09-04-2023, 11:17 AM
(This post was last modified: 09-04-2023, 11:22 AM by Malcolm Parker.)
Belated Happy Returns on your big birthday, Ruairidh, I wouldn't mind being your age again.
On Friday I took the Pytchley out on my quite arduous test circuit up and down the edge of the North Yorkshire Moors. Whilst it was running well, when I opened it up on the old drove road along the top of Sutton Bank, pictured, it was reluctant to pull much over a true 45mph in top, surprising given its light weight and 5.25 rear axle.
I suspected that the cylinder head was holding it back. It was fitted with a bronze 9E1 head that although it has been skimmed, does not appear to have a particularly good compression ratio. I decided to change the head for a late Ruby type. Having got the bronze head off I compared it with the Ruby head and it seemed clear that the bronze head had a much deeper combustion chamber. The depth at the valves was 12mm with the bronze head compared to 9mm for the Ruby one.
I then looked at a new aluminium Ricardo head that I had in stock and this looked to have a better compression ratio than the Ruby head. I am running my RL saloon on a Ricardo head and am very pleased with the performance.
The new Ricardo head was duly fitted to the Pytchley with a new 'early' gasket and the car was taken up the road on my 'test' hill, a steady climb of 951 yards with a couple of easy bends. With the Ricardo head the Pytchley made the climb in 68 seconds on the first run, a full 4 seconds faster than the best I had been able to achieve previously. The speed up the hill was altogether faster, cresting the summit at 38 mph whereas the best was 30 mph previously.
Suffice to say I am a happy Easter Bunny!
On Friday I took the Pytchley out on my quite arduous test circuit up and down the edge of the North Yorkshire Moors. Whilst it was running well, when I opened it up on the old drove road along the top of Sutton Bank, pictured, it was reluctant to pull much over a true 45mph in top, surprising given its light weight and 5.25 rear axle.
I suspected that the cylinder head was holding it back. It was fitted with a bronze 9E1 head that although it has been skimmed, does not appear to have a particularly good compression ratio. I decided to change the head for a late Ruby type. Having got the bronze head off I compared it with the Ruby head and it seemed clear that the bronze head had a much deeper combustion chamber. The depth at the valves was 12mm with the bronze head compared to 9mm for the Ruby one.
The new Ricardo head was duly fitted to the Pytchley with a new 'early' gasket and the car was taken up the road on my 'test' hill, a steady climb of 951 yards with a couple of easy bends. With the Ricardo head the Pytchley made the climb in 68 seconds on the first run, a full 4 seconds faster than the best I had been able to achieve previously. The speed up the hill was altogether faster, cresting the summit at 38 mph whereas the best was 30 mph previously.
Suffice to say I am a happy Easter Bunny!