Topic: 2.5/3.0 heads (Read 3156 times)

Keith ABS · « **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

Diamond Black Geezer · « **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.

Kevin Wood · « **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?

Diamond Black Geezer · « **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)

Marks DTM Calib · « **Reply #4 on:** 06 September 2016, 10:48:32 »

Its far easier than that, the head type is engraved onto the cylinder head

Diamond Black Geezer · « **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.

Keith ABS · « **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

Keith ABS

Entwood · « **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 ..

Diamond Black Geezer · « **Reply #8 on:** 20 September 2016, 09:03:28 »

Back to he 'measure it' method in the link I posted above?

Keith ABS · « **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

Ever Ready · « **Reply #10 on:** 23 September 2016, 08:39:04 »

http://www.machineworldny.com/asp/CylinderHead.aspx?pid=2279&type=A
Three litre Saab (GM) head apparently

Diamond Black Geezer · « **Reply #11 on:** 23 September 2016, 09:05:18 »

Come on Keith, I'm losing sleep over this, the suspense!!

Ever Ready · « **Reply #12 on:** 23 September 2016, 09:35:52 »

Probably turn out to be Wartburg heads

Diamond Black Geezer · « **Reply #13 on:** 23 September 2016, 09:43:51 »

Or two heads of the (3cyl) Corsa 12v, and he's been sold a pup!

Ever Ready · « **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

frostbite · « **Reply #15 on:** 23 September 2016, 10:01:01 »

Not to hijack but could you use 3.0l heads on a 2.5 if you were to supercharge?

Kevin Wood · « **Reply #16 on:** 23 September 2016, 10:03:49 »

Quote from: frostbite on 23 September 2016, 10:01:01

Not to hijack but could you use 3.0l heads on a 2.5 if you were to supercharge?

It would reduce the compression. You'd have to do the sums to work out exactly what you'd end up with. The problem is, folklore has it that these engines start to get bottom end problems if forced induction is used. I think I'd be looking at what SAAB did to the V6s they turbocharged first.

Diamond Black Geezer · « **Reply #17 on:** 23 September 2016, 11:09:15 »

Supercharging has been done, and it's suggested super vs turbo is the was to go re: forced induction. However, for out and out powerrrr these engines aren't the best starting point. They are large, lazy motorway cruisers, that can idle smoothly and slowly, that's what they were designed for. From your 2500cc you get 167bhp... from your old 'redtop XE' of 2000cc you get 150+bhp, and 200bhp in turbocharged form, standard. That's before tuning.

If you wander over at Billing and say all snooty and self-satisfied to some Astra/Cavalier/Nova boys 'Hey guys, My 3-litre V6 has just over two-hundred bhp, year, you heard, two-hundred brake" you'd get laughed at. Scarily, the current Corsa VXR produces that, and that's a 1.6!!

With very little fettle turbo'd little 2-litres are pushing over 300bhp happily. I know that's comparing natural with forced induction, which is never fair, but realistically you might be looking at about 300 bhp from the 3-litre with a supercharger, before serious bottom-end work is required. And that's not really that impressive power for the cc's, as above.

Or, as a comparison, Lotus/GM managed a healthy 377bhp from the old straight-6 lump in the LC/LO... and many owners claim theirs produced more from the factory engine mods, and they have been tuned to even more. Strong engine.

And as Kevin says above - Saab did good things, and had good engine, some GM-derived. To be honest this always surprised me that GM didn't simply whack a Saab unit in the Omega. A new Sports model, all for free.

Doctor Gollum · « **Reply #18 on:** 23 September 2016, 11:23:23 »

If I had the inclination, which I don't, then it would be to fit a blown 2.2 into a manual 2.2 Sport.

That would be a hoot to drive

Nick W · « **Reply #19 on:** 23 September 2016, 11:39:33 »

Quote from: Doctor Gollum on 23 September 2016, 11:23:23

If I had the inclination, which I don't, then it would be to fit a blown 2.2 into a manual 2.2 Sport.

That would be a hoot to drive

I've considered that too. Turbo Astras aren't worth much, and a 2.2 Omega even less. I wouldn't bother with a Sport, as some Bilsteins and some slightly stiffer springs would be on the list. A completely stock looking CD or CDX, still on the 16"wheels but with 300hp under the bonnet should be doable with some scrounging for about £2k.

Diamond Black Geezer · « **Reply #20 on:** 23 September 2016, 11:59:17 »

That would work so well.. and with the added advantage of an engine bay you can get to things to work on!

Kevin Wood · « **Reply #21 on:** 23 September 2016, 12:13:14 »

Indeed. The V6 is great for its' refinement and flat torque output, which you'd lose with a blown 4 pot.

Quite apart from anything else, packaging issues make forced induction on a V6 a non-starter. That and the fact that someone has already made all the expensive mistakes with various other engines.

A blown oxymoron would be a fun sleeper, that's for sure.

Diamond Black Geezer · « **Reply #22 on:** 23 September 2016, 13:01:03 »

Have a feeling the cooling needs addressing, as well, on the V6s? As you say, expensive mistakes; go for something that a large-scale manufacturer has already done for you.

Keith ABS · « **Reply #23 on:** 04 October 2016, 21:27:12 »

Finally had some time to look into this one again. It has come back as X30SE heads. These came from a mechanic who said he always kept a spare set on his shelf for quick changes so he didnt have a headless car on his drive while looking for a pair. he just could not remember if they were 2.5 or 3.0. So, I have a spare set of 3,0 heads

Keith ABS

Diamond Black Geezer · « **Reply #24 on:** 05 October 2016, 09:35:32 »

Happy days!

News:

Author Topic: 2.5/3.0 heads (Read 3156 times)