Two damaged cilinders and pistons - What to do ?

[prebordao]

Due to carelessness on my part - metallic debris entering the cilinders - I know have 2 damaged cilinders / pistons on my 2.7

The top of the pistons are pretty mangled up and the cilinders have some scratches in the walls.

Now, what is the best course of action ? Can the cilinders be resurfaced (I think they're Alusil) ?
If buying new P/Cs can I just replace those 2 or should go and replace all 6 ?

[DRACO A5OG]

PJR,

Sorry to read your troubles.

Course of Action? How many miles do you have on the engine? If not too many miles just pull the two cylinders and pistons, resurface and re-ring. If Pistons are not cracked, it may be okay but please post pictures of them. More experienced can chime in.

If allot of miles, maybe time to do at a minimum top end rebuild ergo all 6.

Break a Leg Brother,

[rwest]

How are the heads? Got to figure if the pistons are damaged, you may have damage to the heads as well.

I ended up in the same boat but with only 1 cylinder group being messed up.

[prebordao]

I'll have to take more pics...

[Prsh356]

Take a look at your head studs while you're there !

[DRACO A5OG]

Oh my goodness. The Pistons are done, sorry.

+1 please post a picture of the heads.

Side note, is that orange stuff on the chain box silicon or 574? If silicon, please remove and use proper 574. The silicon can break off and clog up your engine.

[sugarwood]

Stupid question of the day, but why does it matter if the piston has nicks on top?
It still gets pushed down by the spark plug ignition, no?

[DRACO A5OG]

It may cause hot spots, you want an even burn to get the maximum power output

[Trackrash]

Originally Posted by sugarwood

Stupid question of the day, but why does it matter if the piston has nicks on top?
It still gets pushed down by the spark plug ignition, no?

With damage to the area above the rings, there is a very good chance that the forces either weakened or distorted that area. You would hate for a ring or piston to break after trying to reuse such a damaged piston.

If the rest of the motor is good, I imagine there are good used piston and cylinder sets available.

Check post #6 in this thread. Mag. case for Porsche Historic Racing.

[fred cook]

Fix it right! You will be happy you did in the long run! Patch jobs don't seem to last!!

[T77911S]

i have heard of just replacing 1 PC and head.

looks like damage was all to the top end, but you might consider checking the rods for bending.

you could make a nice 2.8 with carbs,

[pmax]

So, the debris from one cylinder got into another resulting in visible damage to both.

The question is where's the rest of it ?

[HarryD]

When my 2.4L CIS motor ingested a screw and chewed up the top of a cylinder and head, I faced a similar issue.

Options:
1-Get a set of 2.4L CIS (unobtanium) P&C's (if they could be found).
2-Bore out to 2.7 liter (and the a$$ocitated machine work) and external cooling
3-Replace existing motor with a larger one (need to add external cooling as well) and lose my numbers matching car.
4-Send the P&C's to the machinist and see if he can save them.

Option 4 was pursued. The machinist examined the parts and decided the damage was limited to the top and non-critical areas so they were reconditioned, polished and returned.

Get an expert (someone who has see hundreds of these) to physically examine them and see what they say.

[JSV798]

On the first long drive in my first Porsche back in 1978 it holed #4 piston on the bottom side! Someone had left out the cooling tin. I got round that one by replacing just the one barrel and piston so just replace/repair what needs to be done. Hardest part is having the tools to get the camshaft nut off and re-timing the cam but plenty of help here. Wish this forum existed in 1978 - took me 6 weeks to figure it all out and get her running again

[T77911S]

Originally Posted by pmax

So, the debris from one cylinder got into another resulting in visible damage to both.

The question is where's the rest of it ?

did I miss it? I did not see that he said debris went from one cylinder to the next.

a major concern is are they alusil PCs.

[pmax]

Originally Posted by T77911S

did I miss it? I did not see that he said debris went from one cylinder to the next.

a major concern is are they alusil PCs.

I recall reading this was the result of a dropped washer in one cylinder.

[T77911S]

how would it get to the other cylinder?

[pmax]

Originally Posted by T77911S

how would it get to the other cylinder?

The alternative scenario is two dropped washers ?

[yelcab1]

I vote for replacing 2 pistons, 2 cylinders of good condition, measure the con-rod travel, put it back together and drive.

[pmax]

Originally Posted by prebordao

Your pic shows damage on the entire bank based on the fresh marks or debris on the pistons.