I bought a Seven Type at the end of the year. It was cheap as the 1.8 silvertop engine was noted as having an unidentified tapping noise.

The car had also had a fully ported 1.8 head with Piper cams fitted a few months before*. The owner had also had the rev limited removed from the Alpha managment system.

Anyhow, the 'tap', did not sound like big - or little ends as expected, so I tried replacing the tappets with those from a replacement 1.8 engine I already had - just to chance my luck. No change and nothing gained or lost.

So I took the head off and- it looks like the piston (nearest pulleys) is coming out of the bore, past the head gasket and it is striking the bottom of the head/combustion chamber.

Has anyone come across this before? My thoughts are that either:
the bearing is that far gone, that it is allowing too much piston movement,
or (outside chance), the standard rod has stretched!

Not knowing much about Zetecs, I am assuming that at TDC the pistons are supposed to be flat with the top of the block like a Pinto??


Im going to change the block for the other 1.8 for the time being, using the ARP rod bolts (and fit the 1.8 head to a 2.0 later), but I wanted to see what people thought first. - I cannot see the head being at fault, if it is flat.
So, it must be the piston??

 

It shouldn't hit on a zetec, whatever gasket is being used.. Depending on the engine, deck protrusion is possible.. sounds like someone has over-skimmed the block for some reason, perhaps to raise the compression ratio somewhat! badly!

I have a 1.8 engine in pieces you can have if you need it (essex)..

 

Thanks,
I have a complete running 1.8 sitting in the corner, I bought it to test the tappets theory - as at Ł40 it was cheaper than half a new set. I'll use the bottom end from it, but if that turns out to be FUBAR I may come back to you.

Am I right in thinking that the piston should sit flat at TDC? Its flat whilst the engine is at rest, but im wondering if it is only because there is no momentum involved with throwing it up the bore (during 'squeeze' cycle).

I was also concerned taht the head gasket hole is about 2-3 mm bigger all round than the 1.8 bore. Is that usual??

 

I probably wouldn't want more than about 0.35mm protrusion as the thinnest HG you can get, as far as I know, has a compressed thickness of around 0.7mm.

 

I put a straight edge over the block tonight and nos 1 and 4 do not potrude. I tried pulling the offending piston up with a valve grinding sucker, but could not get adhesion.

I thought some pics might help.

Piston No1, you can see the shiny part where it looks to have struck. There is no obvious damage to the piston or the head fces. Just no carbon build up.




The opposite piston for comparison. You can see a carbon covering as expected.



The undersige of the head, - No carbon on the opposing side:


Closeup of just that combustion chamber. Again, no obvious striking damage, just the lack of carbon.

 

Does that gasket look too large in pics one and two????

 

Worn big end bearing? you would also get a knock with that.

Gasket looks to be a 2.0 zetec. 1.8 has the 80.6 mm bore and the gasket is about 1mm+ over that size to allow for max over bore.

 

yeah, definetlyb looks like a 2.0 gasket, remember checking when doing a 2.0 conversion once

 

Looks like the thin blacktop 2.0 gasket is put on to a 1.8 silvertop that is designed for the thicker gasker.