Dropped Valve

[notmytarga]

I dropped my #1 exhaust valve at Thunderhill.

I was not planning to rebuild my 1975 911S California motor for a few more years. It has 54,000 miles but had the thermal reactors removed at least 20-25,000 ago. It has been running well and I took it to Thunderhill for a Hooked on Driving HPD track day Dec 8th. I have done five track days at Thunderhill over the last year.

Braking into turn 14 I felt something change but I didn't pull into the hotpits. The flags were then out that the session was ended. The engine was rough but had OK power driving at 50% around the track to pull in. I didn't hear any horrible sounds when I pulled off but I had lots of blue exhaust. The engine died unless I kept the tach above 1500 RPM.

Looking back, I was having exhaust smoke while in pregrid and someone asked me if I had just added oil. I will presume that the valve guide was really leaking and heating the valve stem. Prior to that the only oil smoke was a puff at startup.

Diagnosis: A few days after the incident I turned the engine by hand to determine which cylinder had lost compression and thought it was #6. That plug was very oily so I thought I had bad rings. Pulling the rest of the plugs I found the #4,5&6 plugs to have about the same amount of oil with #2&3 dryer. The #1 plug came out with some effort like it was stripped. The side prong was gone and the center conductor was bent to one side. I was able to boroscope the cylinders and found a little oil to match the plug condition. #1 was all beat up - a hole in the piston but the circumference was intact and the cylinder looked OK. I could see the exhaust valve lying over its orifice. At first I thought it was mearly open but then I saw the stem facing the piston. I think it was stuck there because the sound didn't seem as bad as I would expect for the ...... 85 mile drive up I-5 home.

Ok - so stupid me. I was more concerned about getting home to my sick family to improve my chances for future track days. The whole drive I figured that the compression loss and oil burning symptoms meant a valve guide was leaking and I feared I could burn out a valve - it had already happened in a big way.

I have now read more of Waynes rebuilding book.

So a few questions for the sages:

1. If there is no ignition in the blown cylinder - what burns the oil?

2. Presuming that metal is everywhere in the engine, what parts are ruined?

3. Presuming oil filter perfection - what parts are ruined (other than the piston)?

4. If I had a rough 2.7 long block core of uncertain internal condition readily available, should I buy it and for how much?

5. No question here - I plan to rebuild myself. Heck, I did the whole restoration - and did a VW rebuild 20 years ago.

More about this car:
The whole Targa Story

Restoration Pics

[Aurel]

First of all, I feel for you and I hope the damage is not too bad.

I can`t answer all the questions, but I`ll try my best:

1. I would assume that unbrunt oil passing through the exhaust will burn in the headers.
2. Depends on the size of the metal particles. Best is to see what you get caught in the oil grid when you remove the oil sump plate cover.
3. I am not expert enough, but I assume piston-cylinder are junk at the very least.
4. Here is a recent e-bay example for $1250. I say they can be had for relatively cheap because they are not as desirable as the 3.0L alu blocks.
5. You are in the right place to get all the help you need !

Good luck!

Aurel

[notmytarga]

Thanks for the sympathy, encouragement and information!

I expect to drain the oil and inspect the sump today. Pictures forthcoming.

As far as the "spare engine" - At first I hoped that I could run it while rebuilding mine, but after seeing it I knew it would be a project to get running because of missing external parts. Know I'm thinking that it could provide a piston, cylinder and head to replace the damaged one. It is likely that all the internal parts are intact. It is local and basically an exact match for my engine. It has a destroyed CIS airbox (with pop off!), no distributor cap, no clutch or pressure plate, no exhaust valve covers, no oil lines but does have updated tensioners, no engine tin. It does have heat exchangers and muffler with Thermal reactor delete manifolds. Fan and alternator spin, no belt.

Should I buy it as a practice/donor, and for how much?

[Eagledriver]

Your exhuast valve guides were worn out which is why you had the oiled plugs and dropped the valve. That head, cylinder and piston will be ruined. Depending on how much metal went through the engine there could be much more damage. When you dismantle the engine look at the bearings to see if metal made it through the oil system. If there is metal there then you need to completely clean the oil system (tank, lines, coolers, etc). If the bearings are clean then you might not need to do the cleaning but it would still be a good idea.

