Inlet valves touching pistons in a LC 205 carb pinto

[sigurko]

Hello everyone, please help shed some light on the following event.

I removed the carb head from a running, LC (pistons are 1.5mm below deck at TDC), 205 block engine and I was amazed to find out that the inlet valves were touching the pistons with their edge that is closest to the spark plug hole.

Contact area lengt of 3-4 mm, caused at least a 1mm deep punch in each and every piston.

That engine was running, I personally drove it before taking it apart.

I thought that the pintos are non-interference engines, and that valves can't touch the pistons no matter what.

What am I missing? Is it possible that I have a machined head/block?

I measured the head width to 91mm, and as I mentioned, pistons are 1.5mm below deck at TDC.

What is going on?

Let me know if I need to post some pictures of this to be clearer.

Any input would be greatly appreciated.

Thanks in advance,
Matthew.

[racing escort]

Are the timing marks correct, maybe the belt was not installed correct ?
Is the cam standard ?

[sigurko]

Back with some pictures that I hope can help shed light to all this...

Inlet valve with a clearly visible scratch (near the spark plug hole) which is the valve contact area with the piston (all other inlet valves have same scratch)


Piston with a clearly visible "ding" caused by the inlet valve (it's about 1mm deep, all other pistons have same "ding")


This is what's stamped on my block


I hope this helps, cause I'm cluless -(

[sigurko]

"Are the timing marks correct, maybe the belt was not installed correct ?" - That's part of my question:
I thought that the pintos are non-interference engines, and that valves can't touch the pistons no matter what. Am I wrong?

I do not know the history of this engine, it most likely had a head work previously done. However, I do not know how to identify the head. It may as well be one from a 1600. How can I identify it correctly?

Here is a close up of the head/cam

[racing escort]

std engine is indeed non interference, but an other cam, skimmed head and/or cambelt misplaced can cause this (or serious over revving the engine)

[sigurko]

In a non-interference engine the piston does not travel into any area into which the valves open. So, I do not see how over-revving or misplaced/snapped cambelt can cause this.

If I'm correct, and it can't, the only other explanation is that either the head/block are machined, or the cam/valves are not STD.

Or, are there any other options?
Or am I not correct with the above assumption?

[rallyrob]

Im surprised it hasnt got 4 bent inlet valves with the amount of contact there...

[sigurko]

There was some damage to the inlet valves for sure.

I was having horrible time to start it after more than 2 days.
Was starting with a flip of the key if was starting it for 5 min every day.
But skip a day and wow... could barely get it going.

On one of such times, when I could not get it started, I gave it a compression test (I know I know, cold engine, but still) - it read 100psi on cyl#1 and 125psi on the others.

So, I decided that it was time for an overhaul, popped it open, and here we are...

[sigurko]

Still, back to the original question -
am I correct to assume that the fact that valves touched pistons, on a Pinto which is a non-interference engine, means that either the head/block are machined, or the cam/valves are not STD?

[theduck]

the valves in the photo are standard, the piston appears to be standard, have you the ability to cc the combustion chamber of the head? that would tell you if heads been skimmed.

[Graham]

without doubt its been skimmed, a standard head is nearly 95mm thick measured from head face to cam cover gasket face, its probably been heavily skimmed to compensate for the low comp pistons

[Forest_rallying]

It's possible that the engine has been running with the cam timing way out of adjustment. With your pistons down the bore 60 thou and a similar thickness for your head gasket you should have bags of clearance, even with a 1600 casting or a heavily skimmed 2.0 head. It's easy to check, get both inlet and exhaust valves on overlap and put a straight edge across the combustion chamber, it there's clearance between the straight edge and the valves then the problem's incorrect timing.

From the photos the engine looks pretty std to the naked eye. Don't forget to renew all valves that have come into contact with the pistons as they'll probably be riddled with fatigue.

