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73-87 Chevy _ GMC Trucks => Performance => Topic started by: mikewb on March 03, 2008, 12:50:07 am

Title: Heads
Post by: mikewb on March 03, 2008, 12:50:07 am

anybody know what head this is? i found this number 8986889X or 3986339X

Title: Re: Heads
Post by: joesgarage71 on March 03, 2008, 07:11:37 am

339X is a 1971 307/350 74 CC head
 couldn't find the 889X you must have read it wrong 3's 9's 8's look alike and sometime the casting gets sloppy. If they are near the same date there most likely from the same motor.
 Steve

Title: Re: Heads
Post by: mikewb on March 03, 2008, 03:11:38 pm

was trying to figure out what valves

Title: Re: Heads
Post by: red4wd on March 03, 2008, 03:48:14 pm

I saw them listed as 1.72 and 1.50

Title: Re: Heads
Post by: mikewb on March 03, 2008, 04:53:37 pm

is that a bad head to have?

Title: Re: Heads
Post by: Captkaos on March 03, 2008, 05:42:23 pm

What are using it for?

Title: Re: Heads
Post by: mikewb on March 03, 2008, 06:27:17 pm

there on my motor right now. 350

Title: Re: Heads
Post by: Captkaos on March 04, 2008, 11:04:42 am

I meant when you say are they bad in what reference are you asking?  If you are asking if they are a good performance head then the answer is no.  If you are asking if they are a good head in general, they would be a good low rpm head.

Title: Re: Heads
Post by: mikewb on March 04, 2008, 02:29:39 pm

i meant for performance

Title: Re: Heads
Post by: mikewb on March 05, 2008, 07:20:32 pm

should the numbers on both heads match or are they different?

Title: Re: Heads
Post by: Captkaos on March 05, 2008, 10:15:23 pm

The should[/b] be the same on both sides.

Title: Re: Heads
Post by: mikewb on March 05, 2008, 10:18:35 pm

I have these . left 3946813 right 3986339X

Title: Re: Heads
Post by: joesgarage71 on March 08, 2008, 11:02:04 am

3946813= 69-79 350 truck. And you know the other one. The casting numbers should match but I have seen untouched motors that had different heads on them from the factory.