kate205gti 4 Posted August 22, 2007 after a bit of advice/suggestions please as im still learning engines! story so far.. 22nd April - Mi16 engine blew up round track at Castle Combe 14th July - finally get new GTi-6 engine in and running makes it to French Car Show 25th July - goes for mapping and pops a cylinder (no. 2) at Emerald whilst on the rolling road the engines been stripped and checked and I picked up a new piston for it (thanks rich!! ) as the old piston was quite pitted (we suspect a bit of debris got sucked in and bounced around in there causing the valves to stick) fitted new piston last night with anthonys help (cheers ant ), put it all back together and timed it up, engine turned over fine then put the spark plugs in, turned engine over again to check compression but now its losing compression on cylinder 4!!! the other pistons looked fine when we put it together any things to check/try/any ideas please? could put it in anyway and do a compression test but will be thats another 1/2 nights wasted if its got to come out and get stripped down again! cheers for any suggestions! Share this post Link to post Share on other sites
Sandy 191 Posted August 22, 2007 Fuel up, run it up to temp and re-try. Share this post Link to post Share on other sites
kate205gti 4 Posted August 22, 2007 hey sandy what are the options could it be though? at the moment the engines still on the floor - will take me a night to put it in and get fluids/wiring/manifold/ etc.. all attached - dont want to be doing that if i have to then take it all out again would go top myself lol Share this post Link to post Share on other sites
Alastairh 47 Posted August 22, 2007 Sure no valves got damaged on number 4 when head was removed and on the shelf. Alastair Share this post Link to post Share on other sites
kate205gti 4 Posted August 22, 2007 how do i check? any way other than taking head off again?? head was on a cushion but is possible i suppose Share this post Link to post Share on other sites
Richie-Van-GTi 73 2 Cars Posted August 22, 2007 (edited) I agree with sandy, get it running first. Could be a dry valve sticking after being stood, a bit of running should sort that out, could just need that pot carbing up again. What were the actual readings out of interest? Worst case is swapping that piston over which can be done with engine in situ anyway, just remove head and sump. A good bodge way of checking if the valves are closing fully is to turn engine so they should be closed then fill the port with paraffin oil, make sure it doesnt 'leak down'. Just make sure you dry as much out as possible before turning engine and then when you do just take the sparks out and crank it over a few times to eject any residue. Ive done it with water before now Edited August 22, 2007 by Richie-Van-GTi Share this post Link to post Share on other sites
welshpug 1,666 Posted August 22, 2007 are you running solid tappets or hydraulic? Share this post Link to post Share on other sites
kate205gti 4 Posted August 22, 2007 when it went before (cyl 2 on the rollers) it dropped to 50psi this time was turning it over by hand with the engine on the floor after fitting the cambelt, went stiff and poffed on 1,3 then ffft not stiff on 4 then stiff again on 2 (my technical description ) Share this post Link to post Share on other sites
rescue dude 0 Posted August 22, 2007 (edited) That's a bit of a bugger Kate. I'd think about fitting it and running it up as suggested by Sandy. If your still getting a low comp reading from 4 i think that if you sucked something into 2 then maybe something may have got into 4 and possibly damaged a valve seat so it's head off and regrind all the seats and check if any of the valves are bent. Sounds like it's definitely a head problem which can be sorted with the engine fitted. Just a thought. Did you strip the head after it went tits up? if so did you put the valves back from exactly where you took them? A mate had a similar problem to you and it turned out he didn't spot a bent valve and fitted it into another cylinder causing the confusion. Edited August 22, 2007 by rescue dude Share this post Link to post Share on other sites
Richie-Van-GTi 73 2 Cars Posted August 22, 2007 stupid question, you did have a spark plug tightened into pot 4 didnt you. Wouldnt be the first person Ive known to do this. Turning by hand isnt always a good indicator either, much better to bolt a starter onto it and spin it on a battery with a compression tester attached. Share this post Link to post Share on other sites
kate205gti 4 Posted August 22, 2007 yeh double-checked that! ooh is it just starter and battery needed for that then?? Share this post Link to post Share on other sites
welshpug 1,666 Posted August 22, 2007 yeh double-checked that! ooh is it just starter and battery needed for that then?? and a gearbox! Share this post Link to post Share on other sites
Richie-Van-GTi 73 2 Cars Posted August 22, 2007 yeah fasten gearbox and starter on, stick a live to starter live, earth from gearbox to battery then short between the starter live and solenoid. Share this post Link to post Share on other sites
Mikey S 29 1 Cars Posted August 22, 2007 its quite normal to reassemble an engine and have hardly any compression when you turn it over. all of the lifters have to re-fill with oil after being apart. vauxhall ecotec engines and rover k series are always like it after a rebuild. Share this post Link to post Share on other sites
