Greetings All, I'm raising this thread to document the build of a 704cc engine. The parts have come from a variety of sources, but suffice to say it's a collection, and instead of having a pile of spare parts laying around I'm gathering everything into what I hope will be a hybrid of 500 and 126 engines
I'll start with the assembly of a 'short engine' that is assembled purely for the purpose of balancing and then I'll run through the different areas and what I have done to modify things.
I have a late 80's 126 crankcase that has needed a lot of cleaning prior to starting assembly and as I'm a little manic about cleanliness the need for everything to be spotless will be noticed. The reader will have noticed that the capacity of the engine will be 704cc this is using an 80mm bore (VW sourced barrels) and stroke of 70mm from the 126 BIS. I have also used a BIS crankshaft that has needed some work to make it acceptable, both the main bearings (+0.4mm) and big end bearings (+0.01mm) needed regrinding and to clean the crank properly the core plugs were removed and the difficult job of removing a great deal of muck from the inside gallery began. Because the gallery is not straight black muck builds up in the corners so my engineer used small stiff brushes to get into the corners. The crank was then washed out. I will add that this crank was removed from a serviceable engine and as it was largely an unknown needed careful preparation. The core plugs were replaced and spot welded to prevent them from blowing out
I'm using copper/bronze bearings (hi quality) from a performance application because they can withstand greater heat, stress and lower oil pressure for longer, but the downside is the price It's a simple job to assemble everything once the engineering work is complete. The flywheel is now 4.56kg and the clutch pressure plate is part of an uprated unit. The rest of the rear of the engine goes together as standard, but I think the crankshaft backlash will need checking after balancing as it seems a little tight
The bearing journals have been lubricated with Graphogen which is a very good engine build paste.
The remainder of the balancing build-up is to have the pistons running in the bores without rings, The max speeding rods are fitted with ARP 2000 bolts, but these will be replaced as the past fitment is unknown and any stretch will be unknown also. The barrels will be clamped down and an original sump fitted so that the assembly can be dynamically balanced by spinning it all at 270rpm on a balance table that detects out of balance forces, as the force is linear it will all be the same at 10,000rpm but I have no intention of going that far even if the bolts can take 220,000psi tensile loading. I'm not sure how long the balance will take, but I'll get back with the result and progress when I can.
Ian.
I'll start with the assembly of a 'short engine' that is assembled purely for the purpose of balancing and then I'll run through the different areas and what I have done to modify things.
I have a late 80's 126 crankcase that has needed a lot of cleaning prior to starting assembly and as I'm a little manic about cleanliness the need for everything to be spotless will be noticed. The reader will have noticed that the capacity of the engine will be 704cc this is using an 80mm bore (VW sourced barrels) and stroke of 70mm from the 126 BIS. I have also used a BIS crankshaft that has needed some work to make it acceptable, both the main bearings (+0.4mm) and big end bearings (+0.01mm) needed regrinding and to clean the crank properly the core plugs were removed and the difficult job of removing a great deal of muck from the inside gallery began. Because the gallery is not straight black muck builds up in the corners so my engineer used small stiff brushes to get into the corners. The crank was then washed out. I will add that this crank was removed from a serviceable engine and as it was largely an unknown needed careful preparation. The core plugs were replaced and spot welded to prevent them from blowing out
I'm using copper/bronze bearings (hi quality) from a performance application because they can withstand greater heat, stress and lower oil pressure for longer, but the downside is the price It's a simple job to assemble everything once the engineering work is complete. The flywheel is now 4.56kg and the clutch pressure plate is part of an uprated unit. The rest of the rear of the engine goes together as standard, but I think the crankshaft backlash will need checking after balancing as it seems a little tight
The bearing journals have been lubricated with Graphogen which is a very good engine build paste.
The remainder of the balancing build-up is to have the pistons running in the bores without rings, The max speeding rods are fitted with ARP 2000 bolts, but these will be replaced as the past fitment is unknown and any stretch will be unknown also. The barrels will be clamped down and an original sump fitted so that the assembly can be dynamically balanced by spinning it all at 270rpm on a balance table that detects out of balance forces, as the force is linear it will all be the same at 10,000rpm but I have no intention of going that far even if the bolts can take 220,000psi tensile loading. I'm not sure how long the balance will take, but I'll get back with the result and progress when I can.
Ian.