[Graham]

It's possible that the engine has been running with the cam timing way out of adjustment.

that would also be my conclusion

[sigurko]

I'll run the test suggested by Forest_rallying and come back with results and pictures. Thank You!!

Also, my head measured only 91mm as opposed to 95mm mentioned by Graham. AFAIK, that's not a reasonable amount to be machined off a head, right? So that makes it a 1600 head, most likely?

I'll cc the combustion chamber, as suggested by theduck, and hopefully it'll help identify the head.

Thanks,
Matthew.

[therealpinto]

If I'm not mistaken the 1600 head is not 4 mm shorter than a 2.0 head, rather the combustion chambers are more shallow (needing longer valves).

So I do think it is possible that you have a 2.0 head that has been heavily skimmed. On standard heads I do think you can see a difference in the mounting face of the heads (1600 vs 2.0) but if it is skimmed 4 mm that may not be visible. But a photo showing the entire face might help.

Gustaf

[alladdin]

2 things, from memory theres a threaded hole in front face of head that gets too close to head face if over skimmed ?

and - it may be the light but that cam looks heavily worn to me ?

[Graham]

1600 head is same thickness as 2.0, combustion chamber is shallower and valves are longer to compensate

[livewire514]

its a 2.0 head, obvious way of telling is the 3 holes at front of head on the inlet side which dont do anything

[sigurko]

Did some head face cleaning, back with some photos.

Also, per Forest_rallying's suggestion, put valves on overlap, in which state they are barely opened in my head (heavily worn cam as alladdin noted?) and are waaay below inside the combustion chamber, no where near the head surface. Didn't even need to put a straight edge over it.

Did not get to cc the chambers yet, will get to it tomorrow.

Head face pictures -

Chambers 1 and 2:


Chambers 3 and 4:


All of it:


Also, found this inside, which has a different number than the one stamped on the block:

[sigurko]

2 things, from memory theres a threaded hole in front face of head that gets too close to head face if over skimmed ?

and - it may be the light but that cam looks heavily worn to me ?

"threaded hole in front face of head" - meaning the surface where the cam pulley resides?

[alladdin]

yes, i think one gets very close to breaking through if its skimmed a lot. look for the lowest bolt hole.

[sigurko]

Okay, I'll take some clear pictures of the head sides, all of'em and post here.

Also, I'm reading this short thread -
http://www.turbosport.co.uk/showthread.php?t=140138

Where "RWD fords rule" mentions that -
"...the std 2.0 head measures 94.9mm at the back of the head"

Why is the emphasis on the back of the head? Is the width not uniform throughout the whole length of the head?

[Graham]

the number inside the head is a casting number, no relevance . head thickness should be the same all the way round

[madragon199]

What condition where your plugs in...when we used to skim the head to its max..we had to change to short reach plugs.because they used to hit the pistons ..
The other option is its a previous damage from another head..and someone just changed the head ...back in the day we used to put the old race engines back in the road car when they were past there racing best...still ok for the road car....or make an engine up from the old bits...cheers mark

[wildo105e]

The other option is its a previous damage from another head..and someone just changed the head ...

Thats what crossed my mind. I snapped a cam belt years a go and bent some valves. Changed the valves and away i went.

[sigurko]

I come back with clarifications and pictures, and - more questions -)

Spark plug condition when I first removed them:


Pistons condition when I first removed the head, before I cleaned them.
All covered with a thick layer of black (burned oil?) but the spots where the valves touched:


And, I've carefully re-measured the head.
It seems that I was originally wrong about it being 91mm, it seems to be of standard width of about 95mm:

[rallyrob]

I come back with clarifications and pictures, and - more questions -)

Spark plug condition when I first removed them:
Attachment 82275

Pistons condition when I first removed the head, before I cleaned them.
All covered with a thick layer of black (burned oil?) but the spots where the valves touched:
Attachment 82276

And, I've carefully re-measured the head.
It seems that I was originally wrong about it being 91mm, it seems to be of standard width of about 95mm:
Attachment 82277

Surely it's got to be cam timing out then hasn't... A tooth or more...

