My old engine

[leon_in_uk]

right guys, stripped the whole engine down... the bores are fine. top end totally fine... even big ends are fine... and the only thing wrong is that the pistons have hit the ....... cant remember to slighlty score them...

my step dad said thats due to over revving....

so only a slight error in the whole engine.... oh and the crappy manifold

[Tem]

the pistons have hit the ....... cant remember to slighlty score them...

my step dad said thats due to over revving....

Valves?

[leon_in_uk]

thats the one. only slight scoring... would that make a diesel sound??:

if so, no effect from pre cats inside the engine... they must of blown out the exhaust..

[SteveJ]

The 1ZZ is a non interference engine, so there is no way the valves can hit the piston unless something has gone very wrong. Over revving will not cause this.

[kanujunkie]

you sure you dont have a broken piston??

[leon_in_uk]

well this is the piston, what could cause this??



and is this the big end?? its very clean and no marks what so ever... the only thing wrong with that engine is the above pic...

[kanujunkie]

ok you got me, strange one this  s:? :? s:?

[aaronjb]

That piston looks fine to me - I'm guessing you've cleaned the carbon off it, hence the 'scrape marks', right? (surprisingly hard to get off, isn't it!)

Odd.

[leon_in_uk]

thats all i have done and took out. no cleaning etc.

if you notice 2 chips/bends to the left.. that is the only thing wrong with the engine...

my step dad has stripped the whole lot down...

so the piston and only 1 pre cat.

[aaronjb]

The two 'dinks' on the left hand edge of the piston are the reliefs for the valves on that side of the head I believe - all the pistons should be the same..

Unless I'm not looking at the right bit of the picture (entirely possible  s:) s:) )

[peppyuk]

That piston looks fine from where I'm sitting, if it had hit the valves your more likely to see valve damage than piston damage, if a piston hits the valves you'll see that the valves which had been hit will be bent and won't close fully.

[leon_in_uk]

oh right. my step dad knows alot aobut engines metal etc. he has just stripped his porsche 944s down and back together.

and from what he tells me there was no damage to that engine!!

he said it burnt oil from what he could smell and look at.. in the sump there was white and black oil left.

so with an engine that looks fine inside. i wonder what made the heavy diesel sound and power loss.

[SimonC_Here]

"Looks fine" is one thing, my failure was down to oval bores. They sent an engineer (2 actually but that's another story) down to measure them with some device or other.

Simon

[markiii]

power loss would be the reecats obstructing teh exhaust

[leon_in_uk]

so after stripping the engine and getting a new one. all i perhaps needed to do is get a new manifold, or gut existing one. and get a new exhaust system..

although a company would of charged about 1k to strip the engine down to find the problem...

[markiii]

possible though from memory you were using loads of oil as well?

and that would have to be engine related

[philster_d]

so after stripping the engine and getting a new one. all i perhaps needed to do is get a new manifold, or gut existing one.

Eh ? why do you want a new manifold ? thats putting pre cats back in again after they busted you once.

or.. ...get a new exhaust system.....

Sounds logical (cat anyway), but its all stuff I recal you where told at the time of the initial failure.

And is stated many times here dont put the same cat back on the new engine etc. etc.

[leon_in_uk]

i know. i wouldnt keep the pre cats in (they arent in now) and i would use a new cat...

but maybe if i gutted the manifold. and got a new cat there wouldnt of been a problem...

and im not convinced it was the pre cats that blew back into the engine.. just blew into my cat and exhaust system....

something else may of caused the oil consumption....

[markiii]

you'd have to be seriously unlucky to simultaneously have 2 seperae issues one causing precat failure and one causing massive oil consumption.

but hey with you anythings possible  s:wink: :wink: s:wink:

[Anonymous]

Did you have the bores measured at all on the old block? - I'm just wondering if oval bores were the cause of your oil consumption rather than any precat related damage.

[leon_in_uk]

not measured. but they are round. and very clean..

my step dad is a metal polisher and he said they are like new, really nicely polished.

[SteveJ]

not measured. but they are round. and very clean..

my step dad is a metal polisher and he said they are like new, really nicely polished.

So if you havent measured them, how do you know they are round - do you have super macro vision that can measure things to within a couple of thousandths of an inch?   s:roll: :roll: s:roll:    s:roll: :roll: s:roll:    s:roll: :roll: s:roll:  

YOU ARE NOT GOING TO SEE THE BORE IS OVAL USING THE NAKED EYE.

[Beowulf]

Yeh,sorry,you will neeed a micrometer to tell they are oval.It might seem like the the internal combustion engine is a basic thing,but when you know how it works,its amazing it works at all  s:shock: :shock: s:shock:  .It is a precision instrument and as such very small things can make a big difference. A rebore and oversized pistons would have been the way to go I think (if you were rebuilding the engine). I have got away with just the shells and rings on my 2 rebuilds in the past (ford cvh and pinto),but oval bores was not a problem in my case.

[red_leicester]

Unless you're looking at one of these bad boys.  CLICKY

Now that's what I call oval.  (And eight valves per cylinder   s:shock: :shock: s:shock:    s8) s8)  )

[Wabbitkilla]

Ah yes, the old Honda NR500 (didn't they do a 750)!

I'd suggest you have the bores checked with a micrometer as above.
A rebore and blueprint would give you a very nice engine while you're at it.