question on matching head numbers

Nova4301 · 11-23-2009, 01:01 PM

I found a set of heads that match the casting number I need except it has an x at the end of it. Is this still a legal head? What does the x mean?

NHRA/GM allowable casting numbers:

3998991 or 3986339

found a set with 3986339x

thanks,

FED 387 · 11-23-2009, 03:31 PM

3986339---1.72 intake/1.5 exhaust-74CC--- 68-69 307 eng

3986339X--SAME SPECS(int/ex/cc)---71 307/350 eng

3998991---1.72 intake/1.5 exhaust--75CC ---68-69 307 eng
72-73 307/350 eng

hope this helps--Comp387

11-23-2009, 01:01 PM	#1
Nova4301 Junior Member Join Date: Sep 2008 Location: Moore, OK Posts: 54 Likes: 0 Liked 0 Times in 0 Posts	question on matching head numbers I found a set of heads that match the casting number I need except it has an x at the end of it. Is this still a legal head? What does the x mean? NHRA/GM allowable casting numbers: 3998991 or 3986339 found a set with 3986339x thanks, __________________ Tim Wilson HR/SST 4301

11-23-2009, 03:31 PM	#2
FED 387 VIP Member Join Date: Jun 2006 Posts: 3,419 Likes: 528 Liked 332 Times in 180 Posts	Re: question on matching head numbers 3986339---1.72 intake/1.5 exhaust-74CC--- 68-69 307 eng 3986339X--SAME SPECS(int/ex/cc)---71 307/350 eng 3998991---1.72 intake/1.5 exhaust--75CC ---68-69 307 eng 72-73 307/350 eng hope this helps--Comp387