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You pull the head off your new, second hand "ran great" 1.8VVT engine and find the following. What do you do?



So, first, Cylinder #1, Ex side:


Cylinder #1, In side:


Cylinder #2: Ex side:


Cylinder #2, In side:


The culprit was the little blob next to the red arrow. He came off and disappeared (probably into the water jacket) while I was cleaning.


It does look like it's been stationary for a while though, which is .... an observation.

First 2 cylinders after some cleanification:


Top of the piston:


The options I've come up with are:
1) pretend it's not there, likely detonate engine once it's built and boosted (not a problem for the time being)
2) new head, sell this one to someone who wants to try their hand at port work.
3) get someone that knows what they're doing to machine it out, get 11:1 pistons.
4) deck the block a shit-ton, hope it solves the problem, get 9:1 pistons.

So, on a scale of one to "sucks to be you", how bad is it?

The pistons I'd replace, it's already apart and weird shapes like that can cause hot spots that increase likelihood of knock.

With the head, take it to your machinist, they'll have a look and let you know if they can machine out the damaged section alone, then deck the head like normal.

check your throttle body screws

noobee wrote:check your throttle body screws

Beat me to it.

If the TB shaft screws are intact, then it was some other screw/nut that went through (or the TB has been replaced). My money is actually on that. I have busted at least four TBs on the racecar, the screws went through with all but one leaving no sign of their passage. That one left a single slight indent in the squish location, nothing like that. Whatever it was, it has bounced around in there for quite a while before exiting.

My racecar ran forged pistons, so I wasn't too worried about piston damage, but those are stock cast pistons - I would replace them.

Agree to talk to a machine shop about the head, I wouldn't worry too much about eliminating all signs of the damage, but you want it cleaned up enough to minimise the risk of detonation, at the very least.

Have you checked the head for hardness, that might make the whole discussion moot? Check the bore too, sometimes the ring land is damaged by the screw, and that can do serious damage to the wall.

I did find the thingy, it's didn't actually exit the cylinder, it just embedded in the head hard enough to stop rattling around, and eventually ended up coated in carbon like the rest of the combustion chamber

it was a 1.5mm dome-shaped thingy-ma-bob, metallic, small, shiny. quite rounded, except on the side that ended up embedded into the head, that was concave - it's the 'lump' that the red arrow is pointing to.

as far as checking for hardness, is that a DIY type event, or a "take it in" type of thing?

It seems like that's step one; a friend-of-a-friend that knows a bloke that works in a machine shop started with that same question.

That sounds like it is the screw (one of two) that holds the throttle plate onto the throttle shaft. When the shaft breaks, it does so where it is drilled to take the screw, and surprise surprise, the screw falls out and gets sucked along with the incoming air. But that is academic now, except that you want to avoid a repetition - a Skunk is the only known sure cure.

You can test yourself, with a steel ball but unless you know what you are looking for it is best to let the experts do it.

If the engine came with the IM and TB, have a close look at the throttle plate and shaft - sometimes it is not immediately obvious that it is broken.

Good luck with it!

I ran a head with much worse damage than that from a piston failure. It was fine for years. Just get it tested for hardness and give very it a little shave to clean it up. That surface doesn't have to be perfect. I probably wouldn't trust the pistons though.

A big shave won't touch the area concerned but quench related bowl shaping and valve head deshrouding along with a big shave would reduce the damage.
I searched for ages without success trying to find a pic of my headwork before the engine was reassembled to give you an idea of how much material was removed around the area in question.
It was expensive and was done by an experienced builder after a lot of convincing on my part.
It may be more pragmatic to acquire another stock long block if you're not looking towards forged bits etc.

I have a spare non vvt head and supertech standard size backcut valves, new bronze guides I'd be willing to provide for a very reasonable price if it helps... i need $$$ for tyres.

The head will be fine. Only part that would worry me at all is the dag that is hanging out into the combustion chamber on the intake side. A few minutes with a hand file will clean it up.

Piston is slightly more of a worry, NOT for potential hot spots but because of potential stress risers in the cast aluminium. That said, I would be amazed if it ever caused and problems.

The potential for hot spot problems in the squish area is very low.
Also remember that it has been running like this for a considerable period of time already. Nothing is going to change now that you know about it. ;)