The other engine idea is a good one if you can get it cheap. If it's a running engine with the missing/broken external pieces then I'd pay around 2000 dollars for it. I'd put your external parts from your blown engine on it and run it while you rebuild yours. Used parts for 2.7's are cheap.

If it were me I'd skip the 2.7 and buy at 3.0 instead. A running 3.0 will set you back about 4-5 k but will be much cheaper than getting a 2.7 up to speed. A core 3.0 will cost about 2500 dollars and take 3k or so to rebuld yourself (assuming most parts reusable). Your car is smog exempt so you could build a nice carbed engine and get 230 plus HP. You'll be on your way to building a spec car to race in the PRC (www.porscheracingclub.com)

These are some ideas.

-Andy

[notmytarga]

I believe there are a thousand words worth up there, but here is some description nevertheless. This shot shows the aluminum chunks from the piston that were collected at the screen. Not much small stuff at all there. The oil looked normal for the 400 miles that it had on it. No metal stuck to the magnetic plugs. The #1 spark plug is also on display.

I thought I was sensitive to the sounds of my engine - I can't believe I missed this. It likely all settled pretty quick and my gentle driving did not dislodge the valve stuck upside down to its intake. It will be interesting to see how easily it moves during disassembly.

As far as moving up to a 3.0 - that makes a lot of sense, but I want to keep the important aspects of this car original. The donor engine was offered very cheap but I would not be willing to put too much into renewing it unless it seems solid on further inspection - using the engine to run the car would be great but seems like a fantasy. grabbing parts off it wouldn't work if I was using it too....

Thanks for your advice - I'll document the donor engine if I can still obtain it.

[notmytarga]

I have slowly moved along and tore down to the piston today. Here is the picture that tells the #1 cylinder story (the engine is upside down)



The head took a beating but obviously the valve pretty much stayed sideways in the valve seat during the 80 mile drive. The nikasil cylinder has some dents - to the trash I suppose.



The strange thing is there is some impact damage in the #5 combustion chamber. The only reasonable path for piston fragments I can imagine would be up and across the CIS system propelled by the back flow from #2 &3 through the exhaust valve. Is this possible???



My 'rescued' engine received all the engine externals, was installed, started and smoked heavily - especially on acceleration. I'm presuming ring wear. Perhaps that engine will donate some cylinders to mate with JE pistons although with the ring wear the likelihood would be that the cylinders are out of tolerances. What should I do?? I had been reviewing the 9.5/1 compression JE pistons with the 964 cam regrind as the build option. But I may have run out of usable cylinders

[3.2 CAB]

Man, that thing took a beating! I have seen before, when the # piston, or connecting rod had severe damage to them, it actually caused a balance issue with the #5 cylinder parts, due to the loss of weight on the #1 cylinder. I can't say that this is what happened to yours, but it looks very similar to other engines that I have seen that have had failures, then additional damage done, from the out of balance condition created, on the same crank plane. Good luck!! Tony.

[notmytarga]

Well lookie here - a majority of the piston remnants were found in the sump - see the total weights

# 4 Piston - undamaged = 593 gm - I'll assume this is a normal weight
# 1 Piston without any carnage = 554 gm 93.4 % of oscillating mass remained
# 1 Piston with Aluminum chunks found in sump = 574 gm
# 1 Piston with all parts found associated with it = 581 gm leaves only 12 gm unaccounted for or 2% lost.

It looks like it escaped into #5 > 2> 4 via the CIS judging from the head and piston dents. I may find more in the case when I open it soon. The connecting rod looks unscathed so far.

I loosened up my case bolts a turn or so tonight and as most of the 15 mm through case bolts on the top were lossened there was a sharp snap or click sound. Is this typical and what might it signify?

