Thread: 2.25 head mods

Sure you have the valve clearance set to the right gap ?

yep, checked that first - I hope I checked it right ops:
all the tappets had min clearance at some stage in their cycle, so none were permanently depressed.

:roll: just to test a theory, before doing any work to the head, try running it on the premium or ultimate unleaded fuels , mite cost a little more but it mite be that the ultra low octane in standard unleaded could be youre problem,if comp's are still good it would suggest to me that it mite not be the head,possibly point gap needs adjustment ?just my two bobs worth 8)

Hi Micheal2
Premium ulp compared to normal ulp should actually work out cheaper,more power/better economy,asuming you dont thrash the guts out of the old girl.
Do you mainly run lpg? An lpg motor can handle higher compression ratios than a ulp engine as the lpg has a much higher octane rating than normal lpg
If headwork has to be done,would be better setting it up for the best performance on the cheaper lpg and using premium ulp when petrol is used to help avoid the pinging experienced with normal ulp on high comp engines.
Andrew

Thanks for the input guys.

I've had the distributor re-weighted to modify the advance curve to suit ULP (about 8 years ago) and last year had electronic ignition fitted. I mainly run LPG, so a compression ratio boost should help.

<span style="font-size:12pt;line-height:100%">Does anyone have an 8:1 head for sale?</span>

If there's one cheap nearby, it may reduce the machining costs. I have tried Premium ULP in the RR with no discernible improvement, though when I once put it inadvertently into an old 1960 SII, the 2.25 flew, it did a 75min trip in 45min!!!! [img]style_emoticons/<#EMO_DIR#>/biggrin.gif[/img] [img]style_emoticons/<#EMO_DIR#>/biggrin.gif[/img] [img]style_emoticons/<#EMO_DIR#>/biggrin.gif[/img] 8O I'll try the premium stuff again, I always intend to, but the price scares me off. :roll:

Taking a side track for a moment. Just wondering where you want to go with this head work as at most with nothing else done would yield a very small improvement :?:

7 : 1 is a low compression however more suited to serious forced induction and fuel worse than ours. 8 : 1 is marginally better without induction help, looking for power probably want 9 : 1 or more so better pistons might be the shot rather than try to play catch up. Since you're motor still seems quite well probably not a propersition at the moment, unless of course your keen for the thing to haul.

Mucking around with the head is normally part of an overall mod, usually after the intake, exhaust and cam are improved. It's not really a bang for buck type improvement. If not already I'd suggest make the engine as good as it can be with cam, carby and exhaust also lighten that 900lb flywheel will help as well. Usually works out more return for dollars, though with low compression whatever you do that left hand is going to be on the stick when it comes to hills.

Back to the power loss Phoenix comes to my mind with his fuel starvation so maybe follow through that topic may have some relevance.

In conjunction with the Head Mods, I've got a set of extractors to fit [img]style_emoticons/<#EMO_DIR#>/biggrin.gif[/img] and I'm pricing a cam from a 2.5 motor . The timing chain will also need to be done as there's a little rattle on start-up. :x

From my reading ported 8:1 heads offer better performance. Going to 9:1 offers even more performance, but is recommended for rally applications, though I think on an LPG vehicle 9:1 would probably be OK, given that I'm running a 4 core H/D radiator, that's always had coolant (from new). The engine recon guy isn't sure about taking a 7:1 head beyond 8:1 for two reasons (1) strength (2) valve clearance.
I'm not sure if the factory 8:1 head has a different combustion chamber size. Does anyone know :?: If I could find an 8:1 head, I could probably get it milled to 8.5:1 or 9:1 without as much concern.

By the way, does anyone know if the pushrods on an 8:1 are a different length from those on a 7:1 :?:

Carby-wise I'm running a Zenith 36IV which is probably the most reliable Land Rover carb (talking from what I've been told, not experience). Turner Engineering, who make performance heads recommend the Zenith. However in the long distance, high speed world of the USA, the Zeniths are often replaced with Rochester or Double Barrell Weber carbs. The Zenith apparently moves 127 cfm and the Weber 191!!!
This carby however requires a remanufactured inlet manifold, total cost of Carby, manifold, linkages is $800AUD

The extractors on their own probably won't do much, as the original exhaust manifold is a good shape, but a larger diameter exhaust may be incorporated into this to assist exhalation, since I ended up with a larger diameter s/s muffler for free [img]style_emoticons/<#EMO_DIR#>/biggrin.gif[/img].

please keep any comments / advice coming.

G'day Micheal,

I would be tempted to post something on the LROI forum, as I know alot of the guys in the UK still use the 4 cylinder for comp vehicles.

http://threads.lro.com/cgi-bin/wwwthreads/...&Board=defender

These would prob be able to help with most of your questions.

Another source could be to contact ACR - these guys still do lots of work on the 2.25 - they even build a 2.8 version!!!

http://www.automotivecomp.com/landrover_perf.html

They quote a 9.1 cylinder head go well on LPG!!!

Hope this helps

LRH