after 220,000 miles on the original motor, compression in cylinder4 was down about 30%. there was some slight scoring in the cylinder and tests showed the piston rings would need to be replaced. i figured since i'll have to take the motor apart and re-hone anyway, why not go to a bigger bore? thus, i decided to go with darton sleeves bored to 2.7 with custom JE pistons to allow the use of the stock rods, crank, bushings, pins, etc. this would allow replacing just the pistons as well as further boring the sleeves (to a 2.8) should the need arise in the future (hopefully never, but you never know).
one thing i've learned early on is that practically every shop wants to do this work and will tell you they're the best at it. i think the most important question to ask any potential shop is:
have you done this to an identical motor before and if so, can i contact the owners (or can you have the owners contact me)?
basically, i wanted some assurance that the motors they've built were still working okay, as well as the general experience and feedback of the previous customers. i wasn't about to be the guinea pig at my own expense, so this was a critical factor in choosing a shop.
another important factor was that the entire work, from disassembly and cleaning, to machining and re-assembly, had to be performed by the same shop if not the same person. the reason for this was because i have been burned in the past when working with more than one shop where one shop would blame the other if something went wrong later. i wanted one shop/person to accept full responsibility from the get-go.
after hunting high and low, i was fortunate to find a local machinist who had already built four of these identical motors, the oldest of which was still being raced at the track going on 7 years now. this motor was probably the very first darton sleeved block in a 951 and the sleeves are so old that they were before darton drilled the coolant holes around the collar. an image of that motor is here;
and it is being used in this race-dominating car;
i figured if it's good enough to be used in a winning race car for the past seven years, it should be good enough for my car.
thus, the trigger was pulled and the build was on.
the donor/spare motor;
what's left of the original cylinders;
cylinders gone;
what's going in;
custom JE pistons going in;
darton sleeves pressed in;
JE pistons installed;
stay tuned, this post will be updated as things progress.