04-06-2021, 02:59 PM
I have written elsewhere about the issues I had with the rebuilt engine, which stood for 15+ years.
Now running and having done about 250 miles it seems to have plenty of urge and is freeing up as the miles add on.
The engine has a 1 ⅛" SU carb, from the last engine, with an AN needle, it has an HC head from the last engine, which is flat, it is fitted with a new Phoenix crank, the dynamo and gear are also from the last engine, as is the Accuspark dizzy. I have listed the pre used parts to indicate that they are known and were previously working satisfactorily. The A - R lever is connected and works.
I got the engine running, at first it was much retarded, I got it into what I would consider the best running position but it is noisy, it has a harsh sound and is a little rough until I reach upper 30's mph when it smooths out and seems quieter. I should add that I have in 55 year of A7 ownership always got the timing to my satisfaction by ear (which of course may have been incorrect, but I have done 20,000 miles in this car in the last 10 years)
Yes, I imagine the common thought will be its too far advanced, this is where I need your guidance please. If you look at Brett's photo in a previous post, I have fitted a similar pointer and have a Gunson strobe which I purchased recently. I also have a notch filed on the pulley at TDC number 1, which I established when the head was off, so I am confident it is in the correct place. I decided I would check the calibration of my ear with the strobe, which is where not having used one before showed up the weakness in my cunning plan. I read all I could on the Forum, but I dont think anyone has done Strobe Timing 101.
Looking from the front of the engine the cam pulley rotates anti-clock. My understanding of the terms for firing, ie TDC, degrees advanced etc have been challenged by what I found. Bear in mind that the dizzy is electronic. I warmed the engine and tried the strobe, set to 0 deg advance on a fast tick over, probably 1,000RPM. I eventually found the pulley mark not by the pointer but about 1 ½" forward of it, ie counter clockwise 1 ½" forward of the pointer (white arrow points TDC mark on pulley), as you will see in the attached photo. At about 2,500 RPM the pulley mark moves back towards the pointer about 1/8".
It looks to me as if the spark is occurring after the piston reaches TDC, is that correct? This was my thought, so I turned the dizzy to try and make the spark occur in advance of TDC, before the timing mark reaches the pointer the engine stops. As the Gumbies used to say"My brain aches!" help please I are confused of Oxford.
Screen Shot 2021-06-04 at 14.43.12.png (Size: 537.51 KB / Downloads: 208)
Now running and having done about 250 miles it seems to have plenty of urge and is freeing up as the miles add on.
The engine has a 1 ⅛" SU carb, from the last engine, with an AN needle, it has an HC head from the last engine, which is flat, it is fitted with a new Phoenix crank, the dynamo and gear are also from the last engine, as is the Accuspark dizzy. I have listed the pre used parts to indicate that they are known and were previously working satisfactorily. The A - R lever is connected and works.
I got the engine running, at first it was much retarded, I got it into what I would consider the best running position but it is noisy, it has a harsh sound and is a little rough until I reach upper 30's mph when it smooths out and seems quieter. I should add that I have in 55 year of A7 ownership always got the timing to my satisfaction by ear (which of course may have been incorrect, but I have done 20,000 miles in this car in the last 10 years)
Yes, I imagine the common thought will be its too far advanced, this is where I need your guidance please. If you look at Brett's photo in a previous post, I have fitted a similar pointer and have a Gunson strobe which I purchased recently. I also have a notch filed on the pulley at TDC number 1, which I established when the head was off, so I am confident it is in the correct place. I decided I would check the calibration of my ear with the strobe, which is where not having used one before showed up the weakness in my cunning plan. I read all I could on the Forum, but I dont think anyone has done Strobe Timing 101.
Looking from the front of the engine the cam pulley rotates anti-clock. My understanding of the terms for firing, ie TDC, degrees advanced etc have been challenged by what I found. Bear in mind that the dizzy is electronic. I warmed the engine and tried the strobe, set to 0 deg advance on a fast tick over, probably 1,000RPM. I eventually found the pulley mark not by the pointer but about 1 ½" forward of it, ie counter clockwise 1 ½" forward of the pointer (white arrow points TDC mark on pulley), as you will see in the attached photo. At about 2,500 RPM the pulley mark moves back towards the pointer about 1/8".
It looks to me as if the spark is occurring after the piston reaches TDC, is that correct? This was my thought, so I turned the dizzy to try and make the spark occur in advance of TDC, before the timing mark reaches the pointer the engine stops. As the Gumbies used to say"My brain aches!" help please I are confused of Oxford.
Screen Shot 2021-06-04 at 14.43.12.png (Size: 537.51 KB / Downloads: 208)