Daan Posted February 9 Share Posted February 9 4 hours ago, Ahmad_sama said: I don't like driving fast so most of time I drive like very old man from 70-80 kmph Like 50mph Is it safe to fit 2.2 head on 2.5? Ok, so low power output. Yes, the 2.25 head fits. I fitted the head of my old 2.25 to a 2.5 diesel block with 2.5 petrol pistons. Both the 2.25 and 2.5 petrol have 8:1 compression ratio, so this should mean that the combustion chamber volume of the 2.25 head is smaller. So if you fit the 2.25 head to a 2.5, this results in compressing the gasses into a smaller combustion chamber, therefore increasing the compression ratio. I have never had a 2.5 head to hand, but I measured the volume of the combustion chamber of the 2.25 head and calculated what I needed for a 2.5 litre to achieve the 9:1 compression ratio. Use water and a syringe to establish the volume you have. Calculator here: https://goodcalculators.com/compression-ratio-calculator/ I still had to have the head skimmed, from memory 2 or 3mm to get to the 9:1 compression ratio. I had new unleaded valve seats fitted, which is potentially wise as leaded fuel no longer exists (not sure if this is the case in your country), and 2.5 valves, which are bigger from memory. This works well, and with today's 95-octane petrol, you should not have any problems with detonation. 1 Quote Link to comment Share on other sites More sharing options...
Ahmad_sama Posted February 9 Author Share Posted February 9 5 hours ago, Daan said: Ok, so low power output. Yes, the 2.25 head fits. I fitted the head of my old 2.25 to a 2.5 diesel block with 2.5 petrol pistons. Both the 2.25 and 2.5 petrol have 8:1 compression ratio, so this should mean that the combustion chamber volume of the 2.25 head is smaller. So if you fit the 2.25 head to a 2.5, this results in compressing the gasses into a smaller combustion chamber, therefore increasing the compression ratio. I have never had a 2.5 head to hand, but I measured the volume of the combustion chamber of the 2.25 head and calculated what I needed for a 2.5 litre to achieve the 9:1 compression ratio. Use water and a syringe to establish the volume you have. Calculator here: https://goodcalculators.com/compression-ratio-calculator/ I still had to have the head skimmed, from memory 2 or 3mm to get to the 9:1 compression ratio. I had new unleaded valve seats fitted, which is potentially wise as leaded fuel no longer exists (not sure if this is the case in your country), and 2.5 valves, which are bigger from memory. This works well, and with today's 95-octane petrol, you should not have any problems with detonation. You are such a good man Thank you for the information And thanks to everyone here 1 Quote Link to comment Share on other sites More sharing options...
Ahmad_sama Posted February 9 Author Share Posted February 9 6 hours ago, Daan said: Ok, so low power output. Yes, the 2.25 head fits. I fitted the head of my old 2.25 to a 2.5 diesel block with 2.5 petrol pistons. Both the 2.25 and 2.5 petrol have 8:1 compression ratio, so this should mean that the combustion chamber volume of the 2.25 head is smaller. So if you fit the 2.25 head to a 2.5, this results in compressing the gasses into a smaller combustion chamber, therefore increasing the compression ratio. I have never had a 2.5 head to hand, but I measured the volume of the combustion chamber of the 2.25 head and calculated what I needed for a 2.5 litre to achieve the 9:1 compression ratio. Use water and a syringe to establish the volume you have. Calculator here: https://goodcalculators.com/compression-ratio-calculator/ I still had to have the head skimmed, from memory 2 or 3mm to get to the 9:1 compression ratio. I had new unleaded valve seats fitted, which is potentially wise as leaded fuel no longer exists (not sure if this is the case in your country), and 2.5 valves, which are bigger from memory. This works well, and with today's 95-octane petrol, you should not have any problems with detonation. Is turning carburetor to injection reliable thing ? And for your experience what was the best injector Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted February 10 Share Posted February 10 15 hours ago, Ahmad_sama said: Is turning carburetor to injection reliable thing ? And for your experience what was the best injector Unless you make a mess of the wiring fuel injection & electronic ignition is more reliable and accurate. You size the injector(s) to suit the power output, for a 2.5 petrol you could probably use almost any injectors from a modern 4-cylinder car as they all make more power than the 2.5, so whatever is available locally and looks easy to fit. Or 4 injectors from a Rover V8 would also get you pretty close. There are also sometimes throttle bodies with injectors built in that replace a carb - common for the larger 4 barrel carbs you get on American V8's but I'm sure I've seen them for smaller single-barrel carbs too, again TBI was used on a lot of small cars in the 90's - might be easier to bolt on to your existing manifold. Of course we don't know your skills or what access to tools / fabrication you have, modifying an inlet manifold to fit fuel injectors could be easy or really hard for you. 1 Quote Link to comment Share on other sites More sharing options...
TD5toV8110 Posted February 10 Share Posted February 10 Keep it simple. Refresh all of the ignition. New plugs, leads, distributor cap, points, condenser. Set valve clearances, set timing. Make sure carburetor is performing properly. (replace if not) The 2.5 is more than enough for your needs/driving style. Cheers Dave 2 1 Quote Link to comment Share on other sites More sharing options...
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