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Old 09-21-2006, 06:39 PM
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zz502 heating problems

Got a ZZ502 gen VI w/rect port alum heads GM pt #12363400 the problem is this the passenger side of the motor runs 55 deg hotter than left side anyone else had this.Have swaped heads side to side, new block, 5 waterpumps... this ones got me stumped. GM has no answer but to remove 2nd guage

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Old 09-21-2006, 06:53 PM
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I have only seen this happen two times. One time the head gasket was not installed correctly on the side that was overheating. The other time the block was cracked on the side that was overheating. You might try a leak down, and compression check before, and, after the engine heats up to see if the readings are the same. Some cracks are invisible until the block gets hot.
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Old 09-22-2006, 12:08 AM
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Tried the leak down test before and after the gaskets on this time around cant be wrong they are marked leftfront and right front, as far as the block being cracked this is the 2nd block this one straight from Mclaren racing engines. Left head heats to 225-230 and when thermostat opens drops to195 right head goes to 230 and when thermostat open doesnt drop 1deg after about 5-10 min at idle starts climbing and never stops
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Old 09-22-2006, 04:39 AM
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Have you tried swapping the temp sensors side to side see if they repeat?

Also maybe its air/fuel ratio related.
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Old 09-22-2006, 05:00 AM
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Does this thing run mufflers?
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Old 09-24-2006, 03:35 PM
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Already been there guys have tried new guages in both sides of heads, still same results. As far as mufflers yes Flowmasters but have run motor with open headers and still same result. The motor is blown 671 BDS But I have removed the blower at one time to rule it out and put on aluminum intake and carb still the same. I have even run a sprint car adapter to the right head to move the sensor out of the head to make sure there were no problems with the sensor being too close toanything
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Old 09-25-2006, 03:25 AM
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No signs of cross firing and resultant detonation on #7 (crossing with #5)?
Dumb question I know but you've been thorough so far.
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Old 09-25-2006, 10:16 AM
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Quote:
Originally Posted by john1955
Got a ZZ502 gen VI w/rect port alum heads GM pt #12363400 the problem is this the passenger side of the motor runs 55 deg hotter than left side anyone else had this.Have swaped heads side to side, new block, 5 waterpumps... this ones got me stumped. GM has no answer but to remove 2nd guage
Two things,
First, the temp sensor on the left (drivers) head should be nearer the front of the motor and the right (passenger) head will be reverse being at the rear of the motor. The water at the front of the motor flows more than the water at the rear because the water pump is at the front and it only circulates the water at the front on the engine. Most motors run hotter at the back than the front. That could be one reason. Now I'm not sure with that particular head but some heads have water jacket plugs on the ends of the head to allow for more centralized water temp sensors.
Second, you didnt say weather you have your block filled or not. Most race motors are hard block filled to stabilize the cylinders and only allow water to flow at the tops of the cylinder and in the head. If this is the case then the previous reason comes into play.
Since youv'e tried all kinds of things to fix the problem and still think you have a problem you might try and install a water crossover/bypass at the rear of the heads to help the water circulate from side to side. The rear water ports are closed off because the distributer is in back and there no place for the water to cross but you can drill and tap the manifold in the back and put a small hose to crossover so the water can circulate at the back of the motor, but with a blower you might not have the room.
You didnt say so I can only assume you are running gas instead of alcohol for fuel, why dont you just change over to alcohol your engine will love you for it.
All you've stated is that you have a temperature problem and nothing about problems resulting for this condition. Has there been any problems you've associated to overheating or just the gage readings have you concerned?

Adam
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Old 09-25-2006, 10:21 AM
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Quote:
Originally Posted by IanRiordan
No signs of cross firing and resultant detonation on #7 (crossing with #5)?
Dumb question I know but you've been thorough so far.
A V8 Chevy small or big block have the same firing order. 1-8-4-3-6-5-7-2
5 and 7 like you say follow in firing order. Problem is 1-3-5-7 are on the left side (driver) side of the motor and he's having problems with the right (passinger) side of the motor thats 2-4-6-8. So no I dont think it would this would have any bearing on his problem.
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Old 09-25-2006, 11:14 AM
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Possible that you have a defective head gasket. It could still be on backwards from some late night wrenching.

Also you said that it only occurs at idle maybe water flow side to side is poor or uneven at low rpm.

You could put a mechanical gage on it to verify temps.
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Old 09-26-2006, 03:23 AM
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Yeah Fultron it was a dumb question 'cause 5 & 7 are on OUR passenger side, I forgot you blokes drive on the wrong side of the road.
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Old 09-26-2006, 06:59 AM
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This is a street motor so the block is not filled, as far as hoses had them running front to rear on both sides through intake, the gaskets are right this motor has had several sets thicker and thinner, crossover from 5-7 none, the guages are mechanical new and used Autometer have been tried. This problem exists all the time worse going down the road not just at idle 5 min on the road and temp on pass side hits 240 and keeps climbing once you hit 250 and above for an extended period of time you have a EXPENSIVE boat anchor . Now for the alcohol good idea but for one reason shouldnt have to run it to keep it cool and with running alcohol still going to have the temp diff doesnt cure the problem only makes it livable. Have you ever seen alcohol burn nobody has, and you run twice as much, and it is hard to build temp on alky
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Old 09-26-2006, 07:14 AM
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Oh by the way Ian 2-4-6-8 are on the passenger side My brain is soggy sometimes too Thanks so far guys and possibly gals keep racking the brains, just in case anybody is wondering it is in a 55 chevy black and narroed 9 " it is a show car but dont ever think it a trailer queen I would rather set it on fire and roll it in the lake than have to trailer it.
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Old 09-27-2006, 03:19 AM
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A couple of BBC v - drive boats I played with had the temp gauges in the rear of the head so the observer could watch them (and occasionally the skier). One had a remote belt drive water pump, the other was cam driven and there was little variation bank to bank.
I have NO experience with mk 6 rats - only mk 4 so please be patient. I assume your 502 is designed to use a 'clockwise' water pump. I have seen a late 351w fitted with an early foreward rotation pump - very bad. As it's the EVEN bank, is the coolant spending enough time in the block? What type of remote thermostat are you using? If you're tapping your top hoses into the front of the heads have you tried restricting the flow to the top tank on either head?
Over the years i've found that regardless of engine type if it's hot in traffic it's not enough fan, if it's hot on the highway it's not enough water. Simplistic maybe but it's a premise that has worked for me in the past.
Have you tried restricting the water pump inlet port to the odd bank? thereby sending more coolant through the even bank. Dunno, keep me posted. I'm having a real beer as I type this and as you should well know, only garbage trucks have the steering wheel on the left - #1 on a Chev is passenger side, #1 on a Ford is drivers side.
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Old 09-27-2006, 05:08 AM
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Quote:
Originally Posted by IanRiordan
I'm having a real beer as I type this and as you should well know, only garbage trucks have the steering wheel on the left - #1 on a Chev is passenger side, #1 on a Ford is drivers side.

it's a good thing your alterd is center steer.
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