[Eagledriver]

The sound indicates that you have a magnesium case. They warp and need to be align bored. Most shops bore it oversize. Then you need the expensive oversize bearings. Then you need to have the case timeserted. It gets expensive.

-Andy

[gigem75]

That is worth box framing and hanging on the shop wall. ouch, good luck!

[Walt Fricke]

Not MY:

Be assured, as engine blow-ups go, you suffered increadibly little damage. When I have dropped a valve the piston broke, the rod end with wrist pin smashed the cylinder, and then continued on to saw a slot in the case. Along the way it broke a hole into the oil pump case. Sometimes snapped the end of the intermediate shaft. Once broke a cam. In addition to the trashed piston and head. Even when the valve head ended up shoved sideways into the seat like yours.

When a CIS blew up I found debris in lots of places in the intake system.

You really need to cut your oil filter open. If it has aluminum particles in it for sure you need to clean the dickens out of all the oil lines, coolers, disassemble the thermostat, and so on. If the bearings are clean when you pull the crank out and the rods off, you may have dodged a bit of a bullet, but I've never been so lucky. You drove quite a while. I never had a chance to do that because mine exploded on the track, or while I stupidly was trying to limp back to the pits after a big bang like a tire exploding (if only it were just that).

And it only makes sense to pull the oil galley plugs and really clean the case. And the oil tank, too - any stuff that made it past the oil filter to get into the bearings will be in the tank also.

I'd not place much faith in the lack of stuff stuck to your magnet. The aluminum piston and head probably didn't file shavings off the valve. But the aluminum particles won't stick to the magnet. All that little stuff in the intake runners (and, since you say it got over to the other bank from #1 to #5, it is in parts of the air box that are hard to get to) is probably but a fraction of what went through the hole in the piston.

But maybe not.

I once drove a VW some 200 miles with a crankshaft broken in half. Someone looks out for us sometimes.

Reusing your case calls for making a lot of careful measurements while it is all disassembled, seems to me, so you can decide on line boring (do not let them do that to the #8, though) and oversize mains, or the nicer shaving of the mating surfaces and then lineboring back to standard (which would, of course, include the #8). or whether things are in good shape, not oval, etc.

And then there is the likely need to replace all your valve guides, and maybe a bunch of your valves if the stems have worn, etc.

Used engines can start to look pretty good at some point. Even a used 2.7 if a) the head nuts will all torque to spec, and b) the leakdowns are not bad (you define bad).

Walt Fricke

[TibetanT]

Holy cow! I really hope you don't find anymore hidden problems. But, since you asked, I would take a good look at the rods, the crank and the bearings. With the carnage, you may have little pieces of metal through out your case and the oil passages that lube the bearings. The oil cooler should be changed out since I don't believe they can be cleaned, but I may be totally wrong about this fact. As others have said here, any part of the oil delivery system is suspect. Check all the specs as has been said.

If you decide to go the 3.0L route, drop me a line.
What part of Northern California are you in, Shasta/Redding or Bay Area?

Good luck.

[3.2 CAB]

Oil coolers can be cleaned. But, it is a PITA and time consuming. I have a parts washer that I have just for coolers, oil or trans. I connect the cooler in line with the fluid pump, it then circulates the solvent throughout the cooler, and it is filtered before going back into the pump and cooler. I also use my pressure washer with soap to finish the cleaning, then rinse without the soap. I have seen people just use a pressure washer to flush the coolers also, and some have gone to the car wash to use their spray wand with the engine cleaner then the hot soap and hot rinse. After flushing, which ever way you go, the cooler needs to be blown out with compressed air to help get moisture out, and to help dry. Then cap off the lines so nothing gets inside till you are in the process of re-installing them. The rest of the oil system is another PITA to clean!
The worst engine grenade I had, was back in the 70's when I was still driving NHRA TF or Double A, when an entire intake and blower set-up, on one of my MOPAR Elephant Motors, launched into orbit. The engine component tie-down systems were not like the type used today. Back then, when one blew like this, everyone ran like hell to GTF out the way! Talk about a bad pre-ignition detonation problem!! Good luck with your progress!! Tony.

