Repair after timing belt failure....pic heavy.

Nissan doctor

trixyben wrote: »

still cant understand today how he didnt see the temp gauge and lights on the dash etc, ah well these things happen and happen more so when someone is driving someone elses motor!!!

Wouldn't happen again if he was made to pay for it!

doctorchopper

If you are lapping a lot of valves, one of this is hady
http://www.mowforce.com/VALVE-LAPPING-TOOL-CRANK-STYLE_p_4989.html
I used to rebuild a lot of old ingersol rand kvs compressor engines. Pistons are about 450 lbs a piece. here's some pictures of one (not me though)

SouperComputer

doctorchopper wrote: »

If you are lapping a lot of valves, one of this is hady
http://www.mowforce.com/VALVE-LAPPING-TOOL-CRANK-STYLE_p_4989.html
I used to rebuild a lot of old ingersol rand kvs compressor engines. Pistons are about 450 lbs a piece. here's some pictures of one (not me though)

Thats's a feckin great tool. Might get one! I rebuilt the top end and turbos in my T6 last year, I'll lob up a thread with some photos. Wont be as detailed as this one mind.

I love rebuilding engines. Hate working on cars, especally **king around with hard to get to bolts/rusted stuff but I could rebuild engines all day. Love looking at a nice clean air pump.

Discodog

Those lappers are OK for people who know what they are doing but it would be easy for a novice to over grind the valve seat. When I did mine they only needed a total of about 5 minutes of lapping by hand per valve.

doctorchopper

Discodog wrote: »

Those lappers are OK for people who know what they are doing but it would be easy for a novice to over grind the valve seat. When I did mine they only needed a total of about 5 minutes of lapping by hand per valve.

You are absolutely correct, they are very quick at lapping the valves, so be careful

CJhaughey

Try this lapper.
http://www.louis.de/_10905472c2a8622ac4322a3cc41ec5c874/index.php?topic=artnr_gr&article_context=detail&grwgr=370&wgr=465&list_total=32&anzeige=0&artnr_gr=10002886

Nissan doctor

Either of the tools mentioned above remove the 'feel' for what your doing.

When lapping by hand you can feel when the paste is working, can feel when it needs to be brought back onto the seat and feel when the surface is getting to the condition you want.

Tools like that make it very easy to over do it IMO.

Personal preference of course.

trixyben

Nissan doctor wrote: »

Either of the tools mentioned above remove the 'feel' for what your doing.

When lapping by hand you can feel when the paste is working, can feel when it needs to be brought back onto the seat and feel when the surface is getting to the condition you want.

Tools like that make it very easy to over do it IMO.

Personal preference of course.

Doc,

On an engine where no damage is done with a snapped timing belt, how are these engines timed and how are the valves operated etc?

Nissan doctor

trixyben wrote: »

Doc,

On an engine where no damage is done with a snapped timing belt, how are these engines timed and how are the valves operated etc?

Non interference(free running) engines work in exactly the same way. The only reason that damage isn't caused is due to how far the valves open in relation to the stroke of the piston. On these engines, when the valves are fully open, they still have clearance between then and the piston crown.

Avns1s

trixyben wrote: »

Doc,

On an engine where no damage is done with a snapped timing belt, how are these engines timed and how are the valves operated etc?

Not wishing to speak on behalf of the Doc (whom I guess will soon be a professor! :-) ), I presume you are talking about a "non-interference" engine.

They operate exactly the same as an "interference" engine but the stroke of the piston does not intercept the valve at any point hence if the belt breaks, the piston does not strike the valve regardless of the valve position.

Avns1s

Nissan doctor wrote: »

Non interference(free running) engines work in exactly the same way. The only reason that damage isn't caused is due to how far the valves open. On these engines, when the valves are fully open, they still have clearance between then and the piston crown.

Hmmm, beat me to it. On the ball as usual, Doc!!

trixyben

makes ya think why (apart from the fact of having to pay garage for repairs) use the interference engine with the possible damage ahead of you?

Is there pros and cons of both?

Avns1s

trixyben wrote: »

makes ya think why (apart from the fact of having to pay garage for repairs) use the interference engine with the possible damage ahead of you?

Is there pros and cons of both?

Well, in fairness, if the timing belts are changed at the recommended intervals, there is rarely a problem with timing belt failure.

trixyben

Avns1s wrote: »

Well, in fairness, if the timing belts are changed at the recommended intervals, there is rarely a problem with timing belt failure.

it happened me on a seat inca van on the motorway, belt snapped and only 30k done on it, required new engine which of course means hassle and €€€€€

just wondered was there maybe a down side to the non interference engine or why they arent used on by most manufacturers

Nissan doctor

trixyben wrote: »

makes ya think why (apart from the fact of having to pay garage for repairs) use the interference engine with the possible damage ahead of you?

Is there pros and cons of both?

There are less and less non interference engine these days. The design of the combustion chamber is the main factor which determines interference or non interference and the most efficient combustion chamber designs require an interference set up.

trixyben

Nissan doctor wrote: »

There are less and less non interference engine these days. The design of the combustion chamber is the main factor which determines interference or non interference and the most efficient combustion chamber designs require an interference set up.

Cheers Doc...

Have you any other well documented repairs in the pipeline?

Nissan doctor

trixyben wrote: »

Cheers Doc...

Have you any other well documented repairs in the pipeline?

I'll have to see what I can do....the problem with things like a clutch change, for example, is that, apart from changing the clutch unit itself, the job(connections, linkages, shafts, box etc etc) is pretty vehicle specific so doing a pic thread of a clutch change on a Focus would give very little pointers to someone wanting to try it on another car. That's why in this thread I went into very little detail on removing/refitting the engine external components.

Leave it with me though.

There might be a thread soon about building a Nissan 200sx from scratch:eek:

Discodog

Nissan doctor wrote: »

Either of the tools mentioned above remove the 'feel' for what your doing.

When lapping by hand you can feel when the paste is working, can feel when it needs to be brought back onto the seat and feel when the surface is getting to the condition you want.

Tools like that make it very easy to over do it IMO.

Personal preference of course.

I totally agree. There is a common misconception that grinding by hand is hard work. If you are replacing worn or damaged valves it shouldn't take more that 5 mins total grinding per valve. You are only trying to achieve a couple of mm of ground seat.

The other huge problem with lapping attachments is you can't hear the paste working. When you lap by hand you can hear when the paste is no longer grinding & it is then time to change to a finer paste.