Rebuild Lamborghini Urraco Engine

17 responses to “Rebuild Lamborghini Urraco Engine”

  1. Paul Preo says:

    Tony,

    I would take the cylinder head to the guy that did the machining, and let him check the spark plug projection on his measuring table, with the plugs torqued to specifications. I didn’t follow the thread at Lambo Talk, but the easy thing to do would have been to put in a short nose spark plug and see how the motor ran.
    How out -of- round were the cylinder liners? I will look for the oil pump photos.

    Paul

    • admin says:

      Paul it does look like this plug reaches a tiny bit further than the others. I can solve that by making sure the plug goes in the right way and by adding an extra washer. However that doesnt explain why this cylinder is down on compression in comparison to all the others or why I was getting back pressure in the sump. Both of these would indicate a broken ring. Its a dissapointment that nothing seems wrong. There is some play in the small end bearing so perhaps a combination of that and the plug reach is too blame. I did try running with a shorter plug and that cylinder still seemed to miss fire. Confusing and frustrating. If the liners are worn that much I probably need to replace all of them which is 1200 pounds.

      I will up load your pictures later as I need a different PC for that.

  2. Paul Preo says:

    Tony,

    In these situations it pays to look at everything again (and again). I would NDT the piston for cracks (Zyglo or magnetic particle), also make sure that the valves for that particular cylinder are in fact sealing and you don’t have a broken valve spring. How oval are the cylinders… is it extreme ?

    Paul

  3. Paul Preo says:

    Tony,

    The first 2 cylinders (from the left) on the “right hand” head are not working correctly…intakes have wet oily look and exhausts are not getting hot (yellow like the others)

    Paul

    • admin says:

      Paul in fact the cylinder on the far left was firing OK. without all the cylinders working I was unable to get the mixture right on the carburetor which applies to those two cylinders. I have checked the valve clearances and am following a process of elimination. I still think that the bores are the problem. The ring gap when measured is around 1mm when it should be half of that which does indicate wear. I have checked the cold valve gap this evening and it is correct at 0.45 on all 4 cylinders.

      I’m not sure what NDT is?

  4. Paul Preo says:

    NDT=non-destructive-testing

  5. Paul Preo says:

    Tony,

    I would check piston to cylinder wall clearance. We have used .0025 with new modern pistons…Lamborghini often uses .0065 + right from the factory; far from ideal. Rings can accomodate a little bit but if the piston is sloppy the ring can only do so much.

    • admin says:

      Paul thats very interesting information. The engineer I spoke to told me that the cylinder wall clearance was between 7 and 10 thousanths which seems a huge amount.

  6. Jesus Rymut says:

    Howdy, i browse your blog occasionally and i have a similar one and i was just thinking about for those who get yourself a good deal of spam remarks? In that case how can you eliminate it, any plugin or everything it is possible to suggest? I get a great deal lately it truly is driving me mad so any assistance is quite a whole lot appreciated.

  7. Can the camshaft pulleys be keyed wrongly to the camshafts?

    • admin says:

      No I dont believe they can. Why do you ask?

      • Caleb Bradley says:

        The previous owner claimed that the pulley is wrongly keyed to the rear camshaft and I see a new timing mark painted on the pulley. Supposedly the car has been set up to run in this state but I have not got it to fire.

        • admin says:

          I would be very surprised if that is possible, in fact you would have to hack the keys off to make it work???If the timing of the cams is out the valves would hit the pistons causing a catastrophe engine wise. Both the heads are off my car at the moment but they are at the engine builders. I could turn the cams round and measure the timing mark at the point the correct valves are closed. Are you sure that you have the timing the right way round. Its difficult to explain this but you set up the manual timing with the marks but then you need to turn the whole lot 180 before you set the ignition timing. I’m trying to remember why exactly. I think the timing is done on the exhaust stroke but you need it to be on the compression stroke for the electronic timing to work. I’m also in the USA all week so I cant look at the heads for you until I get back. I suggest you join either the lamborghini-talk.com forum and raise a question or the vintage lambo site. Both have some real experts on the 250 engine.

        • admin says:

          There are some pictures of the timing marks on the websit but none I think that would reference the valve position but take a look.

          • Caleb Bradley says:

            I have also heard that the timing marks on the cam pulleys are at #1 exhaust TDC instead of the conventional #1 compression TDC but how reliable is that information? Is the Driver’s handbook wrong on page 45 where it says: “The distribution is in phase when: a) The piston n. 1 is at the top dead center (TDC) of compression (inlet stroke) b) The reference marks on the lids of the camshafts are ligned up with signs engraved on the respective pulleys (Fig. 19). ?

  8. Orvin Aquart says:

    Having trouble setting up the timing on my ’74 P250. With the flywheel set with the PMS mark aligned through the sight hole on the transmission and both cam shaft pulleys set with their timing marks aligned with the arrows on engine block, the crankshaft still hits when I turn it over by hand.

    I need some advice on how to correct this.

    I’m located in New York City in case any fellow owners are nearby.

Leave a Reply

Your email address will not be published. Required fields are marked *