Technical UH OH, dead cylinder head, help!

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Technical UH OH, dead cylinder head, help!

faster4_tec

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Well I haven't really EVER had a problem with my punto, and she's now done 97k miles, so she's done pretty well all things considered (y)

last couple of days I've noticed it running a bit tappetty, but nothing a car of her age shouldn't come to expect.
however 2days back, it detoriated BADLY, sound'd like a tractor, tappety as a ford OHV pushrod motor, yet still driving smoothly (apart from low torque at idle) and normal fuel consumption.
no oil consumption
no dirtying of coolant fluids
normal running temps
however it has been warming up quicker than normal.

car is a '98 mk1 1.2 8v running on the std spi stuff again, 97k,
car is now off the road, and head is sitting in my front room.

it ain't pretty. there is NO cracks, however cyl 3 is black'ned and sooty, wheras the other cylinders look lean and dry.
just putting some water down the inlet/exhaust mani's cyl 1/2/4 managed to hold their water pretty much indefantly, but cyl 3 was pishing out of the inlet, (can't remember whether it was exh, or inlet now).

DSCF7472.jpg

head looks like that. cyl 1 (cam belt end) on the right, cyl 4 on the left.

DSCF7478.jpg

cam looks odd, its the 998 75mpi jobby, was correctly shimmed at the time by a bloke I know who works at ford Msport.
cam looks like theres been some valve bounce maybe? as it kind of stutters on the softer end of the profile


ANYBODY any ideas. I obviously need to skim it again now, and gonna rebuild the whole head, with maybe new valves and that (fairly cheap), do you reckon the valve seats have stuffed it, or maybe just some dirt in the valve seat/melted valve?

also got a video to post of the tappety'nesss
 
i'd definately lap the new valves in, as even if the seat hasn't suffered, the chance of a new valve fitting perfectly is slim. Whats wrong with having the existing valves bead blasted, polished and re-lapped in?

Oh and btw the cam is and 866 cam, must have read it upside down lol

Lenny
 
I know to lap them in right.
some aggresive grinding would prob pull out any imperfections in the seats :)


also whilst I'm sat here for the next few days was going to lightly polish out the casting marks from the inlet/exhaust ports :yum: done it before, but not on an aluminium head.

also for the skim, instead of th normal couple of thou, thinking of taking quite a bit off, to raise compression, or do you reckon the ignition would not be able to adjust itself enough (without a remap)

video
 
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just pulled the valve buckets and measured/read the shims.

they are...

cyl 4, inlet = 3.97mm
exh = unknown (burn't off)

cyl 3(problem cyl), inlet = 4.02mm
exh = 4.10mm

cyl 2, inlet = 3.95mm
exh = 4.07mm

cyl 1, inlet = 3.82mm
exh = 4.05mm


seems to me, that cyl 3 (the black one) ain't closing its inlet properly because the shim is quite a bit bigger than the others. Obviously its all relative, at the time of shimming it was probably correct, but wear and tear shows the valve sitting proud (you can actually see air around it with the cam removed!).


hoping that just stripping it down, and rebuilding with fresh shims, cutting it in freshly should sort it out :idea:
 
this might sound harsh, but why not just get another head from the scrappies? i uppose your dealing with a known evil here vs an unknown one, but still :)

plus if you were to raise the CR significantly, IIRC you may/may not need a vernier cam pulley (the timing will be out since the pulleys will be closer together)ive heard this before, but it still doent make sense to me :rolleyes:
 
yeah I know the top pulley would be closer, but the difference is so minuute.

cost wise, if my head is solid (well it is, there ain't any cracks, corrosion, surface damage etc), then its gonna cost me the same to fix this one as it will to get an unknown head.

still got to get it skimmed etc
 
she's now done 97k miles, so she's done pretty well all things considered (y)
however 2days back, it detoriated BADLY, sound'd like a tractor, tappety as a ford OHV pushrod motor,
it ain't pretty.

seems to me, that cyl 3 (the black one) ain't closing its inlet properly because the shim is quite a bit bigger than the others. Obviously its all relative, at the time of shimming it was probably correct, but wear and tear shows the valve sitting proud (you can actually see air around it with the cam removed!).

hoping that just stripping it down, and rebuilding with fresh shims, cutting it in freshly should sort it out :idea:

:shakehead: im glad you said that it was summat to do with the shims (of cousre your motor has been modified a bit in the past lol)

:rolleyes:things would be dire if these engines just popped valves just because they had done 98k!
i was worried, cos i put a 75 cam in my (ex)motor, checked the shims for tolerance, and since they were all within tolerance, left it with the original shims.

so how come yours popped, if it was correctly shimmed at the time? shims and/or cam lobes dont just suddenly start to expand for the fun of it....
 
think I've got it licked.


after stripping the valves out and finding them to be in PERFECT condition. I closly examined the gasket, seems to me and th head skim bloke that the gasket has split between cyl 3 (bad one) and cyl 2 (good one).
its weird because its actually burnt' out the metal ring and gone THRU IT.

its also seperated the paper gasket parts in such a way that its split between cyl2 /3 and oil and water galleys.


anyways. weird. completly unexpected, but it would add up.

so meh. don't buy cheap shatty FAI gaskets, they will fail fair quick. (had 30k miles out of it).
 
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