[ianc]

Wow!

I sincerely hope you reconsider your stance on upgrading to a 3.0 or even a 3.2. You'd have a much more enjoyable ride, and save yourself a helluva lot of cleaning and worrying...

Good luck whatever you decide...

ianc

[notmytarga]

Thanks for the sympathy - I faired well considering the possibilities. My brain got sidetracked with the whole JE High compression piston and 964 cam grind option so I was only really disappointed that the #1 cylinder is minimally scarred and not perfect like the others. Obviously I have more to worry about and soon will be finishing the case disassembly and report on the main bearing condition and whatever else I find in there. The #1 rod looks okay in the spigot but I'll soon know more.

There seems to be something at the base of the headstuds - timecert? - I didn't think this engine had been apart till I found sealant behind the cam O-ring on the Right - please look at the earlier picture and tell me I'm wrong.

The options as I see them:

Starting position -
--One 911/44 (1975 CA CIS 2.7 L engine 54 K mi with # 1 piston and cylinder wasted, #1 head likely unrepairable. Original Engine.
--One "rescued" 911/44 long block with exhaust and trashed CIS of uncertain history which I got running (with my CIS) but it smokes badly and I could only remove one of the head air injectors - makes me suspicious.
--A desire to successfully complete a rebuild but not break the bank.

Any rebuilding will entail valve guides with complete head rehab, & case savers, possible align boring.

1 - Rebuild original engine with all new P & C's - keep original compression and Cams - obtain head to replace #1.

2 - Rebuild original engine with JE pistons and use head and cylinder from 'rescued' engine. 964 grind on cam. Is this a mistake in California?

3 - Rebuild original engine using best parts from "rescued" engine - specifically # 1 Piston, Cylinder and Head.

4 - Purchase a third engine - - (But I really want to do a rebuild.)

4A - A 3.0 or 3.2 of unknown condition.

4B - Purchase running 2.7 for $2000 ship it from MA to Redding CA.

5 - rebuild 'rescued' engine - I'm sure this case is tweaked.

Please feel free to add to these options and help me clarify my next steps. I think I see a spreadsheet with $/HP gain as the final calculation.

Another thing - the only German Machine shop here is mostly VW aircooled (loosely tied to the Bus Boys of VW Van fame) - I visited him and he could do most of the head and casesaver work. He did the work on his '72 rebuild and showed me the specification notebooks amoung his library. Would any of you consider this or should I plan to deliver or ship my parts to the north or south.?

Another picture - because I know I like them - here is the damage to #5 close up. Fifty knocks and out the exhaust - that's 10 secs or so.

[ianc]

I would look at 4A. You want to do a rebuild yourself, so look for old tired engines for cheap, then rebuild yourself adding some upgrades. Undoubtedly it will probably cost more since you won't get much for your existing 2.7 core, but you'll still have fun, and get a much more reliable, powerful engine as well as the fun of doing your own top end\rebuild.

Think of it as an investment in your Porsche. If you buy the 'rescue engine', your matching #'s thing is shot anyway...

ianc

[notmytarga]

What would I do with the two 2.7 liter non-running engines? - short of scrapping (I already 'rescued' one from this end) them or spending lots of time eBaying them away?

Are there untapped resources for engines I don't know about? EBay has a few of varying condition and price. Most are rebuilt for around $8-9K or need rebuilding for $3-4K.

I'm leaning to do #3, sell remaining parts of second engine, clean up the shop and then see if I feel called to do a 3.0/3.2 rebuild

[deanp]

This would get you back in the game and then you could take your time and rebuild your original motor. $2000 as it sits on the pallet, ready to ship.

[notmytarga]

Finally responding - sorry. The engine is too dusty for my application. Just kidding! It looks great and would be a reasonable solution if I didn't already have all the 2.7 parts I need.

Given all the recommendations I have had to move to 3.0 or 3.2 engine I would do that if a similar engine of that type was offered at a proportionally reasonable price.

Hopefully you had an offer for the engine, feel free to use this thread to tell us more about it. In the meantime, cover it.