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Refreshing the engine
Below is the LET block without the pistons:
The pistons fresh out of the block. No need to dismantle the rods for a ring change.
There is no damage on the sides of this piston, and it can be reused with new rings as long as the ring grooves are cleaned and the carbon is scrapped off
A lot of carbon deposits, legacy of a faulty turbo - and tired rings to a smaller extent
Partially cleaned piston crown clearly shows how much carbon was there.
This is the Knock Sensor plug
Knock sensor plug next to the fuel tank vent plug. They are physically identical, and the cable lengths and positions are very similar. It's easy to connect them in the wrong way, running the car with no knock-sensor protection. Theoretically it should go into safe mode, retarding by 10 degrees until the connector is correctly plugged - but apparently it doesn't always work that way.
These are the bores ready for the glaze-breaker. Note the double layers of clean rugs at the bottom, to protect the crank and the bearings from any swarf.
The bores after the attack of the Glaze Breaker. The movement needs to be steady in an up-and-down fashion. 5-10 seconds are enough for each cylinder. No need to overdo it, this is not a boring excersise, just glaze breaking for the rings to settle in.
The Glaze Breaker attached to a power drill. Use one with settings for low speed/high torque
These rod bearings don't look very good. At some point this engine was left with tired mineral oil, or suffered oil contamintation. Frequent oil/filter changes prevent this
New rod bearings. The extra hole doesn't matter.
Underpiston oil jets
Jet closeup: Modified bearing for the jet: How BMW do it:
Jets from Porche 930 turbo fitted by a French enthusiast and posted on the german LET forum view of an LET bearing with these jets fitted
Alternative oil spray bars from a toyota 3SGTE block fitted onto a GM V6 block by Animal
Similar jet from Ford
Here is more on how bearings work in reality (local copy here)
If the pistons have been damaged and have to be changed, then why not go for special, low-compression? Note the shorter skirts on the low-comp ones: they're not designed to last as long as the stock parts.
Here the larger dish area is visible. These are well-designed pistons, they retain the stock squish band (raised perimeter)
A lightened and balanced crank will complement the new high-revving engine. Note the balancing holes drilled at the bottom of the counterweights
High-strength rods. No 500+ bhp LET should be without them!
Here is why everything has to be extremely clean (local copy here)
Block preparation for high-output engines
Simply bolting bits together is not always enough. There needs to be thorough preparation of all surfaces to remove casting flaws and sloppy machining from the factory. What are trivial details on a 200bhp engine can become fatal stress-risers at 500bhp. Attention to detail is what separates the fools from the winners. It's also important to know which details are the most important, and allow more time/effort on them.
This block is prepared by "Chip" and is destined to live in a mini (!).
Turbocharged and fed with copious amounts of nitrous, it's going to be pushed right on the edge of Opel's design limits.
Here we see where the edges around the block have been smoothed out.
Eevery edge has been radiused sligthly in order to better distribute stress away from it.
Casting lines have been taken out the main block walls.
Everything should look nice and smooth as if the casting lines had never been there.
Don't overdo it though, because you might end up introducing extra stress points instead of eliminating existing ones.
The block has been line bored.
The bearing tunnels were measured and found to have stretched out of shape by about 1 thou over size in the vertical plain and a quarter thou under size in the horizontal plane.
This is not unusual for an older block that has 'settled', but it has to be taken into account when re-fitting the crank (or else it will be running off-centre)
Nasty bit of casting in the block under the bearing tunnel which has got "stress raiser" written all over it
With over three times the torque produced in those cylinders (compared to a standard C20XE) the whole block is expected to flex and vibrate in ways that such flaws can become the beginning of the End.
Decent quality pistons and rods are essential in such a block, although the limits of the stock rods can be seriously extended if they are prepared accordingly.
Conrod replacement guide. (local copy here) This fellow has an EVO, but it's pretty much similar. Beware though, changing perfectly good stock bolts with ARP might create more problems than it solves.
Front engine mount after a full boost run:
Best change the engine mounts before they disintegrate under the new-found power.
A couple of documents on metal fatigue are here and here
sqrt((boost+14.7)/14.7) * CR = ECR
sqrt = square root
boost = psi of boost
CR = static compression ratio of the motor
ECR = effective compression ratio
