Have my valves hit my pistons..

skoty · Post by **skoty** » Tue Feb 03, 2009 10:16 pm

Havn't got the answer I've been after on the silvia forums but its a fairly generalised question. My cam chain skipped a few teeth, engine runs but poorly. If say my valves did make any contact with the pistons you surely would be able to feel it by manually winding over the engine right? Ie when i reset the timing with a new tensioner etc she should be fine?

Lloyd · Post by **Lloyd** » Tue Feb 03, 2009 10:17 pm

Do a compression test

FULLOC · Post by **FULLOC** » Wed Feb 04, 2009 10:03 am

reset timing and find out... id say youd know all about it if it had hit

Lloyd · Post by **Lloyd** » Wed Feb 04, 2009 4:22 pm

Duh, stupid me assuming you'd put the chain on already. If they've hit then chances are they're bend out of the way of the pistons anyway so winding it over wont help.

Could whip the rocker cover off and make sure the valves are all sitting up at the same height

skoty · Post by **skoty** » Thu Feb 05, 2009 4:18 pm

FULLOC wrote:reset timing and find out...

Easier said than done, anyone ever had to replace the chain on a nissan sr20? Still in the process now, the sump and the cam gears have to come off to get access to the front cover plate bolts along with all the other shit around it

Its skipped about 4-5 teeth, stressen out if its going to be sweet or not? Was running after it slipped but badly, no unusual sounds though.

skoty · Post by **skoty** » Thu Feb 05, 2009 4:20 pm

HRT wrote:Could whip the rocker cover off and make sure the valves are all sitting up at the same height

Yeah still hard to tell aye

lucasthefallen · Post by **lucasthefallen** » Thu Feb 05, 2009 4:41 pm

a cylinder leakage test would tell you quickly.

rollaholic · Post by **rollaholic** » Thu Feb 05, 2009 5:06 pm

tough to do a leakage test with no cam chain

buy a toyota imo

skoty · Post by **skoty** » Thu Feb 05, 2009 5:11 pm

rollaholic wrote:tough to do a leakage test with no cam chain

buy a toyota imo

Still does have the chain on, just slipped around a few teeth. Yeah bring back the 4ages with the non-interference heads

rollaholic · Post by **rollaholic** » Thu Feb 05, 2009 5:14 pm

oh you made it sound like you had a mess of SR bits on the floor.

will still be difficult to do leakage test with cam chain timing out, particularly if the cams havent skipped in sync

Post by **Mr Revhead** » Thu Feb 05, 2009 5:15 pm

how did it skip a few teeth?

skoty · Post by **skoty** » Thu Feb 05, 2009 5:24 pm

Mr Revhead wrote:how did it skip a few teeth?

When replacing the hydraulic tensioner, when the chain slackened must of slipped or something. SR chains often like to rattle as the tensioners like to play up sometimes

pc · Post by pc » Thu Feb 05, 2009 8:55 pm

Sounds odd... I replaced an SR18 head once and from memory the hydraulic part was only to hold the tension. There is a catch system on the tensioner to stop it completely slacking off, was it broken?
Can you see enough of the tops of the pistons down the sparkplug holes to see if there is any surface damage? Maybe a tiny mirror & an LED on the end of a wire will let you see enough.

Rob · Post by **Rob** » Sat Feb 07, 2009 6:17 pm

Take the rocker cover off and check the clearances between the cam and the buckets. If the clearances are easily visible then you know something is wrong.

Also if the chain needs replacing which sounds like the case, then turn the cams over by themselves (if its possible) to see how tight the valves are

:wink:

skoty · Post by **skoty** » Sun Feb 08, 2009 10:26 am

pc wrote:Sounds odd... I replaced an SR18 head once and from memory the hydraulic part was only to hold the tension. There is a catch system on the tensioner to stop it completely slacking off, was it broken?
Can you see enough of the tops of the pistons down the sparkplug holes to see if there is any surface damage? Maybe a tiny mirror & an LED on the end of a wire will let you see enough.

The chain did completly slacken off unfortunatly. Tryed to look down the spark plug holes but dont want to risk putting anything down there just in case in falls off n I then have to take the head off.