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Discussion Starter #1
Has anyone on the board ever changed a head gasket on a 85 300zx? If so what pitfalls should I be looking for. And is it worth getting the head ported and polished if I will only have headers, intake, msd ignition and exhaust? Thank you in advance.
 

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ZPOOLNZ
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It isn't hard just space confinments. Porting and Polishing will net you gains; I would suggest also getting a more performance oriented cam while you are at it. The thing is the heads typically have pretty bad casting marks so porting cleans up the heads and really helps the VG30E heads flow.

Where in TN. are you?
 

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JAMESZ said:
It isn't hard just space confinments. Porting and Polishing will net you gains; I would suggest also getting a more performance oriented cam while you are at it. The thing is the heads typically have pretty bad casting marks so porting cleans up the heads and really helps the VG30E heads flow.

Where in TN. are you?

Collegedale TN, right outside of Chatt...
 

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ZPOOLNZ
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I live in Tullahoma/Knoxville. Tullahoma is in between Chattanooga and Nashville about half way. And I go to UT. Look into the Middle Tennessee Z Club. Also I think a few of the guys in Chatanooga are looking at starting a Z club down there.
 

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I changed the HGs on my 85 turbo. The biggest thing is to keep the motor clean, any amount of gasket scraping you do have a vacuum cleaner handy and use it religiously. I used a bare razor blade as a gasket scraper, it's easy to control and gets a lot more material off than a regular scraper. It also has less chance of scratching the head or the block.
Interesting that an Hg on a nonturbo engine would blow, mine took 15 pounds of boost quite well. Sure that it is not another problem?
 

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♣Zen31ZR♣ said:
I changed the HGs on my 85 turbo. The biggest thing is to keep the motor clean, any amount of gasket scraping you do have a vacuum cleaner handy and use it religiously. I used a bare razor blade as a gasket scraper, it's easy to control and gets a lot more material off than a regular scraper. It also has less chance of scratching the head or the block.
Interesting that an Hg on a nonturbo engine would blow, mine took 15 pounds of boost quite well. Sure that it is not another problem?
The radiator/ water pump were not providing a constant flow of coolant. That caused the engine to overheat and the gasket to blow.
 

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schris71 said:
The radiator/ water pump were not providing a constant flow of coolant. That caused the engine to overheat and the gasket to blow.
Sorry, I had to ask. There's 2 other ways coolant can get into the engine and make white smoke like a blown Hg. I'm assuming you've done a compression test......
 

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♣Zen31ZR♣ said:
Sorry, I had to ask. There's 2 other ways coolant can get into the engine and make white smoke like a blown Hg. I'm assuming you've done a compression test......
I have not done a comp test yet. I will do that after I have had a chance to pull the heads off and look at everything. The 2nd clue that I had was my overflow is boiling the ant-freeze.
 

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schris71 said:
I have not done a comp test yet. I will do that after I have had a chance to pull the heads off and look at everything. The 2nd clue that I had was my overflow is boiling the ant-freeze.
You can't do a compression test after you pull the heads..... ;) This involves screwing a pressure guage into a spark plug hole and cranking the engine for 5-6 seconds. My advice, do it before you pull the heads, because you may be doing all that work for nothing. If there was inadequate coolant flow that caused your head gaskets to blow, then you have other problems. Such as the heads may be warped. Simply changing the gaskets and plopping the heads back on will not fix the problem, at least not for long........
 
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