[sigurko]

The other option is its a previous damage from another head..and someone just changed the head ...back in the day we used to put the old race engines back in the road car when they were past there racing best...still ok for the road car....or make an engine up from the old bits...cheers mark

This thought crossed my mind, but I (wrongly?) dismissed it because the pistons were all black (burned oil? as can be seen in above picture) with the exception of the clean silver "ding" where the valves touched.
So, to my mind, I though that this is a recurring state, cause otherwise, why would that "ding" also not get covered black?

[sigurko]

Surely it's got to be cam timing out then hasn't... A tooth or more...

Well, actually, I'm even more confused now.

It seems that the head, valves and piston-deck height are all LC STD. And, being a non-interference STD engine, valves should not touch pistons, no matter how bad cam timing is, or even if cam belt snaps.

Only ration explanation is that is really is damage from a previous head, but than I do not understand why was that silver "ding" on the pistons not covered black, as the rest of the piston surface.

Clueless -(

[3.5cologne]

Just a thought. Have you pulled the valve that has been hitting to see if it has maybe been sticking into the guide?

[snapper1]

Plasticine on the pistons, dummy fit head with old gasket, time it, turn it by hand, pull the head check valve impressions in plasticine.
Fit thicker gasket if valve piston distance is to tight.

[madragon199]

The other possible thing is the blocks been decked and the pistons are hitting the valve..(not valves hitting pistons) or the rods are longer..check to see if pistons come past the gasket ..
. Cheers mark

[Graham]

turn the cam to full lift on a cylinder thats got marks and see if a valve comes proud of the head if it does, theres the answer, its probably had a belt snap or been timed way out

[Miniliteman]

From memory a Pinto head measures 94.5 mm unskimmed.
If the marks on the pistons are definately from the valves then it could be that the engine has weak valvesprings and/or has been revved hard (out of gear) which lead to the valve not fully home before piston is in TDC.

[Graham]

If the marks on the pistons are definately from the valves then it could be that the engine has weak valvesprings and/or has been revved hard (out of gear) which lead to the valve not fully home before piston is in TDC.

or someone has selected a gear way too low for the road speed and mechanically over reved it

[katana]

I'm as confused as the OP - if the engine is non interference then if 'stock' there should be never an occasion that the valves can touch the pistons - I snapped a cam belt back in the day in my RS2 driving hard up a hill - engine stopped dead but took a fraction before clutch got dipped so pistons were being driven by road speed..... no contact and no damage. So I figure the ONLY way contact could occur is valve float - weak springs or serious rpm action - I could never get mine anywhere near valve float territory so i'm puzzled. Those dings don't look like a rpm 'kiss' more serious continuous contact abuse so even more puzzling! If the piston was getting close to the head, I'd expect to see the squish zone fairly clean / carbon free - but it isn't.......its a mystery!

[Forest_rallying]

It is a mystery Katana why this thread is causing so much of a fuss for a std Pinto engine. The OP has told us that the pistons are 60 thou off TDC so there's no chance of them hitting the head. The std Pinto engines I had never reved any higher than a modern Diesel engine so the chance of valve bounce would be minimal unless the springs were broken or came from a Bic pen.

It's clear that it's nothing more than a snapped belt or more likely a incorrectly timed cam. Are we all having our Pants pulled down here?

[Escort TC]

In this position it is never a valve contact. This isnt the deepest point of the valve. The mark on The Piston ist also to smal for a valve contact.

[sigurko]

Good people of turbosport, thank you all for your time and the advice that you have so kindly provided.

I will put that to use while rebuilding this engine. But that is for a different thread, which I hope to open soon enough.

Cheers,
Matthew.

[lowscorts]

the dent certainly looks too deep and narrow for a valve edge, maybe somethings gone through it at some point, or a heavy handed stop through the plug holes while timing up?