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Old 05-02-2008, 05:47 PM
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Cooling SBC on test stand

I've finally got my Porsche 911 engine on my test stand with all the gauges and cooing system in place to test before installation.

I'm hoping to get some tips here to stabilize temps before the installation.

Engine setup:
'66 block, '88 Al Corvette heads (58cc), '98 Z28 roller cam, 1.6 roller rockers, Holley 1850 carb, Summit HEI distributor. HyperE pistons were sold as 9.8:1 with 58cc heads.

Electric fuel pump wired to oil pressure sensor.
The aluminum radiator is tightly shrouded around an electric fan from a Ford Taurus.
I pre-oiled and hand turned prior to first start.

What happened today:
The first part was exciting, the engine popped off right away. Nice deep but not too loud sound with cheapo Summit mufflers. Gas is regular, I guess about 87 octane. I forgot to add some octane booster to the gas can, I'll be doing that before the next test session.

First I carefully monitored oil pressure and read about 60 psi. Then I looked really close everywhere for any leaks. No leaks.

I noticed really quickly that the stainless headers (Chinese EBay specials) started to turn a bronze color. Before the end of the session they were blue at #3&5, bronze everywhere else.

Temp got up to 230 and I shut it down. The electric fan operates on a relay with a thermostat plug in the radiator, and was operating when I shut it down.

I noted pressure in the hose coming out of the manifold.

Tonight I plan to test the thermostat on the stove to make sure it is working.

OK, what can you guys tell me?
- Is the coloration on the stainless headers indicative of dangerous heat level? I wasn't expecting it but I've seen it.

- Is the 87 Octane contributing to high temp?

- Any general advice for running on a test stand, and should I tolerate somewhat higher temps then I will expect to see when operating in the car.

Thanks in advance

IFI, there's more pics and some video here
http://picasaweb.google.com/googJam/76Porsche

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Last edited by itstorque; 05-02-2008 at 05:54 PM.
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Old 05-02-2008, 06:18 PM
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Coolant temps that you posted and the discoloration of the headers is an indication of a retarded timing.

Check the total mechanical timing with the vacuum advance hose disconnected and plugged at 2500-3000 RPM. For this testing set the timing in the 34-38 BTDC degree range at the above RPM.

The octane you are running is too low for the compression you posted.

Place a box style house fan in front of the radiator to increase the available flow of air thru the radiator.

Wire the electric fan(s) to run 100% of the time for this test run.

The stainless headers can probably be polished back to the original luster. I have always suggested that for initial startup runs (before the timing is nailed down and the carb(s) adjusted) that an old set of headers should be used. This will avoid the discoloration and possibly ruining of ceramic, chrome or stainless headers. After the timing has been set and the carburetor adjusted the headers can be installed with much less chance of them getting discolored.
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Old 05-02-2008, 09:12 PM
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Thanks for those tips Frisco. I'll bypass the radiator temp relay and set up a box fan. I've put some octane booster in the fuel now, and I've confirmed the thermostat is opening.

I'm confused about the timing comment though. It actually backfired through the carb once, leading me to think of timing too advanced (I know, I withheld information ). Doesn't that occur when the spark ignites fuel with the intake valve open? I'll try to get the timing dialed in tomorrow.

Rich
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Old 05-04-2008, 06:46 AM
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I got the timing set and the set the fan to run constantly while on the stand, and temp is stable in the stand at ~190.

Thanks again for the tips.

Rich
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Old 05-04-2008, 07:26 AM
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Quote:
Originally Posted by itstorque
I got the timing set and the set the fan to run constantly while on the stand, and temp is stable in the stand at ~190.

Thanks again for the tips.

Rich
Good luck with your project! ENJOY!!!
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