26-07-2020, 10:14 AM
Morning all, I'd better give the background to this.
The engine had been commercially rebuilt for the previous owner about ten years ago, but he had done a tiny annual mileage after that, so the car was not properly run in and I suspected had glazed bores. Excessive oil consumption and a smokey exhaust were disappointing but not the end of the world, and I hoped that putting in some mileage and giving it some proper use might improve things, but then oil started gushing from the square headed camshaft bush pin, so action was required.
Compression was reasonable and consistent across the cylinders at around 95psi and I had gone to a slightly hotter B5HS plug.
Initially I just raised the block to get the pin out so as to thread the front bush and make good. I had the camshaft refreshed by Paul Bonewell while it was out. I then decided to lift the block in order to deglaze the bores and this exposed the pistons and con rods. I had intended not disturbing the big ends on the basis it is generally best to leave things alone if they're not broke. Number one big end felt sloppier than I liked and number two was tight, so I was grateful when Nick Turley called in to have a look and advise. Nick reckons the rings are in the wrong way up and that number one big end is not ideal, but OK. Number two has been removed so I can blue the journal and scrape the tight spots. The white metal has burnished and dragged on one side, so I think I am lucky not to have run that big end.
The block is an early one which has been relined and the standard bores were showing very little wear, a maximum of .002" above the standard 2.2" measuring each cylinder at top middle and bottom and both north/south and east/west. Unfortunately there are no standard pistons available just now other than the rather pricey JP jobs, so I decided to buy a set of the well regarded split skirt pistons at + .010" and spend the change having the block bored to suit.
The builder from ten years ago appears to have been given a box of bits and asked to build an engine with minimal expenditure. The reuse of mismatched second hand pistons, old big end bolts with flimsy split pins waving in the wind, an old and virtually threadless camshaft bush pin and a less than pristine camshaft bear witness to this. The RP is intended as a daily driver so split skirt pistons that have reputedly given 65,000 miles without incident will do for me.
I shall gap the rings to a minimum .006" and run the engine in like my Dad did, by not letting it idle or labour and getting in plenty of miles on decent length runs.
I am very much in the early stages of learning about living with a Seven and enjoying gaining experience, picking up the spanners again after a gap of nearly fifty years. I am very conscious of the old saying that "an engineer can do for five bob what any fool can do for a quid" and whilst I hope I'm not a complete fool, I am certainly not an engineer. Learning about what's OK, what can be fixed and what needs replacing is a big part of the joy of Seven ownership for me. But what I really want to do of course is drive the ruddy thing!
The engine had been commercially rebuilt for the previous owner about ten years ago, but he had done a tiny annual mileage after that, so the car was not properly run in and I suspected had glazed bores. Excessive oil consumption and a smokey exhaust were disappointing but not the end of the world, and I hoped that putting in some mileage and giving it some proper use might improve things, but then oil started gushing from the square headed camshaft bush pin, so action was required.
Compression was reasonable and consistent across the cylinders at around 95psi and I had gone to a slightly hotter B5HS plug.
Initially I just raised the block to get the pin out so as to thread the front bush and make good. I had the camshaft refreshed by Paul Bonewell while it was out. I then decided to lift the block in order to deglaze the bores and this exposed the pistons and con rods. I had intended not disturbing the big ends on the basis it is generally best to leave things alone if they're not broke. Number one big end felt sloppier than I liked and number two was tight, so I was grateful when Nick Turley called in to have a look and advise. Nick reckons the rings are in the wrong way up and that number one big end is not ideal, but OK. Number two has been removed so I can blue the journal and scrape the tight spots. The white metal has burnished and dragged on one side, so I think I am lucky not to have run that big end.
The block is an early one which has been relined and the standard bores were showing very little wear, a maximum of .002" above the standard 2.2" measuring each cylinder at top middle and bottom and both north/south and east/west. Unfortunately there are no standard pistons available just now other than the rather pricey JP jobs, so I decided to buy a set of the well regarded split skirt pistons at + .010" and spend the change having the block bored to suit.
The builder from ten years ago appears to have been given a box of bits and asked to build an engine with minimal expenditure. The reuse of mismatched second hand pistons, old big end bolts with flimsy split pins waving in the wind, an old and virtually threadless camshaft bush pin and a less than pristine camshaft bear witness to this. The RP is intended as a daily driver so split skirt pistons that have reputedly given 65,000 miles without incident will do for me.
I shall gap the rings to a minimum .006" and run the engine in like my Dad did, by not letting it idle or labour and getting in plenty of miles on decent length runs.
I am very much in the early stages of learning about living with a Seven and enjoying gaining experience, picking up the spanners again after a gap of nearly fifty years. I am very conscious of the old saying that "an engineer can do for five bob what any fool can do for a quid" and whilst I hope I'm not a complete fool, I am certainly not an engineer. Learning about what's OK, what can be fixed and what needs replacing is a big part of the joy of Seven ownership for me. But what I really want to do of course is drive the ruddy thing!