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Old 03-30-2007, 08:37 PM
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Sbc 400 Overheating And Low Compresion

WELL FIRST OFF IM NEW TO THIS SITE AND WOULD LIKE TO SAY HELLO TO EVERYBODY

OK NOW MY PROBLEMS IS I GOT MY CAR WITH A SBC 400. TRAILERED IT HOME SINCE IT WAS NOT REGISTERED. GOT THE REG FIXED AND DECIDED TO TAKE IT FOR A DRIVE. DROVE IT MAYBE 10 MIN.S AND THE TEMP SHOT UP TO 235. SO I PARKED IT LET IT COOL THEN DROVE IT BACK HOME.

THEN I CHENGED THE WATERPUMP,PUT NEW 180 T-STAT AND HAD MY RADIATOR FLUSHED AND CHECKED FOR PROBLEMS.PUT IT BACK TOGETHER AND TEMP STILL GETTING HOT.THEN I DID A COMPRESSION TEST AND FOUND THE #8 CYLINDER IS AT 30 PSI AND ALL OTHERS FROM 140 TO 150 PSI. SO NOW IM ASKING FOR HELP TO SEE WHAT MY PROBLEM CAN BE.

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Old 03-30-2007, 08:50 PM
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Did you just buy this car/motor? Do you know the history of it?

Head gasket? Cracked water jacket?

Missing coolant?
Check or drain the oil. Is it a milky color?
White smoke coming from the tailpipe?
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Old 03-30-2007, 09:08 PM
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Quote:
Originally Posted by DeathRattle
Did you just buy this car/motor? Do you know the history of it?

Head gasket? Cracked water jacket?

Missing coolant?
Check or drain the oil. Is it a milky color?
White smoke coming from the tailpipe?
WELL I JUST BOUGHT THE CAR,DONT KNOW THE HISTORY NEITHER DID THE SELLER(HE CLAIMS)COOLANT NOT MISSING BUT OVERFLOWS.HAVENT DRAIN THE OIL BUT CHECKED THE DIPSTICK AND IT SEEMS FINE. IT DOES NOT SMOKE WHEN STARTED OR RUNNING
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Old 03-30-2007, 09:37 PM
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Does This Sound Right?

I Was Told Possibly Bad Rings And To Check For This Buy A Fitting That Goes Into The Sparkplug And A Airfitting On The Other End.
Then Put Air And If I Hear Hissingfrom Oil Cap It Maens Bad Ring. If I Hear No Air Hissing From Oilcap What Else Can It Be?
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Old 03-30-2007, 09:37 PM
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...Never mind...
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Old 03-30-2007, 10:18 PM
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I'd bet it's running lean, or the rads plugged, don't see anything else that would make it run hot.
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Old 03-31-2007, 08:49 AM
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If coolant is overflowing then you may have a blown head gasket causing compression to leak into the cooling system and pressurizing the system.
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Old 03-31-2007, 02:40 PM
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To do the leak down test by putting air from your air compressor in the cyl you'll need to back the rockers off so they don't open. The engine will want to roll over to BDC when you put the air pressure to it. Open the radiator cap when checking this I'll bet that #8 is leaking into the coolant.
Check Ignition timing too.
~Scott
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Old 03-31-2007, 06:17 PM
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How does the plug from thedead cylinder look, if it is real clean you probably have a blown head gasket.
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Old 04-01-2007, 02:12 AM
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Do you know if the motor was recently built? If the motor was built using non-stock heads, I'd look into whether the steam holes were drilled in the heads.
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Old 04-01-2007, 02:24 PM
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Quote:
Originally Posted by T-bucket23
How does the plug from thedead cylinder look, if it is real clean you probably have a blown head gasket.
HE PLUGS FROM #6 AND #8 CYLINDER LOOKED LIKE THEY WERE A LITTLE WET ON THE THREADS
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Old 04-01-2007, 02:25 PM
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Quote:
Originally Posted by subtle
Do you know if the motor was recently built? If the motor was built using non-stock heads, I'd look into whether the steam holes were drilled in the heads.
MOTOR HISTORY I DO NOT KNOW. BUT IT LOOKS OLD AND BEATUP SO IM ASSUMING NO WORK HAS BEEN DONE
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Old 04-01-2007, 02:28 PM
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To Do Engine Work On Sbc Motors

Can Anybody Reccomend A Good Book To Buy That Breaks Down How To's On Working On Sbc Motors.

I Know How To Wrench A Little But Would Like More Info On Troubleshooting And Info On Doing Services Myself. I Dont Really Have Money To Pay A Mechanic And Its Good To Learn Anyways
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Old 04-01-2007, 04:11 PM
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I really think you have a blown head gasket. I would pull the intake and the head on the side with the bad cylinder and I think you will find a broken gasket. You have the classic signs of this. This is not a complex job however re-assembly will require some special tools and knowlege. A good book may help. The 400 is a little differnet than other small blocks as the heads require steam holes because the cylinders are so large.
Good luck with it
Chet
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Old 04-01-2007, 07:17 PM
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Quote:
Originally Posted by T-bucket23
I really think you have a blown head gasket. I would pull the intake and the head on the side with the bad cylinder and I think you will find a broken gasket. You have the classic signs of this. This is not a complex job however re-assembly will require some special tools and knowlege. A good book may help. The 400 is a little differnet than other small blocks as the heads require steam holes because the cylinders are so large.
Good luck with it
Chet
THANKS T-BUCKET23
I REALLY DIDNT WANT TO BUT I THINK THAT IS MY ONLY CHOICE,IM GONNA PULL THE HEAD. WHEN I DO THAT SHOULD I HAVE THE HEAD RESURFACED? AND WILL IT BE OK ONLY DOING 1 SIDE?
I REALLY APPRECIATE THE HELP
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