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Old 06-04-2009, 10:00 PM   #1
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83 LG4 heads vs 86 LG4 heads
Are there any differences between 83 and 86 LG4 heads? I know that the motors compression ratios are different because of the pistons but are the heads the same?
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Old 06-05-2009, 12:02 PM   #2
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Re: 83 LG4 heads vs 86 LG4 heads
pop the valve covers and check the casting numbers. They should all be 416s.
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Old 06-05-2009, 07:49 PM   #3
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Re: 83 LG4 heads vs 86 LG4 heads
difference in compression would be pistons.

some later LG4 are higher compression according to GM specs

all the early ones are less
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Old 06-05-2009, 09:01 PM   #4
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Re: 83 LG4 heads vs 86 LG4 heads
Should be. Wasn't until 87 that they started using the centerbolt valve cover heads.

You're correct- the compression ratio differences over the years were due to different pistons being used.
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Old 06-06-2009, 03:43 PM   #5
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Re: 83 LG4 heads vs 86 LG4 heads
ok ill check the casting number. And yeah i think in 85 they uped the cp to 9.5 where as before it was 8.5 or something. Just making sure i wasnt lowering my compression by changing heads. Thanks.
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