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#1060977 - 03/04/19 10:26 PM What's happening here?  
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SSScottSS Offline
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I'm doing some winter upgrades and pulled my one of my heads off today and found this. I did a bit of research online and found some similar situations stating they thought it was a vacuum or intake manifold leak causing the cylinders to run lean. Does that sound accurate? I didn't notice any problems on the intake gasket.


[Linked Image]20190304_155551


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#1060980 - 03/05/19 12:48 AM Re: What's happening here? [Re: SSScottSS]  
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ChasUno Offline
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Bradenton, FL
That could be coolant getting into the left two cylinders.

Did you do a compression check before you took the heads off? Any loss of coolant or brown sludge in the coolant?


1986 Monte Carlo SS

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#1060983 - 03/05/19 01:35 AM Re: What's happening here? [Re: ChasUno]  
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SSScottSS Offline
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I did not do a compression check. The engine was a long block I purchased new about 15 years ago. It's got about 25k on it now. I haven't noticed any sludge in the cooling system either. I've been thinking, and where those two cylinders with the white exhaust valves are, is where I had a push in breather in the valve cover. I wonder if that could have some how contributed to it?


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#1060984 - 03/05/19 02:00 AM Re: What's happening here? [Re: SSScottSS]  
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86ttop Offline
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JMHO, get them checked for cracks, these heads are thin castings and prone to cracking, Good luck!


Leo Paugh
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#1060985 - 03/05/19 03:06 AM Re: What's happening here? [Re: SSScottSS]  
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Buick Runner Offline
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Vacuum leaks are similar to electrical gremlins, they can happen nearly anywhere and can be very difficult to track down. Depending where the vacuum leaks are, they can sometimes make some cylinders run lean and allow others to run normal.


SBC powered 1987 Regal with TES headers, ZZ4 intake, ZZ4 PROM chip, mini starter, THM2004R, 2500 stall converter, 2040 cam, CCC system, and 3.73 posi rear.

2008 ex NPS P71 Crown Victoria, cop motor, cop shocks, cop brakes.

Never argue with an idiot.
They will just drag you down to their level and beat you with experience.
#1061005 - 03/06/19 01:32 AM Re: What's happening here? [Re: 86ttop]  
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SSScottSS Offline
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I'm going to take them to the machine shop and have them checked over before they do any additional work. Hopefully they aren't cracked


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#1061006 - 03/06/19 02:11 AM Re: What's happening here? [Re: SSScottSS]  
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86ttop Offline
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Brooksville, Fl
Good Luck!!


Leo Paugh
It's not an attitude, it's just the way I am.
POW*MIA
You are not forgotten
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#1061009 - 03/06/19 03:09 AM Re: What's happening here? [Re: SSScottSS]  
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Buick Runner Offline
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Hopefully it was just the intake gasket. When mine developed a vacuum leak, it still looked fine ever after removing it. Only way I could tell was to spray each port with carb cleaner while the engine was running and see the computer's reaction. Only one port leaked vacuum but that is all it takes. All four coolant ports didn't leak. The carb base gasket can cause similar issues, which happenedto me last summe. Retorqing the carb mounting bolts stopped the vacuum leak. While the engine has a vacuum leaks, it mimic a low cylinder, even though all 8 had high and bearly the same compression readings.

The vacuum port gaskets are under high stress resisting from being sucked, distorted their shape, and thus breaking the seal. This is why I switched to metal shim core intake gaskets which maintain their shape better. Also be sure to use a thick carb mounting gasket and torque the bolts, once cold and again hot.


SBC powered 1987 Regal with TES headers, ZZ4 intake, ZZ4 PROM chip, mini starter, THM2004R, 2500 stall converter, 2040 cam, CCC system, and 3.73 posi rear.

2008 ex NPS P71 Crown Victoria, cop motor, cop shocks, cop brakes.

Never argue with an idiot.
They will just drag you down to their level and beat you with experience.
#1061016 - 03/06/19 10:15 PM Re: What's happening here? [Re: SSScottSS]  
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SSScottSS Offline
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I just saw a video about engines and the guy recommended people don't use the factory plastic gaskets. He recommended the metal ones like you said. I think I'll take that advice.


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#1061058 - 03/10/19 06:30 AM Re: What's happening here? [Re: SSScottSS]  
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Joe87monteSS Offline
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Memphis,TN
I agree about the gasket.

And 5 out of 6 Vortec heads that come thru my shop are cracked.


Joey
Engine/head builder/machinist
1987 Monte Carlo SS 383/4 Speed
2004 Silverado
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