a little higher to blow out coolant. It took about 21 minutes running at a steady 1500 rpm with the timing set at a constant 8 degrees advance to reach the 205 F temp. Along the way the temp seemed to hang around 180 for a while but then continued on up to 205 F blowout of coolant through the overflow tube. Note this is with the hood off. This morning consultation with my experienced engine builder just up the street at Progressive Performance indicated that he did not think this was a serious heating problem running at 1500 rpm standing still. Thus I would appreciate comments whether this is serious or not and whether the car is streetble allowing for brief stoplight pauses? A further test will try to time the inevitable boilover at a lower idle rpm of about 800 rpm. The advice is to try and run this way for a while. I see only two other options. One is an expensive electrical fan installation which I do not prefer. The second is to use the present shroud with my previous 17" fan because with the existing smaller hole I can measure from the blade tips and mark the exact 1/2" clearance to the 17" blade tips and get an optimum fit of the fan hole as tight as is safe for clearance. My friend at Progressive favors leaving off the vacuum advance on my 327 distributor with the Pertronix Ignitor magnetic points conversion. Comments, suggestions?

Don Shillady
Retired Scientist/Teen Rodder