Bad Tapping! GTI6

[Paul_13]

Been there done that, ended up with with 14 bent valves


That's caused by doing up the 3 x 10mm bolts too tight

10nm from memory

[welshpug]

see the light colour around the inlet valves, thats where they have kissed the pistons most likely.

[craig306]

tonight I got bored so stripped the sad engine

timing pinned up OK although the timing belt was a little slack, started to inspect the pulleys and belt and found this on the inlet pulley.........



once I took the pulley off and undone the bolts the cracked centre fell out!



took head off head looked good no obvious marks on the valves or pistons



took the bottom end off no obvious picked up or spun bearings

not looked at the block yet

so now where?
would a slack belt or damage pulley cause that much noise?
i guess ive got to get the journals sized
and get the valves out the head and spin them up to see if any are bent

put the plugs back in,. when fill up the expansion chamber up with water. but looking at them they dont look bent. show me a pic of the piston in the block.

---

tonight I got bored so stripped the sad engine

timing pinned up OK although the timing belt was a little slack, started to inspect the pulleys and belt and found this on the inlet pulley.........



once I took the pulley off and undone the bolts the cracked centre fell out!



took head off head looked good no obvious marks on the valves or pistons



took the bottom end off no obvious picked up or spun bearings

not looked at the block yet

so now where?
would a slack belt or damage pulley cause that much noise?
i guess ive got to get the journals sized
and get the valves out the head and spin them up to see if any are bent

put the plugs back in,. when fill up the expansion chamber up with water. but looking at them they dont look bent. show me a pic of the piston in the block.

plus iv been listening to the video you posted a few time, and the engine wasn't missing at all.

[welshpug]

these have double valve springs, hence most tappers still return very good compression results, you need to remove the valves and actually check them with a dial gauge.

[cully]

i have the pistons out the block
looking at them carefully within the valve cut outs it is quite clean as is some of the edges on some of the inlet valves

so yes valves have touched pistons slightly
as welshpug says i need to get the valves out and checked
im sure the head casting is good pistons good and bottom end looks good

i have a good head on another engine with a dead bottom end but idealy id like to build this one back up

i need to get the block bore measured to see if i can get away with hone and rings or if it needs a bore

[cully]

here are some more photos
looks like all inlets have touched pistons as piston cutouts look clean
but there is no marks on the valves!

[Toms306]

Wow, good job you caught it, could that pulley have fallen apart on it's own eventually?

[cully]

Wow, good job you caught it, could that pulley have fallen apart on it's own eventually?

yes unfortunatly pulley failiures seemed to be quite common on the earlyer engines

---

billy bonus the head is 137mm so its an unskimmed head

[Niall]

Them pullies had to be torqued EXACTLY right otherwise things like this happened. Thats why on the later ones they replaced them with the single bolt type which I'm led to believe to can just raj up as tight as you like and they won't fail lol

[Toms306]

Seems a pretty poor design for something so crucial!

[Niall]

Seems a pretty poor design for something so crucial!  

Yeah because every car thats ever been released has been perfect without any common faults at all 

[welshpug]

not really, they worked fine till ham fisted mechanics got their hands on them, failures are not that common, I have seen it on the forums but never up close.

[Toms306]

Seems a pretty poor design for something so crucial!  

Yeah because every car thats ever been released has been perfect without any common faults at all 

Of course not, but it must be someones job to make sure things are strong enough for the job, it's not even like they had to skimp with the GTi-6, if it was a 1.4 or diesel then fair enough lol.

[cully]

welshpug do you know the tolerances + - for the crank big end and mains for std bearings?

[welshpug]

not offhand, they're in the Haynes manual though.

TBH seeing as you have it apart I would throw in a set of std bearings anyway, and see how it looks with some plastigauge.

[cully]

plastigauge? i will have to see what that is and how to use it i usually micrometer stuff up

[welshpug]

its more accurate and very very easy, its use is actually detailed in the haynes manual too.

http://plastigauge.co.uk/


you need the red/orange stuff, for the closer tolerance ranges, and you simply build each bearing up with a strip of
plastigauge across the journal, torque to spec, dissemble and check against the gauge how much its been squished.

[cully]

for the big end (BE/PL) is that telling me the plastigauge should read between 0.021- 0.075 mm to be within std tollerance on new std bearings

and

for the mains (MB/HL) is that telling me the plastigauge should read between 0.040- 0.100 mm to be within std tollerance on new std bearings


   

[cully]

I've had new mains and big-ends turn up also the red plastigauge
ive been out and fitted the new mains to the block and plastigauged them all 5 main bearings
they have all come back to 0.076mm on the plastigauge

so if the tollerance for the bearings is 0.040 - 0.100 i would say the mains are within tolerance

now to do the same with the Big-ends

[cully]

[welshpug]

looks good, the other check is end float on the crank.

[cully]

cant find any info on the end float welshpug can you help out there?

no1 big-end measured 0.038mm so its within 0.021-0.075 so thats a good one


3 more to go

[Niall]

Cully have a look in my build thread for the big end float

[cully]

i now have plasticgauged the mains and big ends and they are all within tolerance of a std grind
good news

that is good to be honest as even if the head is toast, i have a rebuilt head on another engine i could swap over

[welshpug]

I doubt the head is toast, but it will likely need a set of valves and a skim to clean up the corrosion.

and pray its never been off when in leicester before.

[cully]

interesting find on the inlet valves
running them round on the desk they dont look bent but all the inlets have a strange ribbed looking effect on the stems

any ideas??

[Paul_13]

Never seen that before

[Lwilliams]

I doubt the head is toast, but it will likely need a set of valves and a skim to clean up the corrosion.

and pray its never been off when in leicester before.

Why's that?