lowering compression
Turbo Mini Forums

The other day my engine grenaded in spectacular fashion leaving pretty much everything fooked. Luckily I have a lovely turbo half engine spare to start on. The spare is a standard 1275 and I don't see the point in doing a rebore as the bores are in great condition as are all the other bits. I've also got a N/A head under the bed with 36 inlets and 31 exhausts. The big question is......is there enough meat on the standard turbo pistons to machine them slightly as the head that's sleeping under the bed was on an engine with 11.1 compression. The plan was to totally get rid of the beak in the head combustion chambers but if there's enough meat to machine the piston bowls a bit it saves me having to get too carried away on the head. Any advice appreciated. P.S I can do most of the work myself

Masturbation is not a crime its a hobby

Engine explosions are always awesome justification for building a more powerful one

Imo, i would leave the pistons, and measure the cc in the combustion chambers and take it from there
If need bee source a second n/a big valve head and have the chambers opened up

Yes i moved to the darkside

Instagram @jdm_brett

have a search; I'm pretty sure there is a thread with a section through a standard turbo piston that had been dished.

I,m using dished standard MT pistons and a 28cc head and calculate I have 8.3:1.

Use up to 18psi and 7200rpm and they seem to be OK

if I were in your situation I would be looking at measuring the head cc. the chances are that it has been skimmed so wont be high.

From this I would then look at either using a set of +20 18cc pistons, possibly with the head that you already have, or sell the head that you have and use a big cc one.

the plan was to measure the head chambers at the weekend Dan as I can't remember how much I had skimmed off the head. If grinding out the 'beak' and slightly machining the pistons is possible I'll do that. I'll be sticking with 10psi boost and have the intercooler so don't need a huge dish in the pistons theoretically. I'll be working on the basis that the BK450 gasket will give me 3cc when the heads torqued down so once I know the chamber cc and piston to deck cc I'll know exactly where I stand

Masturbation is not a crime its a hobby

try to keep the beak

I'd change the Pistons rather than wrecking the head