M20 longblock rebuilt Questions

[Kevin_e30]

Hello buds I just picked this long block m20 2.5l for 60 dollars with a bunch of other parts, my plan is to rebuilt my very 1st motor. But i would like some advice on what parts should I replace from the start. The person I bought the block said the PO the timing belt broke, causing the valves to thrash the head, and damaging one piston. The piston rings are broken on all 6 pistons, should I get a new set of pistons and what kind of brand is good.

Any kind of parts that i would need you can list them below, it would be great guys.

[jlevie]

Broken piston rings probably means the pistons are damaged and may mean damage to the bores. Or the bores may be worn out of spec. Have the bores checked for wear if there is no obvious damage. If worn or damaged an overbore will be needed. You'll be getting new pistons either way. MaxSil pistons are a good choice and usually slightly less expensive than the OE Mahle pistons.

The crank journals must be precisely measured and the bearing picked according to journal dimensions. There is a table in the Bentley.

Do not have the block hot tanked as that will destroy the intermediate shaft bearings.

[SmokeE30]

you will need access to some engine rebuilding tools to accomplish this correctly, do you have the required tools to measure everything, because as jim said you need to be verrrry exact when you do so to order the correct stuff.

[jlevie]

The measuring equipment is rather pricey. Not really worth the expensive for a single rebuild. But the machine shop you'll use will have the instruments and know how to use them. They can do the measurements while the block is there. At the absolute minimum the cylinders will need to be honed, the head decked, and checked for cracks. You will obviously need to replace the bent valves and should replace the rockers for those valves. A valve grind and new seals are called for.

[Kevin_e30]

The measuring equipment is rather pricey. Not really worth the expensive for a single rebuild. But the machine shop you'll use will have the instruments and know how to use them. They can do the measurements while the block is there. At the absolute minimum the cylinders will need to be honed, the head decked, and checked for cracks. You will obviously need to replace the bent valves and should replace the rockers for those valves. A valve grind and new seals are called for.

Well I had a good friend check out the block. And he said it looks pretty clean and for the price I got it and the cylinder walls too. My friend and me will be rebuilding the block, he's a pretty good mechanic he help his brother rebuilt 16valve gti, while I send the crank and the pistons for new bearing and rings to the machine shop. And am waiting till I find me a good head 885.

[jlevie]

The cylinders must be cross hatch honed. If you don't have that done the rings may never seat. And you really can't tell if the cylinders are worn too much from a visual inspection. The bores have to be gauged.