m20b25 head refit

Thu Mar 20, 2008 9:37 am

hi, am in the process of re-building my m20b25 head that i bought from jay, and truth be told im a bit of an amateur, ive got the head down to a bare head now, and will be sending it off for re facing crack testing etc, and im not worried about rebuilding it... however i am concerned about mating it to a m20b25 bottom end (when i find one, see wanted section!) as i have no idea how to time it all up correctly and am terrified that if i do it wrong and fit it all into my touring, the pistons will crash into the valves when i try to turn it over for the first time

so any advice/tips would be much appriciated

please be patient i currently work as a chef and the only things i know about engines is what ive read in books! i.e. what i know has been self taught! cheers lads!

Thu Mar 20, 2008 9:50 am

Get the bentley book as it is most accurate on torque and timing of the M20 engines. Also there are a good number of threads on the zone- use the search facility and you will have a few nights reading material.

good luck - you'll need it

Thu Mar 20, 2008 9:58 am

nice one cheers...

Thu Mar 20, 2008 10:46 am

Before you put the head on, set the crankshaft just before TDC, so that no 1 and 4 pistons are 3/4" down the bores, where theirs no chance of them hitting any valves.
Put the head on, turn the cam pulley so the mark lines up, then advance the crank the last few degrees so that the pulley hub marks line up as well. Put the belt on, release the tensioner, turn the crank forwards a little to tension the belt on the run on the opposite side from the tensioner, tighten the tensioner lock bolt, check the marks still line up, turn the engine over by hand a couple of times, re tension, and finally check again that the marks are aligned.

Thu Mar 20, 2008 3:33 pm

cheers brian, a lot easier than i thought it would be !!!

Thu Mar 20, 2008 9:35 pm

as brian said...... theres timing marks on both cam and crank pulleys that a blind man on a galloping horse would be able to see......... you cant get it wrong.

Thu Mar 20, 2008 11:42 pm

murran wrote:as brian said...... theres timing marks on both cam and crank pulleys that a blind man on a galloping horse would be able to see......... you cant get it wrong.

want a bet, you havent seen me hold a spanner!!! lol