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Author Topic: 2.5/3.0 heads  (Read 3843 times)

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Keith ABS

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2.5/3.0 heads
« on: 06 September 2016, 07:14:40 »
  Hi all, I have aquired a pair of s/h heads. The origional owner cant remember if they were from a 2.5 or 3.0 car as he had been regurly working on lots of both engine sizes and these were a spare pair. As I have yet to look properly at them due to lack of time, what would be any differance between the two please?

Keith ABS
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Diamond Black Geezer

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Re: 2.5/3.0 heads
« Reply #1 on: 06 September 2016, 09:06:20 »
I seem to recall on a forum (possibly this one) that someone with a cambelt failure acquired some heads, but on inspecting them found some numbers, incorrect for their engine. There'll be the engine code stamped on them, or a variation thereupon 'X25XE' 'X30XE' or '25' or '30' etc somewhere. They are different heads, I know that.

How much is to be gained / lost in fitting the 'wrong' heads I don't know. I believe the 2.5 and 3.0 is in bore, not stroke. Hence using 3.0 heads on a 2.5 will have a 'step' in the combustion chamber.  :)
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Kevin Wood

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Re: 2.5/3.0 heads
« Reply #2 on: 06 September 2016, 09:37:22 »
2.5 heads will have a smaller combustion chamber. If they are used on a 3.0 it will increase the compression, which might be good for performance if the increase is not too much. 3.0 heads on a 2.5 will decrease compression and probably make it a bit flat performance wise. 3.0 heads have sodium filled exhaust valves too.

Valve ports are also smaller on the 2.5 head, so there will be a step where they meet the inlet divider. This might be a good way to tell them apart if you have a divider handy?
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Diamond Black Geezer

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Re: 2.5/3.0 heads
« Reply #3 on: 06 September 2016, 09:43:55 »
Here:
https://en.wikipedia.org/wiki/General_Motors_54%C2%B0_V6_engine

gives the engine dimensions, so in theory be very easy to tell with a handy ruler. (Supposing one has a handy ruler)  :)
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Re: 2.5/3.0 heads
« Reply #4 on: 06 September 2016, 10:48:32 »
Its far easier than that, the head type is engraved onto the cylinder head
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Diamond Black Geezer

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Re: 2.5/3.0 heads
« Reply #5 on: 08 September 2016, 16:24:08 »
Keith - found this...

http://www.omegaowners.com/forum/index.php?topic=133682.msg1714237#msg1714237


)proposed) results of fitting 'mismatched' heads.  :y
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Keith ABS

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Re: 2.5/3.0 heads
« Reply #6 on: 19 September 2016, 19:32:46 »
  OK, had time this weekend to look at this pair of heads. Could not find 2.5 or 3.0 on them any where but did find the part numbers. 90 411 846  90 411 847. My pc keeps freezing tonight each time I have tried to either google the numbers or attempt to look on ecat. Anyone have any info to hand with those part numbers? Thanks in advance  :y

Keith ABS
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Re: 2.5/3.0 heads
« Reply #7 on: 19 September 2016, 19:49:50 »
My, admittedly old, EPC does not list either of those numbers as anything, let alone as cylinder heads.

A google search however lists them as opel sintra in english, and opel omega, vectra, sintra, and SAAB 3.0 litre heads in several foreign languages.

Not much help I'm afraid .. :(
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Diamond Black Geezer

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Re: 2.5/3.0 heads
« Reply #8 on: 20 September 2016, 09:03:28 »
Back to he 'measure it'  method in the link I posted above?
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Keith ABS

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Re: 2.5/3.0 heads
« Reply #9 on: 22 September 2016, 07:42:28 »
  Managed to get on to ecat last night. Put in the part numbers of these heads and came back with 'no match found'. Looks like I will be trying the measuring now

Keith ABS
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Ever Ready

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Re: 2.5/3.0 heads
« Reply #10 on: 23 September 2016, 08:39:04 »
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Re: 2.5/3.0 heads
« Reply #11 on: 23 September 2016, 09:05:18 »
Come on Keith, I'm losing sleep over this, the suspense!!  ;D
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Re: 2.5/3.0 heads
« Reply #12 on: 23 September 2016, 09:35:52 »
Probably turn out to be Wartburg heads ;D ;D
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Re: 2.5/3.0 heads
« Reply #13 on: 23 September 2016, 09:43:51 »
Or two heads of the (3cyl) Corsa 12v, and he's been sold a pup!  :)
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Re: 2.5/3.0 heads
« Reply #14 on: 23 September 2016, 09:56:59 »
Good call with the Corsa heads, the Wartburg ones would be obvious as they're off a stroker
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