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Black N Blue?

2K views 11 replies 6 participants last post by  RPO-083 
#1 · (Edited)
I have a question ,can i use blue open chamber heads on a black block ,i would like to use closed chamber blue or black unleaded heads eventualy when i can afford it. I know there isent a lot of difference but haveing not done it before i thought i would ask first.Thanks chris.
 
#2 ·
Yes the heads are interchangeable as the blue/black blocks are essentially the same. You have to take into account the chamber cc differences when calculating the compression ratios. ie closed chambers on a 351 with factory/flattop pistions will give around 10.5:1
 
#3 ·
landau37 said:
I have a question ,can i use blue open chamber heads on a black block ,i would like to use closed chamber blue or black unleaded heads eventualy when i can afford it. I know there isent a lot of difference but haveing not done it before i thought i would ask first.Thanks chris.
As above, the heads are interchangeable. But, black heads aren't "unleaded", the seats are the same as earlier ones. Also, there are actually 3 different heads. The 351 open chamber, and 2 different size 302 heads, roughly 54 and 65 cc (opens are 76). The 54s are a bit small for a 351, unless you are on gas.....
 
#4 ·
silicon said:
Yes the heads are interchangeable as the blue/black blocks are essentially the same. You have to take into account the chamber cc differences when calculating the compression ratios. ie closed chambers on a 351 with factory/flattop pistions will give around 10.5:1
Thanks mate as far as i can tell its a standard motor .How can i tell 54 from 65 cc 302 heads?
 
#7 ·
brenx said:
I've heard about the different CC sized open and close chamber heads. I'm yet to see a factory closed chamber thats under 60cc though.
As a comparison 4V closed chamber heads are normaly 61-63cc, the chamber looks bigger than any 302C heads ive seen so id say 302 CC heads would be more like 55-60cc's. That said valve recess form valve seat wear will effect this figure allot.
 
#8 ·
brenx said:
I've heard about the different CC sized open and close chamber heads. I'm yet to see a factory closed chamber thats under 60cc though.
Me too. I have heard a lot talk about 58cc, but the few sets i have measured were bang on 60cc, but once they are skiimed, 58cc is definatly a reality.
 
#9 ·
yup. All the factory 302cc heads I've cc'd were 60->64cc. There's a pair of genuine 240,000k old 302cc heads sitting in a mates garage off his 302 that was in his XB coupe. I can guarantee they won't be under 60cc.

With machining you can get them there but you can do anything with machining and know how.
 
#10 ·
4Vman said:
Hmmm, never heard that before, are you sure?
Yep, 100%. I haven't got all the spec's any more, but I think it was XY and XA that had the 54s fitted. Probably not many around anymore though...

On a side note, the chamber sizes are basically the same as the 4Vs ( makes sense too...). Three different sizes on them as well. Open chamber, and 2 closed chamber sizes, with the 54s going on the HO engines.
 
#11 ·
RPO-083 said:
Yep, 100%. I haven't got all the spec's any more, but I think it was XY and XA that had the 54s fitted. Probably not many around anymore though...

On a side note, the chamber sizes are basically the same as the 4Vs ( makes sense too...). Three different sizes on them as well. Open chamber, and 2 closed chamber sizes, with the 54s going on the HO engines.
Hmm.. 302 Clevelands weren't fitted to XY's, the 302C first appeared in the XA, 54 cc's sounds right for 302C heads.
If its right there will be different casting numbers to verify the 2 different style 302C heads.

Yes there are 2 different chamber sizes for 4V big port closed chamber heads:

The 4V "no dot" big port heads fitted to the XW, XY and early XA GT's and XW, XY HO's were all 61-63 cc chambers (guarentee'd ive got a set), to give approx 11:1.
The later 4V "dot" closed chamber big port heads used in late XA and early XBGT have very slightly bigger 62-65cc chambers (ive got 3 sets and can verify this too!), to give approx 10.5:1.

Cheers!
 
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