Piston meets Valve, first motor pull! Would like advice moving forward!

[Shoeshear]

Hey guys, I haven't posted in a long time (used to post a little in the B6 A4 section), but just wanted some consultation on what I should be looking at moving forward. Just did my first engine pull on my dad's B5 S4 that just ate its timing belt tensioner. We have valves embedded in the piston on cylinder 6 (??), so the heads will have to come off, cylinders and valves need to be replaced. But are there any hidden things that need to be done at the same time? Just trying to set out a battle plan for what we do next time I come home.

Yes, I know it's probably financially more sensible to have sold the car as it was or part it out, or even swap in a used 2.7t, but my dad seems pretty attached to the idea of keeping this engine for the timing being. It is what it is.

So there will probably be head damage judging from the valves snapped off and embedded in the piston, but I don't really know what "head damage" entails or what rebuilding heads actually means. I just find it obscene that the labor we were quoted "estimate" from a stealership was $5k. Yeah, I know dealerships, but at the time we didn't have many options (car grenaded half way to Phoenix from SoCal).

So what I'm asking is, what should I be expecting to replace minimum? Just want to make sure there aren't "hidden" things that would have likely broken. Thanks for reading guys!

Here are some pictures I took with a snake camera thing. Ignore the time stamp.

[a4kamila6]

Rebuild will cost you at least 1,500 i think.. you would be 500 deep in just valves, add all the seals, gaskets, machine shop work.

I would find a used working motor for time being and rebuild that sucker little by little.

[Shoeshear]

Yeah, that was my go-to option, but dad's money so dad calls the shots in that regard. And time isn't a huge problem. The S4 is the "extra" car at home for my parents, but the longer projects languish, the less likely they'll get done, so I'm trying to keep the drive and motivation going in my dad so the poor S4 gets back together at some point.

My dad's big concern is that the turbos and a lot of the other stuff on the current motor (bone stock) are all in good working order and if we buy a used working motor, we'll be inheriting all the potential problems of that engine that we don't know of. I agree in some respect, but it seems tough to source a good condition long-block with known, well documented history. The last thing I want is to put in a new motor just to have it meet its maker soon after.

But what I was also getting at was that one of my friends was mentioning that when pistons hit the valves you may have to get the crank rebalanced or something? I've never heard of anything like that, so I just wanted to make sure that pistons, gaskets, valves, and head rebuilding (or resurfacing??) was what I needed. And do I need to check if the mating surface is warped? Sorry for the barrage of questions! But really excited that I pulled the engine for the first time haha!

[xalents23]

You might get lucky and just need to replace the heads and new timing belt stuff. Wait, you said the valve went into the piston. Dam... But, only way to tell how bad the carnage is to take the motor apart. If you turn your own wrench. This will be best time to learn more about the car and rebuild it yourself.

[Shoeshear]

Yeah, in the pictures above, that's the top of the piston and the valves are stuck in it... when we hand crank just a little, the valves move with the piston. Kinda nuts. Yeah, the plan is to take the whole thing apart. Doesn't seem like a lot of people do their own heads/head gaskets, but since the motor is toast anyway, doesn't really seem like I can do any more harm than has already been done haha.

[jballou]

Buy a Used motor. I have a line on one if you need it.

[Shoeshear]

Buy a Used motor. I have a line on one if you need it.

I'll let you know! Also thanks for your video man. I used it to pull the motor and basically had no issues at all. Life saver!

[y3ti]

If those valves are stuck, then those pistons are most likely trash. That would mean opening up the bottom end and replacing all the stuff that comes with it. That's a whole different ballgame, both in time and financially.

Check to see if the cylinder walls are damaged, if they are, you need a new block. At that point a used engine is the cheapest, and easiest option.

If you're concerned about reliability, the only way to be certain you have a healthy engine is to refresh a used block yourself.

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[Shoeshear]

If those valves are stuck, then those pistons are most likely trash. That would mean opening up the bottom end and replacing all the stuff that comes with it. That's a whole different ballgame, both in time and financially.

Check to see if the cylinder walls are damaged, if they are, you need a new block. At that point a used engine is the cheapest, and easiest option.

If you're concerned about reliability, the only way to be certain you have a healthy engine is to refresh a used block yourself.

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Wow, alrighty. Figured the pistons would be toast. I guess of the block is damaged then I'd need a new block and new heads which is just a new motor... Justin I PM'ed you!

[S4James]

after two "good" used motors having rusted cylinder walls... its fair to say that nothing is simple or cheap when rebuilding these cars. they are just too old.

[Shoeshear]

So it's been a little bit and the engine has come apart. Here's the progress so far. Any advice on checking connecting rod straightness and bore round? Seems like the tolerances are pretty low and I might be better off taking them to a machine shop or something to get it looked at.

The valve hit the piston pretty hard. When we took the valve out, there's a nice hole in the piston head there that you can see through:


Inside of the valve stem...:


Took the first oil pan off:


And the second one:


The pistons and their con-rods came out pretty easily:


The crankshaft "looked good". I'm probably not qualified to make that kind of claim, but there wasn't any scoring or scratching on the crank pin surfaces:


The poor valves really are bent to oblivion bilaterally:




Edit: I should note that the cylinder walls looked quite nice and shiny and well lubed. I couldn't really make out any scratches. The thought is that maybe we can get away with the old connecting rods. Is that a flat out bad idea?

[Wagonholic]

The old rods are perfectly fine, but you would need new rod bolts (one time TTY bolts) and bearings. You can pick up a set of forged rods from ebay/RPM for less than $3-400, and new glyco bearings for $60. You can just drop them in as they come with ARP hardware. Mine spec'd out perfectly out of the box and required no additional machining. The motor will be set for future power upgrades if you desire as well.

You can also pick up a set of used stock pistons. Just replace the pistons that are nicked, and clean up the old ones. Brake-clean and purple scotchbrite pads work really well. The stock pistons are forged Mahle, and can handle a lot of power easily. Usually re-using rings is fine if you put them back in the same cylinder, but since you are changing pistons new rings wouldn't be a bad idea. The grant rings are $60 for a set and are made in the USA.

I'm currently doing an engine build/rebuild like you, but for more power. I'm reusing pistons and rings, and did upgraded rods with new bearings. Most of the time the crank is fine, and by the recommendations of others (who actually have running cars with results) I avoided touching the crankshaft. Keep in mind that if you remove the crank you'll need to get new crank bolts/studs ($$$), main bearings, and thrust washers. Not to mention some people run into problems down the road after touching the crank

Let me know if you have any questions, or need any help. Which part of CA are you in?

[Shoeshear]

The old rods are perfectly fine, but you would need new rod bolts (one time TTY bolts) and bearings. You can pick up a set of forged rods from ebay/RPM for less than $3-400, and new glyco bearings for $60. You can just drop them in as they come with ARP hardware. Mine spec'd out perfectly out of the box and required no additional machining. The motor will be set for future power upgrades if you desire as well.

You can also pick up a set of used stock pistons. Just replace the pistons that are nicked, and clean up the old ones. Brake-clean and purple scotchbrite pads work really well. The stock pistons are forged Mahle, and can handle a lot of power easily. Usually re-using rings is fine if you put them back in the same cylinder, but since you are changing pistons new rings wouldn't be a bad idea. The grant rings are $60 for a set and are made in the USA.

I'm currently doing an engine build/rebuild like you, but for more power. I'm reusing pistons and rings, and did upgraded rods with new bearings. Most of the time the crank is fine, and by the recommendations of others (who actually have running cars with results) I avoided touching the crankshaft. Keep in mind that if you remove the crank you'll need to get new crank bolts/studs ($$$), main bearings, and thrust washers. Not to mention some people run into problems down the road after touching the crank

Let me know if you have any questions, or need any help. Which part of CA are you in?

Unfortunately, every single piston got hit...

I haven't messed with the crank, so I guess I'll keep it that way. And if the old rods are fine, that sounds awesome to me. I'll run it by my dad to see if maybe some forged rods are in the future. No plans for any power mods except maybe ECU remap and intercoolers. My dad wants to keep it pretty/totally stock. The car is in the east bay area in NorCal (but I'm actually in AZ for med school, so I come back periodically).

The plan right now is to get new pistons, piston rings, valves, and heads. Thanks for the help and input man! I'll let you know if I have questions/need help. Appreciate it!

[chris120391]

I've got a full set of 6 Pistons still attached to the stock rods for sale if you're interested. PM me if so. Perfect if you're not looking to do any major power adders. Complete with pins, rods and rod bolts



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[-Billy]

I still have my stock heads if you're interested.

[Shoeshear]

I've got a full set of 6 Pistons still attached to the stock rods for sale if you're interested. PM me if so. Perfect if you're not looking to do any major power adders. Complete with pins, rods and rod bolts



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PM sent!

I still have my stock heads if you're interested.

My dad jumped the gun and bought some heads off ebay when I wasn't looking... thanks for the offer man!

[S4James]

you can go nutty with replacing everything, and up thousands into it.. Ask me how i know :(

[Shoeshear]

you can go nutty with replacing everything, and up thousands into it.. Ask me how i know :(

Hahaha, yeah it can definitely get out of hand. The line of thought "might as well..." leads to a very slippery slope hahaha.

[Wagonholic]

Unfortunately, every single piston got hit...

I haven't messed with the crank, so I guess I'll keep it that way. And if the old rods are fine, that sounds awesome to me. I'll run it by my dad to see if maybe some forged rods are in the future. No plans for any power mods except maybe ECU remap and intercoolers. My dad wants to keep it pretty/totally stock. The car is in the east bay area in NorCal (but I'm actually in AZ for med school, so I come back periodically).

The plan right now is to get new pistons, piston rings, valves, and heads. Thanks for the help and input man! I'll let you know if I have questions/need help. Appreciate it!

Yup, new rings, pistons, and heads should suffice. Keep it simple, and it shouldn't be too hard on the wallet.






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[Shoeshear]

Just a follow up/thread revival. We did end up rebuilding it and it runs! Still some little things here and there. I think there's a boost leak somewhere, my dad had it throw a fuel rich code, but other than that, it's running really well! Thanks for all the help fellas!